Qass. Book COPYRIGHT DEPOSIT Nutrition and Clinical Dietetics . by HERBERT S, CARTER, M.A., M.D. ASSOCIATE IN CLINICAL MEDICINE, COLUMBIA UNIVERSITY! ASSOCIATE ATTENDING PHYSICIAN TO THE PRESBYTERIAN HOSPITAL! CONSULTING PHYSICIAN TO THE LINCOLN HOSPITAL, NEW YORK PAUL E. HOWE, M.A., Ph.D. ASSISTANT PROFESSOR OF BIOLOGICAL CHEMISTRY, COLUMBIA UNIVERSITY, NEW YORK HOWARD H. MASON, A.B., M.D. INSTRUCTOR IN DISEASES OF CHILDREN, COLUMBIA UNIVERSITY, NEW YORK! ASSOCIATE ATTENDING PHYSICIAN TO THE PRESBYTERIAN HOSPITAL; ATTENDING PHYSICIAN TO THE RUPTURED AND CRIPPLED HOSPITAL, NEW YORK LEA & FEBIGER PHILADELPHIA AND NEW YORK I9I7 .C 3 Copyright LEA & FEBIGER 1917 MIG 10 1917 n/ »CI.A471 59 5 PREFACE. 2-0 In presenting this book the authors are conscious of the fact that dietetics is far from a mature science and that a book founded entirely on facts proved in the laboratory is as yet impossible. So much scientific progress has been made with regard to the nature of food and its utilization and require- ents in health and disease, that were feeding merely a matter of food reactions, analogous to test-tube reactions, it would ; a comparatively simple matter to prescribe a diet. In deal- i g with all things human, however, the personal equation is of immense importance and one can never foreknow how a food will afFect different people under apparently similar con- ditions. It is on this account that accurate clinical observa- tion will always be a prime factor in the successful feeding of patients. . Not only should the probable effect of food under particular circumstances be known, but any variation there- from should be met by an experience wide enough to indicate in which direction the next move may be made. So it is that dietetics must be deduced in part from an accurate knowledge of the chemistry of foods and of nutrition and in greater degree from a knowledge painfully acquired by previous experi- ence in somewhat similar circumstances. It is also a fact that the same goal may often be reached by several roads, so that in most conditions different men may attain the same or almost similar ends by different methods; however, the principles underlying their efforts must be in accord. In choosing data from the literature of dietetics it has been the aim of the authors to use only the more recent statements from reliable sources, the seeming exceptions only occur when facts or statistics of an earlier date have not been superseded by later investigation. The attempt has also been made to present the etiological factors of the disease under discussion iv -PREFACE in order to make the rational use of foods depend on these, as well as on knowledge of nutritional chemistry. Metabolism, in its broader aspects, has been discussed in each disease when enough is known to make such consideration profitable. The symptomatology and treatment of disease, other than by diet, have not been given except insofar as it has been necessary to do so in the interest of a better understanding of the case or where general or special treatment has been indissolubly bound up with the use of diets. No attempt has been made to go into the question of diets for special conditions such as for the Army, Navy, Hospitals, Alms Houses, etc. The requirements for food under different conditions of muscular activity being known, each must have its dietary worked out on this basis. Diets already in use for such conditions may or may not be adequate for this purpose under other circumstances. Hence a repetition of these various dietaries would not be profitable. The authors wish to make grateful acknowledgment to Professors L. Emmett Holt, W. J. Gies, W. T. Longcope of Columbia University and Dr. E. F. Du Bois, for their sugges- tions and criticisms of material presented. To Dr. T. C. Janeway for permission to use certain diet lists, and to Dr. Irving Fisher and Dr. Alida F. Pattee for permission to use their tables on food values, to Dr. H. C. Sherman, Mrs. Mary Swartz Rose and to the Macmillan Company for the use of data contained in The Chemistry of Food and Nutrition, Food Products and Feeding the Family. Acknowledgment should also be made to the Washington University for the use of the library allowed one of the authors. H. S. C. P. E. H. New York, 1917. H. H. M. CONTENTS. Introduction PART I. FOODS AND NORMAL NUTRITION. CHAPTER I. Digestion, Absorption and Excretion. Digestion 23 Enzyme Action 23 Oral Digestion 25 Gastric Digestion 27 Intestinal Digestion 32 Absorption 33 Bacterial Action and Feces 38 Intestinal Bacteria 38 Putrefaction and Feces 40 Excretion . 43 Digestibility of Food 47 CHAPTER II. Energy Requirement. Caloric Value of Food-stuffs 51 One Hundred Calory Portion 52 Determination of Energy Requirement 53 Respiration Apparatus 54 Respiratory Quotient 55 Basal Energy Requirement 56 Body Surface as Unit of Reference 59 Calculation of Energy Requirement 59 CHAPTER III. Protein Requirement. Standard Dietaries — Average Protein Requirement 66 CHAPTER IV. Inorganic Salts and Water. Chlorine Requirement of Man 77 Phosphorus Requirement of Man 82 vi CONTENTS Calcium Requirement of Man "... 85 Iron Requirement of Man 88 Iodine Requirement of Man 90 Water Requirement of Man 91 Vitamines and Accessory Food-stuffs 94 Fasting i 98 CHAPTER V. Normal Feeding and Food Economics. Requisites of a Complete Diet 102 Suggested Menus 106 Factors which Determine the Cost of Food m Unbalanced Diets 117 PART II. FOODS. CHAPTER VI. Introduction — Milk. Milk 122 Chemical Properties; Protein 124 Fats 125 Carbohydrates; Salts 125 Variations in Composition; Influence of Temperature upon Milk . . 127 Action of Bacteria; Action of Heat . .- 129 Digestion of Milk 130 CHAPTER VII. Protein Foods. Sources of Protein Food 132 Protein Classification 135 I. Simple Proteins . 135 Albumins; Globulins 135 Glutelins; Alcohol Soluble Proteins (Prolamines); Albumin- oids; Histones; Protamines 136 II. Conjugated Proteins 136 Nucleoproteins; Glycoproteins; Phosphoproteins ; Hemoglo- bins; Lecithoproteins 137 III. Derived Proteins 138 A. Primary Protein Derivatives . 138 Proteins: Metaproteins; Coagulated Proteins . . 138 B. Secondary Protein Derivatives : . 138 Proteoses; Peptones; Peptides 138 Influence of Heat 138 Effect of Low Temperatures 139 CHAPTER VIII. Meat or Flesh Food. Value of Diet 144 Composition • 145 CONTENTS vii Influence of Temperature 146 Cooking 146 Digestibility of Meat 149 Meat Preparations 152 Meat Extracts 152 Meat Juices; Meat Broths 154 Gelatin 155 CHAPTER IX. Fish and Shell Fish — Poultry and Game. Fish and Shell Fish 156 Cold Storage Fish; Preserved Fish; Cooking of Fish 159 Digestibility of Fish 160 Poultry and Game 160 CHAPTER X. Eggs and Cheese. Eggs 162 Egg White; Egg Yolk * . 163 Cooking of Eggs 164 Digestibility of Eggs 165 Preserved Eggs 166 Egg Substitutes 167 Cheese 167 Digestibility of Cheese; Casein Preparations 168 CHAPTER XI. Protein-rich Vegetable Foods. Legumes in General 169 Soy Bean 171 Peanut; Preparation of Legumes 172 Nuts 173 CHAPTER XII. Carbohydrate-rich Foods. Sugars 175 Sucrose 175 Glucose; Lactose; Maltose 176 Maple-sugar; Invert sugar; Fructose 177 Digestion and Utilization of Sugar . 178 Starch-rich Foods 179 Grains and their Products 181 Barley; Buckwheat 182 Corn 183 Oats; Rice 184 Rye 185 Wheat 185 Bread _. 187 Baking Powders ~ 188 Rolls, Biscuits, Muffins, etc.; Biscuits, Crackers; Cakes; Break- fast Foods 189 Macaroni 190 Celluloses 190 Potatoes 191 viii CONTENTS CHAPTER XIII. Fat-rich Foods. Cream 198 Butter 198 Renovated Butter and Butter Substitutes 200 Oleomargarine 200 Lard 201 Cotton Seed Oil 202 Olive Oil 203 Cod-liver Oil 203 CHAPTER XIV. Foods Valuable for their Salts, Water, and Bulk. Fruits and Vegetables 204 Cooking of Vegetables and Fruits 208 Food Adjuncts 210 Spices 210 Flavoring Extracts; Meat Extracts; Vinegar; Sugar and Salt (Sodium Chloride) ; Sugar Substitutes 211 Beverages 211 Tea 212 Coffee 213 Cocoa and Chocolate 216 Mineral Waters 218 Alcoholic Beverages 223 Wines; Malt Liquors 226* Malt Extracts 227 Distilled Liquors . . • 228 PART III. FEEDING IN INFANCY AND CHILDHOOD. CHAPTER XV. Breast Feeding — Feeding Normal and Abnormal Children. Woman's Milk 229 Colostrum . . 229 General Characteristics of Woman's Milk 230 Quantity < 230 - Composition 231 Fat; Lactose 231 Protein ; Salts ; Iron ; Phosphorus ; Salts of Woman's and Cow's Milk 232 Bacteria; Drugs; Nervous Impressions; Pregnancy; Transmission of Immunity; Diet . 233 Breast Feeding _ . _ 234 Contra-indications for Breast Feeding 234 Intervals of Nursing; Length of each Nursing 235 Mother's Diet and Exercise 236 Vomiting 237 Gas and Colic; Abnormal Stools 238 Mixed Feeding 238 Weaning 239 CONTENTS ix CHAPTER XVI. Artificial Feeding. Food Requirements of the Artificially Fed Infant 241 Energy 241 Protein; Fat 242 Carbohydrate 243 Sugar 243 Starch; Inorganic Salts 244 Water 245 Proprietary Foods 245 Preparations Containing Cow's Milk; Preparations Containing Large Amounts of Maltose ... 245 Farinaceous Foods; Miscellaneous Foods 246 Artificial Feeding 246 Method of Preparing Formula? 247 Increasing Formulae 248 Cereal 249 Higher Fat Mixtures 251 Food Other than Milk 252 Beef Juice and Broth; Beef Juice; Cereals 252 Egg; Vegetables; Rice and Potato; Bread 253 Abnormal Symptoms 254 Vomiting; Gas; Colic 255 Loose Stools; Diarrhea 256 Constipation 257 CHAPTER XVII. Feeding of the Premature Infant. Feeding after the First Year. Feeding during Acute Illness and in Nutritional Disturbances. Feeding of the Premature Infant 258 Feeding during the Second Year 259 Feeding after the Second Year 260 Feeding during Acute Infections 261 Infants * 261 Gavage 262 Children Over One Year 262 Gavage; Long Illness 262 Pyloric Stenosis - 262 Cyclic Vomiting 264 Feeding in Nutritional Disturbances 266 Rickets 266 PART IV. FEEDING IN DISEASE. CHAPTER XVIII. Diet in Diseases of the Circulatory Organs. Functional Cardiac Disturbances 271 Diet in Organic Cardiac Disease 271 Cardiac Decompensation 272 The Karell Cure; Potter's Modification of the Karell Cure . . 273 x CONTENTS Diet in Organic Cardiac Disease : Fatty Heart 275 Adolescent Heart and Cardiac Myasthenia following Infectious Disease 276 Senile Heart 276 Diet in Diseases of the Bloodvessels 277 Arteriosclerosis 277 Diet in Hypertension 278 The Effect of Various Substances on Blood-pressure 278 Aneurysm 279 Angina Pectoris; Tobacco in Relation to Cardiac Disease .... 279 CHAPTER XIX. Diet in Diseases of the Lungs. Pneumonia . 280 Bronchitis 282 Acute Bronchitis 282 Chronic Bronchitis 283 Emphysema ■ 284 Asthma . . . 285 Pleurisy with Effusion. Hydrothorax 286 Empyema 287 Tuberculosis, Pulmonary or General .... 288 Prophylaxis for Children of Tuberculous Inheritance; Plan of Feeding 291 Special Foods for the Tuberculous 292 Milk; Eggs; Fats 292 Complications 294 General Rules for Feeding in Tuberculosis 295 CHAPTER XX. Diet in Diseases of the Stomach. Indigestion 297 Gastric Hyperacidity, Hyperchlorhydria 299 The Reduction of Gastric Hyperacidity by Diet; Diet in Hyperacidity 300 Gastric Hypersecretion 303 Gastric Hypo-acidity and Achylia Gastrica 304 Gastritis . 306 Acute Gastritis 306 Chronic Gastritis „ 307 Diet when Gastritis is Accompanied by Hypo-acidity or Achylia . . 309 Peptic Ulcer (Gastric and Duodenal) 309 Transgastric or Duodenal Feeding . . .' 322 Diet Combined with Alkaline Treatment 324 Ambulatory Diet Cure for Peptic Ulcer 326 Diet after Hemorrhage from Stomach or Duodenum 327 Gastric Atony 328 General Directions in Gastric Atony 329 Organic Gastric Acidity 332 Carcinoma of Stomach 333 Gastric Dilatation 336 Gastric Neuroses 337 Secretory Neuroses; Neuroses of Sensation 338 Motor Neuroses 339 Gastric Test Meals 339 Gastric Motor Meals ■ 340 CONTENTS xi CHAPTER XXI. Diet in Diseases of the- Intestines. Acute Enteritis 342 Chronic Enteritis 344 Schmidt Test Diet ■ . . 344 Acute Colitis or Acute Dysentery 346 Chronic Colitis 347 Membranous Colitis, Mucous Colic or Chronic Mucous Colitis .... 348 Ulceration of the Small or Large Intestine 349 Intestinal Hemorrhage . 350 Diarrhea 350 * Dietary Regulations 352 Foods to Avoid in Chronic Diarrhea; Foods Recommended in Diarrhea; Foods Allowed in Certain Cases 352 Intestinal Neuroses 353 Chronic Constipation 354 Atonic Constipation 355 Spastic Constipation 357 Obstructive Constipation _ 358 The Use of Mineral Oil in Chronic Constipation 358 Intestinal Atony 359 Appendicitis 360 Acute Appendicitis 360 Ochsner's Treatment for Appendicitis 361 Chronic or Larval Appendicitis 362 Chronic Typhlitis or Perityphlitis 363 Intestinal Auto-intoxication 364 Hemorrhoids " 369 Hirschprung's Disease 369 CHAPTER XXII. Diet in Diseases of the Accessory Digestive Glands. Diseases of the Liver and Gall-bladder . . . 371 Dietetic Prophylaxis 372 Acute Hepatic Congestion; Acute Catarrhal Jaundice or Gastro- duodenitis with Jaundice 373 Chronic Hepatic Congestion; Portal Cirrhosis 374 Biliary Cirrhosis; Fatty Liver; Acute Yellow Atrophy of Liver . . 375 Amyloid Liver; Cholelithiasis 376 Acute Cholecystitis and Colic 378 Pancreatic Disease . 379 Acute Pancreatitis; Chronic Pancreatitis 379 CHAPTER XXIII. Diet in Diseases of the Skin. Psoriasis 383 Eczema 385 Acute Eczema; Chronic Eczema 386 Eczema in Nurslings 387 Acne Rosacea 388 Acne Vulgaris 389 Erythema 389 Pruritus 390 Dermatitis 391 Dermatitis Herpetiformis; Exfoliative Dermatitis; Furunculosis; Comedones 391 Hyperidrosis . . 392 xii CONTENTS CHAPTER XXIV. Diet in Diseases of the Genitourinary System. Nephritis 393 Kidney Dietary Tests 395 Water Excretion; Salt Excretion; Nitrogen Excretion .... 395 Albuminuria 401 Acute Nephritis 402 Chronic Nephritis 405 Dietetic Management of Chronic Nephritis 405 Diets in Chronic Nephritis; Diets for Cases with Nitrogen Reten- tion (Chronic Uremia) 406 Diet in Water Retention. Edema 407 Diet in Salt Retention 408 Pyelitis 412 Cystitis 413 Gonorrhea 413 Nephrolithiasis 414 Amyloid Kidney 414 CHAPTER XXV. Diet in Diseases or Pathological States due to Disturbances of Normal Metabolism. Diabetes Insipidus ' 415 Diabetes Mellitus 416 The Relation of Protein Metabolism to Glycosuria 419 The Nitrogen Balance in Diabetes 420 Relation of Fat Metabolism to Glycosuria 421 Hyperglycemia; Dietetic Treatment of Diabetes 422 von Noorden Method 423 Standard Strict Diet 423 Standard Diet with Restricted Protein; Green Days . . . -425 Oatmeal Days; General Diabetic Diet List; Foods Prohibited Except as Allowed in Accessory Diet 426 Foster's System of Carbohydrate Units 428 Sample Diet; Procedure in Medium Severe Cases; Severe Cases with Marked Ketonuria 429 Potato Diet; Bread-and-butter Diet; Allen's Treatment of Dia- betic Mellitus "... 430 Joslin's Resume of Allen's Treatment 436 Menyhert's Theory 437 Diabetic Special Receipts 438 Diet for Diabetics with Gout; Diabetes in Elderly People or in the Young 442 Diet for Obesity with Diabetes; Diet in Diabetes Complicated by Nephritis . ..' 443 Obesity 444 Reduction Cures 448 von Noorden's Cure 448 Banting's Cure 450 Oertel's Cure _ 451 Ebstein's Dietary; Schweninger's Dietary 452 Germain-See Diet; Tibbie's Milk Cure; Salisbury Method; Tower- Smith's Modification of Salisbury Diet 453 Galisch's Cure; Folin-Denis Method of Reduction 454 Exercise and Massage; Water in Obesity 456 Gout 456 Foods in Gout 460 Carbohydrates; Salts; Alcohol 460 Coffee, Tea and Cocoa 461 Diet in Acute Gout or Podagra 461 CONTENTS xiii Diet for Leanness or Fattening Cures 466 Foods to be used in Fattening 467 Carbohydrate 468 Fat; Alcohol 469 Phosphaturia 470 Physiological Phosphaturia; Nervous and Sexual Phosphaturia; Juvenile Type ■. ' 471 Phosphates and Calculi 472 Diet Recommended for Calculi 472 Oxaluria 473 Diet in Oxaluria . 473 Mineral Springs . 474 Diet in Old Age 474 Food Requirements of the Aged 475 Foods Especially Desirable for the Aged 477 Preparation of Food for the Aged 478 Diet Routine in Old Age 479 Osteomalacia 480 CHAPTER XXVI. Diet in the Blood Diseases. The Anemias 482 Treatment of Chlorosis " 483 Rest 483 Iron 484 Diet in Chlorosis; Diets in Anemia (Chlorosis) 485 Secondary Anemia ; Pernicious Anemia . . 487 Posthemorrhagic Anemia 488 Leukemia 489 Hemophilia 489 Purpura Hemorrhagica 490 CHAPTER XXVII. Diet in Deficiency Diseases. Scurvy 491 Diet in Scurvy . : 492 Beriberi 493 Pellagra 495 Goldberger's Conclusions 495 CHAPTER XXVIII. Diet in Diseases of the Nervous System. Organic Nervous Diseases 497 Neuritis 497 Epilepsy 498 Insanity 499 Apoplexy 500 Functional Nervous Diseases 501 Migraine or Periodic Headaches 501 Chorea; Neurasthenia 503 Weir Mitchell Diet and Treatment 505 Digestive Neuroses; Insomnia 507 Delirium Tremens . . 508 Nervous Anorexia ,,,..,,, 509 xiv CONTENTS CHAPTER XXIX. Diet in Acute and Chronic Infections. Fever 510 Diet in Fever 513 Carbohydrates; Protein 514 Fats. 515 Beverages; Alcohol; Intervals of Feeding 516 Typhus Fever 517 Typhoid Fever 518 Older Diets 518 Bacteriological and Physiological Basis for More Liberal Diets . . 519 Carbohydrates . 519 Fats; Protein; Energy Requirement . .521 Results Obtained by Liberal Diet; Typhoid Diets 522 Diet in Typhoid Complications 528 Intestinal Hemorrhage; Perforation; Nausea and Vomiting . . 529 Water; Paratyphoid Fever 530 Malaria Fever 530 Scarlet Fever 530 Smallpox 530 Cerebral or Cerebrospinal Meningitis 531 Measles . ' 532 Influenza (Grippe) 532 Acute Articular Rheumatism 533 Diet in Acute Articular Rheumatism 533 Subacute Rheumatism 534 Chronic Rheumatism (Chronic Infectious Arthritis) 535 Tetanus 535 Yellow Fever 536 Cholera • 537 Peritonitis . 539 Acute Peritonitis 539 Chronic Peritonitis ■ 540 Chronic Infections _ 540 Rheumatoid Arthritis. Arthritis Deformans . 542 CHAPTER XXX. Diet in Relation to Surgical Operations. Preoperative Diet 544 General Directions for Cases of Laparotomy 544 Diet Preparatory to Gastric Operations 545 Postoperative Diet 546 Postoperative Diet for the Digestive Tube; Diet after Tonsillectomy; Postoperative Gastric Diets; Diet after Gastro-enterostomy and Gastric Operations 546 Finney's Diet List following the Operation for Gastro-enterostomy 550 Intestinal Lesions 551 Diet after Appendectomy 552 Diet in Certain Complications following Abdominal Operations . . 552 Vomiting from Acute Gastric Dilatation 553 Prevention of Desiccation of the Tissues 553 Dietary Measures in Postoperative Intestinal Distention . . . 554 Diet after Gall-bladder Operations; Diet after Operation for Hemor- rhoids 555 Feeding after Intubation ... . . 556 CONTENTS xv CHAPTER XXXI. Diet in Diseases of the Ductless Glands. Acromegaly 557 Acute Thyroiditis 55 8 Exophthalmic Goitre . 55$ Diet to Meet Special Indications in Exophthalmic Goitre .... 560 Diarrhea; Inanition 561 Myxedema or Cretinism 561 Addison's Disease 561 CHAPTER XXXII. Diet in Miscellaneous Conditions. Artificial Methods of Feeding • 563 Rectal Feeding 563 Protein 564 Fats; Carbohydrates 566 Precautions in Rectal Feeding 567 Subcutaneous Feeding 568 Protein 568 Fats; Carbohydrate 569 Intravenous Feeding 570 Diet in Pregnancy 57 1 Nausea and Vomiting of Pregnancy 571 Nephritis ; Mild Auto-intoxication 572 Contracted Pelvis or with Oversized Fetus 573 Puerperium 573 Foods Best Avoided; Diet List after Normal Confinement . . 574 Sprue 575 Dental Caries 576 Diet Recommended for Speakers and Singers 578 Diet Adapted to the Use of Brain Workers 578 Diet for Athletes 579 Sugar; Foods to Avoid 581 Feeding of Unconscious Patients 582 Food Poisoning 583 Meat Poisoning; Fish Poisoning; Vegetable Poisoning; Poisoning by Canned Goods 584 Special Dietary Cures 586 The Vegetarian Diet 586 Metabolism of Vegetarians; Vegetarian Diets 589 Fletcherism 590 Fruit Cures 594 Grape Cure 594 CHAPTER XXXIII. Food Protection. Accessory Foods and Beverages 595 Flies, Food and Disease 595 Relation of Flies to Various Diseases 595 Method of Prevention 595 Beverages for the Sick . 595 Artificial Foods 598 Olive Oil and its Dietary Usage 599 Stenosis of Esophagus; Pyloric Stenosis; Gastric Dilatation; Chole- lithiasis; Gastric Hyperacidity 599 xvi CONTENTS CHAPTER XXXIV. Tables of Food Values and Weights and Measures. Average Chemical Composition of American Foods . . . . • . . .601 Table of Measures and Weights 609 Apothecaries' Measures 609 Apothecaries' Weights 609 Approximate Measures 609 Relative Value of Metric and Apothecaries' Measures 610 Relative Value of Apothecaries' and Metric Measures 610 Relative Value of Metric and Avoirdupois Weights 610 Relative Value of Avoirdupois and Metric Weights 611 Relative Value of Apothecaries' and Metric Weights 611 Relative Value of Metric and Apothecaries' Weights 611 Fisher's Table of One Hundred Calory Portions 612 Table Showing the Nutritive Value of the Food Materials Calculated for the Quantities Commonly Required in Cooking Small Portions . . 618 NUTRITION AND CLINICAL DIETETICS. INTRODUCTION. The term food may be applied to any material with the aid of which the body is able to maintain its characteristic functions: temperature regulation, the performance of work, the repair of wasted tissues, the production of new tissues, and those countless factors — connoted by digestion, absorption, circulation, etc. — involved in the preparation and transporta- tion of the ingested food to the seat of action of the prime factor of organization, the cell. In the various kinds of cells of a complicated organism such as the human body, transformations are in progress which are qualitatively similar but which vary quantitatively accord- ing to their specific functions: thus we have the cells of the muscular system, whose chief function appears to be the per- formance of work and the liberation of energy for the main- tenance of body temperature, or the cells of the glandular organs which form substances to be secreted into or from the body, and of the nervous system which are concerned in the conveyance of impulses. Whatever may be the specialized function of any cell, it is imbued with the fundamental char- acteristic activities of all cells. The sum total of the activities of the individual cell or of the body as a whole are grouped under the term metabolism, by which we mean "all chemical and physical changes which occur in living matter and which constitute, the basis of the material phenomena of life." When such changes involve the transformation of simple into more complex substances, they are usually associated with an increase in the energy content of the compounds formed, and are designated as anabolic processes. Changes which are concerned with the disintegration of complex material with the formation of simpler products are designated as catabolic processes, and are ordinarily associated with the liberation of energy. By means of anabolic processes the products of diges- 18 NUTRITION AND CLINICAL DIETETICS tion are built up into the active structural compounds of protoplasm, into secretions, or into complexes suitable for storage and future use. Such processes predominate in growth and in those organs or tissues associated with the elabora- tion of secretions. The catabolic processes involve a disruption of food-stuffs, of cell components, or of reserves, and the liberation of energy in the form of heat or mechanical work, the end-products of this activity being finally eliminated from the body. The cellular activities associated with muscular contraction and the regulation of body temperature are pre- eminently catabolic. In normal individual cells and in the body in general there is a nice balance between the anabolic and catabolic processes. Any disturbance of this equilibrium may result in a pathological condition. Considerations of diet in disease are concerned almost entirely with altera- tions in the balance between anabolic and catabolic activ- ities. Five important classes of food-stuffs are required to satisfy the needs of the body; the lack of any one of these would result in grave metabolic disturbances. They are: proteins, carbohydrates, lipins (fats and lipoids), salts, and water. To this list of general classes may be added a sixth, the accessory food substances designated as vitamines. The collective expression, food, is applied to naturally occurring combinations of the food-stuffs enumerated or to products from these. Since most foods are themselves con- glomerates of materials which have been associated with life, they contain in different proportions some of all the elements required by the human organism. Thus we have such foods as meat, eggs, etc., in which protein predominates, but which contain also fat, carbohydrates, water, and salts; or certain vegetable foods whose solid material is largely carbohydrate and salts, with a very small proportion of protein and fat. The functions of the food-stuffs are varied; proteins, carbo- hydrates, and lipins may be utilized by the body as a source of energy, the greater proportion of the energy requirement of the body is supplied, however, by the carbohydrates and lipins. Protein serves not only as a source of energy but as the source of amino-acids and radicles necessary for the forma- tion of body protein, secretions, etc. Salts and water, while not the source of energy, are essential factors in the constitu- tion and activity of all parts of the body. Proteins are, as we have just indicated, important as the chief source of nitrogen-containing substances necessary for life, being colloidal in nature and capable of combining with both acids and bases, and absorbing or entering into loose chemical INTRODUCTION 19 combinations with salts and water, they share in a most varied activity in the body processes. In the cycle of life protein is synthetized in the vegetable kingdom, and this protein is utilized in the construction of animal protein. Animals appear to be unable to synthetize the greater number of amino-acids present in the protein molecule, particularly those containing cyclic nuclei. Plants, however, can form the amino-acids and conjugate them into protein. The animal organism is, then, dependent upon the plant for the basal units of its protein molecule. Before plant protein can be used it must be broken down into amino-acids or simple combinations of these, which are then built up into the type of protein characteristic of the particular tissue concerned. The object of feeding is to supply not only protein to the indi- vidual, but protein which will furnish the proper kinds and amounts of amino-acids. The second class of food-stuffs, carbohydrates, are used by the body as a source of energy in the performance of its many internal activities as well as of external work. They are, apparently, more readily accessible for such purposes than protein or fat; in all cases in which a sudden expenditure of energy is involved or in states in which the body is forced to draw upon its reserve supplies the depots of carbohydrate (glycogen) are the first to become depleted, after which the fats and proteins furnish the required nutritive materials. The absence of carbohydrates from the diet often results in pronounced metabolic disturbances, e. g., acidosis. Chemically, carbohydrates consist of carbon, hydrogen, and oxygen; the hydrogen and oxygen being often present in the proportions in which they occur in water. This last fact was responsible for the name. From the structural point of view we find carbohydrates to be oxidation products of polyhydric alcohols (ketone- or aldehyde-alcohols). Human food usually contains molecules consisting of chains of five or six carbon atoms or multiples of these. Starch, in which form the greater proportion of ingested carbohydrate food exists, is a polymer of the six carbon sugars — glucose. Lipins serve in a varied capacity in the body. The term designates a number of different types of substances which may be roughly divided into two groups: fats, which are combinations of fatty acids and glycerol or other alcohols, and lipoids, which resemble the fats in certain properties but which differ in chemical constitution since they may or may not contain fatty acids. Of this latter group lecithin and cho- lesterol have been studied extensively; the others, such as complexes containing other lipoids, protein, carbohydrate, 20 NUTRITION AND CLINICAL DIETETICS various organic and inorganic compounds, have received little attention and our knowledge of their functions is limited. The "fat" present in food is a mixture of lipins. Fats are used almost exclusively in the production of energy or in the regulation of temperature. In temperature regula- tion it functions in a twofold manner: it yields energy in the form of heat as the result of oxidation, and it serves as an insulating medium in the form of deposited subcutaneous fat. Chemically considered, fats are combinations of carbon, hydrogen, and oxygen. As contrasted with the carbohydrates, fat molecules contain little oxygen, and consequently yield a greater amount of energy upon oxidation. A gram of fat will yield more than twice as much energy in the form of heat as will a gram of carbohydrate. The body appears to prefer carbohydrates, however, for the production of heat, at least for short intervals of time. It stores its energy-yielding material as fat; the quantity of carbohydrate stored in the body is comparatively small, not sufficient to last a man more than a day or two even when some fat and protein are con- sumed at the same time, as in fasting. Water and salts are concerned not only in the structure of the cells but in the maintenance of normal physical and chem- ical relations between the parts of the cells — intracellular water and salts — and between the groups of cells which con- stitute the tissues and organs of the body — extracellular water and salts. Water gives to the blood its fluidity, and this enables it to permeate the cellular structures of the body, carrying with it the dissolved gases and substances used in the activities of the cell. Suspended in the water (colloidal solution) .are proteins and organized bodies, the blood cells. The salts which are dissolved in the water assist not only in maintaining normal osmotic conditions between all parts of the body, but also a uniform reaction by combining with acids and bases and transporting them to the lungs and kidneys for excretion. Recent work has demonstrated the presence of other sub- stances in food which are essential for the normal functioning of the body. The absence of these materials results in patho- logical changes, and the ingestion of very small amounts is accompanied by rapid recovery. The name "vitamines" has been applied to these substances by Funk. There appear to be at least two more or less distinct types: material soluble in fat, designated by McCollum as "fat soluble A," and material soluble in water, designated as "water soluble B." We know little of the chemical nature of these substances. Their importance in the diet, however, is unquestioned. INTRODUCTION 21 These, then, are the facts which underlie dietetics, and while they are indisputably exact, much of the success of feeding in disease still must rest on clinical experience; for given hard- and-fast scientific facts the personal equation always enters into the picture and it will always be true that certain indi- viduals will not react to food stimuli in the logical way, idio- syncrasy playing a not inconsiderable role. Since this is true in health, how much greater must be the variation in disease when one considers that all people differ in their habits, environment, age, activity of the glands of secretion, and susceptibility to certain food elements, etc. ? It is undoubtedly true that in health some people eat too much, this being the larger error than that they eat too little; on the other hand, in disease many if not most people eat too little and add an element of starvation to an organism already handicapped by functional disturbances, infections or what not. The crux of the matter lies in selecting a diet suited to the individual conditions under varying circumstances, not alone in quantity but in quality as well. Recent advances in our knowledge of the specific dynamic action of food-stuffs have made it easier to say what food should theoretically suit a certain set of circumstances and on this basis one can, to a certain extent, choose suitable feedings, provided the personal equation is not too insistent. In certain diseases the indications for diet are clear cut and are largely a matter of rule, adherence to which will usually bring about the result desired, e. g., in obesity, while in others there is no counting on the results, for the foods which suit conditions in one individual will fail to' produce the desired result in another, so that while the principles remain the same the individual requirements may be quite different and opportunity is afforded for the practise of nice judgment. In such a disease as typhoid fever this is particularly true, and the best feeding results will be obtained by the medical attendant who gives the most attention to details and uses the best judgment in the selection of foods, both quantita- tively and qualitatively. In such conditions it is possible only to indicate the principles to be used in ordering foods, leaving the rest to the individual attendant's discretion. So it is throughout the entire range of disease — there must be a knowledge of the facts in the biochemistry of foods, combined with clinical experience and good judgment if one wishes the best results. PART I. FOODS AND NORMAL NUTRITION. CHAPTER I. DIGESTION, ABSORPTION AND EXCRETION. DIGESTION. Enzyme Action. — Food, when ingested, is, with but few exceptions, potential nourishment. Before it can be used in the body it must be reduced to simpler forms or liberated from structures unavailable for absorption into the blood. Until a food is in a condition readily to pass through the walls of the alimentary tract, it is not available as a factor in metab- olism. Such transformations are accomplished in the processes of digestion. As the result of these, solid masses of food are disintegrated, insoluble carbohydrate, fat, and protein com- plexes are transformed into compounds which are soluble or of such a size (ultramicroscopic) that they may readily tra- verse the walls of the alimentary tract and finally reach the blood and be carried to the various cellular structures of the body. This conversion of heterogenous food masses into a pabulum of comparatively simple and uniform consistency is accomplished with the aid of enzymes (ferments), 1 whose activities are furthered by the mechanical movements of the alimentary tract. Enzyme action is catalytic in nature. In the presence of enzymes the rate of digestive activity increases. In the pres- ence of water or dilute solutions of alkalis or acids, the conver- sion of starch into maltose proceeds slowly. The addition of the salivary amylase, ptyalin, to a starch mixture under suit- able conditions of alkalinity and temperature, increases the rate of the process; instead of requiring a period of days and weeks for the completion of the digestion of a given mass of 1 While we will confine our discussion largely to the enzymes of the digestive tract, it must be remembered that enzymes are present in all tissues and fluids of the body. 24 DIGESTION, ABSORPTION AND EXCRETION material, a few minutes or hours suffice. These changes are produced, furthermore, at the comparatively low temperature of the body. Enzyme action is specific; for each kind of substance to be changed a special enzyme is elaborated. If many intermediate products are formed, more than one enzyme may be required to reduce a food material to its simplest state. Ptyalin, the salivary amylase, can carry the digestion of starch only as far as the maltose stage. Another enzyme, maltase, is required for the cleavage of maltose in the formation of glucose. This enzyme is restricted in its action to maltose and glucose; it cannot change sucrose or lactose or any other carbohydrate. To complete the digestion of food, then, many different enzymes are necessary. Enzymes are classified according to the types of chemical reactions they afTect. They are named by adding the suffix "ase" to the type of reaction, or to the substrate, the sub- stance upon which they act. Practically all the enzymes of the digestive tract are members of the group designated as hydrolases. Their function is to aid in the disintegration of complex food molecules, changes which involve cleavages of the molecule with the addition of the elements of water. The more important digestive enzymes will be discussed in con- nection with the digestive processes. The activities of any particular kind of enzyme are influ- enced by its environment. Such factors as (a) reaction, (b) temperature, (c) concentration of the enzyme, (d) concentration of the products of reaction, ( 000 Rider in a six-day bicycle race . 10,000 ENERGY REQUIREMENT 65 The following daily energy requirements for infants and children have been suggested. Energy Requirements for Children. Total Calories per day. 1 to 2 900 to 1200 2 to 5 1200 to I5OO 6 to 9 1400 to 2000 10 to 13 1800 to 2200 T , toT Jgirls 2200 to 2600 * ' \boys 2500 to 3000 1 Atwater has given comparative values for the metabolism of the different members of a family. On the basis of the father having a rate of 1, the energy requirements of the rest of the family would be : Father 1 . o Mother 0.8 Sons: 14 to 17 0.8 to 1.5 Daughters: 14 to 17 0.7 to 1.0 Children: 10 to 13 o.6toi.o 6 to 9 0.5 2 to 5 0.4 Under 2 0.3 1 Lusk and Gephart have found, from a study of the food eaten by boys in a fashionable boarding school, that an active boy may consume food equivalent to 4000 to 5000 Calories per day. CHAPTER III. PROTEIN REQUIREMENT. In our previous discussions, as well as in our subsequent discussions relating to protein-rich foods, we have taken up the composition of protein material in general, its digestion, absorption, and the change which it undergoes in the process of assimilation. At present we are concerned with the quan- titative relation of protein in the diet and the factors which influence this. Protein as we have already found, is an essential constit- uent of our daily dietary. Energy may be derived from pro- tein, fat or carbohydrate but only protein or its products of hydrolysis can furnish the amino-acids necessary to replace the loss of nitrogenous material in the tissues resulting from the general bodily functions or for the constructive processes of growth. The necessity for the presence of protein in the dietary was early recognized. It was, in fact, a more difficult task to demon- strate that this food constituent was concerned more particu- larly in the structural changes of the body than primarily as a source of energy for muscular work. We no longer say, as did Liebig, that protein is the source of muscular energy, but recognize that this function belongs to the carbohydrates and fats, and consider protein as the chief source of material for the repair of the wear and tear in the muscles and other parts of the body. Admitting that the necessity for protein is so well estab- lished that it is practically self-evident, we may take up the question of the quantity of protein necessary for the body, how it may be supplied, and relative efficiency of protein for the needs of the body. Methods employed for the study of these problems are in general the two considered in our discussion of the energy requirements of the body: the purely experimental and the statistical. In the experimental studies use is made of the nitrogen balance or of the rate of growth of young animals, such as rats, when compared with the normal rate of growth. For the determination of the nitrogen balance the nitrogen content of the food— representing the protein material — feces, PROTEIN REQUIREMENT 67 urine, and in some cases the hair, scurf and excretions from the skin, are analyzed for definite periods of time. The quan- tity of nitrogen found in all of the excretions is then sub- tracted from that in the food. If the result is a positive fig- ure, that is, if there is less nitrogen in the excretions than in the food, then the subject is said to have a positive nitrogen balance, for he has retained in his body a certain amount of nitrogen-containing material. If the result be a negative value, i. e., more nitrogen in the excretions than was contained in the food, the subject has supplied nitrogenous material from his tissues and is said to have a negative nitrogen bal- ance. A normal adult is usually in an approximate nitrogen equilibrium. During growth and regeneration — youth, preg- nancy and convalescence — the organism normally shows a positive balance. In conditions of emaciation, fever or wast- ing diseases a negative balance is obtained. The average daily protein metabolism or plane of nitogen equilibrium varies in the same individual, according to the quantity of protein ingested. A sudden change from a low to a high protein diet, or vice versa, is not accompanied by an equally abrupt variation in the daily excretion of nitrogen. Instead there is a gradual increase or decrease in the quantity of nitrogen eliminated until the new plane of metabolism is finally attained and the subject is once more in nitrogen equilibrium. When the protein food is completely removed from the diet the total nitrogenous excretion is an index of the internal, or endogenous, metabolism of the individual. An exact determination of the endogenous protein metab- olism of man is the ideal basis for the study of the needs of the body. This is a difficult procedure, for many contributing factors modify the quantity of nitrogen excreted — our measure of the rate of the protein metabolism. When all of the food elements are removed as in fasting, we might expect to obtain a measure of the endogenous protein metabolism. Experi- ments upon men and animals have shown, however, that this is not the case, for a number of modifying factors, such as the previous diet and the quantity of fat and carbohydrate (glycogen) present in the body, will modify the course of the cellular activities and the protein metabolism. The plane of protein metabolism in the early stages of fast- ing is affected by the previous dietary regimen. When this diet has been rich in protein, a larger quantity of nitrogen is excreted in the urine than would have been obtained had the diet been poor in protein — just as with a normal diet, if the protein quota be decreased, the nitrogenous excretion changes gradually and not abruptly from one level to another. It is 68 PROTEIN REQUIREMENT evident, therefore, that it would not be accurate to accept the quantity of nitrogen excreted in the early part of a fast as a measure of the endogenous protein metabolism. Neither can we accept the nitrogen excreted after the effects of the previous nitrogenous diet have passed, for during this period of readjustment other factors have been developing an abnormal influence. The normal man is accustomed to derive the greater portion of his energy from the oxidation of carbohydrates and fats. A fast is commenced with a small reserve of carbohydrate, glycogen, and a somewhat larger reserve of fat. During the first few days, while the effects of the previous diet have been disappearing, practically all of the glycogen reserve has been utilized and after this the body subsists upon a diet, so to speak, of fat and protein. The removal of carbohydrate material from the diet of a man who is accustomed to this food element in his diet results in a disturbance of his metabolism, particularly a change in the fat metabolism. Under such conditions the body seems to be unable completely to oxidize fats. Partially oxidized fatty acids are passed into the blood stream and these cause a disturbance of the equilibrium between the acidic and basic radicles which has its effect upon the respiratory and salt metabolism and ultimately, if not directly, upon the protein metabolism. We have evidence of the incomplete oxidation in the beta-hydroxybutyric and aceto-acetic acids, in the urine, and of a disturbed equilibrium in the increased ammonia and acidity of the urine. Such disturbances are experienced not only in fasting man but in diabetes, in which there is a failure to oxidize glucose, and they have been demonstrated experimentally by feeding a carbohydrate-free diet to men and to animals accustomed to a carbohydrate-rich diet. Acidosis increases the rate of protein metabolism. In fasting a further increase of protein metabolism results when the fat supply is reduced and the organism is forced to utilize protein material as a source of energy. A measure of endogenous metabolism cannot therefore be obtained by means of fasting experiments. A study of the metabolic changes on a protein-free diet containing carbohydrates, fats and salts in the proper pro- portions is perhaps a better index of the endogenous protein metabolism. This procedure is also open to question for under these conditions the body is supplying from its own tissues the protein material needed for repair. Studies of the endogenous protein metabolism show that the average man metabolizes from 0.04 to 0.03 gram of nitrogen per kilogram of body weight — 2.1 to 2.8 grams of PROTEIN REQUIREMENT Glutamic acid. Lysine 43-7 26.2 0.15 O 13.0 15-6 16.8 303 6.00 6.00 15-5 10. 1 7.60 7 -5o nitrogen for a 70-kilogram (154 lb.) man — in the form of pro- tein in the processes associated with the general wear and tear of the body. In constitution the protein molecule varies in both the quantity and the kind of amino-acids according to its source. If we compare the quantities of amino-acids in certain pro- teins we see that were a man to eat the vegetable protein, gliadin, alone he would have considerably more glutamic acid than was absolutely necessary, and to obtain sufficient lysine to form a protein of the approximate composition of, say, beef protein he would have to ingest a much larger quantity of gliadin than beef or other animal proteins. Protein. Gliadin . Zein . . Legumin Casein Gelatin . Beef protein Fish protein The chemical structure of the protein ingested must there- fore be considered in determining the protein requirement. If the ingested protein contains a proportion of any essential amino-acid that is less than the quantity needed by the body or lacks the acid entirely, it becomes necessary for the body to synthetize the required amino-acid from other available acids or products, or to supply the amino-acids either by an increased ingestion of the protein itself, if the failure be due only to a lowered content, or by the ingestion of other pro- teins, or of the amino-acid itself if it be entirely absent. Con- versely, if the protein contain a greater proportion of certain amino-acids than the body can utilize they will not be used but deaminized, oxidized and the products excreted. Our knowledge of the synthesis of amino-acids in the body is very limited. Glycocoll is apparently synthetized and, under experimental conditions, perfusion of the liver, the formation of alanine, phenylalanine, and tyrosine have been demonstrated. The extensive synthesis of amino-acids in the body has not, however, been shown. Studies of such prob- lems are complicated by the possibility that apparent synthe- sis may be due to the formation of the amino-acid by bac- teria in the intestines and its subsequent utilization by the body. Synthesis of amino-acids with cyclic nuclei appears to be particularly difficult. The body cannot, then, be depended upon to supply the missing amino-acids; they must be added to the diet as such or in the form of protein containing them. 70 PROTEIN REQUIREMENT The fact that gelatin cannot of itself satisfy the total pro- tein requirement is due to its lack of the amino-acids, trypto- phan, tyrosine, and cystine. The addition of tyrosine and cystine and tryptophan has been found to improve its value and make it satisfactory, for short periods at least. Experi- ments with growing rats have likewise served to demonstrate the efFect of various quantities of amino-acids in the diet. A protein of corn, zein, which is deficient in the amino-acids, lysine and tryptophan, is found to be unable to support growth or even to maintain the rats without loss of weight. With the substitution of equivalent quantities of other com- plete proteins the rats grow normally. The addition of tryp- tophan to the zein diet serves to maintain the rats without growth; while the addition of both tryptophan and lysine makes the diet sufficient for both growth and maintenance. The importance of lysine for growth has been shown in experiments in which gliadin, a vegetable protein containing no lysine but tryptophan, was fed. The rats maintained their body weight but did not grow: the addition of lysine made the diet satis- factory. In one of Osborne and Mendel's experiments with gliadin a rat which failed to grow gave birth to a litter of young which grew at the normal rate on their mother's milk. Later these rats were fed different diets. Those which received complete proteins grew at the normal rate while one which received the diet fed to the mother failed to grow. From experiments of this nature carried out by Willcocks and Hopkins, Osborne and Mendel, and Hart and McCollum, it has become evident that, other necessary factors being pres- ent, the absence or a slight deficiency in the protein fed, of an amino-acid essential in cellular metabolism, determines the extent of tissue construction, or rate of growth. With the absence of such units the other amino-acids which would have been used in the formation of a protein molecule cannot be utilized; they may be used in some processes in the forma- tion of tissue or secretions not involving the missing radicle or are deaminized and oxidized. McCollum has suggested that the processes of repair do not necessarily involve the decomposition and synthesis of an entire protein molecule. The quantity of protein needed also depends upon other factors in the diet. McCollum in studying the presence of toxic substances in natural foods (wheat) and their effect upon growth found that protein tends to neutralize the effect of such substances. He explained his findings as follows: "A single factor (protein) in a ration may appear to admit the maximum performance of the animal with respect to growth, without itself representing the optimum amount or character. When this circumstance prevails it may entirely PROTEIN REQUIREMENT 71 escape notice, yet if in another ration exactly like it, except that a second factor tends to injure the animal, nutritive fail- ure may result. In such a case as the latter the improvement of the protein factor by the addition of more protein or by the substitution of a better protein, the plane of protein intake remaining unchanged, the animal may make the maximum performance notwithstanding the unfavorable character of the injurious factor of the ration." This finding is an argu- ment, in general, for a high rather than a low protein diet whenever the protein is not carefully selected. The addition of protein nitrogen in amounts equivalent to the basal nitrogen requirement, to a diet containing a suffi- cient quantity of fat and carbohydrate may not necessarily serve to prevent a loss of protein from the body. This may be due to the nature of the protein as already discussed, or to the number of portions into which the daily quota is sub- divided and ingested, in other words, the number of meals per day. Ingested protein is rapidly metabolized and there is little storage of protein or amino-acids in comparison to the reserves of fat and carbohydrate in the body. If the protein required for one day be ingested at one time a large proportion of it will be utilized or deaminized in from six to nine hours, and to satisfy the needs of the actively functioning tissues J:he body will draw upon its own protein reserves. By taking the protein in smaller quantities a number of times a day the body will be more continuously supplied with the necessary amino- acids derived from its digestion. A similar effect can be pro- duced in part by mixing the protein with more or less indi- gestible material which apparently delays the digestion and absorption of protein. Nitrogen equilibrium has been main- tained upon a diet low in protein when ingested in six equal portions which was not sufficient when ingested in three portions. The following studies by Thomas of the relative efficiency of protein in the maintenance of nitrogen equilibrium illus- trate the variable usefulness of different proteins. The basis of valuation of the food proteins is such that ioo represents protein which satisfies the basal requirement determined on a protein-free diet when fed in equivalent quantities — with ample quantities of carbohydrate and fat. Biological Value of Proteins Meat Milk Fish Rice Potato Bean Flour (wheat) Corn 104 99 94 88 78 55 39 29 72 PROTEIN REQUIREMENT The high efficiency of meat protein has been ascribed by Thomas as due to the effect of extractives which may be con- cerned in the maintenance of nitrogen equilibrium. This is only one possibility for we know little of the relative structures and combination of proteins in different foods or of associated factors, all of which might be effective. It is certainly true that animal proteins in general are more efficient in the human economy than vegetable proteins. Our discussion has confined itself more or less to partic- ular proteins. In the average diet a mixture of proteins is ingested so that the sum total is entirely sufficient for the needs of the body. In meat insufficient gelatin (collagen) occurs with the eminently satisfactory muscle protein, and likewise in corn the incomplete zein is associated with other proteins which contain the requisite amino-acids. The protein requirement is influenced by the quantity of fat and carbohydrate, energy-yielding foods, present in the diet. The effect of these food-stuffs is to lower or raise the plane of protein metabolism when added or subtracted from a nitrogenous diet; fat is, however, less effective than carbo- hydrate. If the carbohydrates of a mixed diet, upon which nitrogen equilibrium is being maintained, be replaced by an isodynamic quantity of fat, a negative nitrogen balance will result; that is, the body will use some of its protein reserve. The replacement of fat by carbohydrate is accompanied by a lowered protein utilization. This is particularly true when the protein ingestion is low. When carbohydrates are fed to a fasting man or dog, or to one who is receiving a carbohydrate- free diet, either with or without protein, the rate of nitrogen excretion is lowered. Fat also is capable of reducing the plane of nitrogen metabolism of a fasting organism, particularly when the subject is poor in fat. Variations of fat and carbo- hydrates within certain limits when both appear in the diet at the same time do not result in marked variations in the protein metabolism. It may be that the failure of fat to main- tain nitrogen equilibrium when it replaces carbohydrates is due to the fact that the body requires a certain amount of carbo- hydrate for its normal functioning and, that since fat apparently does not yield carbohydrate, and the amino-acids of the pro- tein molecule may do so, the body breaks down an additional quantity of protein to furnish the necessary carbohydrate. Thomas has suggested that the beneficial effect of carbohy- drate is concerned with the synthesis of amino-acid in the body. Lusk has suggested that 10 to 15 per cent, of the total energy requirement be in the form of protein. For the aver- age protein requirement of man see the following discussion of standard dietaries: STANDARD DIETARIES 73 STANDARD DIETARIES— AVERAGE PROTEIN REQUIREMENT. Practically all the standard dietaries which have been pro- posed have been determined by the statistical method. Observations have been made of the quantity and kind of food ingested by a large number of persons under different circumstances; the composition of various kinds of food has been determined; on the assumption that the results of these analyses approximate the composition of the food eaten in the dietary investigated, the amounts of protein, fat, and carbo- hydrate in the diet have been determined. Voit's standard was the first to attract widespread attention and it has been the nucleus of controversy concerning the optimum protein requirement for man. Voit proposed for a man at moderate work: Protein 118 grams. Fat . . 56 " Carbohydrate . ' . . . 500 " Total Calories 3055 Investigations of the dietary habits of groups of people in various countries and conditions have been the basis of other dietary standards. The following table contains some of the standards which have been suggested : Standard Dietaries. Protein, Fat, Carbohydrate, Fuel value Author and conditions. gm. gm. gm. Calories. Atwater (man): Hard work .... I50 4150 Moderate work . 