Class _A k33^ Book _ »Y^ -i^ Copight N" COPYRIGHT DEPOSIT. o o < X u O H > g < U ID Q W O w o w hj hJ o u THE LIBRARY OF HOME ECONOMICS A COMPLETE HOME-STUDY COURSE ON THE NEW PROFESSION OF HOME-MAKING AND ART OF RIGHT LIVING; THE PRACTICAL APPLICATION OF THE MOST RECENT ADVANCES IN THE ARTS AND SCIENCES TO HOME AND HEALTH PREPARED BY TEACHERS OF RECOGNIZED AUTHORITY FOR HOME-MAKERS, MOTHERS, TEACHERS, PHYSICIANS, NURSES, DIETITIANS, PROFESSIONAL HOUSE MANAGERS, AND ALL INTERESTED IN HOME, HEALTH, ECONOMY AND CHILDREN TWELVE VOLUMES NEARLY THREE THOUSAND PAGES, ONE THOUSAND ILLUSTRATIONS TESTED BY USE IN CORRESPONDENCE INSTRUCTION REVISED AND SUPPLEMENTED CHICAGO AMERICAN SCHOOL OF HOME ECONOMICS 1907 LIBRARY of CONQRfSS OfteOw* Received A Oui/yrirm Entry OWN A lUtOiNii. W »ii« ■■ ii T ' ■ II ■ ^ Copyright, 1907 BY Home Economics Association Entered at Stationers' Hall, London A// Rights Reserved, AUTHORS ISABEL BEVIER, Ph. M. Professor of Household Science, University of Illinois. Author U. S. Government Bulletins, "Development of the Home Economics Movement in America," etc. ALICE PELOUBET NORTON, M. A. Assistant Professor of Home Economics, School of Education, Uni- versity of Chicago ; Director of the Chautauqua School of Domestic Science. S. MARIA ELLIOTT Instructor in Home Economics, Simmons College; Formerly Instruc- tor School of Housekeeping, Boston. ANNA BARROWS Director Chautauqua School of Cookery; Lecturer Teachers' College, Columbia University, and Simmons College ; formerly Editor "Ameri- can Kitchen Magazine;" Author " Home Science Cook Book." ALFRED CLEVELAND COTTON, A. M., M. D. Professor Diseases of Children, Rush Medical College, University of Chicago ; Visiting Physician Presbyterian Hospital, Chicago; Author of " Diseases of Children." BERTHA M. TERRILL, A. B. Professor in Home Economics in Hartford School of Pedagogy; Author of U. S. Government Bulletins. KATE HEINTZ WATSON Formerly Instructor in Domestic Economy, Lewis Institute; Lecturer University of Chicago. MARION FOSTER WASHBURNE Editor "The Mothers' Magazine; " Lecturer Chicago Froebel Asso- ciation ; Author " Everyday Essays," " Family Secrets," etc. MARGARET E. DODD Graduate Massachusetts Institute of Technology ; Teacher of Science, Woodward Institute. AMY ELIZABETH POPE With the Panama Canal Commission ; Formerly Instructor in Practical and Theoretical Nursing, Training School for Nurses, Presbyterian Hospital, New York City. MAURICE LE BOSQUET, S. B. Director American School of Home Economics ; Member American Public Health .Association and American Chemical Society. CONTRIBUTORS AND EDITORS ELLEN H. RICHARDS Author " Cost of Food," " Cost of Living," " Cost of Shelter," " Food Materials and Their Adulteration," etc., etc.; Chairman Lake Placid Conference on Home Economics. MARY HINMAN ABEL Author of U. S. Government Bulletins, "Practical Sanitary and Econ- omic Cooking," "Safe Food," etc. THOMAS D. WOOD, M. D. Professor of Physical Education, Columbia University. H. M. LUFKIN, M. D. Professor of Physical Diagnosis and Clinical Medicine, University of Minnesota. OTTO FOLIN, Ph. D. Special Investigator, McLean Hospital, Waverly, Mass. T. MITCHELL PRUDDEN, M. D., LL. D. Author "Dust and Its Dangers " "The Story of the Bacteria," "Drink- ing Water and Ice Supplies," etc. FRANK CHOUTEAU BROWN Architect, Boston, Mass.; Author of "The Five Orders of Architec- ture," " Letters and Lettering." MRS. MELVIL DEWEY Secretary Lake Placid Conference on Home Economics. HELEN LOUISiE JOHNSON Professor of Home Economics, James Millikan University, Decatur. FRANK W. ALLIN, M. D. Instructor Rush Medical College, University of Chicago. MANAGING EDITOR MAURICE LE BOSQUET, S. B. Director American School of Home Economics. BOARD OF TRUSTEES OF THE AMERICAN SCHOOL OF HOME ECONOMICS MRS. ARTHUR COURTENAY NEVILLE President of the Board. MISS MARIA PARLOA Founder of the first Cooking School in Boston; Author of "Home Economics," " Young Housekeeper," U. S. Government Bulletins, etc. MRS. MARY HINMAN ABEL Co-worker in the "New England Kitchen," and the "Rumford Food