125 34OO Sedentary life IOO 2700 Rest (or woman at light work) 90 2450 Voit (Germany): Average diet .... Il8 56 500 3053 Hard work .... 145 IOO 450 3300 Playfair (England) II 9 51 531 3060 Gautier (France) 107 65 407 2630 Chittenden 60 2800 From this table we see that the quantity of food in the form of protein, fat and carbohydrate varies with the kind and degree of work performed; the amount of food required varies also with the age, and with the sex of the individual. The influence of work upon the energy and protein require- ments has been discussed in general. A greater consumption of energy-yielding material is required to satisfy the needs of a man at work than is required by a person at rest. This 74 PROTEIN REQUIREMENT fact has been established by careful experiments in confirma- tion of the results obtained by dietary studies. External temperature also modifies energy requirements. A man exposed to the cold requires a greater quantity of energy- yielding food than the one who does the same work at a moderate temperature. For this reason studies of the daily habits of people of different climates show the ingestion of diets of different energy contents. Differences in the size and age of individuals involve diets of different energy content. The infant has a higher energy metabolism than an adult in the prime of life; and an old man, a smaller requirement. Two adults of the same size and weight, performing the same work, require approximately the same amount of energy. But where there is a difference of size, as in the case of a lean man and a fat man of the same weight, and approximately the same body surface, the energy requirement of the thin man is much higher because of the greater mass of functioning tissue. To these physiological factors, which influence the energy requirement of man, the psychical and economic factors must be added. Such considerations as taste, habit and custom, the kind of food available, and the ability to purchase, modify the quantity and kind of food eaten by any given group of individuals. Hence the standards based upon the study of the food consumption of various classes and races of people reveal not only the actual needs but also the habits and pro- pensities of the people. When considering the basal protein requirement of man we found that muscular activity had practically no effect upon the protein metabolism. An examination of the table con- taining the proposed standard diets of various investigators shows an increase in the quantity of protein where the fat and carbohydrate have been increased to meet the changed energy requirements. The studies on which these standards are based apply to men of different physique and muscular devel- opment, which difference is in itself reason for different amounts of protein in the diets. When it is considered, however, that the protein requirement of a man at moderate labor is already greatly in excess of his basal requirements, it is difficult to understand the reason for large increases in the protein portion of the diet of individuals at hard labor whose muscular develop- ment probably is not greatly increased. The increased production of heat (specific dynamic action) following the ingestion of protein, with the accompanying feeling of warmth is a partial explanation of the desirability of an increased protein ingestion by those exposed to cold; and, conversely, of the undesirability of a high protein diet in the STANDARD DIETARIES 75 tropical climates. The heat derived from such action of protein has been shown to be available for the maintenance of body temperature, but not for work. The optimum protein requirement of man has been a sub- ject of considerable controversy. The discussion concerns chiefly the standards which we have already discussed — approximately ioo to 150 grams of protein per day — and an amount considerably less than this, 50 to 75 grams of protein per day. On the one hand there is the evidence of the amount of protein which various peoples have been in the habit of eating and apparently crave. On the other hand there is a physiological basis for a low protein diet in that the minimal requirements of the average man are much lower than 100 grams of protein per day, that the body can satisfy its energy requirements with fats and carbohydrate and that the protein material taken in excess of the body needs is decomposed, and the nitrogen portion is excreted in the kidneys chiefly in the form of urea, while the carbon moiety is utilized for the production of energy. Chittenden has been the chief advo- cate of the low protein diet. Hindhede, from his work on the use of the potato as the chief article in the diet, has recently advocated an even lower diet than that of Chittenden. Various arguments have been advanced for and against a low protein diet. Those who believe that such a diet is advis- able base their opinion, in addition to the facts indicated above, on observations which indicate that such a diet results in greater strength and endurance, is more economical, and in accompanied by a lowered intestinal putrefaction. Against a low protein diet arguments have been presented to the effect that men do not eat a low protein diet from choice, that there is the danger of the selection of a diet with a low total caloric value, that the "minimum is not necessarily the optimum," and that low planes of mental, moral and physical develop- ment exist in countries in which the population subsist on a low protein plane. One of the most telling arguments in favor of a high protein diet, where the nature of the protein and the qualitative nature of the diet is not known, is the finding of McCullom that an increase of the protein portion of a diet will in certain cases overcome the effect of toxic substances present in food (p. 98). The values for the average protein requirement given in the table on page 73 have been determined chiefly by statistical means. The protein requirement is apparently not affected by as many variables as the energy requirement. Muscular work does not materially affect the protein metabolism provided the increased energy requirements are met with 76 PROTEIN REQUIREMENT sufficient quantities of non-nitrogenous food-stuffs: fat and carbohydrates. When the body is already meeting a part of its energy requirements with protein material, such as might exist in underfeeding or in fasting, increased activity is asso- ciated with an increased protein destruction. There might in the course of time be an indirect increase in the protein metab- olism following work as a result of an increase in the quantity of muscular tissue with its greater "wear and tear." The protein requirement varies with the age of the indi- vidual considered. An infant, which is forming new protein as well as repairing the wear and tear of its body, requires proportionately more protein than does an adult who needs only to supply the protein for repair. An old man, with rela- tively diminished muscular development and tone, requires less protein material than the adult who is in the prime of his life. Muscular development undoubtedly affects the amount of nitrogenous material required; while the protein needs of the pregnant woman or nursing mother are increased because of the storage of nitrogenous material in pregnancy, and the drain upon the stored protein experienced during lactation. Although the average diet contains sufficient protein material to cover any variations in the requirements due to size, age, and sex, these factors must be considered when an insuffi- cient or a restricted diet is prescribed. CHAPTER IV. INORGANIC SALTS AND WATER. The importance of inorganic salts has not been emphasized in dietetics so much as the energy and protein parts of the diet. That this is so has been due in part to the fact that the aver- age mixed diet contains a sufficient amount of the various inorganic constituents for all general purposes. Studies of pathological conditions, however, have repeatedly demon- strated that a diet may be entirely satisfactory from the stand-point of protein and energy and still be lacking in some inorganic constituent, or group of constituents, which, when supplied, rectified the trouble. A consideration of the role played by inorganic substances in nutrition will serve to bring out their importance in the dietary. Whereas fat, protein, and carbohydrate serve to fur- nish energy to the body, inorganic salts are not concerned directly with this. In their capacity, however, of regulating the body functions they contribute toward the oxidation of these various food substances. Iron in particular appears to be concerned in oxidation. We find this element in the red blood corpuscles as an important and apparently active con- stituent of the hemoglobin. Certain investigators have attempted to show that the action of oxidases is due to the inorganic elements or salts which are contained in them. The fluids and tissues of the body are maintained in osmotic equilibrium by the contained salts. The accumulation of water in one portion of the body or the desiccation in another is prevented by the diffusibility of salts or the attraction for water when separated from the surrounding medium by a semipermeable membrane. When there is a perversion of this property by a change in the physical structures or the chemical properties we find pathogenic states to exist, such, for instance as the condition of edema. The inorganic elements occur in the body in two general forms : (a) Combined with organic material as such, as radicles or held in an insoluble form such as the iron of hemoglobin, the phosphorus of nucleoprotein, the iodine of the thyroid gland, and the constituents of the structural tissue and of all actively functioning tissues, e. g., the calcium and magnesium 78 INORGANIC SALTS AND WATER and phosphorus of the bone; (b) in solution as ionizable salts where they are active in maintaining osmotic equilibrium, and the constant reaction of the body fluids, assisting in the trans- portation of the oxygen and carbon dioxide in the blood, concerned in the permeability of the cell walls, and affecting the irritability of muscle and nerve. The mere enumeration of a few of the important uses of the inorganic elements brings out strikingly their significance. The multiplicity of their function has likewise rendered the study of these substances difficult, for with one element having a varied function, its removal from the diet may be respon- sible for many secondary reactions which will mask the direct result. Experiments designed to show the effect of the complete removal of salts have demonstrated that an ash-free diet is detrimental to the organism. It was early shown that a diet containing the requisite amount of carbohydrate, fat, and pro- teid but which did not contain the ash constituents resulted in an early death. Von Bunge suggested that these harmful effects were due largely to an excess of acidic radicles present in the body caused by the sulphuric acid formed in the pro- cess of metabolism from the sulphur present in the protein molecule. Ordinarily this acid would be neutralized by the fixed bases present in the diet. In the absence of these, how- ever, they derive a certain portion of their required base from the alkali radicles in the tissues. He suggested the addition of carbonates to combat this acidity. Studies of the effect of an ash-free diet upon man have been made. In one case symptoms were experienced which were analogous to that associated with acidosis, including muscular weakness and the presence of acetone on the breath. Other investigators failed to obtain any symptoms of acidosis. In both experiments there was a loss of weight as the result of the ingestion of an ash-free diet. It is apparent that individual differences must be considered in the interpretation of such data. The analyses of various foods for the inorganic elements they contain, and a consideration of the latter on the basis of whether they yield an ash which is predominantly acidic or basic in nature, have shown that some foods, upon oxida- tion in the body yield an excess of acidic over the basic elements, while of others the opposite is true. An excess of inorganic acid radicles in the blood, whether they occur as the result of the ingestion of the acids themselves or are produced in the processes of metabolism from neutral compounds, is neutralized in one of two ways — by combination (a) with INORGANIC SALTS AND WATER 79 ammonia or (b) with some of the fixed alkalis of the body. Since there is at all times an equilibrium, both changes occur. Such changes produce an excess of salts in the blood which is excreted in the urine. The fixed bases which accomplish this neutralization may come from the alkaline carbonates of the blood, perhaps from the calcium or magnesium of the bones. The ultimate result, if the diet be continued, is the reduction of the body's store of basic elements. Such a condition we have already considered in our discussion of the effect of a salt-free diet. The effect of an excess of basic elements in the body is not so serious, for they may be neutralized by the carbonic acid formed in the process of oxidation. The urine excreted after the ingestion of a diet which contains an excess of potential basic ash constituents will tend to be alkaline, while that obtained after a potentially acid diet will be acid. Sherman and Gettler have recently considered some of the more important foods on the basis of their acid- or base- yielding properties, .and have called attention to the desir- ability of balancing potentially acid foods in the diet with predominantly base-yielding foods. The accompanying table gives the result of their work, grouped according to predomi- nating acid- or base-yielding power. Excess Acid or Base in Representative Foods in Terms of Normal Solutions. 1 Article of food. Succulent vegetables : Asparagus . Potatoes Carrots (or beets) . Fruit: Cranberries . Pineapple Nuts: Almonds Walnuts . . . . Legumes . . . . Cereal : Oatmeal (or wheat) Rice . . Lean meat . Fish Milk ■ Cheese Eggs Potential acid. Per 100 Per 100 Potential base. gm. 12.9 7-8 I2.0 7-8 II. I calories. Per 100 gm. 23 Per 100 calories. 3-6 8.6 23-7 3-8 15-7 1.8 6.9 2.6 It will be seen in general that, with the exception of milk, animal products yield an excess of acid radicles and the same 1 Compiled from Sherman: Food Products, 19 15. Sherman and Gettler : Jour. Biol. Chem., 1912, xi, 363. 80 INORGANIC SALTS AND WATER may be said of the cereals. Vegetables and fruits are chiefly base-yielding foods. That foods which are rich in the salts of organic acids should yield an excess of base is due to the fact that the acid portion of the molecule is oxidized in the body yielding carbonates which are potentially basic. Calcium, phosphorus, potassium, sulphur, sodium, lithium, chlorine, magnesium, manganese, iron, boron, iodine, fluorine and silicon are the more important "mineral " elements found in the body. The bases are combined chiefly as phosphates, sulphates, chlorides, and carbonates. Of the chlorides in the body the sodium salt predominates. It is the most abundant inorganic constituent of the diet and also of the urine. The fluids of the body are particularly rich in sodium salts and, consequently, in sodium chloride; while the potassium salts predominate in the tissues, chiefly as the phosphates. The quantity of chlorides in the urine is directly related to that ingested, for the body tends to maintain itself in chlorine equilibrium. CHLORINE REQUIREMENT OF MAN. The sodium chloride requirement of the body is difficult to determine. Studies of the minimum chloride requirement in which there is a complete removal of salt, as in fasting or an ash-free diet or sodium chloride-poor diet, fail to determine the optimum requirement; they always show the lowest excre- tion under conditions in which the body has lost its reserve and is tending to conserve that amount which is left. Such studies on man indicate a loss of approximately 10 to 12 grams of sodium chloride, calculated as chlorine, in the course of ten days. The daily excretion decreases gradually until it reaches a low level when between 0.1 and 0.2 gram of chlorine are excreted per day. That, in such cases, chlorides have been lost beyond the reserve that is related to the quantity of chlorine ingested (which results in part from a lag in its excretion) is evidenced by the marked retention of chloride during the first days of feeding after a fast or the ingestion of a salt-free diet. The sodium chloride requirement is affected by the nature of the diet. This is brought out most strikingly by a consid- eration of the quantity of sodium chloride taken by the her- bivora as contrasted with the carnivora. Von Bunge was the first to call attention to the fact that the carnivora do not exhibit the marked craving for salt that is evidenced by the herbivora. He ascribed this difference to the greater quantity of potassium salts ingested with a vegetable diet, which caused an increased CHLORINE REQUIREMENT OF MAN SI Chlorine Content of Foods. Per cent. Chlorine in of edible 100-Calorie portion. portion, gm. Protein-rich foods : Cheese i.o 0.2 Chicken 0.6 0.02 Beef and veal 0.5 o . 05 Cheese, cottage 0.5 Fish: Salmon 0.28 0.13 Cod, haddock 0.24 o . 33 Egg white 0.15 0.28^ Milk, whole 0.12 0.17 Milk, butter 0.10 0.275 - Egg, whole 0.10 0.06 Egg, yolk 0.10 0.03 Lentils 0.08 0.02 Peanuts 0.04 0.007 Peas, dried 0.04 0.01 Beans, dried 0.03 0.008 Walnuts 0.01 0.001 Carbohydrate-rich foods : Potatoes 0.12 0.10 Flour, wheat 0.07 0.02 Cornmeal 0.06 0.02 Rice 0.05 0.01 Oatmeal 0035 0.009 Potato, white o . 03 o . 04 Barley, pearled 0.02 0.005 Rye 0.02 0.005 Honey .0.01 0.01 Sugar Water- and salt-rich foods : Celery 0.17 0.9 Lettuce 0.06 0.3 Cauliflower 0.05 0.16 Radish 0.05 0.17 Beets 0.04 0.08 Carrots 0.036 0.078 Rhubarb 0.035 0.15 Cabbage 0.03 0.09 Tomatoes 0.03 0.09 Spinach 0.02 0.08 Corn, green . . . . . . 0.014 0.014 Cherries 0.01 0.01 Grapefruit 0.01 Grapes 0.01 0.01 Lemons 0.01 0.02 Oranges 0.01 0.02 Peaches 0.01 0.02 Peas, green 0.01 0.01 Squash 0.01 0.02 Beans, green 0.009 0.007 Apples 0.004 0.006 Weight of 100-Calorie portion, gm. 23 45-93 35-50 31 70 216 I96 145 280 68 28 29 18 28 29 14 28 28 29 25 120 28 28 31 540 524 328 341 217 221 433 317 439 418 99 128 104 226 195 242 100 217 82 159 Fat-rich foods : Butter; lard; olive oil; salt pork; bacon; salt content, high and varies. 6 82 INORGANIC SALTS AND WATER excretion of potassium chloride, with the consequent deple- tion in chlorine. That potassium salts do cause an increased chlorine excretion has been shown by direct experimentation. From these considerations it is evident that the estimation of the quantity of sodium chloride required per day is a difficult matter. The quantity of chlorine necessary to protect the body against loss of chlorine has been placed at 3 or 4 grams per day. The average consumption has been estimated at from 15 to 20 grams of sodium chloride per day. Ingestion of large quantities of sodium chloride increases the excretion of nitrogen. The explanation of this is not clear; it seems probable that it is due to the accompanying diuresis. The table on page 81 gives the average chlorine content of various foods arranged (1) according to whether they are particularly valuable as sources of protein, carbohydrate, or for the salts and water which they contain and (2) in each group in the order of their decreasing chlorine content. PHOSPHORUS REQUIREMENT OF MAN. Phosphorus 1 occurs abundantly in the body almost exclu- sively in the oxidized form as the phosphoric acid radicle. As such, however, it appears in a variety of combinations. Thus it occurs in the body or in the combined form with the protein molecule as nucleoprotein of the cell nuclei and as the phospho- proteins casein and vitellin; combined with fatty acids as lecithoprotein, the lecithins, and the phosphatides of the nervous tissue; in simple organic combination in the plant as phytin, and finally in the inorganic state combined with the various bases in the skeleton, particularly with calcium and magnesium and in the body in general as the sodium and potassium salts. As a constituent of the nuclei the phosphoric acid takes part in one of the most vital processes of the body, the formation of new cells. Combined with calcium and magnesium it becomes the constituent which gives permanence and hard- ness to the bones, while as a soluble salt dissolved in the fluids of the body in conjunction with the carbonates and proteins it serves to maintain the neutrality of the tissues. The question of the ability of organic and inorganic phos- phorus to supply the body needs has been one which has received a great deal of attention. This problem is particu- larly important in connection with the artificial feeding of 1 For a review of the metabolism of phosphorus the reader is referred to the excellent and complete review of the literature on this subject by Forbes and Keith: Ohio Agric. Exp. Sta., Tech. Bull. No. 5, 1914. PHOSPHORUS REQUIREMENT OF MAN 83 infants and the treatment of disease. The weight of the evi- dence shows that only a small amount of organically combined phosphorus is necessary in the diet provided a sufficient amount of inorganic phosphorus is present. Forbes has recently summed up the evidence with regard to the availability of organic and inorganic phosphorus. In his review of the fac- tors which might affect the correct interpretation of the data considered — in which he calls attention to the fact, the impor- tance of which has become daily more evident, that it is necessary to consider the presence or absence from the exper- imental diet of such substances as the "vitamines" or lipoids (see p. 94) before we shall be able to demonstrate conclusively the greater advantage of one form of phosphate over the others or their equality. Forbes concludes with the following statement: "It therefore seems not at all unlikely that the many demon- strations of the superior nutritive value of organic phosphorus compounds have been influenced by other beneficial sub- stances occurring in association with them in natural foods, and contained as impurities in these organic phosphorus compounds as isolated and used in nutrition investigations. As to the relative importance of this factor and others we are as yet unprepared to make positive assertions; but these recent studies at least raise the question as to whether the apparent superiority of organic to inorganic phosphorus com- pounds is due to these organic compounds by themselves, or whether their superiority is dependent upon minute quanti- ties of certain associated compounds. However this question may be settled the studies, certainly suggest that, if the natural organic phosphorus compounds are not of superior usefulness, or are not essential to the maintenance of growth in animals, then other nutrients associated with them in the natural foods are essential, and the result therefore is to put a new emphasis on the value of the natural organic food-stufFs as compared with inorganic or artificially synthetized nutrients and certain manufactured foods." The phosphorus requirement of man has not been deter- mined with any certainty. The procedure is difficult because, unlike many of the products of metabolism, a large propor- tion of the phosphorus may be excreted in the feces. The daily requirement of the adult man has been placed at 1.5 grams of phosphorus (P) or 3.5 grams of P 2 5 . Under special conditions the requirement may be as low as 0.9 gram P or 2 grams of P 2 5 . The quantity of food phosphorus that may be retained depends upon the nature of the diet. Since a large proportion 84 INORGANIC SALTS AND WATER Phosphorus (P 2 5 ) Content of Foods (Average Daily Requirement 2.75 Grams). Per cent. P 2 O fi in Weight of of edible 100-Calorie 100-Calorie portion. portion, gm. portion, gm. Protein-rich foods: Cheese, hard ....'.. 1.45 0.39 23 Beans, dried 1.14 0.326 29 Egg, yolk 1.0 0.27 .-■ 28 Peas, dried 0.91 0.24 28 Peanuts 0.90 0.16 18 Beans, lima, dried .... 0.77 0.22 29 Walnuts 0.77 0.11 14 Lentils 0.66 0.29 29 Cheese, cottage 0.50 0.40 - 31 Meat and chicken . . . . 0.50/ ff at) ° ■ 1 5"° ■ J 8 45~93 \ (lean) o . 24-0 .30 Fish 0.40 0.60 50 Egg, whole 0.37 0.24 68 Milk, whole 0.22 0.303 145 Milk, skimmed 0.22 0.60 273 Egg, white 0.03 0.05 196 Carbohydrate-rich foods : Oatmeal, dry 0.827 0.216 25 Barley, pearled 0.46 0.127 28 Bread, whole wheat .... 0.40 0.16 39 Cornmeal 0.30 0.08 28 Potato, white 0.14 0.166 81 Rice 0.203 0.057 2 9 Bread, white 0.20 0.075 39 Wheat flour 0.20 0.05 28 Potato, sweet 0.09 0.08 101 Water- and salt-rich foods : Wheat bran 3.0 Almond 0.87 0.132 15 Beans, green 0.27 0.22 82 Peas, green 0.26 0.24 100 Corn, green . . . ■. . .0.22 0.21 -99 Cauliflower 0.14 0.45 ^ 328 Spinach 0.13 0.54 418 Beans, string .0.12 0.28 241 Carrots 0.10 0.22 221 Celery 0.10 0.54 - 540 Lettuce 0.09 0.47 —" 524 Asparagus 0.09 0.39 450 Cabbage 0.09 0.28 317 Beets 0.09 0.19 217 Squash 0.08 0.08 217 Cherries 0.07 0.09 128 Tomatoes 0.059 °- 2 57 439 Oranges 0.05 0.09 195 Peaches o . 047 o . 1 1 242 Apples 0.03 0.05 159 Lemons 0.01 0.04 226 Fat-rich foods: Cocoa 1.1 0.22 20 Chocolate 0.90 0.14 16 Cream 0.18 0.10 51 Butter . 0.03 0.004 I 3 CALCIUM REQUIREMENT OF MAN 85 is deposited in the bones, the presence of a sufficient amount of the bases, calcium and magnesium, associated with it in such structures is essential. When these are not present the phosphoric acid radicle is excreted in combination with the more soluble bases and thus fails to satisfy the requirements. The ingestion or formation of acids or acid-yielding substances results in an increased excretion of phosphorus. The phosphorus of the food, obtained as it is from both the animal and vegetable kingdom occurs in a variety of organic compounds, the particular advantage of any one of which has not been determined. Feeding experiments in which one type of phosphorus is fed to the exclusion of all others do not neces- sarily demonstrate the true availability of the compound. In selecting diets, then, for their phosphorus content we cannot lay stress on any given food as presenting the constituents in a more available form than another. In considering data with regard to the P 2 5 content of foods and particularly the vegetables, it is to be remembered that in their preparation a certain pro- portion of the phosphorus is removed. This is particularly true in the removal of the outer coating of cereals. The table on page 84 gives the relative quantity of P 2 5 in some of the more common foods. CALCIUM REQUIREMENT OF MAN. Calcium salts play a varied role in the body economy. Cal- cium occurs in the bones chiefly as phosphate. Dissolved in the body fluids calcium is an important factor in the coagulation of the blood and in the contraction of the muscles. Underhill has suggested that calcium salts play an important role in the regulation of the blood-sugar content. During the period of growth the importance of calcium salts is most easily demonstrated, for at this time the body is utilizing relatively large quantities of calcium, the removal of which from the diet at this time results in arrested or poor develop- ment of the bones. It is for this reason that consideration of the calcium requirement of the growing child is very impor- tant. The disease most commonly associated with calcium metabolism, rickets, may not be entirely the result of a lack of calcium in the diet but of a failure to assimilate it. In the adult the temporary removal of calcium is not followed by such marked effects as those observed in growth, for the body can call upon its reserve for a considerable time without showing any undesirable effect. Calcium, like phosphorus, is excreted largely through the intestine, and its excretion is continued in fasting. 86 INORGANIC SALTS AND WATER The importance of calcium and the fact that it is impos- sible to consider each salt by itself is well illustrated in the use of such solutions as Ringer solution and the antagonistic action of salts. Physiological salt solution is sufficient to maintain the osmotic properties of muscle. In such a solu- tion, however, muscle will not exhibit its properties of irrita- bility and contractibility for any length of time. If, to the physiological salt solution, calcium and potassium chloride be added in the proper proportions, it will exhibit these prop- erties for a much longer period; an isolated heart when sup- plied with oxygen will continue to beat spontaneously for a long time in Ringer solution which contains these salts. An excess of calcium may produce a condition of tonic contraction called "calcium rigor." Lceb has recently shown that the ions antagonize each other in their effect upon body processes; particularly the permeability of cell membranes. Membranes such as those surrounding sea-urchin eggs are permeable to certain concentrations of sodium chloride and dilute acids. If to such solutions a bivalent ion, such as calcium or mag- nesium, be added the permeability is greatly reduced. Clowes has been able to produce results analogous to these in purely physical systems. Thus we see that the role of salts in the body, aside from their structural value, is very complex. In discussing the cathartic action of salts Meltzer calls attention to the fact that the salts of magnesium are essen- tially inhibitors of intestinal movement and suggests that the purgative effect produced by such salts is the result of the combined action of sodium salts which stimulate contraction and of magnesium salts which cause a relaxation. This inhibitory effect of magnesium, which extends to other parts of the body, may be counteracted by subsequent injections of calcium salts. Anesthesia has been produced by the injec- tion of magnesium sulphate. The calcium requirement of man varies with the period of life. The growing child requires a greater proportionate quan- tity of calcium per day than an adult in middle life; while an old man requires much less. Dietary studies show that an ingestion of approximately 0.7 gram of calcium (calculated as oxide) per day is the smallest amount which will maintain the average normal adult in calcium equilibrium on an ordinary diet. Since absorption is not always complete, a somewhat larger quantity is desirable, 1 to 1.5 grams per day. Whether or not the average mixed diet satisfies the calcium requirement without special selection of food is a matter which is open to question. When the food consists chiefly of meat and cereals, foods low in calcium, it is probable that the CALCIUM REQUIREMENT OF MAN 87 Calcium (CaO) Content of Foods (Average Daily Requirement 0.7 Gram). Per cent. CaO in Weight of of edible 100-Calorie 100-Calorie portion. portion, gm. portion, gm. Protein-rich foods : Cheese : Hard 1.1 0.25 23 Cottage 0.3 0.30 31 Beans, dried 0.22 0.063 2 9 v Egg, yolk 0.20 0.05^" 28 Milk, whole 0.168 0.24 145 Milk, skimmed 0.465 273 Buttermilk 0.15 0.415 280 Peanuts 0.14 0.04 18 Lentils 0.12 0.04 29 Walnuts 0.11 .. 14 Beans, lima, dried . . . .0.10 0.028 29 Egg, whole o . 093 o . 06 68 Egg, white 0.015 0.028 196 Fish 0.015-0.08 0.033 5° Meat 0.01-0.03 0.005-0.01 45-93 Carbohydrate-rich foods: Oatmeal 0.13 0.03 25 Wheat . 0.06 0.01 27 Bread, whole wheat . . . . 0.04 0.016 39 Bread, white 0.03 0.011 39 Barley, pearl 0.025 0.007 2 & Potato, sweet 0.025 0.02 101 Wheat flour . 0.025 0.007 28 "^"Potato, white 0.016 0.019 81 Cornmeal 0.015 0.004 2 & Rice 0.012 0.003 29 Honey 0.005 0.001 Sugar Starch Water- and salt-rich foods: Almonds 0.30 0.046 15 - Cauliflower 0.17 0.55 328 Olives 0.17 o . 06 40 Celery 0.10 0.54- 540 Dates 0.10 0.03 29 Spinach 0.09 0.37 418 - Beans, string 0.075 0.177 2 4* Carrots 0.077 0.168 221 Oranges 0.06 0.11 195 Rhubarb 0.06 0.26 433 Lemons . .' . . . . .0.05 0.12 226 Lettuce 0.05 0.26 524 Radish 0.05 0.17 341 Asparagus 0.04 0.17 450 Beans, lima 0.04 0.033 82 Peas, green 0.04 0.032 100 Beets 0.03 0.06 217 Cherries 0.03 0.04 128 Squash . .0.02 0.054 2I 7 Tomato 0.02 0.087 439 Prunes (dried) ..... o . 02 . . 33 Apples 0.014 0.022 159 Fat-rich foods: Cocoa 0.14 0.027 2 ° Chocolate 0.14 0.052 16 88 INORGANIC SALTS AND WATER calcium ingestion is not sufficient. If the diet contains milk, eggs (yolk), legumes, and fruits the diet will probably contain a sufficient quantity of calcium. The diet of pregnant and nursing mothers and children requires special consideration. During pregnancy and lacta- tion the mother is nourishing the young through her own system. At this time, too, there is an especial necessity for calcium and the other constituents which are concerned in the structural tissues of the body — magnesium, iron, and phos- phorus. Forbes has recently shown that the cow when pro- ducing milk apparently draws upon her own calcium reserve, even though there be ample supplies of calcium in the diet. It is essential, then, that the mother have a plentiful supply of those foods which furnish these inorganic elements. Decay of teeth during pregnancy, has been ascribed to the drain upon the calcium reserves caused by the secretion of milk. The nature of the diet of a child is also important after it has ceased to depend upon its mother for food. Particular attention should be given to the calcium content of the food, for here the diet changes from one consisting of milk, which is richest in calcium, to a mixed diet which, unless properly chosen, may be poor in calcium. A calcium deficit for a grow- ing child results in soft bones with the resulting abnormalities of structure. The table on page 87 contains the more common foods grouped according to calcium content. IRON REQUIREMENT OF MAN. Iron occurs as a constituent of the blood pigment. We find it also in the chromatin of cells in which it is in part concerned, with the processes of oxidation, not only as a carrier of oxy- gen but as a catalyzer of enzyme action. The total quantity of iron in the body has been estimated at from 3 to 4 grams. The iron requirement of man has been estimated at from 0.01 to 0.012 gram of iron per day. Until a more careful determination of the actual requirements has been established a slightly higher value of 0.015 gram per day has been sug- gested (Sherman). Women require much more iron than men. During the periods of pregnancy, lactation and men- struation of women there is a considerable loss of iron which must be replenished and in the growth period of children there is a greater demand for iron than in the adult. Observation has shown that the body is proportionately richer in iron at the time of birth than at any other time in its development. Analyses of milk and of the newborn and young have shown IRON REQUIREMENT OF MAN 89 Iron (Fe) Content of Foods (Average Daily Requirement 0.015 Gram). Per cent, of edible portion. Protein-rich foods: Lentils . . . . . . 0.0086 Egg, yolk o . 0085 Beans, dried 0.007 Beans, lima, dried . . . o . 007 Peas, dried 0.0056 Fish ....... 0.004 Meat 0.0038 Egg, whole . . . . . 0.003 Walnuts 0.0021 Chicken 0.002 Peanuts 0.002 Milk, skimmed .... Milk, whole 0.00024 Egg, white 0.0001 Carbohydrate-rich foods : Wheat ...... 0.0053 Oatmeal, dry .... 0.0036 Bread, whole wheat . . . 0.0015 Wheat, flour 0.0015 Barley, pearled .... 0.0013 Potato, white . . . . 0.0013 Cornmeal 0.0011 Honey 0.001 Bread, white 0.0009 Rice . . . . "' . . . 0.0009 Potato, sweet .... 0.0005 Water- and salt-rich foods: Dandelion greens . . . 0.027 Spinach 0.0032 Dates 0.003 Olives 0.0029 Beans, lima . . . . . 0.0025 Almond 0.002 Beans, string .... 0.0016 Peas, green 0.0016 Cabbage 0.0011 Asparagus 0.001 Lettuce 0.001 Carrots 0.0008 Corn, green 0.0008 Squash 0.0008 Beets • . . 0.0006 Lemon 0.0006 Radish 0.0006 Celery . . . . . . . 0.0005 Cherries 0.0005 Turnips . . . . . . o . 0005 Tomato 0.0004 Apples 0.0003 Oranges 0.0003 Peaches 0.0003 Onions Fat-rich foods : Butter Cream Cocoa Weight of Fe in 100-Calorie 100-Calorie portion, gm. portion, gm. . 0024 29 - O.OO23 28 0.002 29 0.002 29 O.OOI5 28 O . 0009 80-IOO . 0008-0 . 003 35-50 O.OOI9 68 O . 0002 Q 14 O.OOI3 45-93 O.OO35 18 O . OOO66 273 O . OOO34 145 O . 0002 196 O.OOI4 28 O . OOO9 25 . 0006 41 . 0004 28 O . OOO36 28 O.OOI5 120 O.OOO3 28 . 0003 31 O . 0003 38 . 0003 29 O . OOO4 81 >i . 0044 164 0.0133 418 0.001 29 . 0009 33 0.002 82 . 0003 15 1 . 0038 241 0.0016 100 \. 0.0035 317 0.0043 450 v O.OO5 524 ' O.OOI6 221 O.OOO75 99 O.O0I7 217 0.0013 217 O.OOI3 226 0.002 34i O.OO27 540 128 O.OOI3 254 O.OOI7 439 . 0005 159 . 0006 195^ . 0007 242 O.OOII 205 0.0001 5i . 0005 20 u 90 INORGANIC SALTS AND WATER that during gestation the fetus accumulates a store of iron. During the suckling period the quantity of iron is almost constant and milk is comparatively poor in iron. The con- clusion from these facts is, then, that the child derives from its mother, before birth, a store of iron sufficient for its needs throughout the period when it is nursing, and that the mother supplies, in the milk, approximately enough iron to replace the iron lost in the processes of metabolism. After the child stops nursing it is important that the iron content of the diet be given careful consideration, for both the small daily losses made good by the milk and the iron needed for the processes of growth must be furnished. The degrees of availability of iron, in the organic and inor- ganic forms has been, as in the case of phosphorus, a matter of great controversy. Experiments have shown that both forms of iron are absorbed from the small intestines. That inorganic iron may be used in the production of hemoglobin has not been proven, it does increase the production of hemoglobin, in which case it apparently acts as a stimulant to the cellular activities. Iron in simple organic combination, lactate, has been used successfully as the source of iron for growing rats. There is ample evidence that iron when found in organic combination is assimilated and used in the processes of growth and in the formation of hemoglobin. Although inorganic iron appears to be as effective as organic iron it has been recommended by some that at least a part of the iron ingested be in the "organic" form. Iron is eliminated chiefly in the feces. The table on page 8a contains the iron content of some of the more important foods. In using the table it is essential to remember that fat meat contains a smaller proportion of iron than does a lean piece, for fat contains practically no iron. The preparation of cereals for the market (milling) results in the removal of a consider- able portion of the iron contained in the whole grain. The advantage of foods, such as vegetables and fruits, which are not particularly valuable to the body for protein or a source of energy, is shown when it becomes desirable to increase the inorganic, salt content of the diet. IODINE REQUIREMENT OF MAN. Iodine is present in its greatest amount in the thyroid gland. The function of iodine in the thyroid is not known. The quantity of iodine in the gland is variable. Ingestion of iodine or the application of iodine to the skin is accompanied by an increased iodine content of the thyroid. It appears to be in combination with protein material. The name thyroglobulin WATER REQUIREMENT OF MAN 91 has been given to an iodine-rich protein isolated from the thyroid gland. Regions in which the iodine content of the water is low have been shown to be, in many cases, those in which goitre is prevalent. If, as general observation seems to indi- cate, there is a relation between the lack of iodine and the prevalence of goitre, it is important to know the foods which contain iodine. Iodine is contained in the water of various districts; it also occurs in sea water and in foods grown near the sea. Recent analyses of foods have shown that iodine is not a constant constituent of foods; that when present it is usually found in exceedingly minute proportions, and that in general, at least, it must be regarded as an accidental constituent in the sense of standing in no vital relation to the growth of food prod- ucts. The presence of iodine in most vegetable food products clearly depends upon the fact of its presence in the soil and the lack of a selective capacity in the feeding of plants. 1 Of the plants examined, Irish moss, from which blanc mange is pre- pared, and agar agar are the best sources of iodine. Garden vegetables, some kinds of legumes, or seeds, beans, and peas, are shown to be fair sources of iodine, although the presence or absence of iodine and the quantity contained are uncer- tain. Studies of foods from different sections of the country, particularly from localities in which goitre is prevalent, failed to show any uniformity in the presence or absence of iodine over districts which were comparatively free from goitre. WATER REQUIREMENT OF MAN. Water as an essential constituent of the diet receives very little attention in the usual consideration of the foods. That this is so is but natural, for it is one of the most readily obtain- able and generally used food-stuffs. The lack of water is, however, sooner and more keenly felt than the absence of protein, carbohydrate, or fat. An animal receiving neither food nor water will die sooner than one which is given only water; while an earlier death will result from dry food and no water. The relative importance of water from a quantitative point of view is indicated by the water content of the body tissues. The fat-free organs show a comparatively constant water content, being about 80 per cent. The presence of fat affects the percentage of water content of the tissues as a whole, but being inert so far as holding water is concerned, it does not 1 Cameron: Jour. Biol. Chem., 1914, xviii, 335. Forbes and Beegle: Jour. Med. Research, 191 6, xxxiv, 445. 92 INORGANIC SALTS AND WATER appear to influence extensively the composition of the tissues which hold it. The secretions are particularly rich in water (86 to 99 per cent.), while the skeletal tissues, such as bone and connective tissue, have a much lower water content (io to 50 per cent.). The tissues of young animals, of regenerating and probably of recuperating tissues are richer in water than those of an adult organism. The functions of water are numerous: it is a constituent of all protoplasm; as a solvent it aids in carrying to the cell the food material produced by digestion, in the removal of the waste products; it maintains the osmotic equilibrium between the various organs and tissues; by reason of its high specific heat its evaporation assists in the maintenance of a constant body temperature; and it is the vehicle for the transportation of the blood elements throughout the body. The water present in the body is not necessarily to be consid- ered as free water in the sense that after its complete removal from the cellular structures they will not cease their activities or that its return will initiate them anew. A certain amount of water is probably held in loose chemical combination or by physical attraction with the various molecular structures, such as the protein. It is known that much of the organic material in the body exists in swollen colloidal masses and that the removal of water from them affects their physical and perhaps their chemical properties. Our knowledge on this point is rather meagre. We do know, however, that the complete removal of water results in the disappearance of the phenom- enon known as life. Since the water content of various tis- sues is relatively constant a decided diminution in the water content is fatal. Certain organisms, such as the frog, insects, etc., can lose a considerable proportion of their water under favorable conditions and still remain alive, although usually dormant; seeds exhibit similar phenomena. Water is never' entirely absent under such conditions; there is a minimum which if passed, results in the disappearance of life. Water is ingested either as such or associated with food. Most water contains a considerable quantity of salt. 1 The quantity of water ingested with the food may be considerable, for most foods roughly three-fourths its weight. A certain amount of water is liberated in the tissues as the result of oxidation. The quantity and manner in which water is excreted is 1 The specific effects of certain mineral waters is due to their salt content, it may be, however, that the increased water ingestion, under such circum- stances which usually accompanies the use of such waters, may also contribute to the beneficial effects of water cures. WATER REQUIREMENT OF MAN 93 affected chiefly by the temperature and humidity of the sur- rounding air, the activity of the individual and the quantity and nature of the food and water ingested. Under normal conditions the equivalent of the water ingested in a day is excreted in a similar time chiefly through the lungs and skin, and in the urine and feces. A considerable proportion of the water ingested under average conditions of temperature and humidity appears in the urine within a comparatively short time after its ingestion. After large volumes of water have been taken as much as three-fourths of the amount appears in the urine within an hour after its ingestion. Higher tempera- ) tures outside the body, or excessive muscular activity increase the loss of water through the lungs and skin; while with low temperatures and relative quiet the amount of water which appears in the urine is increased. With an increase in the quantity of water ingested, other conditions being the same, a greater proportion of the ingested water appears in the urine. The body may sufFer a loss of water as the result of excessive perspiration, the action of diuretics or of cathar- tics. Under such circumstances the ingestion of water results in a restoration of the amount lost, for the tissues tend to maintain the concentration of water at a constant level. With the loss of water there is usually a loss of salt from the body either in the urine or through the skin. One investi- gator has studied this loss with regard to increased perspira- tion and the processes attending the restoration of water. He suggests that thirst resulting from excessive perspiration is quenched most readily by water containing salts, or taken with food, than with distilled water; for unless salt is present the water ingested will not be retained but will be rapidly excreted. In the process of recuperation following emacia- tion there is a very rapid restoration of the lost water. Thus the tissues of fasting animals which show an increased water content upon the ingestion of food and water, even though large quantities of water have been ingested throughout the fast, show a marked water retention. Because of the varied activities of man the quantity of water which is necessary for the normal functioning of the body is a difficult matter to determine. It has been placed at from 2 to 5 liters (or quarts) per day. The effect of water on metabolism has been studied from many angles. Ingested water passes rapidly through the stomach and is readily absorbed in the intestines. In spite of this it has been shown that it affects the rate and extent of digestion. Water taken into the stomach in large quantities increases the secretion of gastric juice; small amounts have no 94 INORGANIC SALTS AND WATER effect. When water is taken with food the flow of gastric juice has been shown to be not only greater in amount but to contain more acid. The secretion of bile and pancreatic juice is also stimulated by water, probably because of the inter- relation between the acid reaction in the stomach and the flow of these secretions. The passage of food from the stom- ach has been held to be accelerated as the result of the inges- tion of water. This is not entirely correct, for it has been shown that there is a slight retardation of the passage of bread from the stomach when water is taken after bread. Experiments with fistulous animals and anatomical and ;e-ray studies have shown, however, that water, when ingested alone, does not mix to any extent with the food mass in the stom- ach in its passage to the pylorus. A sort of trough is formed along the lesser curvature of the stomach through which the water flows from the esophagus to the pylorus. Practically neutral water has been observed to pass the pylorus when the stomach is full of food and the digestive processes are at their height. A large ingestion of water serves to increase the excretion of nitrogen in the urine. This effect is the result apparently of stimulated cellular activity and in part to a flushing out of the soluble nitrogenous end-products of metabolism. Mattill and Hawk have studied the influence of copious water drinking with meals and found a more complete utiliza- tion of food, protein, carbohydrates, and fat and decreased putrefaction and bacterial development in the feces. From the results of such work we may conclude that for the normal individual the ingestion of water with meals is not harmful. VITAMINES AND ACCESSORY FOOD-STUFFS. Investigations into the qualitative nature of food-stuffs necessary to body activity, growth and of certain diseases, such as beri ben and scurvy, have led to the conclusion that there are substances, apparently not protein, carbohydrate, fat or salt per se which are vitally essential to normal nutrition. These substances have been designated "accessory substances" or "vitamines." They occur in both plants and animals but appear to be present in greater concentration in some foods than in others. While these substances are present in animal tissues, animals are apparently unable to synthetize them and are therefore dependent upon plants or other animals for their vitamines. Two types of accessory substances have been detected: one, designated "fat-soluble A," is soluble in fats and accompanies them when isolated from food-stuffs. This VITAMINES AND ACCESSORY FOOD-STUFFS 95 substance is widely distributed among natural food-stuffs and is relatively thermostable. It is associated with lipins, such as those contained in butter fat, egg yolk, kidney fat, cod- liver oil and in relatively small quantities, but occurs in high concentration in the leaves of certain plants, particularly alfalfa and cabbage. The second type of accessory substance called "water-soluble B," is soluble in water and alcohol and is found in both the plant and animal world, e. g., in milk, eggs, meats, vegetables, and grains. It is thermolabile. The "water- soluble B" of McCollum is the vitamine of Funk, and is appar- ently the only accessory substance concerned in the cure of polyneuritis. A full recognition of the existence of such accessory sub- stances has come through two channels in particular, the study of deficiency diseases, such as beriberi and scurvy, and quali- tative studies of the diet, in which the rate of growth and incre ase inbody weight are taken as the critera of ist suffi- ciency or insufficiency. As an example of the first class of work we may take beriberi. In considering the diet of individuals sus- ceptible to beriberi it was noted that those living largely upon polished rice were more susceptible than those ingesting a diet of unpolished rice. It has been shown further that when chickens or pigeons are fed on polished rice they develop polyneuritis, a disease similar to beriberi, while those fed unpolished rice do not do so. They have therefore been used extensively in the study of substances capable of curing beri- beri. Analysis of rice polishings has shown them to be richer in phosphorus than other parts of the grain. Yet attempts to associate beriberi with phosphorus metabolism have had little success beyond showing that the accessory substances occur in those parts of grains rich in phosphorus. The injection of an alcoholic or water extract of rice polishings, of certain plants or of animal organs into birds affected with polyneuritis will bring about rapid recovery. Funk has made attempts to isolate the substance which is the active factor in such cures. He has obtained from rice polishings and autolyzed yeast a crystalline product possessing the property of curing polyneuritis even when given in as small quantities as a few milligrams. The exact nature of the material is unknown. Funk proposed the name vitamine for substances capable of curing "deficiency" diseases and suggests that it contains nitrogen of the amine type and that it is related to the pyrimidine nucleus. The substance prepared by Funk is soluble in water and alcohol, insoluble in ether, chloroform, benzene, and acetone; is destroyed by alkalis, but is more stable in the presence of acids; heat, that is by boiling for some 90 INORGANIC SALTS AND WATER time, destroys it. It is readily absorbed by silicious earth, Lloyd's reagent, and extracts prepared by this method have been found to be quite effective. Williams 1 has studied the effect of certain hydroxypyridine derivatives upon birds afflicted with polyneuritis gallinarum in an attempt to determine the nature of the vitamine of Funk. He found partial curative effects less satisfactory than the natural "vitamine" preparation with one of the isomeric forms of hydroxypyridine, while another isomer was entirely ineffective. From this and other considerations Williams came to the conclusion that isomeric changes are at least partially responsible for the instability of "vitamines" in food-stuffs and that antineuritic properties may be related to certain types of isomerism. Other diseases associated with nutritional disturbances seem to result from a lack of certain factors other than protein, fat, carbohydrate, or salts in the diet. Scurvy results from the continued ingestion of a restricted diet of salted and pre- served food — including pasteurized milk in the case of infants — and is cured by the ingestion of fresh food, especially fruits and vegetables. Pellagra is held by some to be due to a lack of accessory substances in the diet as the result either of improper selection of food, their destruction during cooking or their removal in the process of milling. The effect of diet in pellagra may be only secondary in that a deficient diet may be a predisposing factor to infection due to a decreased resistance. The second source of our knowledge of accessory substances, studies in which the rate of growth has been taken as a criterion of the sufficiency or insufficiency of a given diet, has perhaps been more fruitful than the study of diseases in extend- ing our conception of their relation to nutrition in general. Such studies were initiated originally to learn the effect upon nutrition of variations in the amounts and kinds of amino- acids in the diet. It was in the selection of a suitable diet consisting of simple purified food substances which would form the basis for subsequent variations in the diet that the impor- tance of accessory substances for growth became evident. It has been shown (Hopkins and Wilcox; McCollum and Davis; Osborne and Mendel) that when rats are fed on a prac- tically fat-free diet, composed of protein (such as casein or edestin), starch, and a suitable salt mixture which was entirely sufficient with regard to its energy, protein, and salt content, they did not grow normally, nor did they maintain their weight. 1 Jour. Biol. Chem,, 191 6, xxv, 437. VITAMINES AND ACCESSORY FOOD-STUFFS 97 The addition of lard to this diet yielded slightly better but still unsatisfactory results. When, however, milk was added to the mixture containing lard, growth would continue. In studying the constituents of milk which were responsible for this correction in the diet it was found that butter would accomplish the same result. To determine which constituent of the butter carried the accessory substance, the butter fat was separated from the other constituents, protein, salts, and water, by centrifugalizing warm butter. When this purified butter oil, a substance practically free from nitrogen and phosphorus, was fed the results were just as satisfactory as those obtained from ordinary butter, indicating that the active agent was con- tained in butter fat. This substance (or substances) is resis- tant to heat and a certain amount of chemical action for butter which has been heated with live steam or subjected to the process of saponification does not lose its efficiency. The fats closely associated with metabolic activity are more effec- tive in maintaining growth than "storage" fats, lard, beef fat, etc., which are in general ineffective or less satisfactory. The substance contained in butter fat remains efficient for over a year; while "butter oil," in which it is more concentrated, begins to lose its efficiency in half a year and becomes entirely inefficient in a year, even when kept at o° C. and in the dark. Egg yolk fat, cod-liver oil, kidney fat, the ether extract of ripe cod testicle and forage plants also supply the sub- stances necessary for growth. The liquid portion of beef fat obtained by fractional crystallization from alcohol will accom- plish similar results. Certain fats, such as lard, olive oil, cold pressed almond oil, the more solid portions of beef fat obtained in the preparation of beef oil, as indicated above do not con- tain this substance or substances. The deficiency is not due to a lack of the lipoids, lecithin and cholesterol, for phosphorus- containing substances are practically absent from butter oil, and lard contains a greater amount of cholesterol than butter. This active material bears certain quantitative relations to the diet, for there is a minimum value which must be present to produce results. McCollum demonstrated the presence of a water-soluble accessory factor in experiments in which it was noted that while satisfactory growth was obtained with a diet in which fats from butter, egg yolk, kidney, and also from plants were added to a fat-free diet of casein, dextrin, lactose and a suit- able salt mixture, if the lactose of such a diet be replaced by dextrin,, equivalent carbohydrate value, the diet was not effective in promoting growth. The addition of the water 98 INORGANIC SALTS AND WATER extract of egg yolk or the alcoholic extract of wheat germ to such a defective diet was sufficient to correct it. This led them to believe that lactose carried a water-soluble factor and that there were two factors necessary for growth in addition to the customary food-stuffs. Investigations of various lac- tose preparations served to confirm the suspicion with regard to the presence of the water-soluble factor and it has since been demonstrated in a number of foods. Further studies have brought out with renewed emphasis the variety of fac- tors which must be considered and controlled in the regulation of the diet and the possibility and the danger of neglecting modifying factors in our zeal to correct the most apparent defects. It has been found that in the case of rats, a diet containing a proper supply of protein, energy, salts, and "fat- soluble A" and "water-soluble B" may be apparently satis- factory for growth and reproduction, while a diet composed of naturally occurring food-stuffs may be inadequate because of the presence of a substance or substances which exert a toxic influence upon the body, but if to such a diet a substance containing a toxic substance be added, a failure to continue to grow may result. If, however, the protein portion of the diet be increased or a better, more complete protein be sub- stituted, the animal may continue to grow at a normal rate. The disturbances in metabolism accompanying a diet con- taining a large proportion of the wheat germ is apparently, in part, deficient for this reason. FASTING. The fasting state sometimes prevails in disease as a result of obstruction of the alimentary tract or the inability of the individual to retain ingested food. Conditions of under- nutrition from similar causes are much more common than complete fasting. Short fasts are often used in the treatment of various diseases. A knowledge of the changes in the body that result from fasting is of a purely scientific as well as prac- tical interest, for it aids in understanding and explaining the normal metabolism and certain pathological conditions. Life is accompanied by various cellular and systemic changes which we ordinarily designate as metabolism — pro- cesses of synthesis and of decomposition; oxidation with the liberation of carbon dioxide, water, and energy; the formation and disintegration of proteins, and the coordination of these activities in all parts of the body. Even though food no longer be supplied these processes continue. Since the losses sustained in metabolism are then no longer replenished from FASTING 99 ingested material, the more active and essential organs make use of similar substances contained in the body. Thus we find that the heart, brain, lungs, kidneys, testicles, and liver lose a much smaller proportion of their weight during fasting than do the muscles and adipose tissue. From this we con- clude that the former organs which are, in a sense, more essen- tial for life obtain the necessary food material from the blood which in turn is replenished largely from the muscle and adipose tissue. This process of drawing upon the tissues for continued activity is not an unusual one. There are undoubt- edly times between the ingestion of food, particularly late dur- ing the long interval between the evening meal and breakfast, when but little food is received from the alimentary tract and the body lives at the expense of its own stores. Not only does the body draw upon its own tissues for the material necessary for its activity but it appears to be able to utilize these much more economically than it does ingested food. In the light of our present knowledge of protein metabolism in which, as McCollum has expressed it, the pro- cesses of repair do not involve the destruction and resynthesis of entire protein molecules, it seems quite probable that one tissue is able to utilize in part the amino-acids which have been removed from material in another tissue and that the more or less complete disintegration of protein in one part of the body serves to supply material for the repair of the losses from a number of different tissues in other portions of the body. The activity of the kidneys, liver, and digestive tract are reduced to a minimum in fasting, for they are no longer required to take care of an excess of food-stuffs. The kid- neys are concerned only with the elimination of the products of endogenous metabolism which, as we know, is small in comparison with the exogenous metabolism of the average individual. The elimination of abnormal urinary constituents, as aceto-acetic acids and /3-hydroxybutyric acid or bile con- stituents is sometimes imposed upon the fasting kidneys. The period of time during which an organism may fast depends upon a number of factors. The previous nutritive condition has its effect in that the quantity of fat and protein which are available determines in part the body reserves. The size of the individual affects the rate of metabolism; small persons have in general a greater metabolism for the body weight than a large person. Age is accompanied by a varied rate of metabolism; children metabolize at a greater rate than adults and therefore utilize their body stores more rap- idly than an adult. The external conditions surrounding the body, such as temperature and humidity, may either increase or 100 INORGANIC SALTS AND WATER decrease the body activities. The ingestion of water tends to lengthen the period an organism may fast as compared with a fast without water. Finally, fasting experience in a given individual is a modifying factor; as the result of repeated fasts the body appears to acquire such a resistance that it is better able to withstand the effect of each subsequent fast. This appears to be particularly true when the organism is permitted to recover from the previous fast before being subjected to another. Men have fasted for as long as fifty days without apparent harm. There are authentic records of a number of thirty-day fasts. Benedict 1 has recently reported the result of a most care- ful study of a thirty-one-day fast by a man. Animals have been known to fast for much longer periods. The longest fast of a warm-blooded animal is that observed in a dog which con- tinued for 117 days, after which the animal was fed and restored to its original condition and fasted again for the second longest fast, 104 days. Cold-blooded animals, such as the frog, salaman- der, etc., have been known to fast for much longer periods of time. It is evident, therefore, that the body can obtain from itself sufficient material on which to exist for a considerable length of time. Death, as the result of fasting in the case of normal individuals, is probably due to the failure of some organ or tissue and not to the complete utilization of the body stores. Certain investigations seem to show that a definite minimum quantity of nitrogen-containing material is necessary in order that life may exist. During a fast the general rate of metabolism is lowered. Studies of the respiratory changes show that the total quan- tity of carbon dioxide excreted per day is lowered, and the res- piratory quotient falls to a value which indicates the oxida- tion, chiefly, of fat and protein. Protein metabolism is also decreased; the daily nitrogen excretion after the first few days becomes low and fairly constant. It may fall as low as 4 to 6 grams of nitrogen per day. The excretion of salts is also diminished. All phases of normal body metabolism are greatly reduced in fasting. 1 Benedict has reported a very complete experiment on a man during a thirty- one-day fast, Carnegie Institution of Washington, 1914, Pub. No. 203. The data from this fast are published in chart form in Mathews's Physiological Chemistry, New York, 19 15. CHAPTER V. NORMAL FEEDING AND FOOD ECONOMICS. The application of the principles of human nutrition to the feeding of the normal individual or to the family group is at once involved and difficult. Though the scientist may deter- mine and the physician prescribe an ideal dietary, its adop- tion by the individual may be quite impractical, due to cost, inconvenience, or lack of market facilities. But since foods are interchangeable within wide ranges, a summary of the prin- ciples of nutrition which underlie the selection of food, together with typical menus and a discussion of the cost of food may aid in the interpretation and application of these principles. Our previous discussion of the various food-stuffs and their digestibility has shown that the source of food is of no par- ticular-importance so long as it possesses all of the necessary material and is wholesome, that is, does not contain or yield products which are detrimental to the health of the normal individual. For example, disregarding for the moment, the psychological factor, the stomach and intestines can digest a cheap cut of meat or fish as thoroughly as an expensive steak; American cheese as well as Roquefort cheese; cotton-seed oil as well as olive oil. The psychical factor cannot, however, be completely ignored for two reasons : i. Studies of the secretion of the digestive juices and of the rate with which food passes from the stomach indicate that appetite, which in its psychological sense is to a large extent the reflex of palatability, serves to stimulate an early flow of gastric juice and thus facilitate digestion. Once a food is digested and absorbed its value to the body is mainly a matter of its intrinsic composition. 2. A diet which contained all of the necessary food fac- tors might still prove to be unsatisfactory because of psychi- cal objections on the part of those who are to eat it. Such factors as habit, taste, and custom must be taken into con- sideration. The likes and dislikes for food are to a large degree governed by the kind and variety of food, method of preparation, etc., which have been observed in the household or community in which individuals are reared — a change of the usual dietary regimen is accepted with hesitation, which can only be overcome by palatability or force of will. If, in the latter case, the diet prove to be unsatisfactory, its 102 NORMAL FEEDING AND FOOD ECONOMICS continuance is accomplished with greater difficulty or not at all. On the other hand, food well prepared is usually accept- able. It is the factor of palatability, based largely upon the proper selection and preparation, which determines the success or failure of diets selected because they are economical. Pala- tability is, as we have said before, entirely a relative factor, tempered by custom. The diet of the Eskimo, rich in fat and very high in protein, is apparently satisfactory to him. The peasant's diet of porridge and black bread is acceptable, while added white bread or meat constitute luxuries. The absence of choice meats, rich sauces or sweets from the diet of the well-to-do American is regarded as a hardship. A variation of diet outside the range of the dietary habits is a matter of acquired taste or necessity. When it is necessary or desirable to cause a marked change in a diet, careful preparation and serving will do much to accomplish that purpose. A diet which will supply the needs of the body must contain: (a) Energy-yielding food sufficient in quantity to supply the basal energy requirement and to meet the increased need resulting from activity. The energy may be derived from the oxidation of protein, carbohydrate, or fat, although the require- ment beyond that obtained from the protein necessary in other relations, and a minimum amount of fat, is satisfied chiefly by carbohydrates. (b) Protein, containing the necessary amino-acids, or in variety which will yield them in sufficient amount. (6') Carbohydrate. (d) Lipihs (fat), natural and unmodified. ( «f t+-( -t-> W).i5 "3 ' rd ■a O ±2 , ° mS 0-, 03 w WfQQ CD S MO oj^ 8*03 O CU ° CD u 106 NORMAL FEEDING AND FOOD ECONOMICS The table on page 105 suggests the fuel value or calories for the meals of a day apportioned among the various types of foods suitable for persons of different ages, under normal conditions. In this table a distinction is made between the starch-rich vegetables which supply considerable quantities of energy in the form of carbohydrates and the green vegetables which are particularly valuable for the bulk which they give to the contents in the alimentary tract, because of the indigestible cellulose contained, and for the salts and accessory substances in which they are particularly rich. The dishes classed as meat may often be combined with another class of food such as starch-rich foods or milk, as for example meat-pie, creamed beef, or oyster stew. It must again be emphasized that the physician who" pre- scribes as well as the housekeeper who plans meals for a fam- ily must be sufficiently familiar with the composition of most of the common foods to be able to class them as valuable sources of protein, fat, carbohydrate, or salts. If they do not possess this knowledge one type of food may exceed its most satisfactory proportion in the diet. It is necessary, too, that correct dietary habits be established by children. Prefer- ence for a particular food must not lead to the habit of "mak- ing a meal" of it. Likes and dislikes for food are largely a matter of habit, and the importance of an early establishment of good food habits cannot be overestimated. While it is not necessary that each meal or the combined meals of one day be complete in meeting the requirements of an individual, such a balance should be approximated and satisfied at least within the course of a few days. The following menus, and the table giving the relative proportion of protein, fat and carbohydrate in them, will serve to illustrate the possibility that even in an apparently well selected diet, some one food- stuff may predominate. Examples of one-sided diets, predominantly protein, fat, or carbohydrate and an analysis of their composition have been given by Langworthy. 1 Menus with Protein Predominating. Breakfast: Cereal cooked in milk, chicken hash with egg, popovers, butter, and milk as a beverage. 1 Scientific Monthly, 1916, ii, 294. SELECTION OF DIET 107 Dinner: Dried-bean puree, halibut steak, potatoes scal- loped in milk, tomatoes stuffed with chopped beef, bread and butter, and frozen custard with nut cookies. Lunch or Supper: Baked beans, nut bread and butter, old- fashioned rice pudding, and a glass of milk. Menus with a Large Proportion of Fat Breakfast: Oatmeal with cream, sausage, and corn bread and butter. Dinner: Cream of tomato soup, mutton chop with creamed potatoes, greens cooked with bacon or pork, bread, and suet pudding with hard sauce. Lunch or Supper: Creamed salmon, lettuce with oil dressing, tea biscuits and butter, pumpkin pie and a cup of chocolate. Menus with Carbohydrate Predominating. Breakfast: An orange followed by corn cakes with maple syrup, and bread or toast and butter. Dinner: Meat pie and baked potato, green peas, bread and butter, and cottage pudding with chocolate sauce. Lunch or Supper: Rice croquettes with jelly, rye bread and butter, baked apples, and sugar cookies. The Composition of the Nutrients and the Energy Supplied by the above menus used for illustration. Protein meals: Weight of edible food served, gm Protein, gm. Fat, gm. Carbo- hydrates, gm. Fuel value Calories. Breakfast Dinner Lunch or supper • 471 772 639 36 58. 33 50 64 38 54 120 105 8lO 1288 894 Total . . . 1882 127 152 279 2992 Fatty meals: Breakfast Dinner Lunch or supper • 353 617 621 24 33 29 69 88 83 58 108 98 949 1356 1259 Total . . • I59i 86 240 264 3564 Carbohydrate meals: Breakfast Dinner Lunch or supper 509 529 376 15 40 14 32 33 27 168 133 127 1020 989 807 Total 1414 69 92 428 2816 108 NORMAL FEEDING AND FOOD ECONOMICS Cost of Food. — No discussion of the question of normal nutri- tion is complete without a consideration of the cost of food. To those persons into whose hands falls the planning of a dietary for the normal family, the problem is not entirely one of furnishing a diet in which correct relative amounts of pro- tein, fat, carbohydrate, mineral constituents as well as accessory substances are provided. Their problem is, in addi- tion, to select such a diet which can be supplied at a cost not exceeding a fair proportion of the income of the family. The following table shows the proportion of the income to be spent for food, suggested by the Russell Sage Foundation, as suitable for the normal family, consisting of father, mother, and three children. Proportion of Income to be Spent for Food. Amount per day Income Percentage for Total for food for family of Amount per day per year. ood per year. per year. five. per person. $500 .... 55-0 $275 $0.75 $0 15 800 45-6 365 I. OO 20 IOOO 45-0 450 I.20 24 I IOO 44.6 490 i-34 27 I200 45-0 540 1.48 29 + I500 36.8 552 1.50 30 2000 30.0 600 1 .64 33 Fortunately there is not a direct relation between the cost of food and its nutritive value. An inexpensive diet, so far as the needs of the body are concerned, may be as satisfactory as an expensive diet. Too often, however, lack of knowledge and training in the selection and preparation adds unduly to the cost of food, especially among the poorer classes who can least afford unwise expenditures. The physician is particularly interested in prescribing a diet which contains the special nutrients needed by his patient at a cost within the means of the family. Too often diet lists are not flexible, although good results might be obtained by the use of other and less expensive equivalents. The'work of Hess in studying the effect of extract of orange peel and potato water as a preventative of scurvy in infants has shown possibilities in this direction. It would seem, then, incumbent upon the purchaser of the family food supply to familiarize herself with the composi- tion of the common foods and at least roughly with the cost in relation to their total food values. The following tables show foods typically high and low in cost in proportion to their food values. 1 1 Bevier: Planning of Meals, Univ. of 111. Bull., 191 4, xi, No. 30 COST OF FOOD 109 Foods Low in Cost in Proportion to Their Total Food Value. 1 2 Grams of Cost per protein in pound Calories Ounces in Cost of 100 100-Calorie Kind of food. (Jan., 1913). per pound. 100 Calories. Calories. portion. Cornmeal . $0,025 1655 .96 $0.0015 2-59 Wheat flour .03 1655 96 .0018 3-87 Oatmeal . •45 i860 86 .OO24 4.20 Sugar, granulated . .06 i860 86 .OO32 0.00 Beef heart . •05 1320 I 21 •OO37 6.40 Beans, navy dried . .062 1605 99 .OO38 6.82 Cross ribs of beef . .08 1765 906 .OO4O 5.10 Lard, best leaf . .18 4220 37 .0040 0.00 Potatoes at $i bushel .016 385 4 15 .0041 2.64 Peanuts, shelled . 12 2560 62 .OO46 4.69 White bread .07 1225 1 30 •OO57 3.60 Brisket of beef . •07 H65 1 37 .OO60 4.90 Rice .10 1630 98 .0061 2.28 Oleomargarine . .22 3525 45 .OO62 0.00 Flank of mutton •125 1900 85 * .OO65 3-75 Bacon .... .20 3030 52 .0066 1.68 Dates .... .10 1450 1 10 .OO68 0.61 Corned beef .14 I99O 80 .0070 5.22 Skim milk at $0.10 gal. .0125 170 9 40 •OO73 9.26 Whole milk at $0.10 qt .046 314 5 09 .OIOI 4.76 Salt mackerel . .10 "55 1 38 .0086 565 Butter . ... . •36 3605 44 .OO99 4-54 Cheese, cheddar .22 2145 74 .0120 6.50 Walnut meats . •45 3300 48 •0139 2.61 Round steak •15 895 1 70 .OI67 12.62 Foods High in Cost in Proportion to Their Total Food Value. 1 2 Grams of Cost per protein in pound Calories Ounces in Cost of 100 100-Calorie Kind of food. (Jan. 1913). per pound. 100 Calories. Calories. portion. Mushrooms . $0 •65 2IO 7.6 $0,309 $7-54 Lettuce . •15 75 21-3 .200 5-44 Lobster, fresh . •25 140 II. 4 .178 19.07 Black bass . •30 205 7-8 .I46 20.56 Chicken, broiler •30 295 5-4 .101 19.6 Sweetbreads .80 825 i-93 •095 905 Oysters . .20 230 6.9 .087 12.27 Cauliflower . . 12 140 11. 4 •O85 ' 8.16 Rhubarb •05 65 24.6 •077 2.79 Celery •05 70 22.8 .070 4.08 White fish . . .20 325 4.9 .06l 14.72 Oranges . .10 170 9-4 .058 1.6 Tenderloin of beef .60 1330 1 .2 ■045 5-51 Porterhouse steak •30 IIIO 1.44 .027 7.8 Sirloin steak •25 985 1.62 .025 7-58 Roquefort cheese •45 1700 ■94 .024 6.02 Leg lamb, medium fat .18 870 1.80 .020 8. 11 Rib roast, medium :at .20 ii55 1.38 .017 5-52 1 Based on Bulletin 28, "Composition of American Food Materials." Office of Experiment Stations, U. S. Dept. of Agriculture. 2 The] prices given do not apply to the present time (191 7), when the cost of food may be considered as abnormal. It has seemed best, therefore, to give prices which obtained previous to 1914. These prices are to be considered as representing the comparative monetary value of food. 110 NORMAL FEEDING AND FOOD ECONOMICS It is readily seen from such tables that but few foods are obtainable at a cost of less than one-third of a cent per ioo Calories and that few of the foods in the first table are perishable or difficult of transportation. Fresh fruits and vegetables, fresh meat, milk and eggs all cost one cent or more per ioo Calories. Lusk and Murlin have suggested that the labels on food containers should indicate the energy value of the contents and the percentage of protein contained. The nature of the proteins would be indicated by letters — complete proteins, such as animal proteins would be designated as Proteins, of "Grade A," while incomplete proteins, such as gelatin, would be "Grade D." Mixtures of complete proteins "A" and incom- plete proteins "D" are in what would be marked "Grade B," while foods containing a large proportion of incomplete pro- tein, as corn, would belong to "Grade C." The label might read: "This can contains X calories of which Y per cent, are in protein of "Grade C." Mention should be made of the work of Gephart and Lusk upon the cost of portions of food sold in the Childs restau- rants in New York City. A tabulation of their results shows the purchasing power of five cents in these restaurants. These data indicate strikingly that a wise choice means a sufficient meal at a low cost, while poor judgement may result in a low food value at a much higher cost. Purchasing Power of Five Cents in Childs' Restaurants. O 03 °S "9 13 Orders, classed as: 3 u Highest of class in fuel value. £ 2 . Lowest of class in fuel value. a o S3 to t * - 03° -3° 03 ■a » -3° < O Pastry 233 Napoleon 45 Strawberry short- cake ... 92 Beans 204 Boston baked 308 Boston baked beans "on the side" . 134 Sandwiches . 180 Roast-beef sand- Sliced chicken wich with roll 358 sandwich . 78 Dairy dishes 174 Milk crackers 317 Cream of wheat . 63 Meats . . . 174 Lamb croquettes and mashed potatoes . 291 Deviled crab . 83 Oysters . 149 Oyster pie 220 Raw oysters . 19 Eggs .... 141 Plain omelet 231 Poached eggs on toast 66 Salads 136 Potato salad 217 Crab-meat salad . IOO Soups 116 Beef stew 251 Tomato soup with rice .... 37 Fruits 89 Baked apple with cream . 196 Cantaloupe 12 COST OF FOOD 111 In this connection a summary of a series of menus suggested by Miss Rose, shows modifications to comply with cost within certain limitations. A detailed study of quantities used, with the proportion of protein calories to total calories, is given by her to show how the total fuel value may be maintained within safe margins, though the cost of the first menu, ij to 2 cents per 100 Calories, is reduced to | to f cent per 100 Calories in the fourth menu. Typical Menus of Varying Cost of a Family of Eight. 1 Requirements of family (man, woman, baby one year, boy three years, two girls six and nine years, boy twelve years, grandmother ninety years). Protein Calories, 1424-2061. Total Calories, 14.252. Menu I. Menu II. Menu III. Menu IV. lf-2 c. per 100 Cal. li-lj c. per 100 Cal. i-1 c. per 100 Cal. f-f c. per 100 Cal. Breakfast. Oranges. Oranges (small). Bananas (prune pulp Stewed dried apples. Wheatena with top milk. Puffy omelet with bacon. Toast, coffee, milk. 1U1 LVVU ^UUU^COi;. Wheatena with top Wheatena with top milk. milk. Toast, coffee, milk. Toast, coffee, milk, cer- eal coffee. Mid-day Meal. Cornmeal mush with milk and sugar. Bread, pork fat; sau- sage for father and mother. Cereal coffee for older children and adults. Milk. Creamed chicken on toast. Baked bananas. Boston brown bread. Rice pudding. Tea, milk. Creamed dried beef on toast. Baked bananas. Boston brown bread. Rice pudding. Tea, milk. Macaroni and cheese. Stewed apricots. Boston brown bread. Oatmeal cookies. Tea, milk. Baked samp, with cheese. Stewed raisins. Oleomargarine. Brown bread. Oatmeal wafers. Tea for adults, cocoa for children. Consomme. Baked halibut, egg sauce. Potatoes on half shell. String beans, buttered. Bread and butter. Evening Meal. Baked halibut, white Creamed salt cod. sauce. Potatoes on half shell. Baked potatoes. String beans, buttered. Boiled onions. Bread and butter. Bread and butter. Beef stew with vege- tables. Bread and oleomargar- Tomato salad, French dressing. Apple snow with boiled custard. Lady fingers. Cold slaw. ine. Chocolate blanc mange cream and sugar. Plain cookies. Rice pudding, cream and sugar. Date pudding with liquid sauce. Protein Calories, 2202. Protein Calories, 2106. Protein Calories, 1791. Protein Calories, 1526. Total Calories, 14,410. Total Calories, 14,414. Total Calories, 14,330. Total Calories, 14,299. The factors which influence the cost of various foods are, as we have noted before, in many cases independent of their food values, but depend upon quite external conditions, such as source, perishability, supply and demand, proportion of waste, etc. This is particularly true of our most expensive food-stuffs. An understanding of the relative cost of food necessitates, therefore, a knowledge of the factors which underlie the relation between food value and cost. 1 Rose: Feeding the Family, New York," 1916. 112 NORMAL FEEDING AND FOOD ECONOMICS Our food is derived from two sources, animal and vegetable. Animal foods are particularly valuable as a source of protein and fat; they contain little carbohydrate. Vegetable foods are our chief source of carbohydrate, and they are to a less extent a source of protein. Both animal and vegetable food supply inorganic salts and accessory substances; green vege- tables are valuable largely because of these materials. Food derived from animals fed with cultivated fodder is much more expensive than the vegetable foods used in its production. This is true because animal food is developed largely at the expense of vegetable food; a process the efficiency of which is comparatively low. Furthermore, animals must often be kept for a period of years for their proper develop- ment, during which time they must be carefully tended; and they are also subject to disease with the possibility of loss by death. Flesh foods obtained from wild animals, such as fish and game, might be relatively cheaper because the only factors of cost involved are those of catching or killing the animals, preserving and sending them to the market. Although game may be procured cheaply, it is expen- sive to the average individual because of its scarcity. Similarly, fish is expensive in certain parts of the country because of the cost of transportation and storage. The perishability of fresh animal food also tends to make it expensive. With the exception of the isolated fat products, meat decomposes rapidly at ordinary temperatures. It must be preserved therefore by processes which are comparatively expensive, such as refrigeration. Furthermore, care must be exercised in handling it to prevent contamination. In addi- tion there is a certain loss by deterioration when such food passes through the hands of the retailer, and this loss must be made good in the price charged for the remainder. Various methods of preservation of animal food in com- mon use operate to lower its cost to the consumer. Cold storage or refrigeration is a comparatively expensive process of preservation and tends to increase the cost of flesh foods; in spite of this it is a means of actually reducing the cost of such foods because it permits the slaughter of animals in large quantities and their transportation to the consumer with a relatively low loss by deterioration. Refrigeration permits the storage of other perishable animal food, such as eggs, in seasons in which they are plentiful. The net result of such preservation is a gain to the consumer, for while it tends to increase the cost when the foods are in season, it brings the cost of the same food out of season below what it would be were there no refrigeration. COST OF FOOD 113 Other methods of preservation, such as drying (beef and fish), smoking, pickling, and canning, which do not require extensive refrigeration and which are performed where the supply is plentiful, also tend to lower the cost of animal foods. Processes which involve special manipulation of the food, such as the preparation of cheese and the extraction of fat, are also means of lowering the cost of animal foods. Plant foods are cheaper sources of food material than animal foods. They are used directly and the only loss to the body is that which results from a failure to absorb or to utilize them completely. Their cultivation is comparatively simple, and they mature in one season. Artificial preservation is not so essential and, when practised, is comparatively cheaper than the preservation of more perishable foods in their natural state. Plant foods, such as carrots, potatoes and apples when ripe can be stored for some months; with little deterioration; with a slightly increased expense for cold storage they may be kept for even longer periods. Foods which would decay at ordinary temperatures, such as oranges, can be preserved in cold storage. Many plant foods are pre- served in the dry state. Some become relatively dry before they are gathered, such as the legumes — beans and peas — and the grains — corn, oats, and wheat; while other foods used extensively in the fresh state — prunes, apples, apricots — are dried under special, artificial conditions. Milling of cereals and grains helps to extend the period of preservation without deterioration; this is particularly true of fat-rich grains, such as corn. Some plant foods, such as corn, peas, and tomatoes may also be preserved in the fresh, water-rich state by canning. This is done at times when they are plentiful and in districts in which they are produced, thus furnishing a supply of these foods at reasonable prices during seasons in which they would otherwise be unobtainable. Many foods which appear cheap, i. e., are sold at a low cost per pound, are in reality expensive on account of the large amount of waste in skin, bone, seeds, etc.; for example, a chicken weighing 4.65 lbs., costing 16 cents per lb. alive, weighed 4.09 lbs. dressed, and yielded but 1.11 lbs. cooked meat, which brought the cost up to 74 cents per pound. Small prunes prove more expensive than larger ones costing 5 to 8 cents per lb. more, owing to the greater waste in skin and seeds of the smaller prunes. The cost of food is also influenced by supply and demand. In the case of meat, the demand for special cuts of which there are but a few in each carcass, such as tenderloin steaks and sweetbreads, results in prices which are out of proportion 114 NORMAL FEEDING AND FOOD ECONOMICS to the food value of these cuts. These unnatural prices react favorably upon the less desirable cuts, for they are sold at some- what lower rates. Other animal foods, such as game and shad-roe, are plentiful only at certain seasons of the year. Vegetables which are difficult or expensive to cultivate, such as mush- rooms, or are rare or transported long distances when out of season in a particular locality, bring high prices. The relation between supply and demand, and the lack of correspondence between food value and cost, is well illustrated by meat. Studies of the food value of the various cuts bring out the fact that the cost of protein — and meat is most valuable because of its protein content — increases roughly 1.75 per cent, from the tougher cuts to the most expensive cuts of beef. The relative costs of the protein for 1000 Calories in the various cuts of beef are indicated in the following tables which may be used in conjunction with the table and charts on pages 143-146. Cost of Meat Required to Furnish One Pound of Protein and 1000 Calories from Wholesale Cuts at Market Prices. 1 2 Retail Boneless Cost of pound Cost of Cost of price per meat in boneless pound 1000 Cal- Wholesale cuts. pound, the cut, meat in cut, protein in ories in cents. per cent. cents. cut, cents. cut, cents Fore shank . • • 5 59 -56 8.4 50 7 Hind Shank 5 48 84 I0.2 63 9 Neck . . 6 84 31 7-i 46 5 Flank 8 99 44 8.0 85 3 Plate 8 91 23 8-7 82 4 Clod . 10 95 18 10.5 63 10 Chuck 11 87 99 12.5 84 9 Rump 12 79 85 15.0 119 8 Round 15 90 39 16.6 101 15 Rib . 18 85 56 21.0 171 11 Loin . 22 90 23 24.4 188 H Relative Fuel Values of the Boneless Meat of the Wholesale Cuts. 12 Pounds of aoneless meat c Calories furnished by 100 grams of Percentage distribu- required to boneless meat. tion of Calories. furnish 1000 1 "'at x 9. Protein x 4 Total. In fat. In protein. Calories. Flank . . 514.4 4O.5 554-9 92.7 7-3 O.4O Plate 137 • 1 46 483 1 90 5 9 5 O.46 Rib . 365 -6 54 1 419 7 87 1 12 9 O.52 Rump 350-5 55 3 405 8 86 4 13 6 0-54 Loin . 339-4 57 4 396 8 85 5 14 5 O.56 Chuck 247.9 65 8 313 7 79 21 O.70 Neck 235.1 67 9 303 77 6 22 4 0-73 Hind shank . 186.9 7i 257 9 72 5 27 5 0.86 Fore shank . 179.8 73 9 253 7 70 9 29 1 0.87 Round [76.9 73 6 250 5 70 6 29 4 0.88 Clod . [61 6 73 5 2, 35 68 7 3i 3 0.94 1 Hall and Emmett: Univ. of 111. Agri. Exp. Sta., 1912, Bull. 158. 2 See foot-note, page 109. COST OF FOOD 115 Cost of Lean and of Total Meat in the Various Retail Cuts at Market Prices. 1 2 Cost per Retail Cost per pound of pound of Diagram price per pound of lean and fat Retail cuts. number, lean meat in meat in p. 145. cut, cents. cut, cents. cut, cents. Steaks : Porterhouse, hip-bone . 8 25 3 8.6 28.9 Porterhouse, regular 10 25 4O.2 27.2 Club steak 18 20 32.1 22.6 Sirloin, butt-end . . . . I 20 25-3 20.6 Sirloin, round-bone . 3 20 28.3 21 .1 Sirloin, double-bone 5 20 28.7 22.7 Sirloin, hip-bone 7 20 32-3 24.2 Flank steak i 16 19-3 I6.0 Round, first cut .... 2 15 17.O 15-3 Round, middle cut ... 6 15 17-3 15-6 Round, last cut .... H 15 19-3 I6.0 Chuck, first cut .... 2 12 18.3 14. I Chuck, last cut .... 9 12 15-7 131 Roasts: Prime ribs, first cut . i 20 40- 5 22.9 Prime ribs, last cut . 4 16 26.1 18.8 Chuck, 5th rib ... . i 15 22.8 17-3 Rump i 12 19.4 12.8 Boiling and stewing pieces: Round pot roast . 16 IO 11. 6 10. I Shoulder clod .... • H 10 12.3 10.5 Shoulder pot roast . ii 10 14-3 11. 6 Rib ends 3 8 16.2 9.2 Brisket i 8 15.0 8-7 Navel 2 7 12.8 7-7 Flank stew 2 7 10.9 7i Fore shank stew .... I 7 8-5 7.0 Neck . 15 6 8-5 7.0 Soup bones: Round, knuckle .... 2 5 26.3 12.5 Hind shank, middle cut 18 5 7-5 6-3 Hind shank, hock 19 5 62.5 26.6 Fore shank, knuckle 2 5 17.2 12.5 Fore shank, middle cut . 4 5 12.5 9-4 Fore shank, end .... 6 5 28.8 20.9 The cost of lean beef is a rough index of the relative economy of steaks and roasts; in comparing boiling and stewing meats, however, the cost of both fat and lean, gross meat, should have more weight because in the utilization of these cuts the fat is usually incorporated with the lean in the form of meat loaf, hash, hashed meats (Hamburger steak), and corned beef. Since soup bones are of particular value for their flavoring material, their food value is not entirely comparable with the other portions of the carcass, as can be seen from the table. From the table we can see that the cheap cuts of meat actually furnish protein at a much lower price than the expensive cuts. It is to be remembered that in purchasing cheaper cuts of meat one often receives a larger proportion of connective 1 Hall and Emmett: Univ. of 111. Agr. Exp. Sta., 1912, Bull. 158. 2 See foot-note, page 109, 116 NORMAL FEEDING AND FOOD ECONOMICS tissue with its incomplete protein, gelatin, than in the case of the more expensive cuts; this lowered food value is, however, more than compensated by the decreased cost of the complete protein. Fish may be used to vary the diet or as a source of relatively cheaper protein food; they are practically interchangeable with meat and are in general less expensive. In considering animal and vegetable food from an economic point of view, it is necessary to know whether the food-stuffs of the same kind which they contain are of equal value to the body; otherwise the apparently cheaper food may be in the end actually more expensive. Such considerations are par- ticularly important with regard to protein. Comparative studies of the digestibility of foods have shown that as ordi- narily prepared the protein of animal food is more completely absorbed than the protein of vegetables — meat protein, 91 to 97 per cent.; vegetable proteins 80 to 85 per cent.; bread protein, 70 per cent.; rye protein, 40 to 76 per cent.; barley protein, corn protein, 61 to 83 per cent. The lower degree of absorption of vegetable proteins is due chiefly to the cellulose layer which surrounds the protein and prevents its digestion. A larger amount of total food in general must be ingested to obtain the same amount of protein from vegetable than from animal protein. In finely ground cereals and legumes, how- ever, the protein has been found to be as thoroughly digested as animal protein. Certain vegetable proteins are low in their content of the amino-acids necessary for growth and maintenance; but associated with these are other proteins which contain the necessary amino-acids. Consequently the natural mixture of proteins is more or less complete and unless par- ticular isolated or concentrated deficient proteins are involved, vegetable proteins may be used as the sole source of protein. That animal proteins are more efficient in satisfying the body needs than vegetable proteins has been found in studies of the comparative utilization of animal and vegetable proteins. A comparison of proteins of different origin on the basis of their availability (biological value) to the body has shown that the different quantities of protein indicated when added to a carbo- hydrate diet will protect the body from protein loss after it has been reduced to a minimum on a purely carbohydrate diet: Grams. Meat protein 30 Milk protein 31 Rice protein 34 Potato protein 38 Bean protein 54 Bread protein 76 Indian corn protein . 102 ANIMAL VS. VEGETABLE FOOD 117 It is evident, therefore, that naturally occurring protein mixtures of vegetable origin are not as efficient as animal protein and that larger quantities must be ingested not only because of their lower digestibility but also of their lower biological value. The economic question with regard to the use of proteins of animal and vegetable origin therefore resolves itself into which is cheaper, the ingestion of a large amount of vegetable protein or a smaller amount of animal protein. The answer must be tempered by a consideration of the increased activity of the body required to metabolize and excrete the excessive unavailable amino-acids of vegetable origin and of the pos- sible effect of such increased activity upon the general well- being of the body. It is impossible at present to answer the question. When our knowledge of the amino-acid content of proteins is sufficiently developed we may be able to furnish the deficient amino-acids of an economical diet with compara- tively small quantities of a more expensive protein. Even now we recognize the advisability of using a certain propor- tion of protein of animal origin with vegetable protein, for safety; there are very few diets which do not contain such protein, at least in the form of milk, eggs, or cheese. The inclusion of protein of animal origin in the diet is commendable from another point of view, for with the animal protein is purchased a certain amount of fat, a food of high caloric value. This addition of fat is desirable because it reduces the quantity of bulky carbohydrate food which must be ingested to meet the energy requirement of the body and also because it meets the need of a certain proportion of fat which would otherwise have to be purchased separately and added to the diet. A diet consisting largely of vegetables has been objected to on the ground that it is bulky; that a large quantity of food must be eaten in order to obtain sufficient protein, or else one must live on a low protein diet, for, with the exception of legumes and nuts, vegetable foods are relatively poor in protein. Since hunger is satisfied not so much by the quality of the food as by the quantity which is ingested, the appetite is in danger of being satisfied before sufficient material has been consumed to supply the protein requirement. For this reason and because vegetable proteins are less completely absorbed and less efficient in the body economy than animal protein a strictly vegetable diet is likely to be a low protein diet. It has been maintained by people who restrict their diet largely to vegetables, that they are able to utilize their food 118 NORMAL FEEDING AND FOOD ECONOMICS more efficiently and that the body activities take place at a lower level than those who eat meat. Benedict has shown, however, that the basal metabolism of vegetarians is not essentially different from that of those living upon a mixed diet. It is possible that a vegetarian may be able to live on a low protein diet more readily than a man upon a high pro- tein, meat diet, because of the retarding effect of the indiges- tible cellulose upon the rate of digestion and of the absorp- tion of products of digestion of vegetable proteins. Experi- ments have shown that the admixture of indigestible material results in a more uniform rate of excretion of nitrogen in the urine than in the absence of such material; the inference is that the absorption from the intestine is likewise slower. On a vegetarian diet, then, instead of the rapid absorption of protein products of digestion and the disintegration of the excess characteristic of a high protein diet, the material is absorbed more slowly and the amino-acids are consequently more completely utilized for actual processes of repair and of growth. Proof of this fact has been presented in which a man was able to maintain nitrogen equilibrium on a lower plane of protein ingestion when food was taken in small amounts a number of times a day than when food was taken less often. In determining the value of a diet from an economic point of view consideration must be given to the quantity, propor- tion and kind of inorganic salts which it contains. While the average mixed diet contains a sufficient quantity of calcium, phosphorus and iron for the needs of the normal adult, the diet of children and nursing and pregnant women requires special attention in order that the mineral constituents be present in suitable proportions. A diet to be satisfactory with regard to its content of inorganic constituents must have the salts present in quantities which will meet the needs of the body and in such a form that the ash does not predominate potentially in acidic constituents — the same applies to foods which are potentially basic but to a much less degree, for an excess of base is not as harmful as an excess of acid. From a consideration of the kinds and quantities of inor- ganic elements in foods it is evident that the vegetable foods and eggs are, in general, rich in calcium, iron and phosphorus and yield an alkaline ash (oatmeal yields an acid ash), while the ash of the egg is acid; meat is rich in iron and phosphorus and poor in calcium and has an acid ash; milk and cheese are rich in calcium and phosphorus, poor in iron and yield an alkaline ash. Certain foods, particularly the prepared and purified products of both plant and animal origin, such as the fats and sugars, are very poor in salts. ANIMAL VS. VEGETABLE FOOD 119 A diet in which vegetables and milk or cheese are the chief source of protein will therefore be predominately basic and contain, from a quantitative point of view, the most impor- tant inorganic constituents. In such a diet the low iron con- tent of milk or its protein products is compensated by the relatively high iron content of vegetables. A diet in which meat or eggs predominate will, on the other hand, tend to lower the alkaline reserve on the body, because of the acid ash, and meat will at the same time be deficient in calcium, while eggs will furnish this element in comparatively large amounts. Milk and cheese are therefore much more desirable not only as an economical source of animal protein but also for the salts contained in them. They can be included to advantage in a diet even when their cost is comparatively high. Eggs are next in order when the ash constituents are considered, and meat is the most expensive. PART II. FOODS. CHAPTER VI. INTRODUCTION— MILK. The preceding chapters have dealt with the digestion, absorption and utilization of food; and the factors which determine the quantity and nature of food required for the needs of the human body. The discussion was confined almost entirely to the materials which are the basic ingredients of food — protein, carbohydrate, fat, salts, water, and accessories. Oxy- gen is also a food; its presence is so general, however, that it is ordinarily omitted from a quantitative discussion of diet. Any food in the general sense is composed of one or more of these ingredients. One food may contain a preponderance of protein, another of fat, etc. For the discussion of the various foods, a basis of classification is necessary. A classification may be based upon the origin or composition of foods, or on the need which they supply. In the following chapters we classify foods according to their composition in terms of food-stuffs. For complex foods the particular food-stuff* for which they are most valuable to the body determines the placement of them in the classification. Thus, we shall consider protein foods; fat foods; carbohydrate foods; and foods valuable for their salts, water, or accessory constituents, such as fruits, condiments, and beverages. A classification of this kind not only empha- sizes the principal use of the food, but also aids in the search for foods that supply the elemental food factors; and it differs from the usual method of considering only the origin of foods in that there is no distinction recognized between vegetable and animal food. The dried legumes are placed with the protein-rich foods and certain animal products are placed with the fats. There is one food, however, which is difficult to classify under these circumstances but which is of sufficient importance to be considered alone, viz., milk, for it is the most complete food available. 122 MILK MILK. Milk 1 is a complex food — a product of the activities of the mammary gland — prepared for the nourishment of the grow- ing young. It is a whitish liquid with a characteristic odor and sweetish taste. The white color is due to the emulsified state of the fat and to the opalescence of the caseinogen solution. A slight yellowish tinge is imparted to milk, particularly when rich in fat, by certain coloring matters. This pigment appar- ently comes from the coloring constituents of plants »(see p. 199) and consequently varies in amount with the diet. A lactochrome, which is similar to urochrome in urine, occurs in the whey of milk. The specific gravity of milk varies between 1.027 and 1.035. Two counteracting factors influence the specific gravity of milk — the fats, which tend to lower it, and the other solid constituents, protein, carbohydrates and salts, all heavier than water, tend to increase it. The specific gravity is not neces- sarily a criterion of purity, for a skimmed, diluted milk may have the same specific gravity as fresh milk. Milk is an amphoteric liquid and is approximately neutral in reaction, hydrogen-ion concentration 2.6 x io -7 gram molecules. Human milk is slightly more alkaline 0.6— 1.1 x io -7 . The freezing- point of milk is — 0.55 C. A microscopic examination of milk reveals the presence of fine droplets of emulsified fat, leukocytes, and bacteria, par- ticularly streptococci. Milk that has not been carefully handled will contain dirt, and in some cases pathogenic bacteria. Bacteria may come from the udder itself or from the air. Leukocytes are normal constituents of milk that increase in number when the udder is diseased. With proper precautions milk which will contain very few bacteria (200 to 500 per cubic centimeter) may be obtained from a healthy cow. The number of bacteria per cubic centimeter has been taken as a standard of purity. The following values are those recommended by the Commission on Milk Standards as the maximum for each grade. Number of Bacteria Permitted in the Various Grades of Milk. Bacteria count shall not exceed per cubic centimeters. After Before pasteurization Grade. pasteurization. at time of delivery. A 200,000 10,000 B . 1,000,000 50,000 C . . . +1,000,000 —50,000 1 We will confine our present discussion largely to the milk of the cow. Unless otherwise designated the term milk refers to cow's milk. MILK 123 Non-pathogenic bacteria have very little effect upon adults but appear to be detrimental to infants. It is essential, then, that infants receive a milk containing very few bacteria. For the adult a milk of low bacterial count is desirable because of the greater probability of the absence of pathogenic organisms. Chemical Properties. — Milk contains all of the food-stuffs necessary for the growing organism: protein, fats, carbo- hydrates, and salts are present in amounts best adapted to the young for which it is prepared. It is a most satisfactory dietary constituent in the regimen of the adult. Water is quantitatively the most important constituent of milk. It exists to the extent of from 80 to 90 per cent., the average being about 87 per cent. Milk may readily be separated into products which are particularly rich in one or more of its constituents. By grav- ity, or more rapidly by centrifugalization, the greater propor- tion of the fat may be removed as cream. Conglomeration of the fat droplets gives butter; coagulation with rennin or pre- cipitation with acid separates casein or caseinogen respec- tively from the other proteins, salts and lactose. The following table gives the percentage composition of milk and various milk products arranged in the order of their increasing fat content (Jurgenson). Milk and Its Products Arranged According to Their Increasing Fat Content. Fat, per cent. Centrifuged milk 0.2 Skim milk 0.6 Buttermilk 0.6 Whole milk \ Rennin coagulated milk/ 3 ■ 5 Curds 10. o Cream, usual 15.0 Cream, fat 20.0 Cream, very fat 30 . o Butter 85.0 Protein, per cent. Carbohydrate, per cent. 4.4 4-4 4.4 3-0 4.0 4.0 4.0 Milk and Its Products Arranged According to the Protein Content. Whey Whole milk \ Rennin coagulated milkj Curds (cottage cheese) . Cheese, fat . . Cheese, medium fat . Cheese, skim milk . Protein, per cent. 0.8 3-7 10. o 27.0 35-0 35-0 Fat, per cent. 3-5 11 .0 30.0 10. o 4-0 Carbohydrate, per cent. 5-0 4-4 3-0 Protein. — The proteins of milk constitute about 3 per cent, of the total weight or 25 per cent, of the solid constituents. 124 MILK Of the three predominating proteins in milk, lactalbumin lactoglobulin and caseinogen, the latter presents the most characteristic properties. Caseinogen 1 belongs to the class of conjugated proteins called phosphoproteins. It is an acid protein, insoluble in dilute acids and dissolved by alkalis. Neutral solutions of caseinogen are not coagulated by boiling but a pellicle is formed, such as is observed upon boiled milk. The flocculent precipitation observed in sour milk consists of caseinogen which has become insoluble in the acid (lactic) produced by the action of bacteria upon the lactose. The changes in the protein molecule are simple and appear to involve only processes such as occur in the precipitation of inorganic substances. Precipitated casein may be dissolved by the addition of an alkali. Water-soluble casein prepara- tions are of this nature. The phenomena of the coagulation of milk by rennin also concerns caseinogen. The transformations are more profound than those mentioned above for sour milk. In this case the case- inogen is split into two molecules of casein or perhaps into a soluble whey, albumose and casein. The calcium salts of casein are insoluble; in the presence of soluble calcium salts calcium caseinate is formed and the characteristic clot is produced. The coagulum formed holds by absorption or entanglement certain quantities of fat and lactose. A comparative study of cow's milk and human milk shows that the quantity of case- inogen is greater in cow's milk than in human milk. Lactalbumin and lactoglobulin have not been shown to differ materially from the albumins and globulins of blood serum. The albumin forms about 0.6 per cent, of the whole milk or 15 per cent, of the proteins, while the globulin exists only in traces. Minute traces of fibrin and a protein called opalisin have been detected. Fats. — The fat in milk is a mixture of several different fats, the more important of which are the triglycerides of palmitic, stearic, and oleic acids, and to a less extent of myristic, buty- ric, caproic, caprylic and capric acids. Fat is the most variable constituent of milk, the proportion may vary from 25 to 2 per cent.; the average is between 3 and 4 per cent. Further discussion of the fats of milk will be found under butter, p. 198. It is also rich in fats with low melting-points; factors which tend toward increased digestibility. Milk fat 1 There is a certain confusion in the use of the terms caseinogen, the protein existing in fresh milk, and casein, the product of the action of rennin upon casein- ogen. (Halliburton: Jour. Physiol., 1900, ii, 448.) Certain authors, particularly the German writers, designate the protein of fresh milk as casein and the clot as paracasein. MILK 125 exists normally in the form of a fine emulsion. The degree of emulsion of fat in milk differs with the various breeds. The greater availability of the fat from the milk of the Holstein cow over that of the Jersey cow is ascribed to the finer state of division of the fat of the former. The value of condensed milk in the feeding of some infants has been ascribed to the fact that such milks are "homogenized" and consequently the fat is very finely divided. Carbohydrates. — Lactose, or milk-sugar, the principal carbo- hydrate constituent of milk, is a specific product of the mam- mary gland. Chemically it is a disaccharide. Hydrolysis, as in digestion, yields a molecule each of galactose and glucose. Compared with cane-sugar from which it differs only in the arrangement of its atoms, lactose is not as sweet or as soluble. These properties account in part for the use of lactose as a vehicle for drugs and, the lack of sweetness particularly, for its use in diets which must have a high caloric value and still be completely assimilable. Lactose is dextrorotatory, has a strong reducing power and is not fermented by ordinary yeast. Alcohol and lactic acid are formed from it by the action of certain bacteria, chiefly Bacillus lactis acidi and yeast. In these processes lactose is first hydrolyzed into its mono- saccharide components and then transformed into alcohol or lactic acid, according to the organism concerned. The pro- duction of lactic acid commonly occurs in the souring of milk. Alcoholic fermentation is induced in the preparation of "koumyss" and "kefir." The quantity of lactose in cow's milk varies from 4 to 6 per cent, of the whole milk, the average being about 5 per cent., or 38 per cent, of the total solids. Salts. — The salts, inorganic and organic, consist of combi- nations of calcium, magnesium, sodium, potassium, and iron with the acid radicles of hydrochloric, sulphuric, phosphoric and citric acids. In addition there are probably combinations of these substances with the proteins. The proportion and importance of the salts in milk will be considered later (p. 127). Besides their direct food value, particularly for bone forma- tion, the combinations of calcium and the phosphoric acid radicle, calcium phosphates are associated with the casein- ogen in its natural state and are concerned in the coagulation of milk by rennin. The modification of cow's milk for infants by dilution with water, lime water, etc., reduces the proportion of salts in the modified milk. Forbes suggests the use of whey for the dilu- tion of milk which permits the reduction of the quantity of caseinogen without reducing the proportion of the other con- stituents, particularly the salts. 