Laboratory;" Author of U. S. Government Bulletins, " Practical Sanitary and Economic Cooking," etc. MISS ALICE RAVENHILL Special Commissioner sent by the British Government to report on the Schools of Home Economics in the United States; Fellow of the Royal Sanitary Institute, London. MRS. ELLEN M. HENROTIN Honorary President General Federation of Woman's Clubs. MRS. FREDERIC W. SCHOFF President National Congress of Mothers. MRS. LINDA HULL EARNED Past President National Household Economics Association ; Author of " Hostess of To-day." MRS. WALTER McNAB MILLER Chairman of the Pure Food Committee of the General Federation of Womans Clubs. MRS. J. A. KIMBERLY Vice President of National Household Economics Association. MRS. JOHN HOODLESS Government Superintendent of Domestic Science for the province of Ontario ; Founder Ontario Normal School of Domestic Science, now the MacDonald Institute. Food AND Dietetics BY ALICE PELOUBET NORTON, M. A. ASSISTANT PROFESSOR OF'hoME ECONOMICS SCHOOL OF EDUCATION, UNIVERSITY OF CHICAGO DIRECTOR OF THE CHAUTAUQUA SCHOOL OF DOMESTIC SCIENCE CHICAGO AMERICAN SCHOOL OF HOME ECONOMICS 1907 1 A" 35S . Ml COPYRIGHT, 1905, BY AMERICAN SCHOOL OF HOUSEHOLD ECONOMICS COPYRIGHT, 1907, BY HOME ECONOMICS ASSOCIATION CONTENTS Letter to Students The Food Problem Cost of Food .... Food and the Body Food Principles .... Carbohydrates .... Fats ...... Dietary Standards Special Food Stuffs Meat ...... Fish ...... Eggs ... Milk ...... Milk Products .... Cereals and their Products Bread ..... Sugar as Food .... Vegetables .... Fruits . . . . . Nuts . ' . . . Tea, Coffee, and Cocoa Adulteration of Food Special Diet .... Bibliography .... Notes on the Questions . . Protein Metabolism in its Relation to Dietary Standards — Otto Folin, Ph.D. Program for Supplemental Study Index ..... V 3 7 30 41 44 48 SO 63 66 72 77 80 92 98 106 113 119 130 136 138 158 181 191 196 217 223 AMERICAN SCHOOL OF HOME ECONOMICS CHICAGO January 1, 1907. Dear M&dar.: In the study of the lessons on Pood and Dietetics, full use should be made of the mapy interesting and valuable publications of the United States Department of Agriculture These are divided into the popular bulletins and pamphlets sent free to all in the United States and the more technical bulletins for which a nominal price is charged. . ^J^e f'J'ee publications are included chief- ly in the series of Farmers' Bulletins and in EXoracts from Year Books, etc. The "for sale" bulletins are issued by the various divisions of the Department of Agriculture, those on food «nf fi^ n^ ?'^ ^**^i^S.°^ Experiment Stations and the Division of Chemistry. V 1-^ Any or all of the free publications nav be obtained simply by addressing the Department sLe«''iSlili^^' Washington, D. g. For ?he "ISr sale bulletins com or money order must be senf D C ' l^'^rr'"'^?'^^^ °^ Doci;ments^ WaIhin|ton? D. C. Postage stamps are not accepted. lication^^J^i^^^^^ ?^ **^®® ^'^^ "^o^ sale" pub- Lnf of%ricul^urr"V?«rf "^' ^^ ^^^ "^'^^^'^ tK« ™ii.itS.r- ^^®*- * fairly complete list of raphv burni-"^?? r?°^ *' given in the blblfog- published ?h„?^ ^^^w"^ ^""^ constantly being ^ are civen'ln ?hi'' ""?u?'■^• *"1«^ «"\it-ipea soup and crackers (crisped) , potted beef, brown eauce, baked potatoes, bread, rice with milk and sugar. AS'u^^^'e/*.— Brown-bread sandwiches (with a little butter) , white-bread sandwiches with date and peanut filling without butter, cocoa, popcorn salted. MONDAY, FEBRUARY 10. 5r^o*/asi.— Oatmeal with top of milk, cream toast, cereal coffee. Dmner.— Baked-bean soup, crisp crackers, Hamburg steak balls, brown sauce, hominy, turnip, peanuts and dates. Supper.— Fota,to and beet salad, gingerbread, cheese, bread, milk. TUESDAY, FEBRUARY 11. Breakfast.— Whesit breakfast food and dates, creamed codfish muffins (with little butter) , milk and cereal coffee. Dinner.— Beef Stew with biscuits, bread pudding, bread. /S^u^'i'^^-— Scalloped meat and potato, bread (with butter), prunes chocolate candy "fudge." COST OF FOOD 25 WEDNESDAY, FEBBTJABY 12. Breakfast.— 0-d,tinea,l with top of milk, hash, corn calce, milk and cereal coffee. i>i/i«.er.