126 MILK The iron content of milk varies with the species. Cow's milk contains a half to a fifth as much as human milk; human milk, 1.6 to 1.7 milligram of Fe 2 3 per liter; cow's milk 0.3 to 0.7 milligram of Fe 2 3 per liter. This marked difference indicates that children fed on cow's milk get much less iron than when fed on human milk; a difference which is increased when cow's milk is diluted with water. Citric acid is present in cow's milk to the extent of approx- imately 0.1 per cent., roughly three times as much as in human milk. Studies of the rate of growth of rats have demonstrated that there are in milk certain materials which belong to the group of accessory substances or vitamines. Milk contains both the "fat-soluble A" and the "water-soluble B" to large degrees. The constituents of the milk of any species are qualitatively the same. Slight quantitative differences exist due to indi- viduality, the course of lactation, the change of seasons, and the time of milking, night or morning, the first milk drawn, or the last, etc. Variations in the diet have little effect upon the composition of milk. Although the composition of milk fat may be affected by feeding foreign fat; the fat tends to acquire the characteristics of the ingested fat. Milk of different species differs chiefly in amount rather than in kind of the constituents present. The composite milk of a herd of cows, or from a city dairy is quite uniform in composition, although showing slight seasonal variations. Protein and fat are higher in the autumn and winter than in the spring and summer. Lactose remains fairly constant throughout the year. Generally the pre- dominating breed of cow influences the percentage of fat. Individual variations within a given herd, however, have been shown to be as great as the variations between breeds of cows. The following table gives the composition of cow's milk. Composition of Milk. Water = 87.1 Milk = 100 Solids = 12.9 100.0 Fat =3.9 [ Casein = 2.5 Nitrogen compounds = 3.2 J Albumin = 0.7 [Carbon dioxide Gases-j Nitrogen [Oxygen Solids not fat = 9.0 12.9 3.2 Milk-sugar =5.1 Ash (salts) =0.7 9.0 Substances foreign to milk appear in it when fed to a lac- tating animal. Thus strong flavors occur in milk as the result of certain diets; the peculiar taste of milk when the cows begin 1 United States Public Health and Marine Hospital Service, 1900, Bull. 56. MILK 127 to graze in the spring is due to certain foreign constituents derived from the green food which have been transferred to the milk. Drugs and narcotics have been shown to appear in milk following their ingestion. Variations in Composition. — Milk of different kinds of ani- mals show very striking variations in the proportions of their constituents. The accompanying table shows the composition of human and cow's milk. Human milk . Water. 88.5 Protein. Caseinogen. Albumin. 1.2 O.5 Fat. 3-3 Lactose. 6.0 Salts. 0.2 Cow's milk 87.I 3-0 0.53 3-7 4.8 O.7 A consideration of this table, with its many differences and the favorable growth of all young, emphasizes the fact that there is an elaboration of milk best adapted to the young of the particular species. Milk of one species when fed to the young of another may, as we know is the case in infant feeding with cow's milk, prove deficient in one constituent and excessive in another and thus be entirely unsatisfactory. The adaptation of milk to the young of a species has been shown to be pertinent in the case of the inorganic constitu- ents as well as in the organic constituents. The similarity of the composition of the ash of the young and the ash of the milk has been shown by Bunge and others. The following table gives the ash constituents of the young and milk of the rabbit, dog, and man, and the milk of the cow. Comparison of the Composition of the Ash of Milk with that of the Newborn Young for Which it is Intended. • Rabbit Puppy Human Cow's Rabbit's 14 days Bitch's few milk. Infant. milk. milk. old. milk. hrs. old Potassium (K2O) . 35-2 6.2 22.1 10. I 10.8 15.0 II. I Sodium (Na 2 0) . 10.4 8.1 13-9 7-9 6.0 8.8 10.6 Calcium (CaO) . 14.8 40-5- 20.0 35-7 35-0 27.2 29 -5 Mangesium (MgO) 2.9 i-5 2.6 2.2 2.2 i-5 1.8 Iron (Fe 2 3 ) . . 0.18 o.39 O.O4 0.08 O.23 0.12 0.72 Phosphorus (P 2 5 ) 21.3 35-3 24.8 39-9 4I.9 34-2 39-4 Chlorine (CI) 10.8 4-3 21.3 5-4 4.9 16.9 8.4 It will be seen that the species which rapidly increases in weight, a milk is secreted with ash constituents that are quite similar to those of the young, while for the more slowly growing organisms, as man, there is a discrepancy between the two. Influence of Temperature. — Bacteria. — Milk when drawn from the mammary gland contains, in addition to the food-stuffs, 128 MILK organisms and substances, such as leukocytes, bacteria, and enzymes. If raw milk be permitted to stand at ordinary tem- peratures, particularly when exposed to the air, physical and chemical transformations take place. These are chiefly bac- terial; changes caused by leukocytes and the enzymes secreted with the milk are of little practical importance. The bactericidal properties of milk prevent the initial rapid growth of bacteria. Raw milk exhibits, at room temperature, an apparent inhibition of bacterial growth; in some cases a destruction of bacteria has been demonstrated. The restrain- ing action of raw milk extends over a period of from 12 to 24 hours; after this time a rapid multiplication of bacteria takes place. This increase is retarded at low temperatures, 15 C. and below. When heated to 8o° C. or above milk loses its power to restrain bacterial growth. There is a more pro- found change in the latter case, for such milk permits a rapid growth of the bacterial organisms. Heated milk may there- fore become more dangerous than unheated milk unless care is taken to prevent reinoculation of the heated product, otherwise a greater number, and perhaps more virulent types, of bacteria may develop than would have developed in unsterilized milk. The presence of pathogenic organisms in a heterogeneous milk supply, however, demands some means of killing them or restraining their growth, such as sterilization or pasteuriza- tion. In pasteurization milk is heated to 6o° to jo° C. (140 to 160 F.) for from ten to twenty minutes. As the result of this treatment practically all of the bacteria are destroyed. Such a temperature does not affect the spores, hence milk must be cooled and kept at a temperature which will inhibit or restrain their development. Heating to a temperature of 6o° C. for twenty minutes has been shown to have little effect upon the germicidal power of milk or upon the enzymes present in it. Sterilization is the process of destroying all of the organisms present, both bacteria and their spores. Com- plete sterilization can only be accomplished by long-continued boiling or intermittent heating below the boiling-point. Such a procedure also destroys the enzymes and the germicidal property of milk. In both pasteurization and sterilization the water-soluble accessory substance is destroyed. Action of Bacteria. — Bacteria, which produce unusual and abnormal products, find their way into milk as the result of carelessness in handling. They cause alterations in the color, odor, and taste of milk. The formation of blue milk, or red milk, of slimy or ropy milk, and the development of a bitter taste are the result of bacterial action. Certain yeasts cause alcoholic fermentation. MILK 129 Lactic acid is the most important product of non-pathogenic bacterial action in milk; it is the predominating substance formed in the souring of milk. With the accumulation of the lactic and other acids the reaction of milk changes from approx- imately neutral to distinctly acid. Caseinogen is insoluble in this medium as shown by its precipitation, ordinarily called curdling. The precipitated caseinogen settles to the bottom of the liquid, leaving the "whey." Whey contains all of the constituents of milk except the caseinogen and a portion of the fat with the addition of lactic acid, the loss of some lac- tose, and the transformation of a portion of the protein into its cleavage products. The physical evidence of souring is often the secondary result of bacterial action rather than the direct consequence. Action of Heat. — The first evidence of the effect of heat upon milk is the formation of a pellicle or skin upon its sur- face. If this skin is removed another immediately takes its place. An examination of this film shows it to consist chiefly of protein and fat. The evidence favors the view that the pellicle consists of protein (caseinogen) which has entangled the fat, for solutions of caseinogen when heated give the same kind of film. Surface evaporation and fat facilitate the formation of the skin but are not essential. If the milk be slightly acid, such as following bacterial action, heat does not produce a film but coagulation occurs. It is the presence of a small quantity of acid which causes the coagulation of apparently fresh milk in the process of pasteurization. When milk is heated to between 6o° and 70 C. most of the bacteria present in it are destroyed. Such heating has little effect upon the other constituents of milk. If the temperature be raised above 70 C, however, the composition, color, odor and taste are affected according to the extent of heating. The accessory substances or vitamines are at least in part, if not entirely, destroyed by heating. 1 The caseinogen is appar- ently affected by boiling when judged from its retarded coagu- lation with rennin. Pure solutions of caseinogen are not affected by heating, hence the retardation of coagulation may be due in part to the altered state of a portion of the calcium salts which have probably been precipitated as tricalcium phosphate. Experimental evidence indicates that there is no change in the digestibility of caseinogen as the result of heating, and it may even be an advantage for the curd if heated milk tends to be more flocculent than that of raw milk. The biological prop- erties of milk — enzymes, etc. — are destroyed by heating. 1 The addition of orange or potato juice will tend to prevent the development of scurvy when pasteurized milk is used by infants. 130 MILK The albumins are coagulated in the process of heating. Studies on the change in the viscosity of milk when heated have shown that permanent coagulation takes place at 70 C. The liberation of ammonia and of volatile sulphide, probably hydrogen sulphide, are indications of changes in the proteins. These last factors are probably partially concerned in the taste and odor of heated milk. If the boiling be sufficiently long continued, milk acquires a brownish color from the modi- fication of the milk-sugar, lactose. This change is similar to the browning of sugar or caramelization. The influence of heat upon the digestibility of milk will be considered later. Refrigeration of milk retards the growth of bacteria and the action of enzymes but these processes are not entirely inhibited. The changes in the composition of refrigerated milk are due principally to bacterial action. They consist in a gradual proteolysis or digestion of the casein, the fermenta- tion of lactose, and the hydrolysis of fat. Proteolytic changes in the albumin are due to enzyme action; such changes are negligible in the ordinary period during which milk is kept. Digestion of Milk. — The coagulation of the milk protein, caseinogen, through the action of rennin, is the distinctive difference between the digestion of milk and that of other substances. Practically all other proteins are ingested in a solid state. Milk when swallowed passes into the stomach which contains the acid gastric juice. Under such conditions we might expect the caseinogen to be precipitated. This is not the case, however, for it has been shown that milk is coagulated, clotted by the rennin, before acid precipitation takes place. The cause of this is to be found in the nature of milk, in its ability to absorb a considerable amount of acid without changing its reaction appreciably, and in the fact that the gastric juice is not secreted fast enough to furnish sufficient acid to precipitate the caseinogen before the rennin has trans- formed it into casein. The reason for the coagulation of milk before digestion is not clear. Milk can be digested completely in a test-tube without the formation of the insoluble casein. It may be that if the caseinogen were not coagulated, the milk would pass on into the intestine more rapidly than that organ could take care of it and digestive disturbances would result. Coagulated caseinogen must pass through the usual stages of gastric digestion; the intestinal juice continues and completes its digestion. The coagulation of milk apparently concerns but two of its constituents, the caseinogen and the calcium salts. Accord- ing to the views of Hammarsten, caseinogen is hydrolyzed MILK 131 through the action of rennin into two constituents, soluble casein and a peptone-like substance called whey protein. Soluble casein unites with calcium ions (soluble calcium salts), form- ing the insoluble calcium compound usually called casein, or calcium caseinate. More recent work has failed to discover the formation of this peptone-like substance in the process of hydrolysis by rennin. The present conception of the changes in the hydrolysis is the splitting of the caseinogen into two equal molecules of casein, which, being insoluble in the pres- ence of soluble calcium salts precipitate out of solution, form- ing the clot. In the absence of soluble calcium salts hydrolysis occurs, but the formation of the insoluble clot does not take place until they are added. There is a tendency to ascribe to pepsin the changes we have assigned to rennin, i. e., to assume that rennin and pepsin are identical and the hydrolysis just described is the first step in the gastric digestion of caseinogen. The physical nature of the clot is influenced by the condi- tions under which it is produced. In the test-tube cow's milk gives a firm, tough, clot which finally contracts, squeezing out the whey. If the milk be agitated slightly, a fine flocculent precipitate is formed. This is probably the type of clot which is produced in the stomach rather than the tough clot usually described. The presence of fat influences the nature of the coagulum. Fat becomes entangled in the precipitated casein, causing it to form rather dense masses which show a tendency to coalesce in distinction from the flocculent, finely divided coag- ulum obtained with skimmed milk. This fact is of importance in the feeding of infants, and will be discussed later. Boiled milk is held to give a more flocculent clot than unboiled milk. Various methods are employed, particularly in the feeding of infants, to ensure a lively flocculent clot and to increase its digestibility, such as the addition of barley water, dilution with water or lime water, the addition of citrates, or heat- ing. The addition of cream and coagulation before eating (butter milk) also ensures a finer curd, but these methods are restricted to adults. The intestine completes the digestion of the milk. Here the proteoses, caseoses, are reduced to simpler complexes by the trypsin of the pancreatic juice and the erepsin of the intestinal juice. Erepsin has the ability of converting caseinogen into amino-acids, although it is unable to act on most other natural proteins. This is probably an important factor in digestion by infants who, it is affirmed, receive a part of the ingested milk from the stomach without its first being acted upon by the gastric juice. Lactose and the fats are first acted upon extensively in the intestines. CHAPTER VII. PROTEIN FOODS. The protein requirement of the human body is supplied from both the animal and the vegetable kingdoms. A closer analysis of the facts shows the latter to be the ultimate source of protein; for, at least so far as our present knowledge extends, only the plant is able to synthetize this essential food-stuff from inorganic matter. With one or two exceptions, however, we find that protein predominates in animal foods and that the latter are the chief source of this food-stuff in the human diet. In our previous discussion we considered the need for protein, the general products of its digestion, the forms in which its decomposition products are excreted, and the quantity of protein necessary for the functioning of the body. These con- siderations have been confined, so far as possible, to protein in general. The consideration of the differences among proteins has been postponed until a discussion of the various kinds of protein foods could be concluded. The various proteins in one organism differ from those in another. The proteins in the individual organism are also of different kinds. Even proteins of the same kind from various sources are different in composition. These differences are exhibited in the physical properties as well as in the chemical composition. The processes of metabolism are concerned with the utilization of these varied proteins for the maintenance of the supply of the various body proteins. A determination of the elements present in proteins shows them to consist of carbon, hydrogen, oxygen, nitrogen, and sulphur. These elements are combined to form amino-acids, the structural units of the protein. Phosphorus is also present in some proteins, while others contain traces of certain of the metallic elements, such as iron, copper, iodine, manganese, and zinc. A protein is, then, a combination of amino-acids as such, or in combination with certain non-protein substances, such as carbohydrates, lipins (fatty acids), purine bases, phos- phoric acid, etc. In digestion the protein molecule is split by hydrolytic cleavage into simpler complexes — proteoses and peptones; these in turn give rise to less complex compounds, peptides, and finally amino-acids. It is through studies of the PROTEIN FOODS 133 products of these hydrolytic cleavages that we have gained our knowledge of the constitution of protein. Consideration of the kinds and quantities of amino-acids present in proteins of various kinds and from different sources is not only instructive but necessary, for recent investigations have indicated the importance of relative quantities of amino- acids in the diet. The table on page 134 gives the proportions of the different amino-acids obtained from certain proteins. It is important to remember that every protein food is composed of a number of proteins and that the mass of total food at any meal is seldom deficient in any particular amino-acid. The protein content of food is usually estimated from the amount of nitrogen contained in it by multiplying this value by 6.25. This calculation is based on the fact that the aver- age nitrogen content of protein is approximately 16 per cent. This procedure is not entirely correct, for in different kinds of protein variations from 15 to 18 per cent, of nitrogen have been observed. Vegetable proteins are particularly high in nitro- gen. The average for wheat protein is 17.55 P er cent., which would give a factor of 5.7 instead of 6.25. Another error in the use of the value 6.25 is due to the fact that not all nitrogen in a food is present as protein; a certain proportion is present as extractive nitrogen. Calculations of the protein content of foods based upon determinations of protein itself as compared with the calculated values for pro- tein (N x 6.25) show that on the latter basis the flesh of different animals contains various amounts of protein, wheras actually they differ but little in their percentage protein content. Protein . Determined Species. (N. x 6.25). by Janney. 1 Chicken 19.3 16.6 Fish (halibut) 18.6 16.5 Ox 21.6 16.6 Rabbit 20.8 16.3 Cat 2 1. 1 17.8 Dog 20.2 17.4 Man 19.7 16.4 The body proteins differ from one another and from the food proteins. Some proteins are entirely lacking in certain amino-acids. In our discussion of the protein requirement (p. 70) we saw that the effect of the absence of partic- ular amino-acids from the protein molecule, when used as the sole source of protein, was in a failure to grow. In a previous Janney: Jour. Biol. Chem., 1916, xxv, 85. 134 PROTEIN FOODS ph a x i-H^00I>CNCN 00 "3»OlO COOOrH CN CO O i-I CO CN ** lO "*«OJ>"T"t-"T-IiH •sdo^Bog O 00©O CO lOffi^ 00OH O ' •OO^'cn'"' CN CO ^ i> "r »o CN i-i •U35[0TqO l>CO CN©CN 00 CN»OiO COlOI> O CN *" i-I CO CN *" Tfi CO CO CO 's CN O i-l ■* i« t-1 CO i-H b- CO NMN •© • • •ui^pQ iOOOOi-ItJH rH l>OCOCT>CO 00-*Tt< cod^H* •CNCOt>~' - -'#i-ii-i •(3HTUI) U830UI8SBQ lOCN^CN>OiO l> CO ■* CD 00 IQ O IC CO OHNCSCC^O^'COOHiOCOrtCDNH 9 .2 3 UT92 8ZrBJ\[ 00005CDCOCOO O t^ CN©©©CN OCNCO©0 • © CN t> "l CO CO CN •^eaqAl Tt © 1>-©t1< CNCNtO ©°© - "^ i— 1 1— I • •■* • © rti Tj4 +(N rH CN IN m .9 ■§ 3 •(■Bad) -*iH ©00©U5 CN COOt>- O-^iH ©CN •OOeOiH© -CO • "3 l> i-l ' lO CN ICN •ups9pa 00© © l-H i-H Tf CO i-l © IC 00 1> ©r-l CO CO ' © CO CN © © Tt< CN •* 00 i-H +1-H i-l . CN i-li-l u «qij O©O©iCi000i-l© ©■* COCOi-i>OCNCO©!-icO -CN© •"•" • ■ • •UHU9S 9SJOJJ lOCN t>-00>0 >O00 lO") COCN^OOCOCN -i-tCN • CN 00 • ' • • • CO a Xi < UTSOonaT; ©lOCNCOOOCO CN Tt© 0000^ ©^©i-icOCO 5 "' -CO ■CO©iO"l(NCNi-l •(t39d) uqauinS97 iO©t>©00© © iH©iC ©COCO ©©©©^rH 5 " - 1 -^ • t)h CO US +C0 IN r-i •uxumq|'B^O'B r i °CN©©CN© • "# -i-H© ' • • • • ■Uinj9S 9SJOJJ |> OHHOlCO r-lt> ©CN •OCOCNOCN'-l -COI> • "•" • . . CN •23a i-H ."""Jitfl-H .COCO .lOOr-l . l-l © • en ' " • • " • "T • © CN '^TjfrH '©CN 'i-HOOCN CN •(auo^STu;) asjoq 'uiqojSouiaq jo uiqojo CN © CN CO © CO CO © ■* t^ Tt< CO© •Tji •ffi^HOONH^HlOT^IH • CN i-H • (auiuiB'jojd) auirareg CO 00 © rj( . .^' . . .^ .,_, . . .t,' .©© . i-H 00 Glycine .... Alanine .... Valine Leucine .... Phenyl alanine Tyrosine .... Serine Cystine .... Proline .... Oxyproline Aspartic acid . Glutamic acid Arginine .... Tryptophane . Lysine . Histidine .... Ammonia .... PROTEIN CLASSIFICATION 135 chapter the inability of the body to synthetize protein and certain amino-acids was discussed (p. 99). The necessity for a liberal supply of the different amino-acids in the form of a varied selection of proteins, and for a kind of digestion that converts these structural elements in protein into readily available substances either as the amino-acids or simple com- plexes of these is therefore evident. Such a variety is obtained in the ordinary mixed diet; in special diets it is a factor to be considered. The influence of the ingestion of proteins homol- ogous to those present in the body upon the minimum protein requirement has been discussed (p. 69). Proteins are not ordinarily distinguished by their amino-acid content, however, but chiefly by their physical properties. Differences in chemical composition are, however, the basis of distinction between the members of one group — the conjugated proteins. 1 The following outline of the kinds of proteins and their characteristics, the classification adopted by the American Physiological Society and the American Society of Biological Chemists, will be adhered to in our discussion. This classi- fication differs from that of the English societies in a few instances; in most matters they are essentially identical. I. Simple Proteins. — Protein substances which yield only a-amino-acids or their derivatives on hydrolysis: {a) Albumins. 2 — Soluble in pure water and coagulable by heat. Albumins are present in all cells and in the important fluids of the body. Ovalbumin is the predominating protein of egg white. Other important albumins are serum-albumin present in blood plasma, lymph and other body fluids; lact- albumin of milk; the vegetable albumins, leucosin of wheat, and legumelin of the pea. (b) Globulins. — Globulins are insoluble in pure water but soluble in neutral solutions of salts of strong bases with strong acids. Globulins are present in blood, serum globulin; egg, ovo- 1 The terms protein and proteid are often used together. The present-day German writers use the word protein to designate simple albuminous substances, and proteid for combinations with other complexes. The simple proteins and the conjugated proteins of the American classification are proteins and proteids respectively in the German classification. A distinction is sometimes made between protein and proteid among English-speaking writers. Proteid designates definite chemical compounds, or isolated albuminous substances (our proteins), while protein is used to denote the mixture <3f proteids in a food, the measure of which is the quantity of nitrogen which the food yields upon analysis times 6.25, the average percentage of nitrogen in pure proteid. Protein has been adopted by English-speaking scientists as the generic term for the class of sub- stances which we are discussing — and we will use this term in that sense. 2 A distinction is sometimes made between the pure individual substances alburmra and a mixture of proteins occurring naturally together, or albumen, as the white of egg. The term albumen is used very little and is now practically restricted to the expression "egg albumen." 136 PROTEIN POODS globulin; milk, lactglobulin; seeds, edestin (hemp seed); legumin (pea). (c) Glutelins. — Glutelins are simple proteins insoluble in all neutral solvents but readily soluble in very dilute acids and alkalies, e. g., the vegetable protein, glutenin, from wheat. (d) Alcohol Soluble Proteins (Prolamines). — Simple proteins soluble in 70 to 80 per cent, alcohol, insoluble in water, absolute alcohol, and other neutral solvents, e. g., zein, corn; gliadin, wheat; hordein, barley. Gluten, readily obtained from wheat flour by washing away the starch, albumin, etc., is a mixture of members of the last two classes of proteins, glutenin and gliadin. (e) Albuminoids. — Simple proteins possessing a similar struc- ture to those already mentioned, but characterized by a pro- nounced insolubility in all neutral solvents. The proteins concerned in the framework of the body are the most impor- tant members of this group, e. g., elastin and collagen; con- nective tissue; keratin — hair, nails and horn; and fibroin from silk. Acids or prolonged boiling with water convert collagen into gelatin. Gelatin is not, however, classed as an albu- minoid. The English nomenclature aptly designates the albuminoids as scleroproteins. (/) Histones. — Soluble in water and insoluble in very dilute ammonia and, in the absence of ammonium salts, insoluble even in excess of ammonia; yield precipitates with solutions of other proteins and a coagulum on heating which is easily soluble in very dilute acids. On hydrolysis they yield a large number of amino-acids among which the basic ones predom- inate. In short, histones are basic proteins which stand between protamines and true proteins, e. g., globin, one of the constituents if hemoglobin; thymus histone and scombrone from sperm. (g) Protamines. — Simpler polypeptides than the proteins included in the preceding groups. They are soluble in water, uncoagulable by heat, have the property of precipitating aqueous solutions of other proteins, possess strong basic prop- erties and form stable salts with strong mineral acids. They yield comparatively few amino-acids, among which the basic amino-acids predominate. These proteins are obtained from spermatozoa in which they occur in combination with nucleic acid. The various members of this class are designated accord- ing to the animal from which they are obtained, as salmin from the salmon sperm; sturin from mackerel sperm, etc. II. Conjugated Proteins. — Substances which contain the protein molecule united to some other molecule or molecules otherwise than as a salt. PROTEIN CLASSIFICATION 137 (a) Nucleoproteins. — Compounds of one or more protein molecules with nucleic acid. This type of protein is the prin- cipal constituent of cell nuclei and is found in practically all protein-rich foods. Milk and the white of egg are important exceptions. Nucleoprotein is a very complex substance yield- ing upon hydrolysis first protein and nuclein. Nuclein then disintegrates into a second protein, usually basic, as histone or protamine, and nucleic acid. Nucleic acid may consist of one or more combinations of phosphoric acid, carbohydrate, and one of the purine or pyrimidine bases called nucleotids. Upon hydrolysis of a combination of nucleotids, the various nucleotids result. The phosphoric acid is next split off from the nucleotids leaving the purine- or pyrimidine-carbohydrate complex, nucleosid, which finally yields carbohydrate and the base. The following scheme shows the disintegration of nucleoprotein: Nucleoprotein / \ . protein nuclein protein nucleic acid (nucleotids) /\ phosphoric acid nucleosid carbohydrate purine base pyrimidine base The purine bases from nucleoprotein are the chief source of the uric acid which appears in the urine of mammals. (b) Glycoproteins. — Compounds of the protein molecule with a substance or substances containing a carbohydrate group other than a nucleic acid, e. g., mucins and mucoids (osseo- mucoid from bone, tendomucoid from tendon, ichthulin from carp eggs, helicoprotein from snail). (c) Phospho proteins. — Compounds of the protein molecule with some, as yet undefined, phosphorus-containing substances other than a nucleic acid or lecithin, e. g., casein from milk, ovovitellin from egg yolk. (d) Hemoglobins. — Compounds of the protein molecule with hematin, or some similar substance, e. g., hemoglobin from red blood cells, hemocyanin from blood of invertebrates. (e) Lecitho proteins. — Compounds of the protein molecule with lecithin. 138 PROTEIN FOODS III. Derived Proteins. — A. Primary Protein Derivatives. — Derivatives of the protein molecule apparently formed through hydrolytic changes which involve only slight alteration of the protein molecule. (a) Proteins. — Insoluble products which apparently result from the incipient action of water, very dilute acids or enzymes, e. g., myosan from myosin, edestan from edestin. (b) Metaproteins. — Products of the further action of acids and alkalis whereby the molecule is so far altered as to form products soluble in very weak acids and alkalis but insoluble in neutral fluids, e. g., acid metaprotein (acid albuminate), alkali metaprotein (alkali albuminate). (c) Coagulated Proteins. — Insoluble products which result from (i) the action of heat on their solutions, or (2) the action of alcohol on the protein. B. Secondary Protein Derivatives. — Products of the further hydrolytic cleavage of the protein molecule. (a) Proteoses. — Soluble in water, non-coagulable by heat, and precipitated by saturating their solutions with ammo- nium — or zinc sulphate, e. g., protoproteose, deuteroproteose. (b) Peptones. — Soluble in water, non-coagulable by heat, but not precipitated by saturating their solutions with ammonium sulphate, e. g., antipeptone, amphopeptone. (c) Peptides. — Definitely characterized combinations of two or more amino-acids, the carboxyl group of one being united with the amino group of the other with the elimination of a molecule of water, e. g., dipeptides, tripeptides, tetrapeptides, pentapeptides. Influence of Heat. — The effect of heat upon simple proteins is to cause them to coagulate. Such changes are continually occur- ring in the preparation of food for the table. The boiling of an egg, or the roasting of meat is accompanied by the coagula- tion of the protein, and it is to a large extent the coagulation of the protein among expanded gas bubbles which keeps bread and cake " light." Two changes take place in the coagu- lation of protein: there is first a reaction between the hot water and the protein as the result of which the protein loses certain of its characteristic properties, such as solubility, i. e. 9 the protein is denatured. Secondly, the altered particles of protein agglutinate into visible masses or coagula which separate from the solution. When the protein is held in the meshes of connective tissue, etc., the denatured protein shrinks or contracts so that water and dissolved salts are squeezed out. This phenomenon is called syneresis. The accumulation of beef juice around a roast when cut on the platter is the result of syneresis. The presence of acid and small quantities EFFECT OF LOW TEMPERATURES 139 of salt facilitates the coagulation of protein. An excess of acid or alkali results in a solution of the protein and prevents coagulation. Certain proteins of the albuminoid class, such as collagen, are readily hydrolyzed (rendered soluble) particularly so in the presence of small quantities of acid. The long-continued cooking (usually just below the boiling-point) of tough cuts of meat accomplishes the hydrolysis of the connective tissue (rich in collagen) which tends to free the muscle fibers and permit their ready separation, i. e., makes the meat tender. The use of veal for soup stock and the ease with which the fibers of fish are separated is due to the large proportion of easily hydrolyzed connective tissue which they contain. Acid facilitates hydrolysis; it also tends to cause protein material to swell. The value of acid in cooking fish and tough meat is then self-evident. Protein combines with both acid radicles and basic radicles to form protein salts; the insoluble curd formed in the coagu- lation of milk occurs because the calcium salt of casein is insoluble in water; the sodium or potassium salts are soluble, and it is in this form that certain casein preparations are placed on the market. Certain proteins of the legumes form insoluble calcium and magnesium salts, which is the reason for the objection to the use of hard water in preparing legumes for the table. The use of egg white, etc., as an antidote for poisons is due to the insoluble salts which are formed by the protein with the heavy metals. Effect of Low Temperatures. — Low temperatures have no direct effect upon protein. Its properties may be altered, however, as the result of changes produced in the medium in which it is suspended. The crystallization of the intracellular water results in a concentration of the salts. This causes the precipitation of some proteins and the solution of others. Upon the return to the normal temperature the original state is restored. Long-continued low temperatures produce a change in the precipitated proteins so that they will not redissolve. The change just noted has been shown to occur in plants. During refrigeration protein food-stufFs undergo consider- able modification as the result of predominant enzyme action, autolysis, rather than of bacterial action which shares in the transformation at room and body temperatures. Low tem- peratures inhibit both bacterial and enzyme action, the former more than the latter, however. The changes which occur at low temperatures are analogous to those which take place in aseptic or sterile tissues, either in the body or out of it. 140 PROTEIN FOODS The "ripening" of flesh is due to these autolytic changes brought about by the intracellular enzymes. The action of the intracellular proteases is quite similar to that of the diges- tive enzymes, particularly trypsin. Protein passes gradually through the various stages of proteolytic digestion, finally yielding amino-acids. Examination of refrigerated meat, for instance, shows an increase in the quantity of water-soluble proteins, indicating a partial digestion. Other enzymes pro- duce changes in the fats and carbohydrate. The changes which result in foods preserved with certain chemical sub- stances, without the use of heat, are the result of autolysis. Bacterial growth is not entirely checked at comparatively low temperatures and changes undoubtedly occur as the result of their action. At higher temperatures, room temper- ature and above, the activities of bacteria increase. The prod- ucts of their action on proteins are in part similar to those produced in enzymatic digestion. The harmful effects of bacteria from a dietary point of view are not in the bacteria themselves so much as in the products (ptomaines) produced in the food, protein, during their growth. These substances are produced by non-pathogenic as well as by pathogenic organisms. The ptomaines are soluble basic substances closely related to the amino-acids; not all are toxic. The changes which proteins undergo in the course of diges- tion and absorption have already been discussed (p. 34). The rate with which they are made available for absorption depends upon their physical properties, whether they are in solution or solid, dense or finely divided, will imbibe water easily or with difficulty; and upon their chemical properties, such as acidic or basic, complex or simple. Preparation of food for use is often accompanied by change in the digest- ibility as well as in the availability of the food-stufTs. This is particularly true with regard to protein. The total available quantity of the protein is often increased in the course of preparation. The effect of grinding vegetable food-stufTs very fine is to increase their total digestibility. The influence of heat upon the connective tissue of animal food-stufT is to cause a partial conversion of the collagen into gelatin; hence the ease of digestion is increased. In vegetable food-stuffs the indigestible cellulose structure is ruptured through the combined action of heat and water, thus promoting the action of the digestive enzymes upon the contained protein and carbohydrates. CHAPTER VIII. MEAT OR FLESH FOOD. The dietary value of meat is due chiefly to its protein content. It contains in addition a varying quantity of lipin or fat, a small amount of carbohydrate, salts, and certain nitrog- enous derivatives related to the proteins called extractives. The palatability, variety, ease with which the flavor may be modified, facility of preparation, concentration of protein, and digestibility are factors which have made meat the most important protein of the adult human dietary. The fact that the proteins of meat are of the same type as those of the body would seem to indicate a possibly greater adaptability to the needs of the human organism than the vegetable proteins, for instance. There are no facts to show, however, that a suit- able mixture of vegetable proteins is not just as satisfactory as the animal proteins. The dietary and economic advantages and disadvantages of these two types of diet have been dis- cussed (p. 116). Meat is derived almost entirely from the skeletal or striated muscles. Such muscles are composed of fibrils enclosed in sheaths known as sarcolemma (fibers) and bound together in the form of bundles by connective tissue. The fibers terminate in bundles of white fibrous connective tissue, the tendons, by means of which they are attached to the bones. Embedded in the connective tissue of the muscle bundles are cells more or less rich in fat, while between the various muscles compara- tively large masses of fatty tissues are found. Living muscle is practically neutral in reaction, but after death lactic acid is formed and the reaction rapidly changes to acid. An alkaline reaction in meat is an indication of putrefaction. The important proteins of muscle plasma are myogen (a globulin) which predominates, and myosin. After death these proteins become coagulated to form the muscle clot; 1 this is the form in which the greater portion of the protein of meat exists. Immediately after death autolytic changes commence with the formation of lactic acid and protein digestion prod- ucts and are attended by an increase in the quantity of soluble proteins. These are the processes concerned in " ripening. " 1 Myosin is the name given to muscle clot by some investigators. 142 MEAT OR FLESH FOOD The connective tissue contains a large percentage of the albuminoid collagen, which is a source of gelatin — the base of the jelly of cooked meat. The flesh of young animals, as veal and lamb, is particularly rich in connective tissue and their bones in collagen. The readiness with which meat from such animals yields gelatin makes it valuable as the basis of soup. Fish are also rich in gelatin-yielding tissues. Blood remaining in the capillaries and bloodvessels and in the blood plasma surrounding the cells, contains serum albumin, globulin, fibrin, etc. The, hemoglobin in muscle and the residual blood gives meat its red color. The identity of the coloring substance in blood and in muscle is not generally admitted, although the close relation is acknowledged. The quantity of hemo- globin varies; it is greatest in muscles concerned in long- continued and powerful contractions and least in the more passive muscles. The dark and light meat of the birds show this relation. Certain species, as the rabbit, are poor in hemoglobin. The muscle of the young of most species is low in hemoglobin, hence their light color. The decided red color of meat preserved with nitrates appears to be due to the pres- ence of nitrous oxide hemoglobin. The small amount of glycogen normally present in muscle is almost entirely changed to glucose after death. The com- paratively large quantity of glycogen in fresh horse meat is one of its distinguishing characteristics. Fat varies in quan- tity, kind, and color with the condition of the animal, the food ingested, and the cut (portion of the carcass). Flavor in meat is due to the presence of the extractives — substances soluble in water, alcohol, or ether. In addition to the carbohydrates and fat just mentioned these include cer- tain non-protein, nitrogenous constituents, such as creatin, xanthin, hypoxanthin, inosin, etc.; the latter are the chief source of the exogenous uric acid. It is the latter extractives which the gouty patient should avoid and to which vege- tarians and certain food cults object, holding them to be waste products and a burden to the excretory system. The presence of purine compounds in the diet under certain pathological conditions, such as gout, is objectionable. It is important to know, therefore, the relative quantity of these substances in various foods. A table giving the purine contents of various kinds of flesh and of certain other foods will be found in a subsequent discussion of diet in disease. Meat often contains certain substances characteristic of the food ingested which gives to it the flavor so prized by epicures : these are particularly evident in game. COMPOSITION OF MEAT 143 Flesh or meat is ordinarily composed of about three-fourths water, but there is less water in fat than in lean meat and like- wise in old than in young animals. In the ash of muscle the salts of potassium and phosphoric acid predominate. Traces of sodium, calcium, magnesium, iron, sulphur, and chlorine are also found. The following table gives the approximate proportions in which the inorganic constituents occur in meat: Composition of the Ash of Typical Flesh Foods. Beef, lean . Veal, lean Lamb, med- ium fat Pork, lean Poultry Fish . . CaO. O.OII 0.16 O.OO39 0.012 0.015 O.O3 MgO. 0.04 O.O45 O.04 O.046 0.06 O.O4 K2O. O.42 O.46 O.29 0-34 0.56 0.40 Na 2 0. 0.09 0.12 O.O93 O.I3 0.13 1.30 P 2 5 . 0.50 0.50 0.42 o-45 0.58 0.40 ci. 0.05 0.07 O. 12 0.05 0.06 2.4O s. 0.20 0.23 0.23 0.20 0.216 0.22 Fe. O.OO38 . 0003 PER CENT 70 50 30 20 10 3 5 PER CENT 70 60 SO I \ \ \ \ \ / / / / X X X X _ <- — — ™" ™ 1 / \ / \ X X X X X X 20 IO \ \ V t / \ "**•-» VISIBLE TAT BONE O 1 Fig. 3. — Percentages of lean (Courtesy of the , visible fat and bone in the straight wholesale cuts. 1 Illinois Agricultural Experiment Station.) Some meats when purchased contain inedible parts, such as bone, the exterior portions of the carcass, large bloodvessels, connective tissue, gristle, and tendon. In considering a par- ticular piece of meat from a purely dietary point of view allowance should be made in the calculation for the waste Hall and Emmett: Univ. 111. Agr. Exp. Sta., Bull. 158, 1912. 144 MEAT OR FLESH FOOD which these portions represent. From an economic stand- point it is essential to know the quantity of edible material likely to be derived from a given piece of meat. Fig. 3 gives the percentages of lean, visible fat, and bone in the straight wholesale cuts of beef. An inspection of this chart reveals in general an inverse relation between the percentage of lean meat and that of visible fat; the relative weight of bone is more variable. The proportions of the various food-stuffs in meat varies according to the kind of animal and the portion of the anat- omy from which it is obtained. The same "cut" of meat from different animals varies according to its age and nutritive condition. The relative differences in the protein content of the various cuts of beef is shown in the following chart (Fig. 4) prepared by Hall and Emmett, which gives the percentage of the total protein in the boneless meat of whole- sale cuts. z < PER J CENT "■ 17 U £1 Z iw ,--- ......... TOTAL PRO CENT Fig. 4. — Percentages of total and soluble protein in the boneless meat of the wholesale cuts. 1 (Courtesy of the Illinois Agricultural Experiment Station.) The curves show a relative increase in the quantity of pro- tein as we consider the cuts from the left to right. Calcu- lated on the basis of the dry, moisture-free, substance an even greater increase is found, because the cuts on the right con- 1 Hall and Emmett: Univ. 111. Agr. Exp. Sta., Bull. 158, 1912. COMPOSITION OF MEAT 145 HIND QUARTER ROUND Rump I Rump Pound: rump & shank off. L Round steak, first cut. J -13 Round steaks. 14 Round steak, /as/ cut. J5 Knuck/e soup bone 16 Pot roast Hind shank. !7J8 5oup bones 19 Hock soup bone Loin I Butt- end sir/oin steak. Z Wedge- bone s/r/o/n steak. 3, -4 Round -bone 5,6 Double -bone 7 Hip-bone •• Q Hip-bone Porterhouse steak. 3-/5 Regular 16-18 Club steaks. Flank t Flank steak £ 5tew. R/B I 3 4 Chuck J S.-9 FORE QUARTER Htb &mtb R/b roast s>y>3 tot* lib £ QUi Qlh u 5tb R/b roast. Chuck ,s teaks 10 -D Pot roasts. 14 Clod Neck Fig. 5. 15 Plate. / J3riskef Z Navel 3>4- Rib ends fOR£ SHANK I J/etv. £ Knuckle soup hone. 3-6' Soup bones. RETAIL ■ CUTS • OF' BEEF -Method of cutting the three sides, showing retail cuts. (Courtesy of the Illinois Agricultural Experiment Station.) Composition of Typical Flesh Foods. 1 Protein Water, Nx6.25, Fat, Ash, Fuel value per cent. per cent. per cent. per cent. per pound. Beef . . . 70.0 2I.3 7-9 I . I 709 Veal . . . • • • 70.3 21 .2 8.0 I .0 711 Lamb . . . . 63.9 19.2 16.5 I . I 1022 Pork . . . 60.O 25.O 14.4 i-3 IO42 Poultry • • • 63.7 19-3 16.3 I .0 I0I6 Fish . . . . . . 81.7 17.2 0-3 I . 2 324 1 U. S. Dept. Agr., Office Exp. Sta., 1906, Bull. 28, revised 10 Insoluble. Total. 15 -56 16.98 H 88 16.69 14 42 16.50 14 67 16.26 13 94 15-59 13 40 14.87 II 59 12 .96 II 30 12.56 II 12 12.32 9 76 10-59 8 78 9-44 146 MEAT OR FLESH FOOD tain more lean and less fat and also because the lean meat has a greater water content. When the fat is excluded from consideration, the protein content of the various cuts is quite similar. In other words, the difference in the various cuts of beef is due to the varying quantities of fat and water. The differences among the percentages of the food-stuffs in the various kinds of meat are likewise due to similar varia- tions; this is shown in the accompanying table taken from a compilation of analyses by Atwater and Bryant. Percentages of Water-soluble, Insoluble, and Total Protein in the Boneless Meat of the Wholesale Cuts. 1 Wholesale cuts. Soluble. Fore shank 1 . 42 Clod 1. 81 Round 2.0.8 Hind shank 1 . 59 Neck 1.65 Chuck 1 . 47 Loin 1.37 Rump 1.26 Rib 1.20 Plate 0.83 Flank 0.66 Fig. 5 enables one to locate the portion of the animal under consideration. Effect of Heat on Meat. — Cooking. — The objects to be accomplished by cooking meat are the improvement of its flavor and appearance; the modification of its texture, and the destruction of parasites and bacteria. Digestibility of protein is not increased by cooking; it is diminished in many cases. Such changes as the hydrolysis of connective tissue and comminution increase the ease of digestion. The flavor acquired by meat through cooking is due to changes, probably oxidative, in the soluble, extractive, por- tions of the flesh and in the fats. 2 A study of the development of flavor in which the juices were separated from the insoluble portions (fiber) of beef showed the flavors to develop in the juice more than in the residue, and in the extract not coagu- lable by heat more than in the coagulable portion. A study of the effect of various temperatures showed the flavor to develop most at temperatures above ioo° C; below this the taste is more or less insipid. The pronounced flavors developed by dry heat are thought to be due to the higher temperatures attained. The fat of meat when heated sufficiently high also gives rise to characteristic flavors. 1 Hall and Emmett: Univ. 111. Agr. Exp. Sta., Bull. 158, 1912. 2 Grindley and Emmett: U. S. Dept. Agr., Office Exp. Sta., Bull. 162. EFFECT OF HEAT 147 The appearance of meat is also improved by cooking as the result of the coagulation of the proteins and the transforma- tions in the hemoglobin whereby the more or less objectionable reddish-purple color of uncooked, raw meat is changed to the light red or brown color of cooked meat. Those changes in appearance are most evident in roast beef and are enhanced by the crisp outer layer of fat. Three methods are employed to make a piece of meat ten- der : ( i ) Cooking for a long time at low temperature ; simmering at approximately 8o° C. (this is sometimes incorrectly desig- nated boiling) whereby the insoluble collagen of the connec- tive tissue is changed to gelatin, thus loosening the fibers. (2) The mechanical separation of the fiber from the connec- tive tissue by scraping, a tedious process practised in the preparation of a readily digestible protein food for the sick. (3) Grinding, mincing, or pounding by which means the con- nective tissue is mechanically severed. In the cooking of meat two general methods are employed which differ in the mode of application of the heat: {a) The direct application of radiant heat, as in roasting and broiling and (b) the application of heat through the medium of a liquid, as boiling in water and frying in deep fat. Roasting and baking are used synonymously by the aver- age cook. A distinction should be made, however, between so-called roasting or baking and true roasting. 1 True roasting is cooking by radiated heat from glowing coals, but one side of the food being exposed to the heat at a time. Broiling is essentially the same in principle as true roasting, but the food is brought into direct contact with radiant heat. The length of time of the two processes differ, for a thinner cut of meat is used for broiling. Baking is cooking in a ventilated oven. Although frying in deep fat belongs properly, as indi- cated, to the indirect method of cooking, the results obtained are more like those obtained with the direct application of dry heat. The changes produced in meat by cooking, aside from slight differences in flavor, are of two kinds, those characteristic of roasting and of boiling. Combinations of these, as in pot roast- ing, so admirably adapted to the preparation of tough, cheap cuts, yield some of the advantages of each method. In this case the tenderness of boiled meat is combined with the flavor of roasted meat. Grindley and Emmett have shown the effect of roasting (baking) to be similar to that produced in broiling, parboiling, sauteing, and frying. 1 Bevier and Sprague: Univ. 111. Agr. Exp. Sta., Circular 71, 1903. 148 MEAT OR FLESH FOOD Roasting is practised principally for the development of flavor and appearance. The application of a high heat sears the surface of the meat and immediately coagulates the pro- teins, the hemoglobin being changed from bluish red to brown. Such treatment also causes changes in the surface fat, thus developing an additional flavor. The preliminary searing, usually conducted at a higher temperature than the subse- quent cooking, serves to retain the water and the extractives. The subsequent changes which occur within the roast are gradual, for muscle fibers are very poor conductors of heat, and the internal temperatures never reach those of the air surrounding the meat. As the heat gradually penetrates inward the proteins are coagulated at a low heat, and the hemoglobin is changed in color, assuming first the pink color characteristic of rare meat, and finally becomes brownish gray — "well done." This last color is common to all meats heated to a temperature above yo° to 75 C. and is due to the complete coagulation of the hemo- globin. At these higher temperatures the coagulated protein, and consequently the piece of meat, shrinks. Careful studies of the physical changes occurring during roasting have empha- sized these points and established the conditions necessary to obtain the desired kind of roast — rare, medium, or "well done" (Sprague and Grindley). The inner temperature of the meat determines the degree of the roast regardless of the external temperature. When a thermometer placed in the middle of a roast registers a temperature of approximately 43 C, 55 C, or 70 C, if the roast be removed from the oven, the final temperature, will be approximately 55 C, 65 C, or 70 C, and the meat will be respectively rare, medium, or well done. These temperatures hold with the external tem- perature of the average roasting oven (175 to 195 C). At lower oven temperatures the temperature at which the meat is removed will more nearly approximate the final one desired. The most desirable conditions for successful "boiling" of meat are long-continued heating at a temperature below the boiling-point, 8o° to 85 C. Under such circumstances the connective tissue is softened and the protein coagulated with- out becoming hardened (toughened) characterized by the shrinking of the meat. Long experience in cooking has demon- strated the advisability of searing the outside of the meat or plunging it into boiling water and keeping it at this tem- perature for a few minutes before beginning the cooking at the lower temperature. Such a practise is held to assist in the formation of a more or less impervious layer by the coagu- lation of the surface proteins which retains the extractives DIGESTIBILITY OF MEAT 149 and soluble proteins, and thereby improves the nutritive value and flavor. If a rich broth is desired the opposite method is used, beginning with cold water which is gradually heated. The work of Grindley and his associates, studies on the losses in cooking meat (see below for further discussion), has shown, however, that when meat is cooked at 8o° to 85 C. there is practically no difference in the quantity of nutrients (protein, extractives, and ash) which pass into the broth when the cooking is begun in hot or cold water. The length of time and the fat content have a much greater effect upon the losses than the method of cooking. Chemical Changes in Meat as the Result of Cooking. — The chemical changes which occur in meat during cooking, whether by roasting or boiling, consist in an increase of insoluble (coagulated) protein and in the removal of water and extrac- tives (nitrogenous, non-nitrogenous, fat, and ash). Boiling causes a removal of a greater proportion of these substances than does roasting. Fat meats lose less water, protein, and mineral matter, but more fat, than do the lean cuts. Pro- longed cooking at higher temperatures is accompanied by greater losses than at lower temperatures. Under like conditions the larger the piece of meat the smaller are the relative losses. As already mentioned, when "boiling" at 8o° to 85 C, the effect of such preliminary treatment, as placing in cold or hot water has little effect upon the quantity of material found in the broth. It is interesting to note that the beef used in the prepara- tion of beef tea or broth loses little of its nutritive value, although it loses much of its flavoring material. The work of Grindley and his associates has been verified and extended by that of other investigators, particularly with regard to the changes in the protein and extractives under various condi- tions. The table on page 150 taken from their results shows the influence of cooking upon the composition of meat. Digestibility of Meat. — Many conflicting statements are made with regard to the digestibility of meats of various kinds and as prepared by the various methods of cooking. The observations upon which the conclusions regarding the digestibility of meat are commonly based are of two general types (1) the time the food remains in the stomach and (2) the degree of digestion, i. * i— i iO co On eS N r^H r^ (S OO O H rOiO^j- d odd 0) ■ d ""3 On co m I^IOVO M o +3 odd CO d lO (N CO odd S d lO O) tJ- H W Q W M O O t^ rtoo r^ "S OO h n CO COH O) o u Ph CI lOrO d d o o cOvO rt- i-i oo CO t^Tj-M ONVO M ■d o vo n vO vO 00 t^ ^-vo t^ rJ-vO «! m d w lO tj-vO u o d m 1— 1 d 6 6 6 00 VO vO odd _,_? On fO On N 00 Tf-O 0 t-»rj- H CN vo co r^ r^ tJ- on o 0) ? 3 vO nvo fe o vo o VO cOt^ O CON o g _> a 2 O rt O r5 3 H O M "w 1 T pq Q < M w d ■-! M o l-l Q H d < 1 0) 00 o io 55 W w CO CN tn 00 vo vO co NOlO O Is O vO CO H O M 00 O d on 1 1 H U H X) o O iooo i-I d d o vo 00 H O 6 £ en W O 11 iovO CO t^ ta On VO ON00 VO 10CO H Is QO OfO VO 00 -I d d odd O Oh H H (OM g 1 + § H G o 03 ON00 M Q W tn en O Ph g o M cO00 en w U Cfi £ ci o o Ph w XI 6 0) r>- Th W o pq pqp4 o 2Q pq DIGESTIBILITY OF MEAT 151 resulting in the reduction of the food to a semifluid mass, but there is little absorption through the gastric mucosa. More- over, so many variables must be taken into consideration accurately to measure the time required for food to leave the stomach that the results obtained by such experiments must, unless they are very striking, be considered as merely sugges- tive. For example, the ease of swelling and the degree of peptic activity are modified by the mode of preparation. Fat particularly tends to retard gastric digestion; there is no lipo- lytic activity of importance in the stomach. The composi- tion of the flesh likewise affects gastric digestion, very fat meats being less digestible than lean meats. The presence of large quantities of connective tissue, particularly in partially cooked food, serves to hinder peptonization. Finely divided meat is more easily attacked by the gastric juice than large masses. Foods which are acid remain a shorter time in the stomach than do alkaline foods. The quantity, strength, and acidity of the gastric juice have a very pronounced effect upon the rate of ejection from the stomach. The second method of measuring digestibility — the com- pleteness of absorption of the ingested food — indicates only the extent of absorption and does not enable us to judge of the length of time required for its digestion. Food which is completely absorbed leaves little residue and is likely to lead to constipation, while that which is poorly absorbed may (a) be subject to extensive bacterial action in the large intes- tine, (b) increase the rate of peristalsis, or (c) lead to the accumulation of large masses of food residues in the intestines. In a well-selected diet, foods which are completely digested are accompanied by some of those which are difficult of diges- tion, particularly foods low in protein and rich in cellulose, such as vegetables and fruits. In the treatment of patholog- ical cases it is particularly necessary to take into considera- tion the degree of digestibility of the foods prescribed. The extent to which a food is absorbed depends quite as much upon the nature of food as does the ease of digestion. Foods that contain material in quantity which is not acted upon by the digestive enzymes are not only poorly absorbed but retard the digestion and absorption of other foods which are ordinarily completely digested and absorbed. The mode of preparation also influences the extent of absorption, for by its proper preparation connective tissue and cellulose structures are partially or completely hydrolyzed or disintegrated and thus become more readily and completely digested. Conventional consideration of the relative digestibilities of various kinds of meat is based, then, upon data which are 152 MEAT OR FLESH FOOD not entirely satisfactory. Clinical observation is an aid in determining the digestibility of food in its most general sense, but here there may be influences of personal idiosyncrasies as the result of pathological conditions in the patient under observation, and this is particularly true of protein foods. Some individuals show distinct reactions to certain foods. Many cases are known, however, in which the inability to eat eggs, fish or milk is a psychical factor and that the ingestion of such foods is not attended by metabolic disturbances. In feeding persons whose condition necessitates prompt emptying of the stomach, food must be selected which will pass out readily, just as in certain intestinal diseases food must be taken in such a form that complete absorption occurs without extensive intestinal digestion or in which little residue results. These factors are discussed on p. 47. It seems to us that the method of the preparation and the con- sistency of the food are more important factors in the treat- ment of nutritional diseases in which a specific food substance is not involved, such as a specific idiosyncrasy or disease, than the selection of a few from among a number of foods compatible with the patient. MEAT PREPARATIONS. Certain products prepared from meat, particularly from beef flesh, such as digested beef, beef juice, beef broth, beef extracts, and gelatin, contain less insoluble material than meat itself and are therefore held to be desirable not only for general use but for use in the sick-room and for convalescents. Such products are either readily soluble in water or yield fine aqueous suspensions. It is the possi- bility of furnishing protein or its digestion products in a fluid or soluble form which makes these preparations attractive for the special diets of therapeutics. The nutritive value of meat preparations as compared with meat depends upon the mode of preparation. They are pre- pared from lean meat through the action of digestive enzymes, with the aid of heat, or by simple water extraction. Beef extract and some beef broths contain only small proportions of nutritive protein material, whereas cold pressed beef juice, gelatin, and broths prepared with gelatin-yielding meats and flesh in which the proteins have been partially digested are highly nutritious. The table on page 153 gives the compara- tive composition of such products. Meat Extracts. — Beef extract, the most common meat extract, contains the water-soluble, non-coagulable substances in meat in MEAT PREPARATIONS 153 2 o O o o CO 03 CD •o CN O Ph l> »o »o d d il-i £-§.* O o o CN t^ o 1> O ■* IO CN CN d r-l rG <1 co G o o C o CN o OS CO OS co O 2 r-i CO d o d O (Ti o o o 00 CO CM o3 co CO »o CO •-i CO o O l> ,_] ^ d CO ,_,' O M H N rH PQ CO C0t3 o CN c CM CN II iO l> a •"! CN □ rH d tH O d S; Pn 6 .s co co' r^ CO ■* rn DO i> CO CO O H co [3 © d d d d U § Ph < rO M H oJ X! CO .5 o 00 CO CN co g, S 03 CO •<* >""! o 03 CO rH d d d H tn o fe H < a CD co CN CN "■§§ 00 ■* tN O c © o d d d CD < G CO M o rH o TfH CO iO Ph CO 00 d 00 d PSi Ph -* OS CN OS co "3 >* OS OS 1-1 CN H "o %£& ^ T-i r-I d d •< s s-l o 13 S co Eh £ g o o ►J < 5 o 2a iO »o OS d co d CN CN y E^a 1-1 S ^ 03 . H o| r^ (M CD tH C eg CO •* CN S.I © d d d rH rH M o •* O CO co 5 M o P Tfl O ""J LO CO CN 10 CO ^£ d -* 00 d CN CO d d c u CO »o O I> co CN _ CD rH 03 o CN IO •* ,_! OS LO t^ £ CN ■* IO i> CD OS ^ 50 o3 3 "C a rH OJ in 03 CG o 03 rH a o p,g • a a >>.2 '3 03 03 CO O a S ° "a l 1 s Ah K 2 s pq Ph « ' aa ^rQ >.S o a .r2"03 r^G3 ° bC G a -dO 03 S^H rd o3t3-G cc o3 rG oS a +e as .a g-S-o <" 2 ^ 03 01 2 -» a§^ c«Ph cu G += -t-3 g a § u 03 ft 03 o3 3 « op ,_ s3 a u 03 ft 8 u -(J a _ » wi .5 OS'S 38 03 -e ^ 03 Si w 03 s- Is ft 2ft "53 u -£ 03 a 3 03 IS T5 gj CD > -0 — < < & rt O <; Grape : Juice • 91 2 057 0.902 O.237 5.10 0.89 Jelly • 36 3 0.45 0.524 0.175 32.29 60.29 30.52 4,9-33 Pulp • 87 5 0-75 6. 11 0.29 Jam • 43 ■4 O.48 0.744 0.525 33-44 42.45 H-33 7338 Orange : Juice • 93 •9 O.36 0.297 O.581 1.52 2 .29 Jelly • 31 •4 O.3O 0. 171 O.418 3-95 65-59 62.62 4.91 Pulp . 86 •9 O.6I 0.686 O.985 413 3-33 Jam • 19 •5 O.44 0-433 O.944 13-61 69.I3 54-23 21.55 12 178 CARBOHYDRATE-RICH FOODS preparation of jellies, for it aids in the gelatinization of pectin and in the inversion of the sugar. In the latter process a large proportion of the added cane-sugar is "inverted" into non- crystallizing invert sugar. This is an important consideration in preparing such products, for otherwise the cane-sugar would crystallize and the jelly or jam would be physically unpalatable. The following table on page 177 gives the comparative com- position of the expressed juice and pulp and of the jelly and jams prepared from them. Digestion and Utilization of Sugar. — We will confine our dis- cussion to the utilization of sucrose and its products of hydroly- sis, for the quantities of the other sugars ingested are compara- tively small. The only important exception is the lactose in milk, the source of carbohydrate in the diet of infants. The digestion of sugars takes place almost wholly in the intestines. They are there transformed, in the processes of digestion, into monosaccharides and in that form are completely absorbed. Under certain conditions, however, sucrose may be absorbed into the system without being first inverted. When excessive quantities of a sugar are ingested, absorption takes place more rapidly than digestion, i. e., the assimilation limit is exceeded. Sucrose which gains access to the blood stream in this way is not utilized, however, for it immediately appears in the urine. This fact has also been proved by the injection of sucrose into the blood when it is excreted almost quantitatively. The appearance of sugar in the urine under such conditions is termed "glycosuria." An alimentary glycosuria may occur upon the excessive ingestion of any of the readily absorbable sugars. The quantity which may be ingested at one time without causing glycosuria is a rather definite quantity for each indi- vidual. The following are average figures: Grams. Lactose 120 Cane-sugar ' 150-200 Levulose 200 Glucose 200-250 When the ingestion of a sugar is distributed over long periods of time and particularly when it is taken with other food, greater quantities than these can be given without causing glycosuria. Taylor has suggested that the assimilation limit of glucose is not as definite a quantity as formerly supposed but that it depends upon the capacity of the individual to retain it without regurgitation. Cane-sugar, when taken in concentrated solution, has a dis- turbing effect upon the digestive processes. These disturb- ances are likely to arise from the ingestion of candies or sweet STARCH 179 syrups except when accompanied by food or sufficient water. The effect has been shown to be a direct irritation of the gastric mucosa due to the rapid withdrawal of water, causing inflammation and excessive secretion of mucus and a highly acid gastric juice. The repeated irritation of the stomach may lead to serious gastric disturbances. Investiga- tions have shown that with too large an ingestion of sugar (120 grams) the emptying of the stomach is delayed. Invert sugar does not have as pronounced an effect upon the diges- tive processes as sucrose. Since sugars are not absorbed in the stomach, when their passage is delayed fermentation often takes place. The prod- ucts of such fermentation vary — there may be lactic, butyric, or alcoholic "fermentation" according to the conditions which exist. Lactose has been shown to be less likely to give rise to fermentation. Sugar is the most concentrated form of carbohydrate food, for, in the form in which it is usually ingested it contains very little water. For this reason and because they are easily digestible and assimilable sugars are valuable when it is desired to supply food for the performance of work involving a sudden outburst of effort; they become available to the tissues in a compara- tively short time. Experiments with soldiers have shown that they are able to perform a greater amount of work without fatigue after the ingestion of sugar than without it. Since continued effort is accompanied by a depletion of the carbo- hydrate stores, it is necessary, when sugar is being taken for an increase of efficiency, to ingest it at intervals during the whole period. The fact that sugars are completely absorbed is of importance in the construction of a diet in which it is desired to supply the energy requirements without producing a large fecal mass. Valuable as sugar is in certain cases, from a dietetic stand- point there is a certain danger in its use. Von Bunge has pointed out that the excessive use of sugar in the diet is likely to lead to a decrease in the ingestion of vegetable foods and to a consequent failure to obtain the inorganic elements, such as iron, calcium, phosphorus, etc., which are necessary for continued good health. The average diet has been shown to be comparatively low in these food constituents and any tendency to lower the quantity taken is to be guarded against. STARCH. Starch is the principal form of carbohydrate in the food of man. It is the form in which the plant stores the soluble 180 CARBOHYDRATE-RICH FOODS carbohydrate formed in the processes of photosynthesis against the future demands of the embryo or plant itself. It is a member of the group of carbohydrates designated as poly- saccharides. A starch molecule is composed of a number of molecules of glucose which have been united into a complex structure in which one molecule of water has been removed in the union of two molecules of glucose. Upon digestion (hydrolysis) starch is broken down into simple compounds — soluble starch, dextrin, maltose, glucose — according to the nature and intensity of the digestive process. The final product, glucose, is absorbed and used in the body or synthetized into a compound, glycogen, which is similar in .structure and serves as a reserve carbohydrate to the same end in the animal economy that starch does in the plant. In the plant, starch is stored in the form of fine grains or granules. These consist of alternate layers of particles of starch and of cellulose, a more dense and complex compound similar to starch, arranged in concentric rings. The shape of the gran- ule and arrangement of the rings is characteristic of the plants in which they are formed. The microscopic appear- ance of the starch granule thus becomes a valuable means of determining its origin and of detecting the adulteration of foods. Raw starch is insoluble in cold water. Under the influence of heat (or acids) it takes up water, becomes hydrated, swells,, and becomes semitransparent, forming an opaque solution. This is not a true solution but one in which the starch par- ticles are suspended in water — a colloidal solution. Careful treatment of starch with acids gives a partially hydrated product known as soluble starch, the dried form of which is soluble— a colloidal solution — in cold water. The hydration of starch under the influence of heat and in the presence of water causes the starch grains to swell and rupture the surrounding cellulose layers. This is the object sought in the cooking of vegetables. Dextrin is one of the first products of hydrolysis of starch, formed by the action of enzymes (digestion), of acids, or of heat. Although it still retains the complex structure of starch, it is more soluble in water. The carbohydrate of the crust of a loaf of bread is composed largely of soluble starch and dextrin formed during the baking process. The readily soluble and diffusible products of the hydroly- sis of starch, maltose and glucose, have already been consid- ered in our discussion of sugars. Starch itself is readily digested and absorbed. Glucose is the end-product of its digestion — the form of carbohydrate GRAINS AND THEIR PRODUCTS 181 present in the blood stream. The digestion and absorption of starch extends over a considerable length of time being delayed by the associated indigestible cellulose. The result is that starchy foods yield glucose to the body over a much longer period of time than those containing soluble carbohy- drates, sugars. This is in most cases an advantage, particu- larly where severe muscular work is to be performed. The gradual absorption of the carbohydrate keeps the body con- tinually supplied with the most efficient food for the per- formance of work yet without depleting the store of glycogen before the next meal. The digestibility of the various prepared foods, particularly bread and potatoes, will be discussed later (pp. 190 and 192). GRAINS AND THEIR PRODUCTS. This group of foods includes the seeds of various plants such as barley, buckwheat, corn or maize, oats, rice, rye, and wheat, and the products manufactured from them. Grains are harvested in the partially dried state and contain, there- fore, a lower percentage of water (10 to 12 per cent.) and a higher percentage of carbohydrate, protein and fat than the fresh grain. Starch is the predominating food-stuff (65 to 75 per cent, of the dried grain). Small quantities of sugar and cellulose are present. The protein content is rather high (10 to 12 per cent.) and a number of different kinds are pres- ent. The predominating proteins, such as the alcohol-soluble protein, gliadin, and the glutelin, glutenin of wheat, are of a different type from those found in flesh foods. The nutritive value of vegetable proteins has been discussed (p. 116). The fat content of grains may be rather high, oats and corn con- tain as much as 8 per cent.; the values average between 0.5 and 8 per cent., according to the kind of grain. The fat of the grains has a low melting-point and exists as an oil. Approximately 2 per cent, of ash is present in grain. This is distributed chiefly in the outer layers of the kernel and the germ. The tables on pages 182 and 186 give the composition of the various whole grains and of the flours prepared from them. Composition of Various Whole Grains as Marketed by the Farmer. Protein Carbo- Water, (Nx6.25), Fat, hydrate, Fiber, Ash, per cent. per cent. per cent. per cent. per cent. per cent Barley IO.85 11.00 2.25 69 -55 3-85 2.50 Corn . 10-75 10.00 4-25 71-75 i-75 1.50 Oats . 10.06 12.15 4-33 57-93 12.07 3-45 Rye . IO.50 12.25 1.50 71-75 2.10 1 .90 Wheat 10.60 12.25 1-75 7125 2.40 1.75 182 CARBOHYDRATE-RICH FOODS Composition of Prepared Cereals. s al © © © CD "5 s © a © ?►> 0) J3 O ^ rQ © © © a © © a ©"c3 (3 ■n u © . "fcc 00 O §3 fc 3» ,0 .a to §a go Barley, pearled . ii. 9 10.5 2.2 72.8 6.5 2.6 1603 28 Buckwheat flour 13.6 6.4 I .2 77-9 0.4 0.9 1577 29 Cornmeal, granular 12.5 9.2 i-9 75-4 1 .0 1 .0 1620 28 Oatmeal . 7-3 16. 1 7.2 67-5 0.9 1.9 1811 25 Rice .... 12.3 8.0 0.3 79.0 0.2 0.4 1591 29 Rye flour ... 11. 4 13-6 2.0 7i-5 1.8 i-5 1626 28 Wheat flour . 12.0 11. 4 1 .0 75-1 0.3 05 1610 28 With few exceptions the grains are rolled or milled before they are used in the preparation of food. In the various pro- cesses certain portions of the grain are removed, particularly the outer layers of the kernel and the germ. The accompany- ing data related to the polishing of rice gives the important changes in chemical composition during milling. Chemical Composition of the Honduras Type of Rice after Various Milling Processes of Modern Rice Mills. 1 Constituents (per cent.). on < 3 i-, Ph © Ph c © Pi Rough rice .... After removal of hulls . After removal of bran and 11.27 12.32 5-40 1. 18 1.58 I.79 8.67 0-99 7.48 8.57 5-90 2 .42 8-43 9.78 6.65 2-75 most of the germ . After further removal of 12.56 0-53 O.40 0-39 7-79 1.90 8.91 2.17 bran (pearling) After polishing . Coating 12.50 11.89 12 .02 0.47 0.36 0.40 0.28 O.25 0.21 0.30 0.30 0.26 73 00 7.88 8.06 7-75 1-53 1.80 1.66 9.00 9 15 8.81 i-75 2.04 1.88 Total loss 2 . 66.00 85.OO 10.00 32.00 10.00 32.00 Barley. — Barley is not used extensively for human food in this country. As ''pearled barley/' prepared by removing the germ and the greater portion of the bran, it is used in soups. Barley water, prepared from "patent" barley flour is used in infant feeding and in the diet of the sick room. "Patent" barley flour is finely ground pearl barley or barley which has been more thoroughly polished than pearl barley. Buckwheat. — Buckwheat, although ordinarily classed with the cereals, does not belong with them according to its botanical classification. Its use is confined chiefly to the preparation 1 Bulletin 330, U. S. Dept. Agr., 1916. On a moisture-free basis. GRAINS AND THEIR PRODUCTS 183 of pancakes, a hot breakfast cake. In the preparation of buckwheat flour the outer covering is removed and the remain- ing portion rolled and bolted as in the preparation of wheat flour. A rather coarse bolting cloth is used which permits a certain amount of the middlings (see flour) to pass through. A white grade of flour, bolted over a finer cloth, is poorer in protein and fat. Buckwheat is rich in "gluten" the water- insoluble, elastic protein mixture which is the basis of a batter capable of considerable expansion; thus giving a light cake when baked. Corn. — Indian corn or maize differs in composition from the other grains with the exception of the oat, in that it has a high percentage of oil. Corn products are not readily leav- ened because of their low gluten content; wheat flour is often added to rectify this defect. Corn and corn products show the same digestibility as other grains. There are a number of varieties of corn. From a dietetic stand-point distinctions are made among them chiefly on the basis of their use for food: the variety used for cornmeal flour or hominy is field corn; for "popping", popcorn; for use in the green state, green or sweet corn. Field corn is harvested in the semidry state; it is marketed for human food as cornmeal, corn flour, hominy, and corn starch. Cornmeal or corn flour is prepared from the whole grain. "Old process" cornmeal is made by grinding the entire kernel and then separating the larger particles of bran with a sieve; this method gives a flour containing the germ and a certain amount of bran in addition to the starchy portion of the ker- nel. This product is rich in oil and protein. It is difficult to keep such meal, for the oil tends to become rancid. By more careful milling and bolting both the germ and bran are removed, yielding a product which is low in protein, ash, and particularly oil. This flour may be kept for a longer time than the "old process" cornmeal without becoming rancid. But the advan- tage is gained at the expense of nutritive value and accessory substances. Yellow and white cornmeal are prepared from yellow and white varieties of corn respectively. Any preference shown for one or the other of these meals is a matter of taste, for there is essentially no difference between them. Corn starch is also prepared from maize. In its preparation the corn is steeped in warm water; the swollen grain is passed through coarse mills to disintegrate the kernel without break- ing the germ; the germ is removed by a process of differential sedimentation in which the oily germ floats off at the top while the starch granules and other particles settle to the 184 CARBOHYDRATE-RICH FOODS bottom of the separator; the sedimented starch granules and associated hulls are reground and passed over a fine sieve to remove the hulls, and the starch finally purified by fractional sedimentation. Purified starch is sold as such or after being hydrolyzed with acids and steam under pressure, as glucose (p. 176). Green or sweet corn is characterized by its high sugar con- tent. It is eaten in the green state, hence its place in the diet is with succulent vegetables. Large quantities of sweet corn are canned, thus making it available throughout the year. Oats.— Oats, like corn, have a high fat content. The prod- ucts prepared from oats usually contain the whole kernel and are therefore highly nutritious. The use of oatmeal by the Scotch has won for it a reputation as a stimulating and muscle- building food which is perhaps overestimated in comparison with other grain products of a similar character. Oat pre- parations do not leaven readily, since little gluten is present. Oatmeal is used largely in the preparation of porridges and to a smaller extent in bread and cakes. Because of the presence of the germ in oat products the percentage of purine bases is higher than in products prepared from the other cereals in which the germ is removed; for this reason they are ex- cluded from a purine-free diet. Studies of the digestibility and availability of oats show them to be fully as well utilized as bread. Rice. — Rice is particularly rich in carbohydrate. It is used among certain people as the principal constituent of the diet, which is therefore deficient in protein and fat. The lack of protein accompanying a rice diet has been assigned by cer- tain investigators as the cause of the inferior physical and mental development of these races. Rice is supplied in three forms: unhulled; "cured," free from the husk but still retaining the bran; and polished. The polished rice is sometimes coated with talc, paraffin or glu- cose to improve its appearance. In the processes of polishing the outer layers of bran are removed and in so doing a large portion of the mineral matter, particularly phosphorus, is lost. In polishing rice some important dietary constituents (acces- sory substances) are also removed. People who use polished rice as the major constituent of the diet tend to develop beri- beri, a disease which affects the nervous system. The inges- tion of unpolished rice or the addition of foods containing the accessory food substances will cure beriberi. Rice is as readily and thoroughly digested as other grains. The small amount of cellulose it contains makes it a desirable food when the fecal residue is to be kept as low as possible. GRAINS AND THEIR PRODUCTS 185 This applies particularly to polished rice. Because of the low protein and fat content it is advisable to eat protein-rich foods, such as eggs, cheese, and milk, with it. Vegetables should be used with rice, particularly with polished rice, because of its low content of ash and accessory food substances. Rye. — Rye is used extensively in the preparation of bread. In composition it closely approaches wheat. Its proteins are in slightly different proportions; it has considerable protein cor- responding to the gliadin of wheat, but the other constituent of gluten, glutenin, is lacking. Bread made from rye flour is darker, the texture is more dense, and it contains rather more nour- ishment than wheat bread. The digestibility of rye bread is approximately equal to that of white bread. Bread made from flour from which the bran is not removed is not as thoroughly digested as the bolted flour. Wheat. — Wheat is used more extensively in the human dietary than any other grain. Chemical analysis does not indicate any particular superiority of wheat over other grains, nor is it found to be more digestible. It is the appearance of the prepared product and the ease with which it may be leavened that makes wheat prized above the other grains. The fact that wheat flour is comparatively rich in the water- insoluble proteins present in the gluten, the alcohol-soluble gliadin and the alkali-soluble glutenin, makes it the preeminent bread-making grain. For the elastic adherent mixture, gluten stretches and holds the expanding bubbles of gas produced by the leavening agents. It is the coagulation around these bubbles which gives to bread the porous structure in the baked product. With wheat or its products as the basis, the addition of various substances enables the housewife to prepare an endless variety of dishes, and thus use this valuable food without creating a distaste for it because of the monotony of the diet. In spite of its general adaptability to variety in preparation wheat is consumed largely in one form, bread. Rye is the only other grain which approaches wheat in its bread-making properties. Rye bread is, however, a less attractive product for it is darker and slightly more sticky than wheat bread. Wheat is seldom eaten without a certain amount of mechan- ical preparation and modification. The majority of the wheat is consumed in the form of products made from flour. The crushed or whole kernel is often used as a breakfast food after it has been swollen and the starch partially cooked by boiling. A recent preparation has been put on the market in which the whole wheat kernel is subjected to pressure, heated, then allowed suddenly to expand, producing a change in the struc- ture similar to that obtained in popped popcorn. 186 CARBOHYDRATE-RICH FOODS Flour is prepared by a process of grinding and sieving by which the kernel is pulverized and the outer coverings or bran and the germ are separated from the inner portion, which is rich in starch and gluten. Formerly the wheat was ground in one process and the resulting products sifted and graded according to their fineness of division. This gave three gen- eral grades: white flour (finest), middlings (which contain some fine particles of the coarse outer material) and bran. Middlings obtained from the roller process differ from the above in that they contain very little bran. The present method is to crush the grain between a series of rollers which reduce the size of the particles gradually until the desired tex- ture is obtained. Between the different sets of rollers are sieves to separate the finely divided flour from the coarser bran and germ. Early in the rolling process a white flour poor in gluten, called "break" flour is separated; as the grinding becomes finer more and more of the gluten-rich flour with a yellowish color, or the middlings is obtained. A mixture of these two general classes of flour, "breaks" and middlings give a flour containing the proper amount of gluten for bread- making. The highest grades of flour are known as "patent," "standard patent flour," "straight grade flour," "first clear." The lower grades of flour are designated "second clear," "bakers' flour" and the lowest grade is called "red dog." The highest grades of flour are light in color and contain more gluten and show a better granulation than the lower grades. In the latter, the protein content is higher, but the gluten is less elastic and not as satisfactory for bread-making purposes. The best test of a good flour is its baking properties. Analysis of Wheat and the Products of Roller Milling (United States Department of Agriculture). Protein Carbo- Water, (Nx5.7), .Fat, hydrate, Ash, Milling products. per cent. per cent. per cent. per cent. per cent First patent flour . 10-55 II.08 115 76.85 0-37 Second patent flour IO.49 II. 14 1.20 76.75 O.42 First clear grade flour . IO.13 13-74 2.20 73 13 0.80 Straight or standard patent flour 10-54 11.99 I. 61 75 -36 O.50 Second clear grade flour IO.08 1503 3-77 69-37 1-75 "Red dog" flour 9.17 18.98 7.00 6i.37 3-48 Shorts 8-73 14.87 6.37 65-47 4-56 Bran 9-99 14.02 4-39 65 -54 6.06 Entire wheat flour . 10.81 12.26 2.24 73 67 I .02 Graham flour .... 8.61 12.65 2.44 74-58 I.72 Wheat ground in laboratory 8.50 12.65 2.36 74.69 1.80 Germ 8-73 27.24 11.23 48.09 4-71 There are a number of varieties of wheat: spring, winter, soft, and hard. By the use of these and by different methods GRAINS AND THEIR PRODUCTS 187 of manipulation a number of grades of flour are produced which vary chiefly in their gluten content. In baking these differences assume more or less importance. From a nutri- tive point of view, however, it is the relative proportion of the inner portion of the kernel, bran, the outer covering, and the germ which is of importance. Certain grades of flour have distinctive names under which they are sold in commerce. Graham flour is composed of the carefully ground, unbolted entire wheat kernel. As such it contains all the constituents of the wheat, the bran, the germ, and contents of the endosperm (starch and gluten). This flour derives its name from Sylvester Graham who advocated the ingestion of the whole wheat for both economical and dietetic reasons. The greater cellulose content of the bran renders bread from such flour less digestible. The added intes- tinal irritation, the bulk derived from the particles of indi- gestible bran, and certain substances present in the bran and germ have mild laxative properties. Entire wheat flour is made of wheat from which the greater part of the outer covering, or bran, has been removed. It contains the germ with its added fat and protein content in addition to the usual constituents of flour. The increased nutritive value protein— fat and ash — of the flour is of economic importance'. Gluten flours are prepared by removing the greater part of the starch from ordinary flour and are supplied in various grades, according to the quantity of gluten present. They are of particular value as food for diabetics. Gluten flours are discussed further in connection with diabetes. Bread. — The term bread is usually applied to the baked, leavened preparation of wheat flour. It may, however, include similar preparations of all forms of finely divided grains, such as rye bread or corn bread. When the added ingredients used with flour assume importance with regard to flavor and tex- ture, the mixture is no longer distinguished as bread. Thus sugar, butter, eggs, milk, spices, are used with flour in the preparation of cakes, puddings, and pastries. Bread in the sense ordinarily used is a combination of white flour, water, salt, and yeast which have been leavened as the result of the growth of the yeast. In this process carbon dioxide is formed and the mixture "rises," assuming a sponge- like structure. This "sponge" is kneaded with the addition of flour, divided into appropriate masses, permitted to rise again and, at the proper time, baked. In the process of bak- ing heat causes a further expansion of the carbon dioxide and air and by coagulating the proteins retains the sponge-like 188 CARBOHYDRATE-RICH FOODS structure. Various changes take place in the chemical com- position of the flour during the leavening process. A cer- tain amount of sugar is converted into carbon dioxide and alcohol; during baking there is a loss of water and fat, the protein is coagulated, the starch grains are broken, and at the outer surface particularly starch is converted by dry heat into soluble starch and dextrin. The partial caramelization of the starch and dextrin produces the delicate brown color of a well-baked loaf. Leavening may be accomplished in a number of ways — with yeast (enzymatic) which is supplied in both moist (com- pressed yeast) and dried condition; by mechanical incorpora- tion of air; or by the evolution of gas as the result of chemical action (baking powder). When yeast is used the carbon diox- ide is produced at the expense of the constituents of the flour, the starch is partially converted into simpler products in addi- tion to alcohol, and certain amounts of organic acids, such as lactic or acetic, which in quantity are said to injure the flavor of bread. The simplest form of aeration with mechanical incorpora- tion of gas is that produced by "beating up" a mixture of flour and water. The entrapped bubbles of air swell and pro- duce, when baked, porous though rather dense biscuit or bread. Unleavened bread is used in certain religious festi- vals. In the commercial preparation of bread, water satu- rated, under pressure, with gas is sometimes mixed with flour. When the pressure is released the dough swells; it is then baked. This is called aerated bread. Baking Powders. — Baking powders will leaven dough more quickly than will yeast, in a few minutes, instead of in six to ten hours. All baking powders depend in principle upon the interaction between a carbonate and an acid. Sodium bicar- bonate (saleratus or baking soda) is the most common source of carbon dioxide. The old method of making certain breads with sour milk and soda often resulted in a semifailure because of the varying degrees of acidity of the milk. The baking powders now supplied have the acid and alkali so balanced that there is complete neutralization. Preparations vary chiefly in the nature of the acid constituent or its equivalent; thus we have the "tartrate" (tartar), acid potassium tartrate or tartaric acid powders; the phosphate (calcium acid phos- phate) powders, and the alum powders (a sulphate of aluminum). These salts when mixed with bicarbonate are relatively inert in the dry state but in the presence of water react readily to yield carbon dioxide. There are certain objections to the use of baking powders GRAINS AND THEIR PRODUCTS 189 in that the salts resulting from their reactions may be deleter- ious to the health through their action on the system in gen- eral or to their laxative effect. While it is certain that excessive doses of these salts are harmful it is difficult to determine whether or not small amounts, such as are ingested in breads, are detrimental. Rolls, Biscuits, Muffins, etc. — Rolls are similar to bread except that they usually contain more added fat in the form of lard or butter and sometines more sugar. They differ little in composition from bread. In baking they are ordinarily made into small loaves or "rolls" and have more crust in proportion to their size than bread. Such breads are often used while hot or warm. The ordinary baking powder biscuit differs from the roll in that it is leavened with baking powder and contains more shortening, as lard or butter. The effect of the short- ening is to render the gluten less tenacious. Biscuits are, therefore, readily broken into pieces when hot. Muffins are similar to biscuits; they usually contain egg in addition to the other ingredients. Rolls, biscuits and muffins are often referred to as indiges- tible. This indigestibility is ascribed in part to the added fat and in part to the fact that since they are served hot, they are eaten rapidly and without sufficient mastication, thus yielding a sodden mass which does not pass readily from the stomach. Experiments have shown the relative availability of the protein, fat, and carbohydrate of these foods to be fully as complete as those of bread. Biscuits, Crackers. — The term biscuit is used commonly to designate the hard, dry breads baked in thin layers and prepared with the addition of little or no baking power. These are sold in various forms depending upon the ingred- ients used in their manufacture. They are held to be very digestible, no doubt because of their dryness and to the com- plete salivation and mastication necessary in eating them. Cakes. — Cakes are sweetened breads in which eggs, milk, flavoring and spices and considerable shortening, such as butter and lard, are used. They are very "rich" foods in that they contain more fat and protein than the breads. Breakfast Foods. — Certain specially prepared grains are sold as breakfast foods. These are usually patented prepara- tions. Among them will be found representatives of all the more important grains. The changes produced are chiefly of a mechanical nature associated with a certain amount of chemical change resembling the natural processes of diges- tion. The changes are in general of a fermentative nature, 190 CARBOHYDRATE-RICH FOODS such as those produced by the action of malt or yeast and the action of heat upon either the moist or dry grain. Condi- ments, such as sugar and salts, are sometimes added. Those foods which are cooked are sold for direct consumption; the others must be subjected to prolonged cooking before they are ready for the table. Macaroni. — Macaroni is a preparation of a highly glutenous wheat flour and water. It is molded into various forms and sold under different trade names, as spaghetti, macaroni, and noodles. A special type of wheat, durum wheat, is used. The relative composition of macaroni will be found in the accompanying table. The composition of some of these preparations is given in the following table: Composition of Typical Wheat Products. a 05 CD a 03 . 05 fl u 8 a t-T CD PI O 05 O U 05 a >> 05 u t-i a 05 u 03 a 1° a U 03 a 03O FM to O to < Ph O Breakfast food: Cracked Wheat 10. I II .1 i-7 75-5 i-7 1.6 1635 28 Shredded Wheat 8.1 10.5 1.4 77-9 i-7 2. 1 1660 27 Macaroni . 10.3 134 0.9 74.1 1-3 1625 28 Rolls, Vienna Bread: White . . . 37-i 8.5 2.2 56.5 0.4 1 .1 1270 36 35-3 9.2 i-3 53-i 0.5 1 . 1 Il82 38 Whole wheat . 38.4 9-7 0.9 49-7 1 .2 i-3 III3 41 Crackers, soda 5-9 9.8 9.1 73-1 o-3 2.1 1875 24 Cake, cup 15-6 5-9 9.0 68.5 0.3 1.0 1716 26 The digestibility and nutritive value of bread, particularly the comparative digestibility of white bread and the whole wheat or Graham breads assumes considerable economic impor- tance with regard to the diet of the poor and there has been a great deal of controversy over the question. Comparative studies of the two forms of bread have demonstrated a lower digestibility of the protein and carbohydrates of entire wheat and Graham flours. Celluloses. — Celluloses form a large portion of the cell wall of plants. They are polysaccharids having a more complex structure than the starches. Celluloses differ according to whether they are composed of glucose or some other sugar, as pentose or galactose. These carbohydrates are very insoluble in water and more difficult to hydrolyze than starch, and are practically indigestible for man. It is the indigestibility of the celluloses which makes vegetables and fruits a valuable means of adding bulk to the intestinal mass with the resultant POTATOES 191 stimulation of peristalsis. Cellulose is also largely responsible for the low utilization of vegetable foods. Hemicelluloses differ from true celluloses in that they are hydrolyzed by dilute acids. Of this class the sea-weed, agar agar and Iceland moss are of dietetic and therapeutic impor- tance. Because of their comparative indigestibility and their ability to absorb and hold water they yield a soft fecal mass which may be easily evacuated. Potatoes. — The true, "Irish", potato, as well as the sweet potato, is used to a large extent as one of the important sources of carbohydrate. We will therefore discuss these foods here, although they possess properties which might place them with the succulent vegetables, more valuable for their salts and water. Bananas are, from a nutritive point of view, com- parable with potatoes; they are, however, ordinarily classed with fruits. Composition. « u CD "3 i CD O cd u CD ft z Lard 97 35 Beef fat 93 45 Mutton fat 88 50 In the processes of metabolism both fat and carbohydrate are used chiefly in the production of energy. Their role in the structure of the body, while little understood, is highly important; this is particularly true of the lipoids, lecithin and cholesterol, which are constituents of the outer surface of all cells. As a source of energy fats and carbohydrates may, in general, be used interchangeably. It seems necessary, how- ever, that a certain amount of carbohydrate be present in the food for the normal continuance of the metabolic processes. The entire absence of carbohydrate tends to produce certain disturbances, among which acidosis is the most prominent indication. The minimum quantity of carbohydrate needed is not known; that it may be comparatively low is illustrated in the case of the Eskimo whose diet is essentially fat and pro- tein and in which practically the only source of carbohydrate is the glycogen contained in meat. Although carbohydrate appears to be indispensible in the diet, the presence of fat (lipins) is also essential. Studies of growing animals have shown that certain animal fats, e. g., kidney fat, egg yolk fat, butter fat, are the more satisfactory than others or than plant fats for the continuance of growth. The advantage apparently does not reside in the purified fat itself, such as tristearin, or triolein for these are without effect. It is known that there are substances associated with fat which are important for growth and that the absence of these from the diet result in pathological conditions. Such substances as the accessory food substances, 'Tat soluble A" of McCullum, which the body apparently cannot synthetize and must therefore obtain them from the food are present and necessary. It is the absence of these substances which in part explains the failure of some fats to promote growth. The necessary amount of natural fat required per day is not known — the minimum has been estimated at from 25 to 50 grams of fat per day. Fat is a much more concentrated food than carbohydrate or protein in the sense that it yields, because of its lower state of oxidation, a greater amount of energy for a given weight: Calories Calories per gram. per pound. Fat 9.0 4082 Carbohydrate 4.0 18 14 198 FAT-RICH POODS It is therefore the most economical means available to the body for storing energy against future need. But not all the fat of the body comes from fat; it may be formed from carbo- hydrate (glucose). Protein yields complexes which may be built up into fat. Fat is present in the human diet in two forms : (a) that asso- ciated with the food as it occurs naturally and (J?) that which has been extracted from the medium in which it was deposited — flesh, milk, fruits — and which is ingested as such or added to food in the process of preparation. Prepared fats are sim- ilar to the unextracted fats, for the processes of manufacture are essentially physical ones: the fatty substance is separated from its surrounding medium by means of pressing, churning, or heat or a combination of these; very little chemical change takes place except perhaps in some forms of rendering or heat- ing in which there is a partial hydrolysis and slight oxidation of the original fats. We shall therefore confine our discus- sion largely to the manufactured fats and oils, indicating occasionally the relative fat content of certain particularly fatty natural foods when discussing the particular prepared fat which it would yield. Two types of fat-rich foods are obtained from milk: cream, in which the finely emulsified fat is concentrated by gravity or centrifugal force and which contains a small proportion of all the constituents of milk, and butter, in which the fat drop- lets are made to coalesce. Butter contains very little of the milk constituents other than the fat. CREAM. Cream is obtained from milk in two ways, both depending upon the difference in specific gravity between the fat and the other constituents. Formerly milk was placed in a cool place for six to eight hours and the fat or cream permitted to rise to the top; it was then removed or "skimmed off." The separation of the cream from the milk is hastened by the use of a centrifuge or separator which throws the heavier portions of the milk, water, protein, insoluble salts and cells to the periphery from which it is removed while the lighter fat is drawn off from the center. With the separator varying concentrations of butter fat can be obtained in the cream. BUTTER. Butter is obtained from cream by the process of churning, i. e., by mechanical agitation the natural emulsion of milk is BUTTER 199 destroyed and the fat droplets made to coalesce. This pro- cess is facilitated by the slight changes produced in the cream as the result of fermentation or souring. The crude butter collected in the process of churning is separated from the rest of the cream — the butter milk — washed and worked into the final product which we know as butter. The process of work- ing removes most of the particles of curd remaining and the soluble constituents of milk. This gives pure, uncolored sweet butter. Salt is usually added to sweet butter to give it a flavor; it also acts as a preservative. The amount added varies according to the market for which it is intended — from o to 4 per cent. In salting a very good grade of sodium chlo- ride is used. Salted butter is then worked to distribute the salt, to remove the excess of water, to press the particles of fat together into a compact mass, and to give it the texture characteristic of the* butter of commerce. The color of butter will vary according to the nature of the diet of the cow, for the coloring matter of the body fat and milk has been shown to be derived from the coloring matter of plants. Butter made from the milk of cows receiving cer- tain green foods is particularly rich in the yellow color com- monly associated with butter; thus butter made in the spring usually has a deeper yellow color than that made in the win- ter. To ensure a butter of uniform color throughout the year dairymen resort to the use of coloring matter. The presence of bacteria in butter is a matter of fully as great importance as their presence in milk. The processes of butter-making tend to increase the number of bacteria: centrif- ugalization so generally employed for the separation of cream from milk tends to leave the bacteria in the cream and the conglomeration of the particles of fat in the process of churn- ing results in a concentration of bacteria in the butter. The result is that butter often contains many more bacteria than the cream from which it is prepared. The souring of cream before its use in butter-making results in an accumulation of lactic-acid-producing bacteria with an accompanying decrease in the rate of growth of certain other types. The Bacillus tuberculosis has been found in butter prepared from milk containing this organism; cold storage does not result in the death of the bacillus. The following table gives the composition of American creamery butter: Per cent. Fat 82.41 Water 13 .90 Lard 2.51 Curd 1. 18 200 FAT-RICH FOODS Variation from these figures will occur, depending upon the process of manufacture. Dividing the sample of butter into classes according to the fat content, the following general variations were observed in the case of the data given above : butter fat 5.0 per cent., water 2.9 per cent., salt 1.74 per cent., and curd 0.39 per cent. Butter fat is a mixture of the glycerides of various fatty acids with small amounts of lipoids — lecithin and choles- terol — and coloring matter. The relative proportions of these individual fats, or as they are usually expressed in analysis, "fatty acids," varies with the food, particularly with the fat content of the food, the individuality of the cow and stage of lactation. The taste and odor of butter is influenced by the food given the cow; garlic, for instance, gives to milk and butter a decided odor characteristic of the plant. The following table gives the distribution of the more im- portant fatty acids found in a particular sample of butter: 1 Percentage of Acid. triglycerides. Dioxystearic 1 . 04 Oleic 33.94 Stearic 1.91 Palmitic 40-51 Myristic 10.44 Laurie 2 . 