— Vegetable soup, croutons, baked stuffed beef's heart, brown sauce, rice, cornstarch blanc mange, caramel sauce. 5i/;;;je/-.— Potato and celery salad, white and graham bread, fried corn- meal mush, sirup, THUESDAY, FEBBUABY 13. Breakfast.— Corn-iaea,! mush with top of milk, hashed meat on toast, milk and cereal coffee. Binner.-Salt salmon, drawn butter sauce, baked potatoes, parsnips, bread, evaporated apple shortcake. Supper.— Cold sliced beef's heart, creamed potatoes, cocoa, bread (white and graham) , ginger snaps. "The family in this experiment consisted of 30 stu- ^j^^ dents — 26 women and 4 men — ranging in age from 25 Family to 45 years. Considering the 4 men as equivalent to 5 women as regards food consumption, the family for six days was equivalent to 186 women for one day. "The cost of the diet, 9.4 cents per woman per day, cost of was just within the limit set, but the quantities of nu- trients and energy (75 grams of protein and 2,243 calories) were somewhat smaller than was intended. "The low cost of the diet in this experiment was made possible by the selection of simple and inexpensive food materials and by reducing the quantities of some foods commonly used rather abundantly, as meat and butter. Most of the students felt quite satisfied with the food. The curtailing of the amount of butter served at the table was considered the greatest deprivation; a small pat, about half the customary size, being served to each where butter is indicated with bread on the menu. 26 FOOD AND DIETETICS Economy and Nourishment Dainty- Serving: "The importance from the standpoint of economy of selecting foods which are nourishing rather than those having a low food value but which please the palate and add to the attractiveness of the diet, is illustrated by a dietary study made of a family in New Jersey in which it was found that $2.16 was expended in three weeks for oranges and $3 for celery, making a total of $5.16 for these two articles, which together furnished only 150 grams of protein and 6,445 calories of energy. During the same period $5.16 was also expended for cereal foods and sugars, which supplied 3,375 grams of protein and 184,185 calories of energy, or about twenty-five times the amount furnished by the oranges and celery. Of course, the sum expended for these articles was not excessive and they undoubt- edly helped to make the diet palatable and pleasing, a by no means unimportant consideration, but it is evi- dent that they were not economical sources of nutri- tive material. '*In the present investigation it was found to be well worth while to use special care in arranging the dishes for serving, that they might be as appetizing in appearance as possible. Much care was also ob- served in avoiding waste both by careful preparation and by the use of all 'left overs.' " In the following table is given the details of cost, weight and nutritive value of the food used in this nivestigation. COST OF FOOD Weights and Cost of Food and Nutrients 27 Food consumed during the entire study (6 days). Cost, nutrients, and fuel value per woman per day. Kinds and amounts. ■4J Cost. Pro- tein. Car- bohy- drates. pa ANIMAL FOOD. Beef: Hearts, 11 lb., 38c. ; round, 10.5 lb. , $1.05 ; rump, 10 lb., 80c. : shank, fore, 3 lb. ; brisket (stew), 7.25 lb., 50c.... Pork: Bacon, 2 lb., 30c.; salt pork, 2 lb. , 18c. ; lard, 1 lb., 12c . . Fish: Cod, salt, 4 lb., 42c. ; salm- on, salt, 5 lb. , 40c Dols. 2.73 .60 .82 33 2.25 .30 2.70 Cts. 1.5 .3 .4 .2 K2 .2 1.4 Gms. 15 1 5 Gms. 19 8 2 Gms. Cal. ories. 229 75 38 Eggs, 1 lb., 33c Butter, 91b., $2.25 ...... 17 19 2 20 '■■26' 169 Cheese, 2 lb., 30c 22 Milk, 210 lb., $2.70.. 350 Total animal food 9 73 5.2 1 39 1 70 2fi 883 1 VEGETABLE FOOD. Cereals: Corn meal, 101b., 29c.: pop corn, 1 lb., 5c.; hominy, 1.44 lb., 5c.; oatmeal, 4.5 lb.. 15c. ; rice, 4 lb., 28c.; graham flour, 101b., 25c.; white flour. 66 lb., $1.55; crackers, Boston, 0.751b., 4c 2.CC 1.60 • 2.36 1.07 1.4 .9 1.3 .6 27 1 7 1 4 1 1 2 178 54 41 13 856 Sugars, starches, etc.: Sugar, granulated, 20 lb., $1; mo- lasses, 2. 33 lb., 36c. ; cornstarch. 0.33 lb., 2c.; cocoa, I lb., 17c.; chocolate, 0.12 lb., 5c. 229 Vegetables: Beans, lima, 2 lb.. 18c.; beans, pea, 2.44 lb.. 10c. ; beets, 1.25 lb., 4c.; cabbage, 5 lb., 10c. ; carrots, 1.25 lb.. 2c.; celery, 2.061b., 10c. ; parsnips, 4.69 lb., 15c.; peas, split. 1.69 lb., 13c. ; potatoes, 80 lb., $1.47; turnips, 5.51b., 7c. 201 Fruits, nuts, etc.: Apricots. 1.5 lb., 17c.; bananas, 7 lb., 30c.; dates, 2 lb., I2c. ; prunes, 2 lb., 18c.; raisins, 0.25 lb., 2c.; pea- nuts, 2 lb., 25c.; crab-apple jelly, 0.2 lb., 3c 74 Total vegetable food 7.69 4.2 36 8 286 1,360 Total food 17.42 9.4 75 78 312 2,243 28 FOOD AND DIETETICS Chart of Composition of Foods Nutrients. Protein. Fats. Carbo- Mineral hydrates, mattera Non-nutrients. Water. Refuse. Fuel value. Calories. • wuhoui bone. COST OF FOOD Chart of Pecuniary Economy of Food fivtkut. fait Caxhokydrates nutValuJS) 29 From Fanners' Bulletin, No. 142. Composition Function of Food FOOD AND THE BODY It is impossible to decide intelligently how the money available for food shall be distributed among different food materials without understanding something of the composition of these food materials, and of the rela- tion of food to the needs of the body. Experience has taught us many things, but the accumulation of experi- ence needs interpretation by definite scientific knowl- edge. Until lately this knowledge was in the hands of only a few, and even then in so indefinite a form that it was not available for the housekeeper, no mat- ter how well trained, and hardly for an educated phy- sician. Much progress has been made, but even to-day the housekeeper is often a little slow in availing herself of the knowledge she needs. This is partly because of the common feeling that what our fathers and mothers knew is enough for us, and partly because so much of the information is still locked up in more or less technical books, and the ordinary housekeeper, even though she be well educated, has not the key. It is to furnish the key to some of this knowledge that this series of lessons is written. We all know in a general way that food nourishes us and makes us strong. But when we try to inter- pret this general idea into specific terms we find that we do- not realize its meaning. Nothing is in the strict sense a food unless it performs at least one of three 30 FOOD AND THE BODY 31 functions, (i) that of building the body, (2) furnishing heat, and (3) giving power to work. The first function of food, that of building the body, is exercised not only in the growing child, where the material that can be transformed into bones and muscles, blood and nerve tissue, must be furnished by food, but in the adult, since even after growth has ceased, the constant waste of the body tissue must be repaired by food. So far as this function is concerned, the composition of the body must determine to a great extent the kind of material that may be used as food. It is easy to see that the body can be built only by foods containing the same elements, and that the pro- portion of these elements must bear some relation to their proportion in the body. It is reasonable to ex- pect that the elements are combined in food in a way similar to that in which they are combined in the body The body of a man of average weight has been esti- mated to contain the following amounts of the various combinations known as the proximate principles : Water 108 lbs. Mineral matter 1 1 .00 Proteid 29.75 Fat 5.00 Carbohydrates .25 Total 154.00 It will be judged from this that so far as the organic food principles proteid, carbohydrate and fat are con- cerned, proteid holds the chief place as a tissue former. Building Foods Composition of the Body 32 FOOD AND DIETETICS Fuel and Not Only must the body have its actual material Foods furnished by the food, but from this also must be derived its energy. Heat Work ATWATER'S RESPIRATION CALORIMETER. A Man Lives in the "Box" for Days and the Actual Heat and Energy- Obtained from the Food Consumed is Determined. (Seepage52.) The two forms of energy with which