73 Capric 0.34 Caprylic 0.53 Caproic 2.32 Butyric 6.23 Butter fat is practically completely absorbed. The average caloric value of butter, based upon an 85 per cent, fat con- tent is approximately 3500 Calories per pound or 7.7 Calories per gram. Renovated Butter and Butter Substitutes. — When butter which has become rancid is treated to restore its sweetness the product is designated as "processed or renovated" butter. The rancid butter is melted, the curd and brine drawn ofT, the fat separated and aerated and then rechurned with milk or cream to restore the texture and flavor. Such butter is in many respects as satisfactory as the average grade of butter; it is not equal in quality to the better grades of butter. Oleomargarine. — A fat product prepared from various animal and vegetable fats and oils which resemble butter in its con- sistency is sold under various names, of which oleomargarine or margarine are the most common. Its manufacture is restricted by the government; a tax is levied against it, a 1 Browne: Jour. Amer. Chem. Soc, 1899, xxi, 807. LARD 201 fourth cent per pound for the uncolored product and ten cents per pound for oleomargarine artificially colored to resemble butter. Yet oleomargarine is a satisfactory substitute for butter; it is often more desirable than some good grades of butter. One objection to oleomargarine is that it is many times sold as butter with the intent to deceive. Containing as it does a higher percentage of stearin, we might expect to find oleomargarine less readily absorbed than butter; experi- ence has shown, however, that the losses in digestion are nearly the same for the two products. Butter is, however, in many ways a finer product and more palatable. It is much richer in the accessory substances or vitamines than oleomargarine and is from this point of view a much more desirable food. The materials used in the manufacture of oleomargarine are chiefly neutral lard, "oleo oil," and cotton seed oil. Neutral lard is prepared from the fresh "leaf lard" of the hog. This is ground up, worked with water, and rendered at a temperature of 40 to 50 C. Only a portion of the lard is removed from the fat. The product obtained is almost neutral in reaction and practically free from taste or odor. Oleo oil is prepared by a somewhat similar process. Fat from the abdominal cavity of beef or caul fat is thoroughly worked in water, chilled, the hardened fat ground up and finally rendered at a low tem- perature. The liquid fat obtained by this process is permitted to cool, when stearin and palmitin partially crystallize out. The fluid portion is pressed out of the semisolid mass, run into cold water and allowed to solidify. This product is desig- nated as "oleo" or "oleo oil." The cotton seed oil used is especially prepared for the purpose. Cocoanut fat and peanut oil are also used. In the final stage of preparation the fats and oils are mixed in the desired proportion; the quantities of the various constituents used depends upon the market for which the oleomargarine is intended. For warm climates more of the oleo oil and lard are used than for cold climates. The properly mixed fats are then churned with milk or cream, or with an emulsion of milk and butter to give the flavor of butter to the product. This yields a coarse emulsion which, upon cooling, is washed, salted, and worked into the final product. The following is the composition of oleomargarine, given by Koenig, in per cent.: Water, 9.07; fat, 87.59; nitrog- enous extractives and lactose, 0.99; ash, 2.35; sodium chloride, 2.15. LARD. Lard is the rendered fat of the hog. The fat is extracted by means of heat which liquefies it and gradually frees it from 202 FAT-RICH FOODS the connective tissues. Lards are designated according to the portion of the animal from which they are prepared and the mode of rendering. "Neutral" and "leaf" lard are obtained from the fat surrounding the kidneys. The preparation of the former has already been indicated (p. 201). "Leaf lard" is obtained by heating the leaf fat or the residue from neutral lard to a higher temperature with steam. Kettle-rendered lard is made from leaf and back fat by heating in open jacketed kettles. Steam lard is made from the remaining portions of the hog not used for direct consumption by the direct applica- tion of steam. Various substitutes for lard are prepared and sold under trade names. They are ordinarily mixtures of cotton seed oil and beef fat or specially treated cotton seed oil. COTTON SEED OIL. Cotton seed oil is used extensively as a substitute for olive oil or in the preparation of substitutes for animal fats. In the preparation of cotton seed oil the cotton seeds are cleaned and ground, the meal heated under pressure to 210 to 21 5 F. and the oil expressed with hydraulic presses while still warm and the crude oil refined. The best grades of cotton seed oil are practically free from any characteristic flavor and are suit- able substitutes for olive oil. As with the butter substitute, oleomargarine, the real objection to its use is the economic one, that it is often sold as olive oil. However, it lacks the characteristic natural flavor of olive oil. By a process of chilling and pressing the higher melting- point fats of cotton seed oil are partially separated from the more liquid ones. The former are used as substitutes for lard while the latter become a satisfactory oil for cold climates. Cotton seed oil is used extensively in the preparation of lard substitutes in which the fatty acids of the liquid unsaturated fats are transformed, reduced into their corresponding satu- rated compounds, which are solid at the ordinary tempera- tures. These transformations are brought about by heating with hydrogen in the presence of finely divided nickel. The nickel is added as a catalyst to hasten the reaction between hydrogen and the fatty acid. Small quantities of nickel remain in the final product and there is a possibility that they may be detrimental to health. This point has not as yet been determined. Such prepared products are as well utilized as lard and other fats and might well be substituted for them when cheaper were it not for the nickel present. COD-LIVER OIL 203 OLIVE OIL. Olive oil is prepared by pressing the flesh of the ripe olive. The selection of the olive and the mode of preparation deter- mine in general the grade of oil. The highest grade of oil, virgin oil, is from selected hand-picked olives. The product is obtained by slight pressure of cold olives. Subsequent pressure of the mass, first cold and then later heated with water, gives the various more or less inferior grades of oil. In some pro- cesses the olives are macerated and crushed before being sub- jected to pressure. The various oils obtained are subjected to a refining process in which foreign particles are removed by filtration and by gravity in settling tanks. Of the fatty acids present in fats of olive oil palmitic and oleic are the most important: there is little, if any, stearic. Other fatty acids are present but only in small quantities. Practically all of these fatty acids occur as neutral fat or glycerides; the small per- centage which exists as free fatty acids varies with the ripe- ness of the fruit and the mode of preparation; most of the high grades of oil contain less than 3 per cent. Olive oil is eaten principally in salads; it is used to some extent in cook- ing. Other vegetable oils are used for food, such as peanut oil, sesame oil, cocoanut oil, etc. Vegetable oils have been found to be fully as digestible as animal fats. COD-LIVER OIL. Cod-liver oil is prepared by means of pressure from the raw fresh livers of codfish. It has been used extensively because it is apparently assimilated under conditions in which other fat foods are not effective. It contains a number of low melt- ing-point saturated fats in addition to olein, which is present to the extent of approximately 70 per cent., cholesterol, a small amount of iodine, and a number of basic substances are also present. The presence in cod-liver oil of specific sub- stances necessary for growth and maintenance, such as are found in butter and egg yolk, may be one of the reasons for its successful use in therapeutics. Cod-liver oil is sometimes adulterated by the admixture of other fish oils which results in an inferior product. Preparations are also sold which pur- port to have all of the therapeutic properties of cod-liver oil without the peculiar oily taste which is repugnant to some persons. Those preparations from which the fat has been entirely or largely removed are practically useless as substi- tutes for cod-liver oil since the therapeutic value rests as much in the readily assimilable oils as in any other factor. CHAPTER XIV. FOODS VALUABLE FOR THEIR SALTS, WATER, AND BULK. In addition to those foods which furnish primarily protein, carbohydrate, or fat is a group of foods which, while supply- ing these food-stuffs to a certain extent, are not sufficiently rich in them to be valuable sources of such material. They form, however, an important part of the diet because they are valuable sources of inorganic salts (particularly the salts of organic acids), of water, and of certain "accessory" food- stuffs essential for a satisfactory diet. They are compara- tively indigestible. It is the indigestible residue which serves to give bulk to the intestinal contents and thus promotes peristalsis. Some of these foods contain a certain amount of soluble material which in itself stimulates peristalsis — laxa- tives. These water-rich, indigestible foods are then a means of adding salts, accessory substances and bulk to the diet without markedly increasing the energy or protein portion of the regimen. In addition to these purely material advantages they are in most cases appetizing and are in this way valuable as aides to digestion. To this class of foods belong the succulent plant foods — the vegetables and fruits. A clear-cut classifi- cation is difficult in a few cases. To classify dried legumes as protein foods, and fresh and canned varieties of the same food as valuable chiefly for their salts and their value as appetizers may appear illogical. A consideration of their usual place in the diet, however, makes this the most desirable classification. Our discussion will confine itself, therefore, unless otherwise stated, to the succulent fruits and vegetables. Fruits and vegetables are composed largely of water; cellu- lose, the chief structural material; starches; sugars; organic acids; gums; mineral matter; protein, and a small amount of fat. So far as nutritive value is concerned, the quantities of the food-stuffs present are so small as to be practically negli- gible. The small amount of protein is poorly absorbed; carbo- hydrate, exclusive of cellulose, and fat are almost completely digested, but the small quantity ingested is very seldom of practical importance. This is particularly true of the fat. The indigestibility of fruits and vegetables as a whole is due FOODS VALUABLE FOR SALTS AND WATER 205 to the cellulose content. Cooking will increase the digestibility of this carbohydrate to a certain extent, particularly in the case of raw fruit and the starchy vegetables, for it softens the cellulose structures and ruptures the starch grains. The accompanying table gives the composition of some of the more important fruits and vegetables. Chemical Composition of Typical Fruits. fresh. Fruits. a a Jo CO X! .5 s c u a> -d 15 fl v_/ a> a> .a a cfl . a u a) £ . _Ot3 * a ? a bo e a) o> eS CO 3 u -n a> a a e3 t, ^2 a) aj'a? -d en 3,2 a > — 1 09 a> a> CO is £ fa fa O O -5 fa O Apples 84.6 0.4 0-5 14.2 I .2 0-3 285 159 Bananas . 75-3 1-3 0.6 22.0 1.0 0.8 447 101 Blackberries . 86 3 1-3 1.0 10.9 2-5 05 262 173 Cherries . 80 9 1.0 0.8 16.7 0.2 0.6 354 128 Grapes 77 4 i-3 1.6 19.2 4-3 0-5 437 104 Huckleberries 81 9 0.6 0.6 16.6 0.3 336 Lemons 89 3 1 .0 0.7 8-5 1. 1 o-5 201 226 Muskmelons . 89 5 0.6 9-3 2.1 0.6 180 252 Oranges . 86 9 0.8 0.2 11. 6 0.5 233 195 Peaches 89 4 0.7 O.I 9-4 3-6 0.4 188 242 Strawberries . . . 90 4 1 .0 0.6 7-4 1.4 0.6 177 256 DRIED. Apples 28.1 1.6 2.2 66.1 2.0 1318 34 Dates .... 15-4 2.1 2.8 78.4 i-3 1575 29 Figs .... 18.8 4-3 0.3 74.2 2.4 1437 Prunes 22.3 2.1 73-3 2-3 1368 33 Raisins 14.6 2.6 3-3 76.1 3-4 1562 29 Chemi cal Compositions of Typical Vegetables. S" Ots c^ a) z Is a 2 OQ Vegetables. O CD G u CO a c a o3 aT rt . 1* jj X. 9, * — a> 3g s> a ?£ a (0 (h a og ©ft 15 ;3— . a> a; ■2 £ £ fa «j fa Asparagus 94.0 1.8 0.2 3-3 0.8 0.7 101 450 Beans, fresh: Lima 68.5 71 0.7 22.0 1.7 i-7 557 82 String 89 2 2.3 0-3 7-4 0.8 189 241 Cabbage . 91 5 1.6 0.3 5-6 1 .1 1.0 143 317 Carrots 88 2 1 .1 O.4 9-3 I.I 1 .0 205 221 Celery- 94 5 1 .1 O.I 3-3 1.0 84 540 Lettuce 94 7 1.2 0-3 2.9 0.7 0.9 87 524 Potatoes : White . . . 78 3 2.2 O.I 18.4 0.4 1.0 378 120 Sweet . 69 1.8 0.7 27.4 1-3 I . I 558 81 Pumpkins 93 1 1 .0 O.I 5-2 1 .2 0.6 117 389 Spinach 92 3 2. 1 0.3 3-2 0.9 2.1 109 418 Tomatoes 94 3 0.9 0.4 3-9 0.6 o-5 104 439 206 FOODS VALUABLE FOR SALTS AND WATER Fresh vegetables and fruits have long been known for their antiscorbutic properties. These have been ascribed to the pre- dominance of the basic elements in the ash. While this may be a factor, recent work has shown the presence of the acces- sory food-stuffs, vitamines, which may be of much more importance. The constituents of vegetables and fruits which make them so desirable as foods are the salts and in fruits, the acids or acid salts, soluble sugars, and the essential oils, esters and ethers which give the pleasant taste. Cellulose is important for its laxative effect. The pleasing appearance of fresh and cooked vegetables and fruits has some esthetic value. Most fruits and many vegetables are palatable even in the raw state, in which form it is the crispness of the pulp or leaf which is particularly attractive. The delicate coloring matter which these foods contain is not only attractive to the eye but serves to stimulate the appetite. When cooked with sugar, as pre- serves or jellies, these coloring matters and flavors are the means of increasing the appetite not only for the conserve itself but for insipid foods, chiefly carbohydrates, to which they are added. In this way they are valuable in the diet of the sick room. Vegetable foods are comparatively tasteless. To make them palatable it is necessary to add fats, usually in the form of oil or butter, and condiments, particularly acids, e. g. y vinegar. The addition of salt to vegetables is also necessary. The importance of vegetables and fruits as sources of salts is indicated by the following table which gives the percentage of individual ash constituents of typical vegetables and fruits: Composition of the Ash of Typical Fruits. 1 fresh. Fruits. CaO. MgO. K2O. Na 2 0. P2O5. CI.' s. Fe. Apples . 014 .014 •15 .02 03 .004 .005 .0003 Bananas 01 .04 •50 .02 055 .20 .013 .0006 Blackberries 08 •035 .20 08 .01 Cherries 03 .027 .26 •03 07 .OI .01 .0005 Grapes 024 .014 •25 •03 12 .01 .024 .OOI3 Huckleberries . 035 .025 07 .02 .013 .OOII Lemons 05 .OI .21 .01 02 .01 .012 .0006 Muskmelons 024 .02 .283 .082 035 .04I .014 .0003 Oranges 06 .02 .22 .01 05 .01 .013 .OOO3 Peaches 01 .02 •25 .02 O47 .01 .01 .OOO3 Strawberries 05 •03 .18 .07 O64 .01 .OOO9 DRIED. Dates . 10 ■13 12 • 32 .066 .003 Figs . . . 299 •H5 I.48 .064 332 .056 .056 .OO32 Prunes . 06 .08 I .2 . I 25 .01 • 03 .OO29 Raisins . 08 .15 I .0 .19 29 .07 .06 .005 1 Sherman: Food Products, 1914, p. 347. COMPOSITION 207 Composition of the Ash of Typical Vegetables. Vegetables. CaO. MgO. K2O. Na 2 0. P2O5. CI. s. Fe. Asparagus . . .04 .02 20 01 09 .04 04 .001 Beans: Lima . .04 .11 7 12 27 .009 06 .0025 String • 075 •043 28 03 12 .018 04 .0016 Cabbage . .068 .026 45 05 09 •03 07 .0011 Carrots • -077 •034 35 13 10 .036 022 .0008 Celery . .10 .04 37 11 10 •17 025 .0005 Lettuce • -05 .01 42 04 09 .06 OI4 .OOI Potatoes : White . . .016 .036 53 025 14 ■03 03 .0013 Sweet • -025 .02 47 06 09 .12 02 .0005 Pumpkins . ■ -03 .OI5 08 08 11 .01 02 Spinach . .09 .08 94 20 13 .02 O4I .0032 Tomatoes . .02 .017 35 01 059 •03 02 .OOO4 Green vegetables and fruits are an important source of iron. Investigations have shown that combined iron, such as occurs in nature is in a readily assimilable form, probably in the most desirable state. The iron of meat is chiefly in the form of hemoglobin, which is comparatively indigestible. The iron compounds of vegetables and fruits are, however, quite readily digested and absorbed. It is the availability of the iron which makes plant foods desirable in the diet for the iron they contain. The tables indicate only the relative amounts of the various elements, or their oxides, present in fruits and vegetables. If we consider them with regard to the form in which these elements exist we find the basic elements combined with both inorganic and organic radicles. The organic acids exist in many cases as the acid salts, chiefly the acid potassium salts. As the organic acids occur in the fruit or vegetable they exhibit in some cases a considerable degree of acidity, as is the case of lemons or apples. After absorption in the body the organic acid is oxidized and the base, associated with the acid, com- bines with carbonic acid to form the carbonate which func- tions as a potential base. An examination of the ash of fruits and vegetables shows it to contain an excess of base- over the acid-forming elements. In our discussion of inorganic salts it was noted that animal food is, with the exception of milk, potentially acid-yielding. Vegetables are then important in the dietary, for their ability to neutralize the acids produced in metabolism. In the case of fruits and vegetables it is the small amount of nutritive material associated with the salts which makes it possible to balance the diet with regard to its acid- and alkali-forming properties, so as to aid in the main- tenance of the neutrality of the blood. For the same reason, vegetables are important when it is desired to reduce the potential acidity of the blood and urine. An excess of base- 208 FOODS VALUABLE FOR SALTS AND WATER forming elements is not as objectionable as an excess of acid- forming elements because of the ever-present excess of carbon dioxide to form bicarbonate with the base. The natural ten- dency to ingest plant food with meat in a mixed diet has had, therefore, a scientific foundation. The greater solubility of uric acid in an alkaline urine, resulting from the ingestion of an excess of basic material, than in a neutral or acid urine is also an advantage. The sugars of fruits and vegetables are chiefly sucrose (cane- sugar), dextrose, and levulose. Some fruits, such as the grape, often contain a high proportion of sugar. The more important plant acids are citric (lemon), malic (apple), tartaric (grape), and in some oxalic acid. The acids occur in varying proportions in the different fruits and vege- tables. The fruits designated in parentheses above are repre- sentative of the class of fruit in which the particular acid predominates; other acids are also present. The relative pro- portion of starch, sugar and acid in fruits varies during the process of ripening. The following table gives the variation in the composition of an apple at various stages of its growth. Composition of Baldwin Apple at Different Periods in Its Growth 1 , Per cent. Free Invert Total malic Condition. Water. Solids. sugar. Sucose. sugar. Starch. acid. Ash. Very green • 81.5 18.5 6.4 1.6 8.0 4-1 1.2 O.27 Green . • 79-8 20.2 6-5 4-1 IO.5 3-7 Ripe . . ' -80.4 I9.6 7-7 6.8 14-5 0.17 O.65 O.27 Overripe . • 80.3 19.7 8.8 5-3 14. 1 O.48 O.28 Green fruit, in general, contains considerable starch. As the fruit ripens there is a gradual reduction in the quantities of the starch and acids and an increase of sugar. Pectin, the carbohydrate which forms the basis of jellies, gradually decreases as the fruit ripens. Cooking of Vegetables and Fruits. — Vegetables and fruits are cooked to soften the cellulose structure, rupture the starch grains, improve the texture and flavor, and thereby increase digestibility and palatability. Many fruits and vegetables which are also eaten in the raw form are cooked to add variety to the diet and for purposes of preservation. Heat converts the water in the cells into steam, the expansion of which rup- tures the cells, freeing the enclosed starch; an exaggerated example of the expansive action of steam is seen in the pop- ping of corn, in which expansion takes place suddenly through- 1 Browne: Penn, Dept. Agr., Bull. 58. COOKING OF VEGETABLES AND FRUITS 209 out the whole mass of starch cells when the internal pressure is sufficient to rupture the tough outer layer of the kernel. During the process of cooking hydrolytic changes occur: the starch and cellulose are partially hydrated, take up water, and are transformed into simpler products — glucose and sugars; protein is coagulated; the mineral salts are only slightly affected. Since inorganic salts are, from a dietetic point of view, one of the important food factors in fruit and vegetables, it is desirable, then, to conserve them as much as possible. In boiling, the method usually employed for cooking vegetables, a large proportion of the salts and also protein may be lost; by direct removal before cooking, as in peeling; by extraction in the water used in washing and soaking, or discarded with the water poured off at the end of the cooking process. Methods which will avoid these losses should be used. Baking or steaming, with the least removal of outer coverings, is the most desirable. Some vegetables, such as spinach and chard, which are cooked by steaming in the water contained in them, are found to lose a large proportion of their salts when the liquor is poured off before they are served. Losses in Cooking Vegetables (Percentage of Fresh Edible Portion). 1 Kind of vegetable. Solids. Spinach : Boiled • • 31-59 Steamed .... . . 0.18 Cabbage : Boiled . . 32.86 Steamed .... • • 2 . 54 Carrots : Cut up and boiled . . 10.05 Boiled whole . . . 6.28 Ash. P 2 s . CaO. Mg 51-65 9-34 52.33 5-23 6.89? 8.69 60. 7- 42.62 11.47 33-93 1.79 27.66 9-31 26. 4- 11.48 7-38 22.88 17.97 10.88 8-77 19- 19- Fruits and vegetables may be kept at ordinary temperatures for a considerable length of time before they begin to decay, wilt, or dry up. With proper refrigeration many of them can be kept for a comparatively long time. Such a method of preservation is becoming more prevalent, and some vegetables and fruits may be had throughout the year. Apples in par- ticular are commonly preserved in cold storage. The process of canning fruit and vegetables has long been used by the housewife to preserve them for use when out of season. Canned foods can now be purchased in the stores in great variety, tomatoes, corn, and peas being supplied in the greatest quantity. Since canned fruits and vegetables retain Berry: Jour. Home Economics, 1912, iv, 14 210 FOODS VALUABLE FOR SALTS AND WATER most of the properties of the freshly cooked food they are excellent sources of this type of food in the winter when green vegetables are generally "out of season." In canning, vege- tables and, to a certain extent, fruit are heated only enough to sterilize them. This is done after the can is sealed. Sugar is often added to fruit to aid in their preservation and increase the flavor. The juice of fruits is also sterilized and kept for use as beverages or mixed with sugar and made into jellies. It is the pectin of fruit which gelatinizes and forms the basis of jellies. FOOD ADJUNCTS. Food which is entirely satisfactory, in its quantitative com- position, with regard to proteins, fat, carbohydrate, salts, and even the accessory substances or vitamines, may be in such a form that it is not relished; we have no desire to eat it. This distaste may be due to the appearance or taste of the particular food, or to a lack of interest in food in general. Such condi- tions are not confined to man alone. These factors do not affect the ultimate absorption of food so much as is sometimes thought, for food-stuffs which are ingested with much effort have been found to be just as thoroughly digested as those which were appetizing. The extent of variation in the diet is a matter largely of personal taste. Some people relish the same diet day after day, while others require frequent changes. Animals fed artificial diets of similar composition from day to day often refuse to eat. If to the same diet small amounts of flavoring substances, having no nutritive value, be added and the flavor changed from time to time, it will be eaten readily during long periods of time. There are also experi- ments on the flow of gastric juice which show that when there is desire for food, the mere sight of food results in a flow of highly acid and strongly active gastric juice which starts the process of gastric digestion, the products of which are capable of causing a continued secretion. Certain food con- stituents, such as the extractives of meat and some condi- ments, are capable of stimulating such a flow of gastric juice, and this in turn affects the secretion of the other digestive juices. The garnishing of food when served likewise has through the increased attractiveness of the dish a beneficial effect upon the digestion of food. There is a fundamental reason, therefore, for the use of condiments and for different methods of preparing food. Spices.— Spices are used almost exclusively for their flavor. Such spices as allspice, cloves, cinnamon, ginger, caraway, BEVERAGES 211 etc., are used chiefly in cooking. The peppers (black and white), paprika, mustard, and horse-radish are often added to food after it has been prepared. Flavoring Extracts. — Many alcoholic extracts of various plants of which vanilla, lemon, orange, peppermint, spear- mint, and wintergreen are the most common, are used to add an agreeable flavor or taste to foods. Meat Extracts. — Meat extracts are to be classed with the food adjuncts (see p. 152). Vinegar. — Vinegar is the product of the alcoholic and acetic acid fermentation of fruit juices; its distinguishing constituent is acetic acid. It may also be prepared from the products of alcoholic fermentation of grain or is compounded from acetic acid and substances to give a flavor and color which will simulate the natural vinegars. Vinegar is used with more or less insipid foods to intensify the flavor, and to soften food somewhat; for colloidal material tends to swell in acid solutions. Sugar and Salt (Sodium Chloride). — Sugar and salt may both be classified differently but may, for convenience, be included here as condiments, for they are used to add flavor and stimulate the appetite. Sugar Substitutes. — Saccharine, dulcin, granatose and saxin, benzene derivatives, are sometimes used in place of sugar to sweeten food. These products are used particularly to sweeten the food of diabetics and of the obese to increase its palatability without increasing the carbohydrate content. When taken in sufficient quantity these substitutes for sugar are harmful. It is the contention of manufacturers that small quantities are not deleterious to the health. While this may be true during short periods of time, it is doubtful whether their continued ingestion may not cause serious disturbances in the body. Their use in diabetes is defensible on the basis that the harmful effects are overweighed by the possibility of reducing the carbohydrate content of the food. BEVERAGES. Many foods are ingested in a liquid or semiliquid form. There are, however, liquids which possessing a certain amount of food value, are taken for their stimulating effects upon the nervous and digestive systems. The pleasurable condi- tions under which they are ordinarily ingested should not be neglected in considering the effect of these beverages. Those beverages most commonly taken with food and most 212 FOODS VALUABLE FOR SALTS AND WATER properly considered a part of the diet are tea, coffee, cocoa, choco- late, and the malted and spirituous (and carbonated) liquors. Tea. — Tea is prepared from the leaves and leaf buds of various varieties of hardy shrubs, The a. Two general types of tea are used, green and black. This classification refers particu- larly to the general method of preparation. Green tea is pre- pared by steaming the withered leaves and then drying them in the sun or artificially, thus retaining the green color. Black tea has undergone a fermentation (or oxidation) process which darkens the color of the leaves and reduces the quantity of tannin. Numerous varieties of both kinds of tea may result from the selection of leaves from different parts of the shrub or twig or from the country or locality from which they are obtained. The active constituent of tea is theine or caffein, but cer- tain volatile oils and tannin contribute to the aroma and taste of the prepared beverage. In the preparation of the beverage it is the relative proportion of these three con- stituents to which most attention is given. The end com- monly believed to be desirable is the extraction of the maxi- mum amount of caffein and volatile oils, with the minimum quantity of tannin. From a study of the nature of the products extracted from tea leaves the Lancet has come to the conclusion that it is the relative proportions of caffein and tannin extracted which determine the quality of tea. They show that when caffein and tannin are present in the proportion of one part of caffein to three parts of tannin they may be precipitated completely by acidification in the form of caffein tannate. Caffein tannate has neither the astringent taste of tannin nor the bitter taste of caffein, and it is precipitated by acids. It has been suggested that the caffein of tea, unlike the caffein complex of coffee, is precipitated in the stomach and is not absorbed until it reaches the alkaline intestine. A comparison of the valuation of tea by tea-tasters and the proportion of caffein to tannin in the tea shows that the infusion of those teas classed as "good" con- tain these two substances in the proportion in which they exist in caffein tannate, and that inferior teas yield an excess either of caffein or of tannin in the infusion, usually the former. The following table shows the extractives from teas of three different types and the relative proportion of caffein and tan- nin contained. It will be seen that the high-priced teas con- tain a greater proportion of tannin and caffein (caffein tannate), BEVERAGES 213 Tea iNFUSIOJl s (5 Gr A.MS OF Tea to 400 c.c. Boiling Water). Tannin Caffein Caffein com- com- Caffein Tannin tannate. bined bined not not Deter- with with Total Total com- com- Price Te&. mined. caffein. tannin. tannin. caffein. bined. bined. cents India 8-54 6.4I 2.I3 6.80 2.56 O.43 O.39 15 I3-36 10.02 3-34 IO.92 4.32 O.98 O.9O 46 Ceylon . 8.88 6.66 2 .22 6.3O 2.80 O.58 17 12 . 00 9.00 3.00 8.4O 3 . 60 . 60 33 China 5-36 4.02 i-34 3.02 1.92 0.58 13 6 .48 4.86 1.62 4.60 2.80 1. 18 35 The chemical composition of the water used in making tea may affect the composition of the infusion, for, should the water be rich in calcium, the calcium will tend to precipitate the tannin and leave an excess of caffein. The period of extrac- tion affects the composition of the infusion; continued extrac- tion of good tea results for a time in a proportionate increase in both caffein and tannin so that the balance is but little disturbed; inferior teas, on the other hand, yield an excess of either caffein or tannin. Prolonged boiling of tea tends to extract a greater proportion of tannin. The Lancet believes that caffein and not tannin is the injurious constituent of tea, for tannin is rarely in excess of the ratio in which it exists in caffein tannate. Studies of the quantity of caffein and tannin present in tea steeped for varying lengths of time have shown that practically all of the caffein is extracted in the first three to five minutes. A longer period of extraction results in an increased proportion of tannic acid in the infusion. For those, then, who desire to obtain the maximum aroma and exhilarating effect of the caffein without the bitter, stringent tannin, tea should be extracted for a short period. The total quantity of caffein and tannin present in the average cup of tea after an infusion of five minutes varies with the kind of tea — it has been found to be roughly 1 grain (0.07 gram) of caffein and three or four times as much tannin. The effects of tea are discussed with those of coffee on p. 216. Coffee. — The beverage coffee is prepared from the roasted bean, of the Caffea arabacia. The coffee berry contains a bean composed of two elongate, hemispherical halves enclosed in a thin membranous sheath, which is surrounded by an outer layer of pulp. The berries are separated and roasted to preserve them, to render them brittle and readily ground, and to develop certain flavors and aroma. In the roasting process a large proportion of the sugar is caramelized, and there are losses of water and to a certain extent of caffein. Caffeol is the name given to a mixture of substances present in the roasted 214 FOODS VALUABLE FOR SALTS AND WATER product which gives to coffee its characteristic flavor and aroma. The alkaloid of coffee is, as in tea, largely caffein. The caffein of coffee is combined in a different manner from that of tea; it is almost entirely extracted by cold water while that of tea is not. It appears to be combined with an acid designated as caffetannic acid related to tannin but exhibit- ing properties different from those of the tannic acid of tea. The caffein of coffee is soluble in both an acid and an alkaline medium, while that of tea is precipitated by acids. This fact may account for the greater stimulatory effect of coffee than of tea, for the caffein being in solution may be absorbed by the stomach, while that of tea must pass to the intestines for solution and absorption. The several kinds of coffee vary chiefly according to the country from which they are obtained. As with tea the advantage of the different kinds is to a considerable extent a matter of taste. The coffee bean contains roughly one-third the quantity of caffein present in dry tea. The greater quantity of coffee used gives approximately the same quantity of caffein in both prepared beverages. Coffee contains a greater amount of total extracted material. In the process of preparing coffee for its most pleasureable effects the caffein and the aroma are the two constituents which it is desirable to extract. It has been found that when 2 ounces (60 grams) of coffee are used, a teacupful of coffee will contain approximately 1.7 grains (0.1 gram) of caffein, a value which is slightly higher than that of tea; the smaller quantity of infusion taken when cream or milk are used will make this value slightly lower. The quantity of caffein and caffetannic acid extracted in the preparation of coffee varies considerably with the mode of preparation. Cold water extracts approximately the same weight of material from coffee as does hot water, but hot water extracts oils which improve the odor and taste of the beverage. Four general methods of preparing the beverage coffee are used: boiling, steeping, percolation, and filtration. Boiled coffee is prepared by heating medium-ground coffee placed in cold water to the boiling-point and maintaining it at that temperature for five minutes. This method gives the greatest proportion of extract, and one which is rich in caffein and caffetannic acid. Steeped coffee is similar to boiled coffee except that the infusion is poured off soon after the. boiling-point is reached. This method yields the lowest caffein content. Percolation consists in passing warm water through finely BEVERAGES 215 ground coffee in a specially constructed coffee pot. The tem- perature of the water which is forced over the coffee seldom reaches the boiling-point. A low total extract high in caffe- tannic acid and caffein is obtained. Filtered coffee is made from finely pulverized coffee which has been placed in a muslin bag and over which vigorously boiling water is poured. The product is lower in total extrac- tives and contains less caffetannic acid than boiled coffee. If the water be poured through more than once a darker liquid is obtained which has a less agreeable flavor because of the additional tannin and other objectionable substances. This method of preparing coffee is in many ways the most satis- factory. 1 The cloth used should not be allowed to dry but should be kept in clear cold water. A comparison of the relative quantities of caffein and tannin extracted by the various methods is given below. Tannin and Caffein Extracted by Various Methods of Preparation (7 Tablespoonfuls (80 Grams) Coffee to 6 Cups (750 c.c.) Water). Method of preparation. Boiled Tannin, Caffein, grains. grains. 2.44 2.5 (0 . 5 medium ground \1.75 finely ground 2 .40 2.21-2.90 2-75 0.2 -0.25 2.50 Steeped Percolated Filtered Specially prepared coffees are sold for the use of those who cannot take coffee because of its caffein content, usually with the implied statement that some or most of the harmful ingredients of coffee have been removed. After a comparison of some of these with three types of pure coffee the following statement has been made: 2 ' Kaffee Hag' is almost caffein-free but contains the normal amount of caffetannic acid. ' George Washington Coffee' (a soluble, concentrated coffee) contains about four times as much caffein and caffetannic acid as normal coffee. 'Cafe des Invalides' contains about 80 per cent, as much caffein as ordinary coffee, the decrease being due to its dilution with other vegetable substances; its caffetannic acid is somewhat higher than in normal coffee. 'Richelieu Vacuum Coffee' contains practically the same amount of caffein and caffe- tannic acid as ordinary coffee." Certain coffee substitutes prepared from roasted grains are sold for the use of those who desire a beverage simulating 1 Aborn: Tea and Coffee Trade Jour., 1913, xxv, 568. 2 Food Products and Drugs, Report of Conn. Agr. Exp. Sta., 191 1, Pt. 5. 216 FOODS VALUABLE FOR SALTS AND WATER coffee but who do not wish to ingest the alkaloid caffein. These products accomplish this end more or less satis- factorily, although their action is chiefly that of a warm beverage. The general effect of tea or coffee is to produce wakefulness and relief from fatigue, increased strength and rapidity of the heart beat and increased blood-pressure. In some people drowsiness rather than wakefulness is induced by coffee: this is usually followed by a period of wakefulness. These effects are to be ascribed chiefly to the caffein contained in them; caffein also has a diuretic effect. The feeling of well-being which accompanies the ingestion of coffee after a meal has been ascribed as due to the local action of the contained oils. The effect of coffee upon digestion is to increase the period of gastric digestion without affecting it quantitatively. Since the direct effect of water when taken with food is to delay evacuation of the stomach, the best results are obtained when water and other liquids are taken after food rather than when mixed with it. On the other hand, the ingestion of bread or cake with coffee is desirable, for they prolong the feeling of satiety and delay diuresis. Coffee infusion has been found to tend to inhibit the coagulation of milk and to inhibit peptic activity outside the body while tea has a less retarding action on coagulation and appears to promote peptic activity. The harmful effects of tea and coffee are sometimes referred to the tannin content because tannic acid precipitates pro- tein, simple protein cleavage products, and digestive enzymes. The work performed for the Lancet tends to show for tea, at least, that in good teas the tannin is so combined with caffein that it will be precipitated out by the gastric juice and only become absorbable in the intestine in which the alkaline tan- nate would not have the precipitating power of tannic acid. They are therefore inclined to ascribe the harmful effect of tea to caffein. The slight laxative effect of hot drinks is probably to be ascribed chiefly to the hot water. Cocoa and Chocolate. — Cocoa and chocolate are prepared from the seed or bean of the tree Theobroma cacao. The beans are removed from the pod, fermented in boxes or in holes in the ground, and then dried in the sun until they assume the char- acteristic brown color of the beans shipped to the market. In the preparation of the products cocoa and chocolate the dried beans are cleaned, roasted, crushed, and finally ground, after which the ground mass is molded or specially treated according BEVERAGES 217 to the nature of the final product — chocolate or a special variety of chocolate such as milk chocolate or cocoa. It is during the fermentation processes just after picking and the subsequent roasting processes that care must be taken if the product is to develop the most desirable flavor. Ground cocoa nibs, obtained by crushing the roasted beans, constitute the ordinary chocolate of commerce. Sugar, dried milk, flavoring extract (particularly vanilla), etc., are added to the ground mass in the preparation of sweet chocolate, milk chocolate, etc. In preparing cocoa a portion of the oil or fat is removed from the ground seeds. This fat is removed by pressure — usually when warmed slightly; the residue is the finely pulver- ized cocoa of commerce. The expressed fatty material is cocoa butter, a semisolid fat used in the manufacture of chocolate and particularly in pharmaceutical preparations. Alkaline salts, sodium, potassium or ammonium carbonate, are often added to the ground cocoa ostensibly to increase the solubility of the product; such products are sometimes designated as "Dutch process" cocoa. The addition of alkali neutralizes any fatty acid present. Tests of these preparations in com- parison with untreated preparations have failed to show any marked increase in solubility; such treatment would tend, however, to aid in the emulsification of the cocoa fat and thus produce an apparent increase in solubility. Specially prepared cocoas are sold which have been treated with alkali as indicated above or with the addition of sugar, starch, etc. Com PARATIVE Composition of Products of the Cocoa Bean - 1 Cocoa nibs. Chocolate. Cocoa Original Original Original material. Fat-free. material. Fat-free. material. Fat-free Ash . . 3-32 6.66 3-15 6-59 5-49 7-49 Soluble ash i . 16 2-33 1. 41 2-95 2.82 3-85 Sand . 0.02 0.04 0.06 0.13 0.24 0.32 Nitrogen 2.38 4-77 2.26 4-73 3-33 4-54 Fat . . 50.12 52.19 26.69 Fiber . 2.64 529 2.86 5.98 4.48 6. 11 Starch . 8.O7 16.18 8. 11 16.75 11. 14 5.20 Cocoa and chocolate differ, as indicated above, particu- larly in the quantity of fat present. Cocoa contains roughly one-half as much fat as chocolate. The fat is largely a mix- ture of the glycerol esters of palmitic, stearic, lauric and ara- chidic acids, melting-point 38 to° 33 C. The active principle of cocoa and chocolate is theobromine, 1 Winton: Conn. Agr. Exp. Sta. Report, 1902, p. 282. 218 FOODS VALUABLE FOR SALTS AND WATER or trimethylxanthin, and is closely related chemically to the caffein of tea and coffee. There is roughly about as much theo- bromine in cocoa as there is caffein in tea or coffee, between I and 2 per cent., less in the specially prepared products because of the dilution with other substances; a small amount of caffein is present. Tannin is also present; the reddish color of the finished product has been held to be an oxidation product of the tannin present in the raw bean. Cocoa and chocolate contain theobromine which does not have the stimulating power of caffein, and these drinks are therefore less objectionable from that point of view. Because of the high fat content they tend to retard the passage of food from the stomach. While these beverages are prepared from substances with a high food value the prepared liquid is comparatively low in such value because of the relatively small quantity of material used; the added milk is often of more importance. Mineral Waters. — Water may be roughly divided for conven- ience into three classes: hard, soft, and "mineral" water. The presence of considerable quantities of the salts of the alkaline earth metals, particularly calcium and magnesium, is the chief characteristic of a hard water. Water analysts recognize two degrees of hardness: temporary and permanent. The quantity of calcium and magnesium present in water as the bicarbonate which may be precipitated through the removal of carbon dioxide by boiling or by the addition of lime is an index of the temporary hardness of water. When combined with the chloride or sulphate radicle calcium and magnesium are not precipi- tated readily by heating and the water is said to be perma- nently hard. 1 Soft waters are comparatively free from dissolved inorganic matter. Distilled water is an artificially prepared soft water and is free from inorganic salts; it may contain a certain amount of ammonia. Rain water, when properly collected is virtually free from inorganic salts. It often contains a certain amount of organic material, particularly when collected from the roof. The term "mineral water" is applied to those naturally occurring (and also artificially prepared) waters rich in par- ticular salts or gases as distinguished from the usual table water 1 The temporary hardness of water may be removed by adding to it a saturated solution of calcium hydroxide, "lime water." In the presence of calcium hydrox- ide the calcium bicarbonate is changed into normal calcium carbonate which precipitates, and in this way both the calcium of the water and the calcium of the added lime water are removed. The quantity of lime water to be added to any water must be determined by experiment or it may be approximated from published analyses of the water under consideration. BEVERAGES 219 poor in such constituents and having no specific effect. The name has developed particularly in conjunction with the therapeutic use of such water. The classification of mineral waters has not been standardized. Since they are ordinarily used for their medicinal efFect it is perhaps best to classify them according to the nature of the substance contained, as lithium water (lithia); sulphurous water; sulphate water (aperient); iron water (chalybeate); radio-active water. To these should be added the alkaline waters, a type which may include one or more of the types of water just named. Many waters are rich in sodium chloride and are sometimes desig- nated as saline waters. Some waters are naturally charged with carbon dioxide while others are sold artificially charged. The classification indicated above recognizes only the most characteristic constituent of mineral water; it may contain one or all of the other constituents. Lithium waters, or lithia waters, are waters which have been advocated because of the supposed solvent effect of lithium upon uric acid in the body. Consideration of the ionic equi- librium in the body makes it appear very improbable that the ingested lithium salts could dissolve uric acid to any consid- erable extent. Since most lithia waters are comparatively poor in lithium, large amounts of water would need to be taken to produce even a slight efFect. Sulphurous water contains hydrogen sulphide gas as the most characteristic constituent. The gas is liberated readily, unless properly bottled; to obtain hydrogen sulphide, there- fore, the water should be taken at the spring. The curative power of such waters is probably due to other constituents than the gas itself. It may be in the sulphur, sometimes "used as a blood purifier." Sulphurous waters are found at the Anderson Sulphur Springs in California, French Lick Springs, Richfield Springs, and Cold Sulphur Springs. Sulphate waters are rich in alkali and alkali earth sulphates, such as sodium sulphate (Glauber's salt) and magnesium sul- phate (Epsom salt); these two salts usually occur together. Such waters are laxative and purgative, the efficiency varies with the amount of magnesium and sodium present. Many of these waters are concentrated by evaporation and are to be diluted or dissolved before using. Salts (sulphates) are sometimes added to the natural water to increase its concen- tration. Some American waters rich in sulphates are found at the Mendenhall Springs, Isham and Nuvida Springs in California; the Warm Springs, Hot Springs and Healing Springs in Virginia. Foreign waters such as Hunyadi Janos, Kissengen, Seidlitz and Friedrichshall are of this type. 220 FOODS VALUABLE FOR SALTS AND WATER Iron waters usually contain other mineral constituents which may have as great an effect as the iron itself, such as carbon- ates, sulphates, lithium, and arsenic. Many waters used as table waters are rich in iron. The presence of the associated salts must be considered in prescribing iron waters; a water containing bicarbonates is preferable as a tonic. The Berkely Springs, West Virginia, and the Round Spring at the Aurora Springs, Missouri, are examples of American iron- containing bicarbonate springs. Similar foreign waters are to be found at Spa, Belgium; St. Moritz, Switzerland; Schwalbach, Germany; Trubridge Wells and Flitwick Well, England. Radio-active Water. — The presence of traces of radium in certain waters has lead to their use in therapeutics. It has been found that such waters lose their radio-activity with time. Springs which have been advocated for their healing properties because of the presence of various salts have been found to be, in addition, radio-active. Many waters, such as those at Hot Springs, Arkansas, the mineral springs of Yellowstone Park in America, and the foreign waters at Carlsbad, Gastein, Wiesbaden, Kissengen and Bath have been found to be radio-active. Radio-active water is arti- ficially prepared and sold or may be prepared with suitable apparatus. Alkaline waters include particularly those of the lithium, sulphate and iron types. They are valuable as a means of administering alkaline salts. The alkalinity of these waters is due to the presence of bicarbonates, primarily of sodium, potassium, or lithium and secondarily of magnesium and cal- cium. Many alkaline waters are effervescent. Vichy water is perhaps the most generally used alkaline water. Some Ameri- can alkaline waters are: White Rock and Clysmic (Wakeshau, Wisconsin); Vichy (Saratoga Springs, New York); London- derry Spring (New Hampshire); Hot Springs (Arizona); Vichy (France); Carlsbad (Austria), and Fachingen (Germany) are alkaline European waters. An analysis of the various medical data with regard to the use of mineral water has brought out the following facts: 1 (a) many patients are improved in health under mineral water treat- ment; (b) waters of widely different composition have been recommended for the same disease; (c) curative properties are ascribed to many waters whose mineral content is the same as, or lower than, the city supplies used daily by many people 1 R. B. Dole: The Production of Mineral Waters in 1911, U. S. Geol. Survey, advance chapters for Mineral Resources of United States, 1912. This discusson of water is taken in part from this paper. BEVERAGES 221 without peculiar physiological effects; (d) treatment at resorts is often recommended for those afflicted with chronic organic diseases, many of which are obscure in nature or are caused by failure of nutrition. Such facts lead to the conclusion that the beneficial effects are to be ascribed more to the free use of water itself, augmented by dietetic treatment, exer- cise, and other hygienic restrictions and possibly change of climate and freedon from business and household cares than to the contained mineral constituents. The demonstration of the value of various waters will depend upon the concentration of the dissolved constituents. The determination of the effects of a particular water are difficult to demonstrate because of the difficulty in control- ing the physiological factors associated with their ingestion. The specific action of salts may occur in three ways : as stimu- lants to (a) increase or (b) depress the activities of an organ or function or (c) as irritants which cause a change in form, growth, and nutrition, rather than of activity. The action of mineral waters is due to the contained ions rather than to the undissociated salt. The effect of any particular ion will depend upon its associated acidic or basic radicle and the presence of other ions in solution. When two ions occur together one ion may neutralize the effect of the other. Such an effect is apparently specific and not necessarily in the ratio of the combining power of the ions; thus, roughly, one part of cal- cium chloride will neutralize or antagonize the effect of one hundred parts of sodium chloride in its effect upon the per- meability of membranes. This antagonistic action of ions may be the explanation of the tolerance of comparatively large quantities of some mineral waters. We know that a tolerance for a water is acquired; the development of diarrhea in some persons upon moving from one locality to another may be looked upon as of this nature. 1 The fact that an individual dose of a salt is not harmful does not mean that its continued ingestion may not be injuri- ous, for small repeated doses of a salt will in some cases induce symptoms which are more marked than from a single dose, such as in lead poisoning, or an abnormal tolerance may be acquired as in the case of arsenic. Analyses of water do not tell the manner in which the various ions are combined but only their proportionate dis- tribution. From such analytical data we say by inference that the ions exist in certain combinations. These com- binations are hypothetical, for the complex combinations of 1 Diarrhea may be due to infection from a water new to the individual. 222 FOODS VALUABLE FOR SALTS AND WATER various salts and the effect of loss of dissolved gases, particu- larly carbon dioxide, alter the molecular and possibly ionic complexes actually present in the original water analyzed. The results of water analyses are usually expressed in parts per million. The following equivalents of certain methods of expressing analytical results will aid in understanding the significance of this expression: Equivalent in parts " per million. I part in ioo i part in 10,000 1 part in 1000 1 part in 1,000 1 gram in a liter 1 part in 1 ,000 1 milligram in a liter 1 part in 1 ,000 Grains per imperial gallon -v- o . 07 gives parts per million. Grains per U. S. gallon -5- o . 058 gives parts per million. Dole has suggested the use of the quantity of a specific salt in four kilograms of water (the water intake for a day) as the basis of differentiation between medicinal and common water with reference to the minimum dose of the individual con- stituent in the absence of other ions which have a pharma- cological effect, ignoring as difficult of demonstration the effect of associated ions. The following table of the minimum dose of constituents common to mineral waters has been prepared by Dole: Average Equivalent minimum dose, concentration, Radicle. grams. mg. per kg. Arsenite (As0 3 )\ 0002 i / 0.2 Arsenate (As0 4 )/ 0.0002 ^ Q ^ Fluoride (F) 0.002 0.5 Barium (Ba) 0.003 °-7 Hydroxide (OH) 0.013 3.0 Aluminum (Al) 0.011 3.0 2 Iron (Fe) 0.024 6.0 Lithium (Li) 0.075 I 5° Ammonium (NH 4 ) 0.078 20.0 Manganese (Mn) 0.12 30.0 Metaborate (B0 2 )\ m n n _ e /30.0 Pyroborate (B 4 7 )j u °° 35 \30.0 Iodide (I) 0.12 30.0 Calcium (Ca) 0.2 50.0 Magnesium (Mg) 0.2 50.0 Orthophosphate (P0 4 ) 0.23 50.0 Carborate (C0 3 ) 0.281 70.0 Sulphite (S0 3 ) 0.315 70.0 Thiosulphate (S 2 3 ) 0.300 ' 70.0 Nitrate (N0 3 ) .0.5 100. o Bromide (Br) 0.53 100. o Sulphate (S0 4 ) 0.60 150.0 In preparing the table care was taken that the concentration expressed should represent a minimum below which thera- 1 Equivalent as arsenic (As); 2 in acid solution; 3 equivalent as boron (B). BEVERAGES 223 peutic activity could not logically be attributed to the radicle in question. The significance of the last column may be illustrated as follows: If the average quantity 0.53 gram of bromine were in four kilograms of water the concentration of the radicle would be 132 milligrams per kilogram (reduced to 100 in the table), that is, a person who drank 4 kilograms of water containing 132 milligrams per million by weight of bromide might exhibit symptoms produced by bromides, if the water did not contain some other radicle which was antagonistic; 530 kilograms, roughly quarts, of bromide water containing one part per million of bromine would have to be ingested to obtain a similar effect. Alcoholic Beverages* — Beverages containing alcohol are used chiefly for their psychological effects. They have, as a rule, a pleasant taste, often a fragrant odor, and are usually cooled, fac- tors which make their consumption a pleasure. In sufficient quantities their use is accompanied by pleasurable after-effects, a sense of exhiliration, relief from fatigue, and warmth, followed, however, in many cases by depression. The effect of moder- ate quantities, 30 to 40 c.c, of alcohol, is to quicken the heart beat without materially raising the blood-pressure; larger quantities produce a fall in blood-pressure except in certain abnormal conditions of the circulatory system, a result which is due to a depressant action on the nervous centers and in part to a weakened heart. The general effect is that of a narcotic rather than of a stimulant. There is an increased rate of respiration, disturbed heat regulation, and secretion of saliva and gastric juice. While alcohol produces, for the time being, a feeling of well-being and ability to work, these are more or less subjective effects. The true result appears to be a lowered capacity for work, particularly work requiring thought, and lessened endurance. A thorough and far-reaching study of the effect of alcohol upon the body processes is being undertaken by Benedict in the nutrition laboratory of the Carnegie Institution of Wash- ington. This series of investigations has only been started. The results of a psychological study indicate that the period of response in the simple reflex arcs in the lumbar cord, the patellar reflex, and the protective-lid reflex and to more com- plex cortical arcs, certain eye reactions to peripheral stimuli, speech reactions to visual word stimuli, and free associations were increased following the ingestion of doses of alcohol containing 30 c.c. and 45 c.c. of absolute alcohol; memory and free association were only slightly affected. As a food, alcohol is of the type of the energy-yielding food- 224 FOODS VALUABLE FOR SALTS AND WATER stuffs, fats and carbohydrates. It can be substituted for them at least to a limited extent and is capable of exerting a similar sparing effect upon protein. Its use must, however, be con- sidered in connection with the fact that alcohol has also a toxic effect foreign to fat and carbohydrate. It is not con- verted into sugar by the diabetic and may then become a source of energy. It is not, however, an antiketogenic sub- stance. The use of alcoholic beverages as food is of only secondary importance. Alcohol or even beverages fortified with sugar, such as some wines, are not economical sources of energy and there is no proof that alcohol itself is more effi- cient than carbohydrate in the body economy. The trend of the evidence is rather against such a possibility. Discussion of the use of alcohol as food has therefore little practical dietetic value; the food or fuel value of alcohol is a bone of contention between those advocating its use in general and their opponents. Studies of the food value of alcohol have shown that from 90 to 98 per cent, of alcohol ingested in small quantities is oxidized; that the effect of the addition of the equivalent of 500 calories in the form of alcohol, 72 grams, to a standard diet was practically identical with the addition of an equiva- lent amount of sugar, and that alcohol is not as efficient in sparing protein as carbohydrate or fat. Certain investigations have demonstrated in short experiments that for small amounts of alcohol there is an increased protein metabolism. Experi- ments of longer duration have shown that there is an initial rise in the nitrogen excretion (loss of protein) but that in the course of a few days the metabolism returns to the normal, or there may be a retention of nitrogen. The utilization of foods is unaffected by the ingestion of small amounts of alcohol. These observations, which apply only to small quantities of alcohol, have demonstrated quite clearly that it may serve as a food. Large doses of alcohol exert a toxic effect, increase protein metabolism, and also the respiratory exchange; as the result of the restlessness of partially intoxicated per- sons. With complete intoxication the energy exchange is decreased. The desirability of using alcohol as a food under all cir- cumstances is doubtful; the associated danger of excessive consumption should certainly bar it as a constituent of the diet. While it can replace in part fats and carbohydrates it does not serve as a reserve food in the sense that these foods do, for it is oxidized immediately. The therapeutic use of alcoholic beverages in medicine, such as in the treatment of fevers on the basis that it is a readily BEVERAGES 225 assimilable and oxidizable type of food in a condition in which food is more or less contra-indicated, loses its importance some- what in the light of our present knowledge of the effect of food in such cases. With regard to the combined stimulating and food value of such beverages and their effect upon the appetite, little of a definite nature can be said. Alcoholic beverages are products obtained as the result of the alcoholic fermentation of sugar or prepared from fer- mented products. They are of two types, fermented and dis- tilled. Fermented liquors are the result of naturally occur- ring fermentations. Of these there are (a) the products of direct spontaneous fermentation of saccharine fruit juice, such as wine and cider, and (b) beverages produced from starch- bearing grains in which alcoholic fermentation takes place after the conversion of starch into sugar, and as the malted and brewed liquors, beer, ale, etc. Distilled liquors, sometimes designated as "spirits," such as whisky, brandy and rum, etc., are obtained by the distilla- tion of naturally fermented products. Composition of Alcoholic Liquors. _ o5 T3 Alcohol. l l a Acidity. X GO T3 o t3 £ 3 o T5 a o ■8 "8 >> > o 1 i 03 tn 1 JO 'o "3 O J3 CO 6 o PQ n H £ m o PE| > H < PL, Beer, lager .... 0.4 4.3 5.6 4.2 o.« f > 1.10 1.6 0.06 0.20 0.06 Porter 0.4 6.1 7.7 5.9 o.<< 5 0.57 2.8 0.15 0.37 0.05 Ale . . . 0.5 5.7 7.1 4.4 0.1 > 0.49 2.2 0.12 0.31 0.07 Malt extract, 1 U. S. P 76.6 3.1 L 65.40 0.24 6.9 0^39 0.02 0.17 0.26 0.60 1.20 0.21 0.56 Claret 9.7 Sherry 17.8 3.00 0.29 0.16 0.49 0.50 Port 18.1 13 '.7 3.67 2.54 1.92 0.31 0.09 0.43 0.40 0.23 Champagne .... Whisky 43.6 51.2 0.11 3.36 Brandy 41.1 48.5 0.67 3.75 Gin 40.2 47.5 0.05 1.92 Liqueur 38.5 52.0 36.00 32.60 0.41 Cider: Hard trace 5.2 6.5 0.04 0.402 0.38 Sweet 1.4 1.7 0.( )6 .. 0.21 0.32 Fermented liquors, cider and wines, are beverages in which the alcohol is formed as the result of direct fermentation of fruit juices. Cider is the fermented juice of the apple. It contains from 3 to 8 per cent, of alcohol. Sweet cider is the freshly expressed juice and contains only small amounts of alcohol. Perry, or pear cider, is made from the pear. 1 Diastatic action complete in ten minutes. *5 2 As malic acid, 226 FOODS VALUABLE FOR SALTS AND WATER Wines. — The term wine is customarily used to designate the fermented juice of the grape. A number of wines are to be had which differ particularly in their method of prepara- tion and to a certain extent according to the country or locality in which they are prepared. Classification of Wines. — A number of terms are used to express the type or quality or variety of wines. 1 With regard to the method of preparation we have: Natural wines, wines which are prepared from the juice of the grape as expressed and to which no sugar or alcohol have been added, e. g., hock and claret; and fortified wines, to which alcohol has been added, usually before the natural fermentation is completed, e. g., Madeira, sherry, port. According to the intrinsic prop- erties of wines we have the non-effervescing or still wines which contain little dissolved carbon dioxide; effervescing or spark- ling wines, more or less heavily charged with carbon dioxide (a) from natural fermentation of added sugar in the corked bottles — champagne; or (b) artificially charged with carbon dioxide; red wines, Burgundy and Bordeaux wines or claret; white wines, e. g., Rhenish and Moselle wine and sauternes; dry wines, in which the sugar has been exhausted by fermen- tation; and sweet wines, which possess a considerable amount of unfermented sugar and to which sugar is often added. Of the different varieties of wines champagne is an effer- vescing, selected, sweet, white wine fortified with sugar mixed with brandy. It contains 8 to 10 per cent, of alcohol; claret is a light red wine somewhat acid and astringent, contains very little sugar, is high in volatile ethers, alcohol 8 to 13 per cent.; Madeira is a strong white wine generally fortified with alcohol and possesses a rich, nutty, aromatic flavor, alcohol 17 to 20 per cent.; sherry, a Spanish wine, is a sweet wine sometimes fortified with alcohol, deep amber colored, slightly acid and possesses much fragrance, alcohol 8 to 20 per cent.; hock, German wines, are white wines mildly acid, alcohol 9 to 12 per cent.; port, an astringent wine, always fortified with alcohol, dark purple in color, alcohol 15 to 18 per cent. Malt Liquors (Beer, Ale, Porter, Stout). — Malt liquors are made by the alcoholic fermentation of malt with hops; other grains are sometimes added. To obtain the sugar from which the alcohol is to be formed, grain is malted; that is, it is per- 1 The particular mode of preparation and more specific details of their compo- sition may be found by consulting such books as, Leach: Food Inspection and Analysis, New York, 19 13. BEVERAGES 227 mitted to sprout. In the processs of sprouting, starch is trans- formed in part into soluble sugars, particularly maltose; the quantity of the enzyme, diastase, formed is often sufficient to change the starch of added grains, rice, corn, etc., to a considerable extent. The sprouting process is stopped at the proper point and the germinating mass is dried. The temper- ature at which the malt is dried determines to a large extent the depth of color of the final product; higher temperatures give the darker beers. In some cases caramelization of the starch is permitted as in stout. To complete the conversion of the starch the dried malt and admixed grain, if there be any, are crushed and mixed with water to permit the diastase to continue its action. The saccharine liquor or wort is con- centrated, mixed with hops and a selected yeast and per- mitted to ferment. The nature of the yeast added for the alcoholic fermentation is a matter of great importance in the production of good malted liquors. After fermentation has pro- ceeded to the proper stage the beer is drawn off from the greater portion of the yeast and stored in casks or vats for an after-fermentation. When this process is completed the liquor is clarified and stored in casks or bottles. Of the different varieties of malt liquor we have beer, pre- pared as above without special modification; ale, essentially a light colored beer which usually contains more hops than beer; porter, a dark ale, and stout. The latter are prepared from roasted, partially caramelized malt. Such liquors are dark colored, usually heavy, and contain considerable quantities of dextrin and starch. Malt liquors contain in addition to water, alcohol, and sugar, a variety of substances formed in the processes of malt- ing and fermentation. Of these the carbon dioxide, which produces the effervescence, the volatile oils and the bitter principles which contribute to the taste are the most impor- tant; certain nitrogenous substances, chiefly peptone and amino- acids are also present. Malt Extracts. — True malt extracts are free from alcohol and contain the soluble principles of malt. Such extracts have a high percentage of sugar, maltose, 48 to 70 per cent., a certain proportion of dextrin, 2 to 16 per cent., and a high diastatic activity. Many of the malt extracts sold have been found to have the general characteristics of beer. Some have been analyzed which contained approximately from 2 to 9 per cent, of alcohol. Such extracts have no diastatic activ- ity and their nutritive value depends essentially upon the sugar content, which is in many cases low. These extracts should not be compared with the U. S. P. malt extract 228 FOODS VALUABLE FOR SALTS AND WATER described above. The following table gives the composition of commercial malt extracts in comparison with the U. S. P. extract. Analyses of twenty-one samples of commercial preparations sold as malt extract gave the following maximum and minimum values '} Commercial Preparations. u. s. P. Maximum. Minimum. (for comparison). Alcohol 9 . 1 1 2 . 52 Extract 15.32 5.39 76.6 Ash 0.37 0.14 1.2 Nitrogenous constituents, protein 1.09 0.34 3.1 Sugar solids 14.04 4-84 Maltose 11. 17 1.41 65.4 Dextrin 5 . 80 2 . 03 6.9 Distilled Liquors. — Distilled liquors, as the name implies, are the product of the distillation of fermented liquors. By this process a liquor is obtained which is high in alcohol and con- tains in addition certain of the higher boiling-point alcohols, their esters, and acids which pass over with the alcohol. The distillation process is usually repeated and the intermediate portions taken for the best liquors, while the first and last distillates yield inferior products. The liquor obtained is harsh to the taste and must be stored for a time in casks and aged, to soften and refine their flavor. Whisky is the product of the distillation of fermented grains, usually mixtures of corn, wheat, and rye, which has been stored in casks for at least four years, alcohol content approximately 30 to 50 per cent. Brandy is the aged product of the distillation of fermented grape juice or wine. The term is sometimes applied to the distillation of the fermented juice of other fruits, alcohol 20 to 50 per cent. Cognac is a brandy distilled in certain parts of France. Rum is the dis- tillation from fermented molasses or cane juice, usually dis- tilled twice and stored for a long time. Gin is an alcoholic liquor flavored with the volatile oil of the juniper berry; other aromatic substances are sometimes used, such as coriander, anise, cardamom, orange-peel, fennel. Gin is water-clear and is kept in glass and not wood as are the other distilled liquors, alcohol 27.5 to 42.5 per cent. Liqueurs and cordials are manufactured beverages contain- ing a large proportion of alcohol, sugar, and essential oils. They are often highly colored. 1 Conn. Agr. Exp. Sta. Report, 1914, p. 254. PART III. FEEDING IN INFANCY AND CHILDHOOD. CHAPTER XV. BREAST FEEDING— FEEDING NORMAL AND ABNORMAL CHILDREN. WOMAN'S MILK. Milk is a secretion of the mammary glands, but a few of its normal constituents are the result of transudation from the mother's blood. The composition of human milk is qualita- tively similar to cow's milk, but quantitatively quite different. Furthermore, women's milk varies in amount and compo- sition at different times, depending upon the length of time which has elapsed since the labor, upon the health of the mother, and upon whether or not the breasts are completely emptied at each nursing. Colostrum. — Colostrum is the term applied to the milk secreted during the first few days (i to 12) postpartum, before lactation is well established. Czerny and Keller include under this term all milk that shows evidence of absorption. Colos- trum is deep yellow in color, has an average specific gravity of about 1.040, a strongly alkaline reaction, and is coagulated by heat. Its composition varies considerably. The follow- ing table gives the average composition of five early colos- trums as compiled by Holt, Courtney and Fales : x Average Composition of Five Colostrums (1 to 12 Days). Fat 2.83 Lactose . Protein . Ash . . Total solids 7-59 2.25 0.3077 13-42 The fat droplets of colostrum are more unequal in size than those of milk. Colostrum contains, besides the usual constit- uents of milk, many large nucleated granular bodies, called "colostrum corpuscles," which are about five times as large ^mer. Jour. Dis. Child., 1915, x, 229. 230 BREAST FEEDING as ordinary leukocytes, contain many small fat droplets and have ameboid motion. They are present in large numbers for the first few days, rapidly disappear after lactation is well established, but reappear when lactation is interrupted. Czerny considers them leukocytes that appear when the breasts are not sufficiently emptied of milk and help in the absorption of fat. General Characteristics of Woman's Milk. — Woman's milk is bluish white in color, odorless and sweet to taste. Micro- scopically it shows many fine fat droplets which are smaller than most of the fat droplets in cow's milk. It contains a few epithelial cells and leukocytes. The number of the latter is greatly increased when there is any inflammation of the breast. Its average specific gravity is 1.031, but it may vary between 1.026 and 1.036. Woman's milk is neutral or slightly alkaline in reaction; and is amphoteric. The latter condition is due to the presence of both mono- and diphosphates, the former being acid and the latter alkaline in reaction. The casein of woman's milk does not coagulate in such large clots as the casein of cow's milk. On the addition of acetic acid a fine flocculent precipitate is formed. Rennin alone does not coagulate it. Quantity. — The quantity of milk secreted increases rapidly for the first six to eight weeks, after this more slowly. To a cer- tain extent the quantity is governed by the demands of the infant. A large, vigorous infant will obtain more milk than a smaller, less vigorous infant. Furthermore, a wet-nurse will secrete more milk while nursing two or three infants than while nursing only one. The following table gives the average daily amount of milk drawn by an infant (from Czerny and Keller) : l Average weight The calcu- Average weight The calcu- Age of breast-fed lated day's Age of breast-fed lated day's in infants according amount of in infants according amount of weeks. to Camerer. milk. weeks. to Camerer. milk. gm. lb. and oz. gm. oz. gm. lb. and oz. gm. oz. I 3410 7 2 291 9-7 14 5745 11 15 870 29.0 2 3550 7 6 549 18.3 15 5950 12 6 878 29.3 3 369O 7 11 590 19.7 16 6150 12 13 893 29.8 4 3980 8 5 652 21.7 17 6350 13 4 902 30.1 5 4115 8 9 687 22.9 18 6405 13 5 911 30.4 6 4260 8 14 736 24-5 19 6570 13 11 928 30.9 7 4495 9 6 785 26.2 20 6740 14 1 947 31-6 8 4685 9 12 804 26.8 21 6885 14 5 956 3i-7 9 4915 10 4 815 27.2 22 7000 14 9 958 31-9 10 5055 10 9 800 26.7 23 7150 14 14 970 32.3 11 5285 11 808 26.9 24 7285 15 3 980 32.7 12 5455 11 6 828 27.6 25 7405 15 7 990 33-0 13 56i5 11 11 852 28.4 26 7500 15 10 1000 33-3 1 Des Kindes Ernahrung, Ernahrungsstorungen und Ernahrungstherapie, Leipzig und Wien, i, 353. WOMAN'S- MILK 231 Composition. — Woman's milk varies widely in its composi- tion. Its principal ingredients are the same as those in cow's milk: namely, fat, lactose, protein, salts and water. The average composition is as follows: Average Composition of Woman's Milk. Fat . Lactose Protein Salts Water 3-50 7.00 1.50 0.21 87.29 Holt, Courtney and Fales 1 divide lactation into four periods : the colostrum period (1 to 12 days), the transition period (12 to 30 days), the mature period (1 to 9 months), and the late period (10 to 20 months), and give the following figures as averages for these periods: Percentage Composition of Woman's Milk. No. of Period. analyses Fat. Sugar. Pro- tein. Casein. Albumin. Ash. Total solids. Colostrum, 1-12 days 5 Transition, 1 2-30 days 6 Mature, 1-9 mos. . 17 Late, 10-20 mos. . 10 2.83 4-37 3.26 3-i6 7-59 7-74 7-50 7-47 2.25 1.56 115 I.07 .. O.3077 O . 2407 O.43 O.72 0.2062 O.32 O.75 O.1978 13-42 13-39 12 . 16 12.18 The sugar content remains practically constant throughout the entire period of lactation. Protein and ash are highest in the colostrum period and fall quite rapidly to the mature period, after which they vary little. The fat content is low- est in the colostrum period, rises rapidly in the transition period, and then falls in the mature period. These analyses of Holt, Courtney and Fales are particularly important, because many of their specimens were entire twenty-four-hour amounts. Fat. — The fat in human milk is held in permanent emulsion. The average percentage of fat is 3.5 or 4 per cent., but it may vary from 0.75 to 10 per cent. As a rule the amount of fat in the milk increases from the beginning to the end of each nursing. Volatile fatty acids form 2.5 per cent, of the total fat of woman's milk and 27 per cent, of the total fat of cow's milk. Oleic acid forms about 50 per cent, of the non-volatile fatty acids, the remainder being composed of myristic, palmitic and stearic acids. Lactose. — The percentage of lactose in woman's milk is more constant than that of the other constituents, being about 7 per cent., which is nearly twice that of cow's milk. It is in solution. 1 Loc. cit., 239. 232 BREAST FEEDING Protein. — The proteins of woman's milk comprise casein, which is insoluble in water, and lactalbumin and globulin, which are soluble in water. Besides these there are some nitrogenous substances which do not give the protein reac- tions. A large part of the latter is supposed to be urea. There is considerable difference of opinion as to the proportions of these substances. According to Talbot the probable division of the total nitrogen is as follows: "Casein 41 per cent., lactal- bumin and globulin 44 to 39 per cent., residual nitrogen 15 to 20 per cent." Thus the lactalbumin and globulin form a much larger part of the total protein in woman's milk than they do in cow's milk. Salts. — The average ash content of woman's milk is less than a third that of cow's milk, being only 0.21 per cent. The following table gives the average salt content of 100 c.c. of woman's milk according to Holt, Courtney and Fales: 1 Averages for the Different Periods. No of Total analyses, ash. CaO. MgO. P2O5. Na 2 0. K 2 0. CI. Colostrum, 1-12 days 5 .3077 .0446 .0101 .0410 .0453 .0938 .0568 Transition, 12-30 days 6 .2407 .0409 .0057 .0404 .0255 .0709 .0580 Early mature, 1-4 months ... 9 .2056 .0486 .0082 .0342 .0154 .0539 .0351 Middle mature, 4-9 months ... 8 .2069 -°458 .0074 .0345 .0132 .0609 .0358 Late milk, 10-20 months ... 10 .1978 .0390 .0070 .0304 .0195 .0575 .0442 The average percentage composition of the ash by the same investigation is as follows: Average Percentage Composition of Ash for the Different Periods. Colostrum .... Transition .... Mature Late CaO. MgO. P2O5. Na 2 0. K2O. CI. I4.2 3-5 12.5 13-7 28.1 20.6 17.0 2.4 16.9 10.9 30.8 22.9 23-3 3-7 16.6 7.2 28.3 16.5 19.8 3-6 15-5 10. 1 18.8 22.3 Iron. — The iron content of woman's milk is about three times that of cow's milk. This makes the iron intake of an infant fed on diluted cow's milk much lower than that of a breast-fed infant. Phosphorus. — Woman's milk contains much less phos- phorus than cow's milk. About three-fourths of the phos- phorus of woman's milk is in organic combination, as against one-fourth of that of cow's milk. Salts of Woman's and Cow's Milk. — The total ash content of cow's milk is about three and one-half times that of woman's 'Am. Jour. Dis. Child., 1915, x, 243, 245. WOMAN'S MILK 233 milk. The proportion of the different salts is quite similar, the chief differences being in the larger amount of iron and the smaller amount of phosphorus in woman's milk. Holt, Courtney and Fales 1 give the average composition as follows: Comparison of the Percentage Composition of the Ash of Woman's and Cow's Milk. CaO. MgO. P 2 5 . Na 2 0. K 2 0. CI. Mature woman's milk . . 23.3 3.7 16.6 7.2 28.3 16.5 Cow's milk 23.5 2.8 26.5 7.2 24.9 13.6 Bacteria. — A few bacteria, usually staphylococci, are found in the milk of healthy women. Typhoid bacilli have been demonstrated in the milk of a woman ill with typhoid fever. Syphilis can probably be transmitted by the milk when the breasts are apparently normal. Pathogenic bacteria may be present in the milk when the mother is suffering from a local infection of the breast or a general sepsis. Drugs. — Some drugs are excreted in woman's milk. They lare alcohol, bromides, iodides, salicylates, mercury, calomel, antipyrin, arsenic, urotropin, the saline cathartics and sal- varsan. Probably morphine and atrophine also are excreted in woman's milk. Most of these are found in very minute amounts. Nervous Impressions. — Any severe, acute or prolonged ner- vous strain may so alter the mother's milk as to seriously upset the infant. For this reason it is important that a nurs- ing mother should lead a quiet life and avoid all nervous strain and excitement. Women that are prone to nervous disturbances, as hysteria, are seldom able to nurse their infants successfully. Menstruation. — Menstruation does not, as a rule, seriously affect the milk supply. Not infrequently the infant is uncom- fortable and has undigested stools at the onset. Only rarely is the disturbance more serious and prolonged. Pregnancy. — If a nursing mother becomes pregnant her milk rapidly deteriorates both in quantity and quality. Weaning is imperative. ^ Transmission of Immunity. — An immune mother transmits I her immunity to her nursing infant. Diet. — Within narrow limits the amount and composition of the milk may be altered by changes in the diet. The best results are obtained when the mother has been underfed, and the milk is abundant but poor in quality, especially in fat. Increasing the diet generally, but especially the fat and carbo- hydrate, will usually increase the fat content of the milk. When the fat is too high, reducing the fat and carbohydrate Am. Jour. Dis. Child., 1915, x, 246. 234 BREAST FEEDING in the diet and increasing the mother's exercise will usually reduce the fat. Low protein can be overcome by increasing the diet when the mother has been underfed, but is rarely influenced when the mother is already receiving a plentiful diet. Reducing the diet and increasing the exercise will sometimes reduce a too high protein. The percentage of lactose in woman's milk is more constant than that of either the fat or the protein and is little influenced by diet. An increase in the fluid intake will often increase the quantity of milk. BREAST FEEDING The simplest and best way to feed an infant is to nurse it. No artificial food has been evolved which gives nearly as uniformly good results. Therefore every mother that can do so should nurse her infant. The great value of breast feeding as compared with artificial feeding is proved by the much higher mortality rate among artificially fed infants. Lateiner, Meyerhofer and Progulski 1 found the mortality at the Lem- berg clinic to be 16 per cent, of the breast fed and 34 per cent, of the artificially fed. Another factor of importance is the greater frequency of rickets among the artificially fed. With premature infants, full-term infants that are feeble and under- developed, and the occasional infant that is unable to digest cow's milk, breast milk is essential. Among the poor there is very little opposition to breast feeding, unless the mother is the wage-earner and has to be away from home during the day, and even these mothers usually nurse their infants night and morning. Among the well-to-do the mothers are less frequently able to nurse their infants and they find the fre- quent nursings and especially the restrictions which nursing places upon their time very irksome. Contra-indic: tions for Breast Feeding. — The most frequent contra-indication is insufficient milk, but every effort should be made to increase the amount of milk before resorting to artificial feeding. Another important contra-indication is serious illness of the mother, as tuberculosis, typhoid fever, puerperal fever and mastitis. When a nursing mother develops an infectious dis- ease of short duration, as tonsillitis, she may stop nursing during the febrile stage and resume it later. The breasts should be emptied two or three times a day by massage and the breast pump. Many women resume nursing in this way after intervals of as long as two weeks. 1 Oester: Sanitatsw., 19 14, xxvi, 1. BREAST FEEDING 235 Frequently an infant is taken from the breast of a healthy mother and given a cow's milk mixture because he does not thrive or has indigestion. If the amount and quality of the mother's milk is insufficient and cannot be improved by diet and regulation of her mode of living, there is nothing else to do. When, however, the supply of milk is ample and the quality good, every effort should be made to adapt it to the infant before beginning artificial feeding, and in only rare instances is this impossible. Occasionally a nursing mother will become pregnant. When this occurs her milk deteriorates rapidly in amount and qual- ity. At first the infant stops gaining, later he loses weight. Artificial feeding should be begun at once. Intervals of Nursing. — Formerly an infant was nursed whenever he cried and appeared hungry, and this is today the usual procedure among the ignorant. Many such infants thrive and gain steadily, but they are usually irritable and frequently upset the entire household. Habits are soon formed by infants, and regularity of nursings is an important one. Six to eight hours after birth the infant is allowed to nurse for five minutes. After this the nursings are repeated every six hours for the first two days. When the breasts begin to secrete milk, which usually occurs on the third or fourth day, the intervals are shortened to three hours, with one nursing omitted at night. At the same time the length of time that the infant is allowed to nurse is increased to ten to fifteen minutes. From this time to the third month the infant should nurse at 6, 9, 12, 3, 6, 9 and once during the night, usually about 2 a.m. Always after the fourth month and occasionally earlier the night feeding may be stopped. It is well to stop this feeding as soon as possible, as the long undisturbed sleep is good for both the mother and infant. After the fifth month the intervals may be lengthened to four hours and the number of nursings reduced to five. The hours will now be 6, io, 2, 6, io. These intervals are somewhat longer than those frequently recommended for the first few months. Feeble and premature infants frequently do better when nursed every two or two and one-half hours. Normal infants, however, gain just as rapidly on three-hour intervals, which have the advantages of allowing the stomach to empty more completely between nursings, giv- ing the mother more freedom and lessening the likelihood of cracked nipples. Even four-hour intervals from the beginning are recommended by some physicians. Length of each Nursing. — After lactation is well established, most infants will nurse fifteen to twenty minutes each time for 236 BREAST FEEDING the first few weeks. Later they will frequently be satisfied in ten minutes. An infant should never be allowed to nurse a few minutes, play a few minutes and then nurse again. They should be taught from the beginning to nurse steadily, with an occasional rest, until they are through. An infant should never be allowed to sleep in the same bed with his mother, as this encourages him to nurse frequently during the night. An infant should seldom be allowed to nurse more than twenty minutes. If he is not satisfied by this time, he is either taking too much or the supply of milk is scanty. Weighing him before and after nursing will settle this point. Mother's Diet and Exercise. — A nursing mother should take a plentiful diet of easily digested food, with some extra fluid, as milk, egg and milk, cocoa or gruel in the middle of the morning and afternoon and before going to bed at night. Besides this she should drink a plentiful supply of water. She should avoid all articles of diet that are highly spiced, very rich or difficult of digestion, such as peppers, pickles, relishes, vinegar, rich puddings and sauces, lobster, crabs, Welsh rarebit, and excessive amounts of coffee, tea and alco- hol. Most nursing mothers can take moderate amounts of raw or cooked fruits and vegetables. Occasionally, however, even moderate amounts of fruit, especially the more acid ones such as grapefruit or green vegetables, particularly tomatoes and onions, will cause colic and indigestion in the infant. When this happens the particular fruit or vegetable causing the trouble should be omitted from the diet. If it is impos- sible to determine which fruit or vegetable is causing the trouble, it is well to omit all fruit and green vegetables until the infant is normal again. Then they may be resumed one at a time, the infant being watched for any return of the symptoms. In this way the cause of the disturbance can usually be identified and so eliminated. A nursing mother should be relieved, as far as possible, of all strenuous work and exercise. Moderate exercise, on the other hand, is essential for her health and counteracts the tendency to too rich milk. Walking in the open air is one of the best forms of exercise. More essential even than exercise is sufficient rest. She should have at least one long period of sleep during the night, and at least two hours of sleep during the day. The longer intervals between nursings and the early stopping of the night feeding all help toward this end. It is possible to influence the quantity and composition of the mother's milk to a considerable extent by altering her diet and mode of living. BREAST FEEDING 237 If the quantity is too small the mother's diet should be increased, especially the amount of milk, eggs and meat. Also her water intake should be increased. Her exercise should be limited and sufficient rest assured. Frequently relieving her of the physical and mental strain of caring for the infant helps a great deal. If she is anemic, run down or unable to take sufficient food because of lack of appetite, appropriate medication is indicated. If the milk is too rich, which usually means a high fat and protein content, lessening the mother's diet (especially meat, eggs and milk), increasing the amount of water which she takes, and increasing her exercise will usually reduce the fat content of the milk. At the same time the infant may be given one-half ounce of sterile water before each breast feed- ing and the length of the nursing reduced or the interval between nursings increased. When the milk is poor in quality, that is, has a low fat content, the procedure is the same as when it is insufficient, except that it is more important to increase the solids in the mother's diet than the fluids. It is easier to correct an abundant supply of overrich milk than an insufficient supply of milk which is poor in quality. Vomiting.— Most infants, whether breast or bottle fed, will occasionally regurgitate small amounts, from a few drops to a teaspoonful or two. This is to be expected and need cause no alarm. When, however, a breast-fed infant vomits large amounts after a good many feedings, something is wrong either with the milk or the method of handling the infant. The possibility of pyloric stenosis must always be kept in mind. Not infrequently it is due to the infant's efforts to rid himself of air swallowed during the nursing. This is apt to happen when the infant is placed in his bed immediately after nurs- ing. C. H. Smith 1 has demonstrated that under these cir- cumstances the gas is water-locked in the stomach, and an endeavor to belch it on the part of the infant is sure to cause some vomiting. If the infant is held erect for a minute or two after nursing he will belch the gas without losing any milk. Too much milk or too high fat will cause vomiting. The amount can be determined by weighing before and after nurs- ing. If the infant is taking too much, the length of the nurs- ing should be shortened. If analysis of the breast milk shows a too high fat content the mother's diet should be cut down slightly, especially the solid food, and her water intake and 1 Am. Jour. Dis. Child., 1915, ix, 261. 238 BREAST FEEDING exercise increased. Also the infant may be given one-half ounce of sterile water before each nursing. Gas and Colic. — Both gas and colic occur much less often when an infant is breast fed than when he is artificially fed. The usual cause of gas has been explained in the previous section on vomiting. Occasionally certain articles in the mother's diet will cause colic in the infant. The most frequent are the raw acid fruits and green vegetables. The method of handling this situation has been explained in the section on the mother's diet. Abnormal Stools. — Constipation is unusual in the breast-fed infant unless the milk is insufficient either in quality or quantity. Loose, too frequent stools, often containing considerable mucus accompanied by colic may occur when the mother is menstruating, after an indiscretion in diet on the mother's part, when the mother is suffering from an acute infection, or when the milk is not adapted to the particular infant. All but the last condition are transient and easily righted. If the milk is at fault the first thing to do is to determine the quantity taken by the infant and the composition of the milk. The quantity taken can be determined by weighing the infant before and after nursing. If the quantity is too great the length of each nursing should be shortened. If the composition of the milk is wrong an endeavor should be made to correct the fault by changing the mother's diet and routine as is explained in the section on the mother's diet. This is at times impossible, especially when the milk is both scanty and poor in quality. Unless some improvement is made within two weeks it is rarely wise to persist any longer. MIXED FEEDING When a woman has an insufficient supply of milk for her infant, supplementary feedings of cow's milk may be used. This is mixed feeding, and it is indicated whenever the breast milk is of good quality but insufficient in amount to properly nourish the infant. One of two procedures may be employed, either small bottle feedings may be given after each breast feeding, or bottle feedings may be substituted for some of the breast feedings. If the former method is followed the infant is given only one breast at a nursing. The amount of breast milk obtained is calculated by weighing the infant before and after nursing. Then a sufficient bottle feeding is given to make up the proper amount. As a rule it is not necessary to weigh the infant before and after nursing for more than a WEANING 239 few days. If the second method is chosen, one, two or three of the breast feedings are omitted and a full bottle feeding given at these times. At the breast feedings it is best to give the infant both breasts each time, as otherwise the long inter- vals between nursings tend to diminish the amount of milk secreted. It is rarely possible to keep up the supply of milk if the infant nurses less than four times in each twenty -four hours. There is a distinct advantage in always giving one bottle feeding a day to all breast-fed infants. By so doing they become accustomed to taking the bottle and their digestion becomes adapted to cow's milk. Furthermore it allows the mother one long interval during the day in which she may rest or be out of doors. If at any time it becomes necessary to wean the infant suddenly it can be accomplished with much less likelihood of disturbance. In beginning mixed feeding a relatively low formula should be used at first. A three-months-old infant should begin with about a 6 in 20 and a six-months-old infant with an 8 in 20 mixture. The full amount for the infant's age may be given from the beginning. The strength of the formula may be increased quite rapidly, about an ounce of milk being added every three days, provided there are no evidences of indiges- tion, until the strength of the formula is proper for the infant's age. The advantages of mixed feeding over artificial feeding are that it gives the infant a considerable amount of breast milk, that it allows the infant to become accustomed to cow's milk gradually, and that it simplifies weaning. WEANING. Few women can nurse their infants to advantage after the eighth or ninth month, and many have to give supplementary feedings long before this. Where it is possible to obtain good cow's milk it is a distinct advantage to give the infant one bottle feeding a day after the third or fourth month. This accustoms the infant to the bottle and greatly lessens the difficulty of weaning if the latter becomes necessary at any time. Infants that have never had a bottle feeding until they are six months of age or older will frequently refuse it abso- lutely as long as they are given the breast at all and sometimes for several days, even after the breast feedings have been entirely stopped. During this time they lose weight rapidly and not infrequently develop considerable fever. Little is gained by forcing them to take the bottle under these cir- cumstances. The best method is to offer the bottle at the 240 BREAST FEEDING regular intervals and take it away if refused. They always give in finally. No serious results follow this method. A three-months infant, on the other hand, soon becomes accus- tomed to taking one feeding from the bottle. The indications for early weaning are insufficient milk, severe illness of the mother, and pregnancy. When possible it is better to wean gradually. If the infant has been taking one bottle a day another of the same strength is added and after a few days another until all of the breast feedings have been stopped. The rapidity with which this is done will depend upon the cause of the weaning and the amount of milk which the mother has. If the infant is already taking a bottle feeding, the other feedings should be of the same strength. If the infant has never taken any cow's milk the first formula should be considerably weaker than a normal artificially fed infant of the same age would be taking. After the first few days the strength of the formula should be gradually increased until the food is sufficient for the infant. When it is neces- sary to stop all breast feedings at once it is more important to begin with a relatively weaker formula than when the bottle feedings can be gradually substituted. When the mother is able to nurse the full eight or nine months the process is much simpler. The various foods other than milk are added to the diet in the same order and amounts as with the artificially fed infant, except that it is not neces- sary to make these additions quite as early. When cereal is begun, a small amount of cow's milk (i or 2 ounces) diluted with an equal volume of boiled water is given with the cereal. As the cereal is increased the strength and amount of milk is increased. Then one feeding of diluted milk is substituted for a breast feeding. If the mother is well and strong and has an abundant supply of milk she may be allowed to nurse to the twelfth or thirteenth month. When this is possible it may not be necessary to use bottles at all, the infant being weaned directly to the cup. In no normal case should bottles be continued after the fifteenth or sixteenth month. CHAPTER XVI. ARTIFICIAL FEEDING. FOOD REQUIREMENTS OF THE ARTIFICIALLY FED INFANT. Energy. — Repeated efforts have been made to formulate some law or laws by which the caloric requirements of a given infant could be calculated. The first work was based entirely upon the body weight. It was soon found that the caloric requirement per pound was considerably larger for thin infants than for well-nourished infants. Then it was suggested that the surface area, and not the body weight, was the governing factor. As it is obviously impossible actually to measure the surface area of all infants, different investigators have worked out formulae by which the surface area of infants can be cal- culated. The results obtained by this method are more uni- form than those obtained where the weight alone is consid- ered, but the calculations are too complicated to be of practical use in every-day practice. Recently it has been suggested that the caloric requirement of an infant varies directly with the mass of active protoplasmic tissue in the body. This would explain why a thin infant requires more calories than a fat infant of the same weight. Unfortunately we have no means of calculating the mass of active protoplasmic tissue in any living infant. Muscular exertion has a marked influence upon the require- ments of the infant. Hard crying may increase the energy output by ioo per cent. Thus a very active infant always requires more energy than a quiet, passive infant. For practical use the body weight must be the guide at present. The usually accepted requirement is ioo calories per kilo or 45 calories per pound of body weight for each twenty-four hours from the end of the second week to the ninth month. At the same time we must remember that a very thin infant will frequently require considerably more than ioo calories per kilo, while a very fat infant may gain and do well on considerably less. During the first two weeks the caloric requirement is considerably less than 45 calories per pound, averaging only about 30 calories. After the eighth month the requirement falls to about 40 calories per pound. 16 242 ARTIFICIAL FEEDING Protein. — Protein is required by the infant to replace that lost in tissue waste and for the formation of new tissue in growth. This double demand makes the protein requirement of a growing infant relatively greater than that of an adult. Furthermore, as the most rapid growth takes place during the early months, the protein requirement is greatest during these months. Morse and Talbot 1 say, "The average protein need of infants is at least 1.5 gram per kilogram, or 0.7 gram per pound of body weight." In order to obtain this amount an infant must take nearly an ounce of cow's milk per pound of body weight. The generally accepted rule of one and a half ounces of cow's milk per pound of body weight furnishes considerably more than this amount. Almost all cow's milk mixtures contain more protein than woman's milk. This is especially true of whole-milk mixtures. The low fat content of the latter makes it necessary either to use a very high sugar content or to raise the protein consid- erably above the theoretical requirement in order to furnish the necessary calories. Thus the whole milk mixtures which are commonly used, contain about if ounces of milk per pound of body weight. Animal protein is more easily digested and more completely absorbed than vegetable protein. The protein of milk is most readily digested by infants, that of woman's milk more easily than that of cow's milk. Formerly most of the digestive disturbances of infants were attributed to the protein, but of late the tendency has been to minimize the importance of protein as a cause of indiges- tion. Some justification for the larger amounts of protein frequently fed in cow's milk mixtures is found in the smaller amounts of some essential animo-acids in the protein of cow's milk. Fat. — As fat furnishes approximately twice as many calories per gram as carbohydrate or protein, it is a very impor- tant element in the food, and small variations in the fat content of the food have a marked influence upon its energy value. In health from 90 to 98 per cent, of the fat in the food is absorbed. In digestive disturbances, especially those condi- tions which are associated with diarrhea, a much smaller portion of the fat ingested is absorbed. During the first few days postpartum about one-half of the dried stool is composed of fat. Later the amount of fat in the stools falls rapidly and varies between 14 and 25 per cent, of the dried stool. 1 Diseases of Nutrition and Infant Feeding, 19 15, p. 201. THE ARTIFICIALLY FED INFANT 243 There is considerable difference of opinion as to the amount of fat which a normal infant's food should contain. Many physicians use top milk mixtures and thus keep the fat con- tent of the food about twice that of the protein. Others use whole-milk mixtures which make the fat content of the food only slightly greater than the protein. Both methods have their advantages and disadvantages. An infant fed on the higher fat mixtures will gain more rapidly and be satisfied with smaller amounts of food, especially during the early months, than one fed on whole-milk mixtures. Furthermore, the higher fat content permits the use of smaller amounts of sugar, which is necessary in feeding infants with an intolerance for sugar. The disadvantage is that infants fed on high fat mixtures are more apt to have digestive disturbances. For this reason whole-milk mixtures with their lower fat contents are safer in the hands of those with comparatively little experience. Carbohydrate. — Sugar. — All milk contains lactose or milk- sugar. The sugar content of woman's milk is about 7.5 per cent., which is nearly twice that of cow's milk. When cow's milk is diluted its sugar content is still further reduced so that a considerable amount of sugar has to be added to cow's milk mixtures in order to bring their sugar content up to the required amount. As a rule sufficient sugar is added to make the sugar content of the mixture about 6 per cent., never more than 7 per cent. An infant fed on woman's milk receives slightly more calories in fat than in sugar, while an artificially fed infant taking cow's milk mixtures receives a rather large part of his calories in the form of sugar. Three sugars are used in infant feeding, lactose (milk-sugar), saccharose (cane-sugar), and maltose. All of these sugars are disaccharides and in the process of digestion they are broken down into monosaccharides. The rapidity with which they are absorbed differs and hence their effect upon intestinal fermentation and peristalsis. Lactose is more slowly absorbed than either maltose or saccharose. Its longer stay in the intestinal canal is supposed to favor the normal fermentation processes and thus to hold in check excessive putrefaction. Furthermore, it is slightly laxative. For these reasons it is the sugar of choice for feed- ing normal infants. Pure maltose is never used in feeding because of its cost. The maltose used is always a mixture of maltose with dextrin, the maltose forming about 50 per cent, of most of the preparations. The dextrin content is more variable. The following table taken from Morse and Talbot 1 1 Diseases of Nutrition and Infant Feeding. Macmillan, 1915, p. 194. 244 ARTIFICIAL FEEDING gives the percentage of maltose and dextrin in the more common preparations used: Food. Loflund's nahrmaltose .... Mead's dextrimaltose .... Neutral maltose (Maltzyme Co.) . Loflund's malt soup extract . Maltose (Walker-Gordon laboratory) Mellin's food Malted milk Maltose, per cent. 40.00 51.00 63 . 00-66 . 00 58.91 57-io 58.88 49- 15 Dextrin, per cent. 60.00 47.OO 8 . 00-9 . 00 15-42 30.90 20.69 18.80 In digestion one molecule of maltose is split into two mole- cules of dextrose. For this reason it is more rapidly absorbed than either lactose or saccharose. This rapidity of absorption and the fact that some infants that have developed a fermen- tative diarrhea while taking lactose will digest maltose easier than lactose are the chief reasons for its use. Saccharose (cane-sugar) is split into dextrose and levulose in the process of digestion. As the levulose has to be changed into dextrose before being absorbed, cane-sugar is more slowly absorbed than maltose. Cane-sugar is somewhat less laxa- tive than lactose. Furthermore it is much cheaper than either of the other sugars. Many normal infants will thrive as well on cane-sugar as on lactose or maltose. Its cheapness is its chief recommendation. Starch. — Starch is used for two purposes in infant feeding, first, to prevent the formation of large casein curds in the. stomach, and second, to increase the strength of the food For the first purpose only a small amount of starch is neces- sary, 0.75 per cent, of starch in the food being as effective as larger amounts. This amount of starch may be added to the food of very young infants. After the second month some form of starch is usually added to most artificial mixtures. At first a cereal water, made by boiling one level tablespoonful of either oat or barley flour and a pinch of salt in a pint of water for three-fourths of an hour, is used. After the fifth month two level table- spoonfuls of flour may be used. Barley water is generally believed to be slightly more constipating than oat water. Inorganic Salts. — The salt content of cow's milk is about three and one-half times that of woman's milk. The result is that the ordinary infant fed on diluted cow's milk receives a considerably greater amount of salts than a breast-fed infant. Furthermore, the relative proportions of the various salts differ somewhat in the two feedings, the chief difference being in the phosphoric acid. These differences are believed to have a considerable influence upon the growing infant, espe- cially in disturbances of digestion. PROPRIETARY FOODS 245 The following table from Holt 1 gives the relative percentage of the different salts in both cow's and woman's milk. Cow's. Woman CaO 22.8 23-3 MgO 2.8 3-7 P 2 5 27.4 16.6 K 2 24.7 28.3 Na 2 IO.9 7.2 CI 15-5 16.5 Water. — The amount of fluid required by an infant increases rapidly during the first three months and more slowly after that. A normal infant usually requires about 12 ounces at the end of the first week, 24 ounces at the end of the first month, 30 ounces by the end of the third month, 36 ounces by the fifth month, and 40 ounces by the eighth month. As a rule the fluid intake is about one-seventh of the body weight. As long as all the food is fluid, little additional water need be given, but as soon as part of the food is solid additional water must be given. PROPRIETARY FOODS. There are many so-called "infant foods" on the market. While these differ greatly in composition they all have cer- tain common characteristics. Almost all contain large amounts of carbohydrate and small amounts of fat and pro- tein. It is well to remember that similar mixtures can be produced with the usual ingredients of infants' food without using these proprietary preparations. They may be divided into four classes: first, those contain- ing cow's milk; second, those containing considerable amounts of maltose and dextrins; third, farinaceous foods; and fourth, miscellaneous preparations. Preparations Containing Cow's Milk. — This group includes the malted milks, Allenbury's milk food No. 1 and No. 2, and Nestle's food. The basis of all of these is milk that has been evaporated to dryness. All have considerable quantities of carbohydrate added. Their fat content is considerably higher than that of any of the other classes. Preparations Containing Large Amounts of Maltose. — Mellin's food which contains about 60 per cent, of maltose, is the best example of this group. Mead's dextrimaltose No. 1 contains about 52 per cent, of maltose. The malted milks are usually included in this group but their fat content is a great deal higher, due to the milk used in their manufacture. These foods may be used when maltose is indicated but should never be used without milk. 1 Diseases of Infancy and Childhood. Appleton, 7th ed., 1916, p. 150. 246 ARTIFICIAL FEEDING Farinaceous Foods. — This group includes imperial granum, Ridge's food, Robinson's barley and oat flour, Brook's barley flour, and the Cereo Company's flours. The group differs from the first in that they contain almost no fat, and from the second in that they all contain considerable amounts of unchanged starch. They may be used when it is desirable to add some carbohydrate partly in the form of starch to the food. The Cereo Company also furnish an enzyme preparation called cereo. By its use from 70 to 98 per cent, of the starch is converted into soluble carbohydrates. Miscellaneous Foods. — Eskay's albumenized food is made from egg albumen and cereals. Peptogenic milk powder is largely milk-sugar. The following table 1 gives the composition of most of the foods mentioned: Name. Fat, per cent. Sugar, per cent. Protein, per cent. Starch, per cent. Ash, p. c. ' milk 1 ) Horlick's malted milk 8.IO 67-95" malt dextrin milk J 49- 15 . i8.8o < 42 . 00' 15.00 4.OO Allenbury's food No. 1 13.80 66.55 < malt ( dextrin ' milk 14.00 - IO.OO ( 36.00' 9.88 3-98 Allenbury's food No. 2 14.20 70 . 90 < malt ( dextrin ' milk 20.00 I3.00 6-57 9-75 3-70 Nestle's food . 5-70 58.93 < cane malt 25.0 J27-36 11.94 20.25 i-45 dextrin Mellin's food . Mead's dextrimaltose No. 1 .... 1.80 79-57 ^ 93-00 < 1 malt > dextrin ' malt 1 dextrin 58. 881 20.69J 52.oo\ 41.00/ 11. 31 4-45 2.00 ( dex- Imperial granum . 0.50 1 . 80 \ trose { dextrin 0.421 1.38/ 13-88 72.79 0.50 Ridge's food . 0-33 2.96 10.31 70.93 0-75 Robinson's barley 1.40 2.92 6-75 70.20 0.85 Brook's barley 1.03 3-48 8.69 68.51 0.88 Cereo barley . 2.03 5.20 14.88 58.39 1.48 Cereo oat .... 6.40 2.36 54-i2\ 1.70/ 16.44 56.31 2-53 Eskay's food . 1.28 55 • 82 \ dextrin 7-75 31-95 1.58 ARTIFICIAL FEEDING. None of the rules for the artificial feeding of infants so far advanced apply to the newborn, because these infants are 1 The figures for fat, protein, starch and ash in the above table are taken from the Report of the Connecticut Agricultural Experiment Station, 191 6, p. 328. Those for sugar are for the most part from Morse and Talbot : Diseases of Nutri- tion and Infant Feeding, 1915, p. 230. ARTIFICIAL FEEDING 247 unable to digest cow's milk in sufficient strength or amount to satisfy completely their theoretical requirements. Hence we are forced to begin with such dilutions and amounts as experience has taught us are safe, and increase them as rap- idly as the infant's digestion will allow, until a sufficient amount of food is taken. After that the food may be calcu- lated with reference to the caloric requirement. For the first twenty-four to forty-eight hours many infants vomit repeatedly, especially when given any fluid. During this time it is best to give boiled water or a 5 per cent, solution of lactose in boiled water. One or two ounces should be given every three hours. After thirty-six hours, provided the vomiting has ceased, a weak dilution of milk may be given. Although many still use top-milk mixtures, it is safer to use whole-milk dilutions with a small amount of lactose added. Infants fed on whole-milk mixtures do not gain as rapidly at first as those fed on top-milk mixtures. On the other hand, they are much less likely to become upset. The intervals between feedings should now be three hours, with one feeding omitted at night. The first formula 1 should be Milk 2 ounces Milk-sugar 2 level tablespoonfuls Boiled water 18 ounces Method of Preparing Formula. — To make up a formula of whole milk the following articles are needed: Bottles — As many as there are feedings in twenty-four hours. They should be graduated in ounces. Measure — The best is an enamelware vessel marked on the inside in ounces and large enough to hold the entire twenty-four-hour amount. A glass graduate may be used but they break easily, especially if they are boiled. A small enamelware funnel. A tablespoon. Non-absorbent cotton. Milk. Lactose (milk-sugar). Boiled water. The bottles, measure, spoon and funnel should have been washed and boiled. The bottle of milk is well mixed so that the cream is evenly distributed and the desired amount of milk poured into the graduate. The desired amount of sugar is measured (three level tablespoonfuls equal one ounce), dissolved in part of the boiled 1 All formulae in this section are made up to 20 ounces. This method has been adopted because it is simpler and more widely understood than the other methods. As soon as the total twenty-four-hour amount exceeds 20 ounces, one and a half times or double the formula is made up, depending upon the total amount of food required. 7 248 ARTIFICIAL FEEDING water and added to the milk. Then boiled water is added to the mixture to make up the desired amount. It is now mixed and poured into the bottles, the proper amount for one feed- ing into each bottle. Finally the bottles are stoppered with cotton and placed in the ice-box. Increasing Formula. — The amount of milk and sugar in the formula can usually be increased every second or third day until the infant is taking 7 ounces of milk in each 20 ounces of food with two and one-half level tablespoonfuls of lactose added. After this the increase has to be slower. By the time the infant is two and a half months old he will usually be taking equal parts of milk and diluent with two and one- half tablespoonfuls of lactose added to each 20 ounces of food. While this increase in strength is taking place the amount is also gradually increased. It is best to begin by offering the infant 1 or 2 ounces at each feeding. Thus after the second day he will receive seven feedings of 2 ounces each, making 14 ounces in each twenty-four hours. As soon as he is not satisfied with 2 ounces he may have more. The best method is to increase each feeding J ounce at a time. Such increases can usually be made about every five days until the infant is receiving 4 ounces at each feeding, making 28 ounces in each twenty-four hours. Most infants will reach this point about the fifth or sixth week. After this the amount may be slowly increased, reaching 5 ounces about the end of the third month, when the night feeding is usually dropped. At this time the infant will be receiving six feedings of 5 ounces each, making 30 ounces in each twenty-four hours. The strength and amount of the food is still gradually increased so that by the fifth or sixth month the infant is taking 36 ounces of a mixture containing two-thirds milk and one-third diluent with 1 ounce of sugar added to the twenty- four-hour amount. It is well at this time to increase the intervals between feedings, so that the total twenty-four-hour amount is not lessened. Thus an infant who has been receiv- ing six feedings of 6 ounces each, 1 every three hours, will receive five feedings of 7 ounces each, one every four hours. From the sixth to the twelfth month the strength and amount of the food are increased very slowly. Most infants are taking whole milk undiluted and with no additions when they are ten to twelve months old. Delicate infants and those who have had digestive upsets frequently cannot digest whole milk until they are fifteen months old. The amount of each feeding is increased about an ounce each month until the infant is taking 40 to 45 ounces in each twenty-four hours. CEREALS 249 Usually this point is reached at eight or nine months. After this the increase is in the form of other food, the total amount of formula given being gradually reduced as the proportion of milk is increased. Cereal. — Frequently some cereal, usually barley water, is added to the food from the start. It is best to omit the cereal for the first two or three months in most cases, as its addition complicates the formula and adds one more factor which has to be considered when the food disagrees. After the third month it should be added, as it seldom disagrees by this time and, furthermore, it increases the carbohydrate content of the food slightly. The cereal most frequently used is barley, either as a flour or pearl barley. The desired amount of barley flour and a pinch of salt are brought to a boil in an amount of water slightly less than that used in the formula, and then simmered for three-quarters of an hour. It is then strained, partly cooled and added to the milk. After the fifth month a stronger cereal mixture is used. If pearl barley is used it has to be cooked much longer. In other respects its preparation is similar. If the infant is inclined to be constipated, oat water is pref- erable. There are several oat flours on the market. They are prepared exactly like barley flour. If oatmeal is used it should be cooked at least four hours. Some infants do better with imperial granum water prepared in the same way. It may be tried when barley and oatmeal cause colic or indigestion. A considerable portion of its carbo- hydrate content is in the form of dextrins. Many infants like its taste better than that of either oat or barley water. The table on page 250 gives the composition of a series of formulae such as have just been described with the approxi- mate age at which they should be used. While this table will serve as a guide it cannot be followed absolutely, as some infants will take more food or stronger food at the respective ages than that given in the table, and others will not be able to keep up to the schedule. Each infant has to be fed accord- ing to his individual needs and any schedule can serve as an approximate guide only. Dr. F. H. Bartlett has devised a ready method of compound- ing a formula for older infants. The caloric requirement of the infant is calculated by multiplying 45 (the required calories per pound) by the weight of the infant in pounds. From this he substracts 120 (the calories furnished by 1 ounce of sugar). The remainder he divides by 20 (the calories furnished by 1 ounce of whole milk). This gives the number of ounces of whole milk which the formula must contain. 