we are espe- cially concerned in our study of the body are heat and power to work. Heat is required to maintain the body temperature necessary in order that the processes of life may be carried on. The work performed may be considered as of two kinds, internal and external. The internal work is that used in maintaining the different functions of FOOD AND THE BODY 33 the body itself. The beating of the heart, breath- ing, the absorption of food, all require the expenditure of energy ; this internal work requires a large portion of the available power. As in all machines, energy is lost in the form of radiant heat, but the body is con- sidered an efficient machine because a larger propor- tion of energy is available for external work than in most engines constructed by man. The amount of energy required for external work is a variable factor, and the work to be done is conse- quently important in determining the amount of food necessary. So far as present knowledge goes, we may say that the energy of the body is derived from the oxidation (or combustion) of food that takes place in the tis- sues of the body. The process is undoubtedly a com- plex one, far from the simple union of the food with the air we breathe, and probably implies the actual building of the food into body substance, but we are concerned chiefly with the final result rather than the process by which it is reached. All combustible substances have what is known as potential energy. This might be defined as stored-up energy. It implies that energy from some exterior source has been used in producing the substance in its present form. For instance, heat from the sun has been utilized in the formation of the starch or proteid in the plant, and this energy is again set free in the oxidation or the decomposition of the substance. External Work Variable Source of Energy Potential Energy 34 FOOD AND DIETETICS Potential energy may perhaps be most easily under- stood by thinking of one form of it, energy of position. A weight lifted to a height has by virtue of its place a certain amount of potential energy. The fall of the weight from its position will convert its potential energy into active or kinetic energy by which work is accomplished. The waste materials of the body have little or no potential energy, and the outgo of the body differs in this important respect from its income. If the foocj taken in is only partially oxidized, the waste material still contains some energy, and this potential energy must be substracted from" that of the income in order to find the amount available for the use of the body. Unit of The value of a food to produce heat and mechanical "^Energy energy is measured by the amount' of heat that may be produced by it, and the unit of measure is the calorie. A calorie is the amount of heat required to raise about one pound of water four degrees Fahrenheit, or, accurately, the amount of heat required to raise one kilogram of water one degree centigrade. This is the large calorie, and it is sometimes written with a capital C to distinguish it from the small calorie. The small calorie has a value one-thousandth as great. The term used in this paper means the large calorie. It has been found that there is an exact quantitative relation betwen heat and work, expressed by the term mechanical equivalent of heat. Experiments have shown that about 778 foot-pounds of work are con- FOOD AND THE BODY 35 sumv:d in heating one pound of water one degree Fahr- enheit, or 1400 foot-pounds in heating the same amount of water one degree Centigrade. In other words, the same amount of energy would be ex- pended in heating a pound (about one pint) of water one degree Fahrenheit, as in raising a weight of 778 pounds one foot, or a weight of one pound 778 feet. By the same calculations a calorie is equivalent to 3,087 foot-pounds. The calorie then is used as a convenient meas- ure not only of quantity of heat, hut of mechanical energy, or pozver to work. One gram of proteid has been found to The "Bomb" of ^ ^, a Bomb Cal- yield 4.1 calories; a gram of