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CD +J S3 „S S .-^^ CT3 5h 1> >> 5- ,_ O o vo b£ a IO CD ii o « p o O^ 5-, u o3 cd ^§£§g W ° CD £ O Fl W **H ^ TO ^ M W 03 ffl iO NEPHRITIS 411 Salt-poor Diet No. 4. 1 Breakfast. Dinner. Oatmeal (cooked) 150 gm. 5 oz. Potato . 100 gm. 33 oz Oatmeal (raw) 25 gm. f oz. Eggs . . Tomato . 100 gm. 3l oz Coffee . . . 200 c.c. 6| oz. Steak 120 gm. 4 oz Bread . 40 gm. if oz. Broth . 200 c.c. 6\ oz Butter . 31 gm. 1 oz. Bread . 30 gm. I oz Sugar . 10 gm. 1 oz. Butter (unsalted) 31 gm. I oz 456 gm. 14! oz. 581 gm. 19 oz Supper. This Diet Contains: Eggs (2) . 80 gm. if oz. Protein . 64.8 gm. 2 OZ Prunes . 50 gm. if oz. Fat . . 124.7 gm. 4 oz Rice (cooked ) . 150 gm. 5 oz. Carbohy- 140. 1 gm. 42 oz Rice (raw) . 25 gm. 1 oz. drate Cream . 50 c.c. if oz. NaCl 0.9 gm. \ oz Tea . . . . 200 c.c. 6| oz. Fluids . 650.0 c.c. 2l| OZ Bread . 30 gm. 1 oz. Nitrogen 10.3 gm. \ oz Butter (unsc ilted) 31 gm. 1 oz. Calories . 2000 . Sugar . 7 gm. \ oz. 623 gm. 16 oz. Bread, butter, sugar, may be given as desired, providing total is unchanged. Table of Salt Content of Common Foods. Per cent. Milk 0.18 Beef broth 0.735 1 egg 0.086 Chicken broth 0.35 Pea soup o . 499 Ordinary white bread (not salt-free) .... 0.701 Rice 0.748 Boiled potato o . 058 Chicken 0.01 Beef 0.04 Lamb chops 0.97 Pickerel 0.10 Cod 0.59 Salmon 0.46 Haddock 0.59 Oatmeal gruel o . 075 Macaroni 0.07 Beans 0.0058 Carrots 0.029 Applesauce 0.0025 For full list of salt in foods see Table, p. 8 1 . (Coleman) Schall-Heisler Constructed by Miss A. S. Foster, Dietitian to the Department of Diseases of Metabolism, Presbyterian Hospital, N. Y. 412 DISEASES OF THE GEN ITO-URI NARY SYSTEM General Protein Contents of Some Foods. 1 Per cent. 7.0 to 12 23.0 to 25 6 . O to 8 3.0 to \ to 3.0 to 2.0 to about 0.3 to 2.8 22.0 to 29 Cereals contain Peas and beans Breads . Puddings Soups Pea, bean, cream soups Green vegetables Root vegetables Fruits Cream cheese . Stilton Swiss Edam Holland J Conclusion. — Thus it will be seen that if care is taken in determining the type of nephritis, whether acute or chronic, and as well, which of the functions are principally disturbed, much can be done by dietary regulation to spare a diseased kidney unnecessary labor, and at the same time furnish the organism with the food distinctly appropriate to the needs of each individual case. PYELITIS. Whatever the cause of the irritation in the pelvis of the kidney may be, whether from calculus or infection, the dietetic indications are plain enough. As soon as the trouble is recog- nized the patient should be put on a milk diet with a certain allowance of farinaceous gruel and large amounts of water urged, either as plain water or mild, alkaline drinks, such as Vichy or Vichy and water, equal parts, or water with 1 gm. or 15 grains of bicarbonate of soda added to each glassful. (If urotropin is used to combat the infection, nothing should be used to reduce the natural acidity of the urine, as this drug is only decomposed in an acid medium.) As soon as the fever is over one may give a lactofarinaceous diet with green vege- tables and later return to a mixed diet, but with the meat strictly limited to a very small portion, not more than once a day. No condiments of any kind should be allowed and alcohol in every form is contra-indicated. If nephritis occurs as a complication of the infection the diet should be regulated in much the same way except that the return to mixed feeding should be delayed until all signs of the acute process in the kidney substance have subsided. Attention must be given to preventing constipation, and for this purpose some of the mild saline laxative waters may be 1 Forchheimer's Therapeutics, iv, 42. GONORRHEA 413 used or aloes and podophylin, cascara, etc. If edema develops as a consequence of nephritis it will be necessary to make use of one or other of the salt-poor diets, as detailed under nephritis. One important fact to remember is, that a continued flush- ing of the kidney pelvis by large quantities of ingested fluid removes the products of irritation and helps greatly in the healing process. CYSTITIS. Practically the same dietetic rules given for pyelitis hold good in cystitis, for the difference in the location of the infec- tion does not cause any change in the dietetic requirements. A bland diet at first, largely fluid, and always containing con- siderable amounts of liquid, is the factor of chief importance; the same abstinence in the use of alcohol and condiments or irritants is observed as in pyelitis. GONORRHEA. Even with a specific infection of the anterior and posterior urethra and possibly the complicating cystitis and prosta- titis the diet conforms very largely to that already recom- mended for pyelitis and cystitis. In the early stages a milk diet for a few days, to reduce the irritation, combined with alkaline drinks, to change the reaction of the urine to alka- line, will make the patients much more comfortable. The diet may then be enlarged by the use of all farinaceous and vege- table foods, eggs, milk products, cheese, etc., and, when the inflammatory process reaches the subacute stage, the addition of meat once a day is entirely allowable. Foods to be particularly avoided are: all forms of spiced and highly seasoned food and condiments, alcohol in any form whatever, strong tea and coffee, acid fruits, tomatoes and asparagus. It should be remembered that a discharge that is almost cured may be readily started again by an indulgence m irritat- ing foods or drink. This is especially true of the use of alco- hol. If it should seem necessary for any reason to take some form of alcoholic drink, a diluted light claret or white wine is best, using an alkaline water, such as Vichy or Apollinaris as a diluent. However, too much stress cannot be laid upon the avoidance of any alcohol. 414 DISEASES OF THE GEN I TO-URINARY SYSTEM NEPHROLITHIASIS. The majority of calculi belong to one of three classes, uric acid, phosphates or oxalates. Uric acid and oxalate calculi are found in acid urine, phosphatic calculi in alkaline urine and these latter are more apt to come secondary to infection and fermentation. The diet must be simple, avoiding all rich foods and sauces or a great variety at one meal and should be sufficient for the needs of the body but with no surplus. If the stone is of uric acid, a purine-free or low purine diet should be insisted upon, omitting meats, particularly gland- ular organs and soups and all highly seasoned foods. Sugar and fat may be taken moderately. When the stone is of the oxalate variety all the foods that contain oxalic acid in excess should be left out of the diet, notably strawberries, rhubarb, figs, apples, peas and spinach. Most of the other vegetables except beans and peas are also best left alone, as they all contain an excess of lime, rendering the oxalate more insoluble. Meat, in all except glandular form, is allowed freely. This same general dietary rule holds for phosphatic calculi. In all but phosphatic stones the use of alkaline mineral waters is allowed and does good not by virtue of dissolving the stone but by flushing the kidneys, rendering the urine less acid with the consequent lessened chance of further calcareous deposit. It is best to keep the urine faintly acid or neutral but not alkaline, in the latter instance it favors the deposit of phos- phates either as calculi or as a coating to a uric acid calculus. Water in large amounts is recommended to dilute the urine and flush the kidneys, so preventing much of the further deposition of salts. AMYLOID KIDNEY. There are no special indications for diet in this condition so far as the amyloid disease itself is concerned, but since in this condition the excretory power of the tubules is diminished the nitrogenous foods should be kept at rather a low point, 40 to 60 gm. (ij to 2 oz.), per day while the total food value of the diet should be high to help combat the chronic infection almost always present somewhere in the body, which is the active cause of the amyloid degeneration. CHAPTER XXV. DISEASES OR PATHOLOGICAL STATES DUE TO DISTURBANCES OF NORMAL METABOLISM. Of course in all diseases there are disturbances of metabo- lism, so in setting apart a classification such as this we mean merely that in the following diseases the abnormal anabolism or catabohsm assumes the chief role, notwithstanding every- thing else. On this account it is not always easy to say just which diseases shall be included in this class, and as in the other classifications it is more than probable that a certain amount of rearrangement will be necessary as time passes. In all these states the resultant conditions are more com- parable to the results of hyperfunction or hypofunction of certain sets of glands which control growth and body exchange, rather than to actual disease, although the line is often not sharply drawn between the two, for that which starts merely as a functional disturbance may progress to the proportions of a fatal disease, e. g., alimentary glycosuria and severe diabetes. DIABETES INSIPIDUS. This disease, characterized by the passage of large amounts of urine of low specific gravity, is probably due to a functional or organic disease of the brain and there is also a possibility that the center in the medulla which controls the renal blood supply as well as excretion, is affected. 1 Disease in or about the hypophysis is often associated with diabetes insipidus and Frank 2 has suggested the theory that excessive function of this gland is the cause of the disease. The injection of pituitrin often helps these cases, which would rather make it seem as if a hypofunction of the gland were more probable than excessive secretion. "Minkowski 3 advises that the amount of chlorides and spe- cific gravity of the urine be determined after the ingestion of considerable salt. If both increase relatively more than the urine does, he believes that the power of excreting a concen- trated urine is still possessed by the kidneys. Therefore 1 Ref. Handbook Med. Sc, 3d ed., p. 516. 2 Berl. klin. Wchnschr., xlix, 9. 3 Therapeutic die Gag., 1910, p. 1. 416 DISTURBANCES OF NORMAL METABOLISM diminishing the amount of water drunk by the patients will help them. If the amount of urine increases, relatively the more a salt-free diet and one poor in protein will be a help." In choosing a diet it is necessary to avoid foods that cause indigestion or flatulence, particular restriction being placed on sugar, for when an excess of this is taken it tends to raise the percentage of sugar in the blood, which aggravates the polyuria. Cold drinks which are diuretic must be given up, as cold milk, beer, cider, also watery fruits. A salt-poor and low protein diet tends to diminish the quantity of urine when the kidneys do not concentrate the urine normally. DIABETES MELLITUS. In perhaps no other disease is diet such a matter of vital importance as in diabetes mellitus, for as time has gone on and one after another procedure or drug has been vaunted as a cure only to be cast aside as entirely wanting, diet has remained as the one factor which is capable, if properly employed, of resting the glycogenic function of the liver, and in all but the most severe and necessarily fatal cases is also capable of bringing about a condition more or less approach- ing the normal. By its proper employment the mild cases are clinically cured, the moderately severe are rendered mild and the most of the very severe are changed to cases of moderate severity. An extended discussion of the pathological physiology and disturbed metabolism of diabetes is not necessarily a part of a book on dietetics but it is necessary to discuss the important changes of metabolism if one is to appreciate, to even a small degree, the importance and significance of diet in the varying phases of this disease. Interest naturally centers about carbohydrate metabolism which formerly was thought to be the only matter of impor- tance and that the metabolism of protein and fat in no way entered into the question for the diabetic. Following this, the importance of fats in the production of acidosis was discovered, and last of all the fact that the body could synthetize sligar out of protein. With this last the whole question of diet in diabetes was revolutionized at a stroke and an explanation was at hand as to why certain cases failed to become sugar- free on a meat-fat diet. Another significant change of thought has been that formerly attention was focussed on the glyco- suria as the most important index of a disturbed sugar metab- olism, whereas now the hyperglycemia, which always accom- panies glycosuria, except in the few cases of so-called renal DIABETES MELLITUS 417 diabetes, occupies chief attention, since it is found that many cases of diabetes get rid of their glycosuria and would formerly have been pronounced cured but are found to retain their hyperglycemia, thus still showing evidence of a disturbed sugar metabolism. When we come to study the various aspects of the sugar question we do not find unanimity of opinion. Claude Ber- nard, Lowe and von Noorden believing that diabetes is due to disturbance of sugar production, while Naunyn and Min- kowski believe it due to a disturbance of sugar burning. 1 Hepatic disorders or pathological states were blamed in time past while now the liver is believed by most to be little more than the organ which stores sugar or glycogen and is "played upon" so to speak, by other organs by which the process of sugar excretion by the liver is stimulated or depressed. If we will refresh our memories by reference to normal physi- ology, and then its application to diseased states, we will get a better idea of the question which is so well put by von Noorden. 2 The liver is the organ which renders sugar available for an immediate source of energy and maintains the sugar content of the blood at 0.075 to 0.1 per cent. If the liver produces more sugar than is required by the tissues, there is an increased amount of it in the blood (hyperglycemia) under which condi- tion some escapes in the urine. If, on the other hand, the liver does not supply enough sugar to the blood, the muscles are the first to suffer and the individual feels fatigue, as occurs after severe labor. In a condition of alimentary glycosuria the amount of sugar ingested is excessive and cannot be used up, so is excreted in the urine. In order to prevent this, however, the liver stores the sugar as insoluble glycogen which forms a reserve sup- ply. By the action of glycogenase, also found in large amounts in the liver and more or less universally in the body, the glyco- gen is reconverted into soluable sugar again and so goes into the blood. If for any reason the ordinary supply of carbo- hydrate is withheld the liver can form sugar out of protein and fat. In health the supply and demand for sugar in the blood are exactly balanced and regulated, i. e. y the liver does not split up more glycogen for the use of the body than necessary. There are at least two factors which according to von Noorden influence the function of sugar making, viz., the pancreas and the suprarenals, the former a depressant, the latter excitants to 1 Berl. klin. Wchnschr., 1913, p. 2161. ? Am. Jour, Med. Sc, 1913, cxlv, j. 27 418 DISTURBANCES OF NORMAL METABOLISM sugar formation. According to this theory, from the pancreas there goes to the liver a specific secretion (an internal secre- tion, presumably from the islands of Langerhans) which acts as a depressant to sugar formation in the liver. If the pan- creas is removed, so is this break in sugar production, and the diastase acting unhindered causes an excessive sugar output from the liver, which is excreted in the urine. This, von Noorden says, is really a severe diabetes. Adrenalin excites the production of sugar by the liver and a small amount of it is constantly being excreted by the supra- renals and absorbed by the blood. Therefore the supra- renals antagonize the action of the pancreas in its relation to sugar production and these two glandular systems really con- trol the sugar production by the diastase in the liver. The suprarenals do not act alone, for "they are especially under the control of the nervous system. " The Claude Bernard center in the medulla is the point from which go out impulses that stimulate the suprarenals to hyperfunction through the sympathetic nerves and thereby cause glycosuria. The pan- creas is not independent either, for it is under the control of the thyroid and when the thyroid overfunctionates the pan- creatic function is paralyzed and the glycogenase in the liver again acts unhindered, resulting in the overproduction of sugar and glycosuria. So in Graves's disease we see glycosuria and in myxedema increased sugar tolerance. The pancreas is also probably affected by other factors as yet unknown. This theory is vizualized by the following diagram. The arrows represent the direction of the stimuli and the plus or minus signs whether the stimulus is an excitant or depressant on the next organ. Adrenals etc. DIABETES MELLITUS 419 Besides the disturbance in carbohydrate metabolism we have to consider carefully that of protein and fat. The Relation of Protein Metabolism to Glycosuria. — Protein metabolism in the mild forms of diabetes probably proceeds normally and requires no further discussion, but in the more severe varieties we have other factors that must be taken into consideration. In 191 3 Cammidge 1 called attention to the fact that in estimating the degree of toxicosis in diabetes, one should take into consideration the complete picture and that three stages should be distinguished. In two of the three "the defect in metabolism is confined to a more or less com- plete inability to make use of the sugar derived from the carbo- hydrate foods, but amino-acids are still available as a source of energy and the body makes use of these supplemented in the milder forms by a certain amount of sugar derived from starchy foods and fats, for its needs. In the third form, to which the name ' diabetes' is confined by some writers, the power to metabolize amino-acids is diminished, with the result that these bodies appear in the urine and gradually increase in amount as the metabolic defect becomes more pronounced. Even in the most serious cases, however, some of the amino- acids are diaminized and converted into dextrose, thus con- tributing to the sugar excreted in the urine, while the fatty acids of others are imperfectly oxidized and give rise to the 1 acetone bodies' (acetone, aceto-acetic acid and /3-hydroxy- butyric acid) that are passed at the same time. Estimations of the amino-acids, ' acetone bodies' and sugar give therefore a much more complete picture of the state of the metabolism than any one of these taken alone, and by considering them in conjunction with the efFects produced by a diet of which the qualitative and quantitative composition is known, we can determine the stage that has been reached and the probable expectation of life." These findings go with the clinical observation that when the diabetes is severe, the protein should be curtailed and intervals of a meat-free diet given. Animal food is rich in those forms of protein which the dis- turbed organism finds it difficult to break down and utilize, while vegetable proteins are poor in these constituents and a larger proportion of amino-acids which can be made use of to supply the energy needed by the tissues. Egg protein is more like vegetable protein in this respect and can be used safely where other animal protein is forbidden. Milk, however, is like the meat protein. 1 Lancet, 1913, ii, 1319. 420 DISTURBANCES OF NORMAL METABOLISM When we find a patient with amino-acids in the urine we must determine whether they are from the food or from break- ing down of their own tissues and if from the food whether they can still take care of the protein from egg and vegetable. If omitting animal proteins results in freeing the urine of amino-acids, as is the case in gout, the prognosis is better and the outlook with proper diet of getting rid of glycosuria is good, but if we are not able, by regulating the diet, to get rid of the amino-acids the outlook is poor. This constitutes the third or true diabetic stage. The Nitrogen Balance in Diabetes. — Cammidge 1 in calcu- lating the intake and output of nitrogen in a severe case of diabetes found that with an intake of 12 gm. nitrogen and 52 gm. carbohydrate, the urine showed 31.8 gm. nitrogen with high acetone bodies, ammonia nitrogen, calcium and mag- nesium and 229 gm. sugar. This demonstrated that the patient was forming sugar from his own tissues. This together with the abnormal excretion of amino-acids, uric acid and creatinin showed that there was a high degree of tissue waste accom- panied by defective protein metabolism. When in this case the nitrogen intake was reduced to 3 gm. still keeping the sugar value of the diet at nearly the same level, resulted in the fall of sugar excretion to less than one-half its former amount, the blood sugar fell from 0.3 to 0.2 per cent, and the alveolar carbon dioxide rose to 4.6 per cent, from 0.75 per cent, before; the /3-oxybutyric acid also fell from 19.7 to 3.6 gm. accompanied by a clinical improvement. Sufficient has been said to leave no doubt in the mind that the sugar excretion is markedly influenced by protein metabolism and that it is not possible in severe diabetes to make up a deficiency of carbohydrate in the diet by feeding large amounts of protein. Until this fact was learned it was not understood why a diabetic continued to excrete sugar on a carbohydrate-free diet and that it was not until the protein was reduced or changed from a meat to an egg protein that the patient began to be sugar-free. In this connection reference should be made to coma occur- ring in some cases of severe diabetes due to a perverted pro- tein metabolism not associated with a ketonuria. Kraus, 2 Rumpf 3 and Lepine 4 and others showed that cases of dia- betic coma occurred without any increase of organic acids in the urine and Rosenbloom 5 reports 3 cases of typical coma 1 Lancet, 1915, ii, 1187. 2 Zeit. f. Heilk., 1906, x, 1899. 3 Berl. klin. Wchnschr., 1895, xxxii, 185, 669, 700. 4 Rev. d. med., 1887, xii, 224; 1888, xiii, 1004. 5 New York Med. Jour., August 7, 19 15. DIABETES MELLITUS 421 occurring in severe diabetes with no carbohydrate tolerance, and even with a restricted protein intake the glycosuria was not diminished. They were observed weeks or months during all of which time the urine contained an average normal amount of ammonia nitrogen, no ketone bodies nor was there any evidence of kidney disease. All 3 cases died in typical diabetic coma. Here we have an effect from abnormal pro- tein metabolism which must be taken into account when deal- ing with severe diabetes, and its clinical application to dietetics is plain. Relation of Fat Metabolism to Glycosuria. — As is well known the normal end-products of fat metabolism are water and C0 2 ; the body fats are chiefly palmitic, stearic and oleic acids, all of which contain an even number of carbons in their respec- tive molecules. Although protein can add to the formation of acetone bodies, they arise mainly from fat. The complete breaking down of the fatty acids is not altogether an inde- pendent process, as it is largely dependent on the presence of carbohydrate in the diet as well upon the ability of the organism to metabolize carbohydrates. 1 Fat does not act as a stimulant to sugar production as does protein but is a source of sugar, although it is only used by the liver in making glycogen when other supplies fail. In severe diabetes, however, the body fat is used in large amount so result- ing in emaciation. 2 In severe diabetics with no carbohydrate tolerance the buty- ric acid molecule formed in intermediary metabolism of the fatty acids becomes incompletely oxidized only to /3-oxy- butyric, aceto-acetic acids, and acetone which last is derived from the two former acids. Ringer believes that "one of the func- tions of the glucose molecule in normal metabolism is to make /3-oxybutyric acid, which arises constantly in the catabolism of the higher fatty acids, combustible," and he concludes that if we could find fats with an uneven number of carbon atoms they would be oxidized into glucose instead of acetone bodies. In these conditions of perverted fat metabolism and ketonuria, although we speak of acidosis, by this is meant the accumula- tion of acid bodies in the blood and tissues sufficient to neu- tralize enough of the sodium bicarbonate there present to reduce the alkaline reserve to a level below normal; it does not mean that blood and tissues become actually acid in reaction. 3 Although ketonuria is more apt to be extreme when there is no carbohydrate tolerance, it is a fact that considerable 1 Ringer: Tr. Assn. Am. Phys., 1913, xxviii, 469. 2 Von Noorden: Am. Jour. Med. Sc., 1913, cxlv, 1. 3 Stillman: Med. Rec., 1916, lxxxix, 390. 422 DISTURBANCES OF NORMAL METABOLISM amounts of acid bodies may be excreted when the carbohy- drate tolerance is 20 to 30 gm. In long fasting, man shows a fall in his respiratory quotient while the diabetic shows some tendency to a rise. Such observation leads to the belief that the diabetic even in the severest cases burns some sugar or some other body substance to compensate for it. Joslin 1 says there is much experimental evidence that the other body sub- stances are the acids. /3-oxybutyric acid has a high caloric value and yields a high respiratory quotient. Hyperglycemia. — Before proceeding to the discussion of diets in diabetes a word about hyperglycemia is in place, the various causes of which as given by Dock 2 are as follows : 1. Excessive ingestion of sugar. 2. Reduction of liver function. 3. Exaggeration of the glycolytic function of the liver. 4. Reduction of the glycolytic function of the muscles. 5. Exaggeration of the glycolytic function of the muscles. 6. Reduction of formation of fat from glucose. 7. Reduction of combustion of glucose in the muscles. Since in diabetes mellitus one or more of these functions may be disturbed we see what a various etiology of hyper- glycemia there may be, and it is a much more accurate index of perverted carbohydrate metabolism than is glycosuria. Dietetic Treatment of Diabetes. — The dietetic treatment of diabetes mellitus resolves itself into the questions as to how much carbohydrate the individual can utilize and how a tolerance for carbohydrate can be obtained or increased. If, as Allen says, we compare the glycosuria to a gastro- intestinal indigestion, due to either a functional or organic dis- turbance, we see at once that what is needed is rest for the deranged function, followed by a gradual system of dietetic reeducation, principally so far as the carbohydrates are con- cerned, until step by step the body can take care of slowly increased amounts of this food element. The avoidance of overstrain of the glycogenic function must be kept ever in mind, for if during the process of reeduca- tion sufficient food is given to again precipitate the glycosuria this puts off the further advance disproportionately and if it is continued, quickly results in the loss of the bettered function obtained by previous careful dieting. In other words "over- strain weakens while rest strengthens any damaged function." 3 In considering the details of dietetic management we have two principal methods of treatment, one the European, best 1 New York Med. Jour., 1915, ci, 628. 2 Int. Cong. Med., 6 Med., p. 234. 3 Foster: Diabetes Mellitus, p. 183. DIABETES MELLITUS 423 exemplified perhaps by the von Noorden routine, and the other an American method, known as Allen's fasting cure for diabetes. While there are of course numerous modifications of these methods and to a certain extent they are modifications of each other, the von Noorden cure puts the emphasis on first finding the carbohydrate tolerance, if any, by beginning with increasing or diminishing amounts of carbohydrate with a certain amount of modified starvation in severe cases, for a day or two. Allen's method lays stress on the fasting phase of the treatment, the reduction of weight of the patient and keeping the total caloric value of the food low when feedings are begun. The fats are kept particularly low, for if given in any considerable quantities the carbohydrate tolerance is reduced. The fast is persisted in until the urine becomes sugar-free and the ketone bodies usually drop, but do not as a rule disappear until the patients are fed after their fast. When the patient is sugar-free, carbohydrate is allowed in small amount and gradually increased to tolerance, quite as much emphasis being also put on the protein and fat tolerance in their relation to hyperglycemia. Von Noorden Method. — For a differentiation of the treatment we may arbitrarily divide diabetics into three classes of cases. 1. Those in whom the sugar excretion is less than 50 gm. without ketonuria. 2. Those in whom the sugar excretion is more than 50 gm. also without ketonuria. 3. Those in whom the sugar excretion is more than 50 gm. with ketonuria. 1 The first step is the determination of the individual's carbo- hydrate tolerance if such be present. In the very mild cases associated with overeating of sweets and starches it is usually only necessary to order a rational diet curtailing these food elements to promptly and permanently render these people sugar-free. On the other hand any glycosuria even a so-called alimentary form due to excessive ingestion of sugar-forming foods must be viewed as a real diabetes, although mild, and with potency for developing into a severe grade if neglected. (Even these mild cases should be taught to examine their own urine with Benedict's solution once in so often in order to be sure that the sugar does not recur.) In all but these very mildest cases it is necessary as the first step, to determine the individual's carbohydrate tolerance. This is done by gradually reducing the patient's carbohydrate allowance until after about five days they are put on a stand- 1 Foster: Diabetes Mellitus, p. 188. 424 DISTURBANCES OF NORMAL METABOLISM ard strict diet containing only 15 gm. of carbohydrate in the green vegetables allowed. To this is added a definite carbo- hydrate allowance in the form of white bread (55 per cent, carbohydrate), Huntly and Palmer biscuits, 5 gm. Uneeda biscuit, 4.6 gm. carbohydrate each. A convenient method is to allow with the Standard Strict Diet 25 gm. carbohydrate in any one of these three forms, at each meal, testing the urine of the second twenty-four hours. If it still contains sugar, reduce the carbohydrate allowance one-half and so by a process of reduction or addition, in case the tolerance is over the 75 gm. carbohydrate, the point at which sugar just fails to show in the urine is reached. The amount of carbohydrate that will accomplish this constitutes the carbohydrate tolerance. When this is determined the patient is put on a diet which contains not over one-half the tolerance. The reason for this being that while the urine may become sugar-free on the full tolerance, the hyperglycemia does not disappear so easily and ordinarily needs a greater reduction in the carbohydrate to reduce this to normal. After the patient has been on this tolerance for some weeks it is safe to gradually increase the amount of carbohydrate and deter- mine its utilization by frequent urinary tests. In this way over a period of months by resting the disturbed function it is usually possible to materially increase the amount of carbo- hydrate beyond the original tolerance and gradually bring the patient up to an improvement which allows of a fair diet. In order to vary the diet as much as possible it is necessary to know the actual carbohydrate content of the different food- stuffs and to construct a diet that shall not be monotonous. The use of the table of carbohydrate equivalents will materi- ally aid in doing this. One prerequisite of success is the actual weighing of the foods, in the mild cases only of the carbohy- drate foods, in the more severe the protein and fats must also be weighed. Standard Strict Diet: Breakfast: Eggs, two; ham, 90 gm. (3 oz.); coffee (without sugar); butter, 15 gm. (| oz.), this used on bread or biscuit; if no carbohydrate is allowed, cooked in with the eggs; cream, 45 c.c. (i| oz.). Luncheon: Meat (chops or steak), 120 gm. (4 oz.); green vegetables allowed from list, 2 tablespoonfuls; wine, white or red (2 claret glasses), 6 ounces, or brandy or whisky (2 tablespoonfuls) 1 ounce; butter, 15 gm. (J oz.), cooked with the vegetables or on bread if allowed. Afternoon tea with 15 gm. (J oz.) cream (no sugar). DIABETES MELLITUS 425 Dinner: Clear soup; fish, 90 gm. (3 oz.); meat (fowl, beef or mutton), 120 gm. (4 oz.); green vegetables, 2 table- spoonfuls (see list); salad, with 15 gm. (J oz.) of oil with dressing; cream cheese, 30 gm. (1 oz.); red or white wine or whisky as at luncheon; coffee, small cup; butter, 30 gm. (1 oz.) on the fish, meat or green vege- tables in case no bread is allowed. Bedtime: A cup of bouillon with a raw egg. This represents: Protein, 112 gm. (3! oz.); nitrogen, 18 gm. (270 grains); fat, 160 gm. (5 J oz.); calories, 2200. Standard Diet with Restricted Protein: Breakfast: Eggs, two; bacon, 15 gm. (J oz.); coffee, with cream, 45 gm. (ij oz.); butter, 20 gm. (f oz.). Luncheon: Egg, one; bacon, 15 gm. (J oz.); meat (ham, steak or chops), 60 .gm. (2 oz.); salad, with 15 gm. (J oz.), oil for dressing; wine, white or red, 2 claret glasses, 180 c.c. (6 oz.), or whisky or brandy, 2 table- spoonfuls, 30 c.c. (1 oz.); butter, 40 gm. (if oz.). Afternoon tea with 15 gm. (i oz.) cream. Dinner: Clear soup; meat (mutton, beef, turkey or chops), 90 gm. (3 oz.); vegetables from list, 2 tablespoonfuls; salad, with 15 gm. (J oz.) oil; cream cheese, 30 gm. (1 oz.); wine, red or white, 2 claret glasses, 180 c.c. (6 oz.) or whisky or brandy as at luncheon; coffee; butter, 30 gm. (1 oz.). Bedtime: Bouillon with one egg. This represents: Protein, 70 gm. (2 oz.); nitrogen, 10 gm. (150 grains); fat, 180 gm. (6 oz.); calories, 2500. Green Days: Breakfast: Egg, one; cup of coffee, without cream or sugar. Dinner: Spinach with one egg, hard-boiled; bacon, 15 gm. (J oz.); salad, with 15 gm. (i oz.) oil; wine, red or white, 250 c.c. (8 oz.) or whisky or brandy, 30 c.c. (1 oz.). 4.30 p.m. Cup of broth or beef tea. Supper: Egg, one, best scrambled with a little tomato or butter; bacon, 15 gm. (i oz.); cabbage, sauerkraut, string beans, cauliflower or asparagus; wine, red or white, whisky or brandy as at dinner. Give 15 to 30 gm. (i to 1 oz.) of bicarbonate of soda in the twenty-four hours. This diet represents the following values: Protein, 32 gm. (1 oz.); nitrogen, 5 gm. (75 grains); carbohy- drate, 5 gm. (J oz.); fat, 65 gm. (2 oz.); calories, 575. In any of these diets if there are reasons for not using bacon, beef 30 gm. (1 oz.) may be substituted for it. 426 DISTURBANCES OF NORMAL METABOLISM Oatmeal Days : Porridge made from oatmeal, 250 gm. (8 oz.); butter, 250 gm. (8 oz.), salt and pepper. The oatmeal should be boiled all night in a double boiler with the butter and whites of six eggs added next morning. "This constitutes the food for one day and may be eaten as gruel, mush or fried mush, divided into seven equal parts, one part to be taken every two hours." Two cups of black coffee and 180 c.c. (6 oz.) of red or sour white wine or 30 c.c. (1 oz.) of whisky or brandy may be taken during the day. This represents: Protein, 63 gm. (2 oz.); nitrogen, 16.8 gm. (i oz.); carbohydrate, 170 gm. (5! oz.); fat, 212 gm. (7 oz.); calories, 3300. General Diabetic Diet List : May take — Soups: Meat soups and broths. Egg, cheese or allowed vegetables may be added. Meats: All kinds of fresh, smoked and cured meats (except liver), poultry. Pate de fois gras, no sauces that contain flour. Fish: Every kind (except shell fish), dried, fresh, smoked or pickled. Egg: Cooked in any style but without flour. Fats: Lard, butter, oils, suet. Cheese: Swiss, English, cream, pineapple cheese. Vegetables: Cabbage, cauliflower, celery, chicory, cress, asparagus, beet tops, sprouts, cucumber, eggplant, endive, lettuce, Kohlrabi, okra, pumpkin, radish, rhubarb, sauerkraut, spinach, tomatoes, string beans, vegetable marrow. Salads and Pickles: Made of above vegetables, unsweetened. Mushrooms and truffles. Cream: If allowed in tolerance, 90 c.c. (3 oz.) per day. Condiments: Pepper, salt, curry, cinnamon, mustard, nut- meg, caraway, capers, vinegar. Desserts: Custards, ice-cream, made with eggs and cream. Lemon water-ice, jellies made with gelatin. No sugar to be used but saccharine only for sweetening and flavored with brandy, coffee, vanilla or lemon. Beverages: Tea, coffee sweetened with saccharin. Whisky or distilled liquor, 150 c.c. (5 oz.). Red or white wine (sour) up to 500 c.c. (1 pint) per day. Foods Prohibited Except as Allowed in Accessory Diet: Sugars or sweetening other than saccharin, saxin, garantose, dulcin. Puddings, preserves, cake, pastry or ice-cream. Bread, biscuit, crackers, toast, etc. Cereals of all kinds, macaroni, potatoes or other underground vegetables, as carrots, parsnips, beets, turnips, also beans, peas and corn. DIABETES MELLITUS 427 Fruit, fresh or dried. No flour allowed in soups or gravies. Ale, beer, porter, sweet wines, sparkling wines, cider, milk, chocolate, cocoa, sweet drinks, liquor. 1 Table of Carbohydrate Equivalents. Carbohydrate equivalents. Grams 4 8 16 25 32 40 Drams 1 2 4 6 8 10 Grams. Potato 22 44 88 132 176 220 Hominy (cooked) .... 25 50 100 150 200 250 Oatmeal (cooked) .... 40 80 160 240 320 400 Rice (cooked) 15 30 60 90 120 150 Farina (cooked) 25 50 100 150 200 250 Shredded wheat 5 10 20 30 40 50 Indian-meal mush .... 27 54 108 162 216 270 Macaroni 30 60 120 180 240 300 Corn bread 10 20 40 60 80 100 Barker's gluten food, A . . 102 204 408 612 816 1020 Barker's gluten food, B . 74 148 296 444 592 740 Barker's gluten food, C . . 54 108 216 224 432 540 Almond meal 65 130 260 390 520 650 Gum gluten (ground) ... 12 24 48 72 96 120 Soja-bean meal 50 100 200 300 400 500 Casoid flour ...... 55 no 220 330 440 550 Pure gluten biscuit . . . . 50 100 200 300 400 500 ProtopufI No. 1 45 90 180 270 360 450 ProtopufI No. 2 12 24 48 72 96 120 Salvia sticks 25 50 100 150 200 250 Milk (whole) 112 224 448 672 896 1120 Cream 112 224 448 672 896 1120 Grapefruit weighed with skin . 187 375 750 1125 1150 1875 Rice pudding 14 28 56 84 112 140 Tapioca pudding .... 15 30 60 90 120 150 Beets (cooked) 65 130 260 390 520 650 Custard (baked) .... 30 60 120 180 240 300 Carrots 65 130 260 390 520 650 Corn (canned or green) 22 44 88 132 176 220 Egg plant 90 1 80 360 540 720 900 Parsnips 35 70 140 210 280 350 Green peas 30 60 120 180 240 300 Turnips 56 112 224 336 448 560 Baked beans 22 44 88 132 176 220 Apples 45 90 180 270 360 450 Bananas 20 40 80 120 160 200 Oranges 40 80 160 240 320 400 Peaches 50 100 200 300 400 500 Pears 50 100 200 300 400 500 Prunes 24 48 96 144 192 240 Watermelon 225 450 900 Method of using the table of carbohydrate equivalents: Take for example a case with a carbohydrate allowance of 32 gm. (1 oz.). These diets are adapted from Janeway, in Musser and Kelly's Therapeutics. 428 DISTURBANCES OF NORMAL METABOLISM Proto puff No. i 45 Potato 22 Oatmeal 40 Beets 33 Orange 40 Rice pudding 56 236 jm. = 4 gm " = 4 " " = 4 « " = 2 " carbohydrate it a a " = 2 " " = 16 " 32 Foster's System of Carbohydrate Units. — For the milder grades of the disease Foster has devised a system of carbo- hydrate units, each unit representing 10 gm. of carbohydrate. Of course these quantities are not absolutely accurate but are approximately so and when the tolerance has been determined the allowance of carbohydrate can be conveniently taken from this table without weighing, the patients soon learning to* remember the units. 1 Soups: Bean Average portion equals 1 unit Clam chowder Cream of corn Pea puree Potato Vegetables: Beans, baked ....... 2 tablespoonfuls Beans, butter 2 Beans, lima 2 Beans, kidney 2 Beets 2 Corn, canned 2 Corn, green 1 ear Onions 2 onions Green peas 2 tablespoonfuls Potato, baked 1 medium sized Potato, boiled 1 Potato, mashed 2 tablespoonfuls Fruits: Apple .......... 1 medium sized Blackberries 2 tablespoonfuls Cantaloupe One-half Currants 3 tablespoonfuls Huckleberries 2 Orange . 1 medium sized Peach 1 Pear 1 " Plum .2 Raspberries 3 tablespoonfuls Strawberries 4 Cereals : Bread Slice 3x4x5 inch Hominy, boiled H. O. (oatmeal), boiled Macaroni, boiled Macaroni, baked with cheese Oatmeal, boiled .... Rice, boiled Shredded wheat biscuit Spaghetti, baked with tomato tablespoonful 2 2 2 2 " 1 1 biscuit 2 tablespoonfuls 2 units 1 unit 2 units 2 " 1 unit 2 units 2 " 1 unit 1 " 2 units 3 " 2 " 2 " 1 unit 2 units 1 unit 1 unit 2 units 1 unit 2 units 1 unit 1 unit 1 unit 2 units 1 unit 1 unit 2 units 2 " 1 unit 2 units 2 " 2 " Foster: Diabetes Mellitus, p. 201. DIABETES MELLITUS 429 Sample Diet (six units allowed, i. e., 60 gm. starch): Breakfast: Bacon and eggs; cereal (equal to 1 unit), with tablespoonful of cream. Lunch: Clear soup; meat and green vegetable; bread, \ slice (1 unit); mashed potato (2 units) Dinner: Soup; meat and green vegetable; baked beans (2 units); salad and cheese. Foster suggests that this table of units should not be used when the glycosuria is over 70 gm. Procedure in the Medium Severe Cases (over 50 gm. glucose in urine). — If the case has no carbohydrate tolerance and does not become sugar-free on the Standard Strict Diet without added carbohydrate, the next step is to put the case on the Standard Strict Diet with restricted protein. If after two or three days the glycosuria does not clear up, put on two green days, then back on Standard Strict Diet with restricted protein for a few days. If this results in freeing the urine of glucose then the regular Standard Strict Diet may be used and if the .urine still remains sugar-free it may be possible to add carbo- hydrate, preferably in the form of green vegetables as recom- mended by Joslin, using weighed amounts of vegetables con- taining 5, 10, 15 or 20 per cent, of carbohydrate (p. 435). These are ordinarily better borne than any form of bread or biscuit, although bread may be tried tentatively in definite, small amounts. Often this routine will result in freeing the urine of sugar and with care a certain amount of carbohy- drate tolerance may be developed but in any case the total amount of carbohydrate allowed should be kept distinctly below the point of tolerance for the reasons already explained. In these cases the use of the table of Carbohydrate Equiva- lents or Foster's carbohydrate units will be found useful. Severe Cases with Marked Ketonuria. — The best plan is to put the patients at once on the oatmeal diet for several days, two to ten, without regard to the sugar in the urine, at the same time giving considerable amounts of bicarbonate of soda, enough to render the urine alkaline, which should be attained if possible. If the acidosis diminishes but the sugar content of the urine remains high, patients are often benefited by two green days and from this to the Standard Strict Diet with restricted protein, then the full Standard Strict Diet, if the acidosis remains in control. Von Noorden recommends what he calls a "set of days" consisting of two days restricted protein diet, two days of green diet and three days of oatmeal diet. We then return to the restricted protein diet or even full protein, but if sugar again appears the "set" is repeated. Often the patients 430 DISTURBANCES OF NORMAL METABOLISM become sugar-free and acid-free on this plan when a little carbohydrate can again be tried, preferably in vegetable form. When the acetonuria is extreme or coma threatens, von Noorden found "alcohol days" of great benefit and recom- mends giving 90 to 150 c.c. (3 to 5 oz.) of whisky daily well diluted and no food. This often diminishes the ketonuria and the general condition is much improved. The alcohol diet is limited to one or two days and then the oatmeal days, etc., are again tried as before. This is practically a fasting cure and in some form has been found by many observers to be of great service under these conditions. Instead of using oatmeal some clinicians prefer to use potato days or bread-and-butter days, or as Falta recommends, a rotation of the different starchy foods taking one at a time. Potato Diet: 1 Breakfast: One baked potato with butter; one cup of coffee, cream, 25 c.c. (1 oz.). Luncheon and Dinner: Potato boiled, butter; green vege- table; whisky or wine. Bread-and-butter Diet : 2 Breakfast: Two pieces of bread or toast, buttered; yolks of two eggs, cooked. Luncheon and Dinner: Two slices of bread and butter; green vegetable, with oil or egg sauce; a rasher of bacon; wine, whisky or coffee. Allen's Treatment of Diabetes Mellitus. — This treatment, based on results of extensive animal experimentation, has only been used for human diabetes during the past two or three years and although apparently very successful it has not as yet stood the test of time nor has it been used long enough to judge of the late results years after treatment was begun. As already stated in this form of treatment emphasis is placed upon an initial fast period sufficient to clear up the glycosuria and acidosis, if that is present, and it has been found practically without exception that fasting from two to ten or twelve days at the outside will accomplish these ends. As Allen says in speaking of this treatment in dogs: "It was found that the grave condition of diabetes yielded to an initial fast of days or weeks with a subsequent diet which kept the animals at a low level of weight and metabolic activity. Anything that tended to increase the weight or metabolism brought back the glycosuria and acidosis. If the animal was allowed to go down by glycosuria with emaciation, weakness 1 Foster Diabetes Mellitus, p. 186 2 Loc. cit. DIABETES MELLITUS 431 and death, it was found that degenerative changes took place in the islands of Langerhans and if this decline was prevented the islands remained intact." The two cardinal points in Allen's treatment are: 1. An initial fast to the point of clearing up the glycosuria accompanied by a reduction in weight which should be permanent. 2. The subsequent diet which does not allow of a return of the glycosuria but if by chance there is a return an immediate fast day or two is given to clear it up again. Before speaking in detail of the method, it is necessary to emphasize one point upon which Allen lays great stress and which is entirely contrary to the older teachings, namely, that a loss of weight is of distinct advantage, as it tends to increase carbohydrate tolerance and makes the patients feel much better, which suggests the possibility that the weakness and many of the other symptoms are due to an intoxication and more than likely from the unexcreted end-products of protein metabolism. If these patients are made to gain by adding fats to the diet or trying to give larger amounts of food, as is the custom with the older forms of treatment, at once glyco- suria and the acidosis returns. This loss of weight is of course of greatest benefit in those cases who are rather overweight to begin with, but even the moderately well-nourished or spare individuals bear the fast advantageously with the consequent loss of weight, although surprisingly enough the diabetic does not seem to lose weight as rapidly as in starvation of the nor- mal man, due to the fact that a certain amount of energy is derived from the burning of the ketone bodies. In a few cases the starvation causes alarming symptoms of nausea and vomiting which disappear on feeding and when a second fast is instituted, after a few days or a week or two, these patients stand it perfectly well and become sugar-free. The old theory that a dangerous acidosis is engendered by a prolonged fast has absolutely to be given up as untrue. During the fasting period, the patients being kept in bed, are allowed the following diet: Whisky, black coffee, bouillon, water, tea. Thrice-cooked green vegetables (whereby all starch is removed) may be given, but are not a necessary part of the diet in the period of starva- tion. They merely give a sense of fulness to the patient. The whisky given in amounts of 50 to 120 c.c. per day (if to 4 oz.) is not an essential part of this period but may be used and if so furnishes 7 calories per c.c. It has no influence on sugar formation and aside from this the other articles allowed have practically no food value. (Whisky is said not 432 DISTURBANCES OF NORMAL METABOLISM to have any influence on acetone formation in normal indi- viduals.) 1 Twenty-four to forty-eight hours after the urine becomes free of glucose, cautious feeding is begun, individualizing the diet as much as possible, but it is absolutely essential that the patient remain sugar- and acid-free. In the feeding, one usually begins by using carbohydrates most easily by pre- scribing ioo to 200 gm. (3 \ to 6§ oz.) of green vegetables (cooked once) of the 5 and 6 per cent, classes according to Joslin's classification. This is increased in amount daily until possibly a trace of glucose appears which is at once cleared up by a fast day. This marks the patient's carbohydrate tolerance. Next the protein tolerance is determined in the same way by giving the whites of one or two eggs, then meat is added until either glycosuria appears or the patients reach a fair, physiological protein allowance, or one tests the protein tolerance first, then the carbohydrate; in either case in finding the tolerance, only one food element is used at a time, protein or carbohydrate. If for example in a given case we were to have a protein toler- ance of 60 gm. (2 oz.) protein and 20 gm. (f oz.) carbohydrate, such a patient would be put on a diet with probably 50 gm. protein and 10 gm. carbohydrate which is gradually increased. In other words, just as we saw in the von Noorden regimen the patients do best when they are allowed only about one- half their carbohydrate tolerance at first, which can be gradu- ally increased. In the mild cases Geyelin recommends beginning with what he calls a 15 130:30 formula, i. e., 15 gm. (^oz.) carbohydrate, and 30 gm. (1 oz.) fat, and 30 gm. (1 oz.) protein, increasing these one at a time until either the tolerance is reached or the patient is on a fair protein and fat allowance. In those cases accompanied by old age, obesity or nephritis, it is better to omit the initial fast at first and put them directly on a 15 130 130 food formula, as food fasting sometimes causes these patients to pass rapidly into coma. If this brings about a sugar-free urine, that is favorable, if not, then it may be advisable to try a fast, watching the ketonuria carefully. Allen says that "fat is less urgently needed except in very weak and emaciated patients and can be added gradually." 2 In the severe cases it is necessary to test in this way the toler- ance for all classes of foods, carbohydrate, protein and fats one at a time. Carbohydrate is given if possible, but is kept safely below the limit of tolerance. Protein must be kept 1 Jour. Am. Med. Assn., September 9, 1916, p. 84. 2 The Treatment of Diabetes, Boston Med. and Surg. Jour., February 18, 191 5. DIABETES MELLITUS 433 fairly low, sometimes very low. With a dangerously low pro- tein tolerance the working rule has been to exclude all carbo- hydrate, then feed as much protein as possible without glyco- suria. Experience seems to indicate that every patient can tolerate his necessary minimum of protein and that glyco- suria appears only when this is exceeded. The severe diabetic is often thin and weak because he cannot metabolize enough food to be strong and well, but as long as his weakened func- tion is not overtaxed he seems to be able to retain such weight and strength as he has, at least for a considerable period. Any attempt to build him up with any kind or quantity of food beyond thac which he is able to metabolize perfectly, apparently hastens a fatal result. 1 The mild or moderately severe cases are usually cleared of their glucose and acetone with a fast of one or two days, the subsequent period of observation being devoted to an educa- tion of the patient in food values (after determining the carbo- hydrate tolerance), for these cases can usually take a full allowance of protein and fat. With the really severe cases, of course, the initial fast is usually necessarily of longer duration and with no carbohydrate tolerance the feeding of the proper amount of protein becomes a nice problem. With persever- ance, almost all the cases can be taken along to a point where they can take their minimum of protein, some fat and later probably a little carbohydrate which if the progress be fortunate, may be gingerly increased. There is still a small class of cases that resist every effort at reaching a maintenance diet and who must inevitably per- ish of their disease, fortunately these are few and the favor- able reports of Allen's treatment makes it seem probable that they may be still further reduced in numbers. The best results in this treatment are naturally obtained in hospitals or sanatoria where everything is readily con- trolled, butGeyelinhas had marked success with this treatment in ambulatory cases at the Vanderbilt Clinic, New York City. The patients are taught when leaving the hospital how regu- larly to examine their own urine with Benedict's solution and to take one fast day every seven, ten or fourteen days, accord- ing to the severity of the case when under treatment. Allen recommends exercise in the cases which reach a fair tolerance, not only light but very active and vigorous exer- cises, as tending to keep the patients in better physical condi- tion and actually increasing carbohydrate tolerance. One fact needs repetition, when after a fast of eight to ten days the 1 Loc. cit. 28 434 DISTURBANCES OF NORMAL METABOLISM T3 3 oS Ph >> a . . 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