carbo- orimeter. hydrate yields the same amount, while a gram of fat yields 9.3 calories. Or more than twice as much heat can be obtained from a given amount of fat as from the same amount of either proteid or carbo- hydrate. The number of calories any particular food will yield theoretically is determined by the use of the bomb calorimeter. A portion of food of a given weight is enclosed in an iron shell or "bomb," which is then immersed in a given amount of water and the temperature of the water taken. By means of an electric spark the contents of the bomb are ignited and burned, and the temperature of the water is again taken at the end of the combustion. For instance. Mechanical Equivalent of Heat Bomb Calorimeter 36 FOOD AND DIETETICS if the burning of one gram of meat raised the tem- perature of one kilogram (about two pounds) of watei seven degrees Centigrade, that amount of meat would be said to yield seven calories. CHART OF HEAT AND ENERGY Values in Calories of some Common Foods Calories it\ I MILK Butter CHEESE EOGS BEEP feiTJoin atcsW BEEE (Toufld^ MUTTONf LEG FOWL COD (boneless salt) CODCfresK) OYSTERS APPLES BANANAS SUGAR' FLOUR O-'liitd FLQUP^ttre wKcjct) BREAD CRACKERS MACARONI CORN IVIEAL -I^ICE POTATOES. DRIED BEANS^ DRIED PEAS LETTUCE ALMONDS RAISINS CHOCOLATE lb -600 laOO 1500 2000 2500 300O 3500 I I The chart given shows the number of calories yield- ed by several dififerent foods. There is one factor that is often not sufficiently considered in determining the amount of energy ob- FOOD AND THE BODY 37 tainable from food. A food may yield excellent re- sults in the calorimeter and yet be of little service in the body because of its lack of digestibility. It is CHART OF COMPOSITION OF FOODS Percentage of Nutrients of Edible Portion, i, e., Without Bone, etc. lOX ^''>y- 30X -yy; soy. 60X tox box QOK too^ MILK BUTTER CHEESE EGGS BiZEF ("sirloin steaK) BEEF (round) MUTTONJ LEG FOWL COD (boneless salt) CODCfresli) OYSTERS APPLES BANANAS SUGAR FLOURCwh.te) FLOURCentire wheof) BREAD CRACKERS MACARONI CORN MEAL RICE POTATOES DRIED BEANS DRIED PEAS LETTUCE ALMONDS RAISINS CHOCOLA~E PROTEID^ FAT CARBOHYDRATE WATER[ ASH ■ by no means the food we eat but the food we assimilate that nourishes us. The portion of food that is really absorbed by the body differs greatly under different conditions and with different food materials. Many 38 FOOD AND DIETETICS Digestibility of Food careful experiments have been made of late, and more will be made to determine the amount assimilated in different cases. This element of digestibility is fre- quently not taken into account, and the value of a food is estimated wholly from its chemical composition. Some reasons for this are the great difficulty in de- termining the digestibility of a food, the fact that this digestibility may vary from time to time according to the condition of the body, and the fact that the personal equation enters largely into the matter. The accompanying tables showing the comparative digestibility of some common foods are therefore merely a general statement, and represent average re- sults. Table of Digestibility and Fuel Value per Pound of Nutrients in Dif- ferent Groups of Food Materials. (Atwater.) Kind of food. Meats and fish Eggs Dairy products ■ Animal food (of mixed diet) . . Cereals Liegumes (dried) Sugars Starches Vegetables Fruits. Vegetable foods (of mix'd diet) Total food (of mixed diet) . . . . Protein. Digest! bilitv. Per cent. 97 97 97 97 85 78 Fuel value per pound Calories. 1,940 1,980 1,940 1,940 1.750 1,570 1.410 1,520 1,840 1,820 Fat. Digesti- bility . Per cent. 9P 95 95 95 90 90 Fuel value per pound. Calories. 4,040 4,090 3,990 4,050 3,800 3,800 3.800 3.800 3.800 4,050 Carbohydr'ts Digesti- bility. Per cent. 98 98 98 98 98 97 98 98 95 90 97 97 Fuel value per pound. Calories. 1,730 1,730 1,730 1,730 1,860 1,840 1,750 1,860 1,800 1,630 1,820 1,820 FOOD AND THE BODY 39 Table of Comparative Digestibility, Commencing with the Most Digestible and Ending with the Least Digestible of Meats and Other Common Animal Food. Oysters. Soft-cooked eggs. Sweetbread. White fish, boiled or broiled, such as bhiefish, shad, red snapper, weakfish, smelt. Chicken, boiled or broiled. Leanroast beef or beefsteak. Eggs, scrambled, omelette. Mutton, roasted or boiled. Squab, partridge. Bacon. Roast fowl, chicken, capon, turkey. (From W. Gilman Thompson.) Tripe, brains, liver. Roast lamb. Chops, mutton or lamb Corned beef. Veal. Ham. Duck, snipe, venison, rabbit, and other game. Salmon, mackerel, herring. Roast goose. Lobsters and crabs. Fork. Smoked, dried, or pickled fish and meats in general. It should be noticed that the fuel value obtained w the body from the various classes of foods is somewhat less than the theoretical amount mentioned on page 35, because they are not completely digested and as- similated nor completely oxidized in the body. The following values are used in the U. S. Government reports as representing average conditions : Proteid, fuel value, 4 calories pey gram, or 1.820 calories per pound. Fats, fuel value, 8.9 calories per gram, or 4,040 calories per pound. Carbohydrates, fuel value, 4 calories per gram, or 1 ,820 calories per pound. The foods that are particularly useful in furnishing heat and energy for the body, the carbohydrates and fats, are frequently called the fuel foods, although proteid can act as fuel just as readily as can these. Since the proteids, however, have a more important function and are most expensive, the other foods are used as proteid sparers. The amount of these fuel foods that IS to be taken depends not upon the amounts Fuel Value in the Bod^ Fuel and Energy Foods 40 FOOD AND DIETETICS present in the body, but upon the amount of heat and energy to be produced. The Body The Comparison is frequently made between the An Engine body and an engine, the food representing the fuel, the air taken in through the lungs representing the draft, the waste matters of the body corresponding to the smoke and ashes from the engine fire. In many ways this is a helpful comparison, but we need to keep in mind the essential differences between the human body and the mechanical engine as well as their like- ness. Combustion in the body is much slower than in the machine, and is therefore not accompanied by light, though by the oxidation of the same amount of fuel the same total amount of heat is produced. Oxi- dation in the body takes place not in one central cavity, but in every tissue, and, most important of all, the fuel furnished the body probably becomes part of its own substance before it is oxidized. Moreover if it is not sufficient in amount the waste of tissue proceeds faster than its repair, and there is a constant loss of body substance. FOOD PRINCIPLES In this and other series of lessons we have already discussed the food principles to some extent. Let us consider them now somewhat more in detail. PROTEIDS The proteids are more difficult to understand than the other food principles because different members of the class seem at first sight to have little in com- mon. A few simple experiments that will isolate some typical proteids in a more or less pure state will serve to give a clearer image. To a quarter of a cup of flour add very slowly a tablespoon of water and stir it until the flour is com- pletely moistened, then work the dough in the hands until it becomes smooth and elastic, and finally wash it under cold water until fresh water added no longer grows milky. This will take from fifteen to twenty minutes. If a little iodine is at hand add a drop. If no blue color appears the starch is all washed out. There will be left in the hands a sticky, elastic mass, called gluten. Save part of this for comparison with other proteids and bake the rest in a hot oven. Add a little acid, such as lemon or vinegar, to some milk, and heat it gently. Wash the curd thus formed in order to separate it from the whey. The curd is chiefly composed of casein. With. a knife scrape a piece of lean meat until the tender -muscle fibre is separated from the firm white 41 Different Proteids Gluten Casein 42 FOOD AND DIETETICS Myosin Legumin Composition of Proteids connective tissue. The fibre represents one of the chief proteids of meat, called myosin. Beside the glu- ten, the casein, and the myosin, put the white of an egg, and you have before you the four chief represen- tatives of the proteids of our food. If we could add to them legumin, the proteid found in peas, beans, and other members of the pulse fam- ily, we should have a fifth important member of the class. If we compare these substances, we shall find that although at first they seem very different, they yet have certain properties in common. All, for instance, to a greater or less extent, show the elasticity and tenacity that is so marked in gluten; all of them are toughened by a high temperature ; and all when dried may be ground to powder similar in texture and ap- pearance. These physical likenesses, however, would hardly be sufficient to place these substances in one group. It is only when we consider the chemical composition of each and the function that each has in the body that we are justified in classing them together as pro- teids. Proteids are substances containing the elements carbon, hydrogen, oxygen, nitrogen, sulphur and fre- quently phosphorus. They alone of the food princi- ples are able to supply nitrogen, one of the essential elements in all living things, whether animal or vege- table, and one that we are forced to obtain from our food, since, although we are surrounded by an atmos- FOOD PRINCIPLES 43 phere that is nearly four-fifths nitrogen, we cannot utiHze it in this form. Beside the true proteids, there are certain other sub- stances which also contain nitrogen, but which are classed separately because they cannot alone supply the nitrogen needed by the body, though they can re- place part of the proteid in the diet, and perform its function. Gelatine is one of the test known of these substances. They are called gelatinoids or albumin- oids. Ossein, of which bone is largely composed, ker- atin, the horny material present in the hair and in the horns and hoofs of animals, collagen, forming the greater part of the connective tissue of meat, are all representatives of the same class of substances. All these named may be changed into gelatin by boiling. Certain other nitrogenous substances called extrac- tives, are present in some foods. It is these that give flavor to meat, and that form the chief ingredients of the extracts of beef on the market; and it is these that give the chief value to beef tea and to clear soup. The extractives act as stimulants rather than as true foods since they neither build tissue nor act as fuel, but they seem to play some role in digestion. The proteids, gelatinoids, and extractives, are sometimes classed together under the general name of protein. This is the usage of the United States Government pamphlets. The nomenclature applied to the nitrogenous substances is very confusing, since each author seems to have adopted his own. Albumi- Gelatin Extractives Nomen- clature 44 FOOD AND DIETETICS noid, for instance, is sometimes used to designate the true proteids, and sometimes is applied to the gelatin- oids. Proteid is sometimes used in a much more Hm- ited sense than we have given to it, inckiding only certain classes of the substances ordinarily designated by the term. In studying the subject, therefore, one rnust first of all ascertain the writer's use of terms. CARBOHYDRATES Composition The carbohydrates are so called because they are composed of the elements carbon, hydrogen and oxy- gen, the last two in the pro- portion in which they are found in water. This last statement, although it is generally made in defining carbohydrates, is not strict- ly true, since a few of the less common members of the class are found to vary somewhat from this pro- portion. The principal carbohydrates may be classed in three groups. The following table shows the chief mem- bers of these different groups, so far as our food is concerned. Grains of Potato Starch. FOOD PRINCIPLES Classification of Carbohydrates 45 Starch (or Amylase) . Group. Starch Dextrin Cellulose Gums Glycogen Cane Sugar (or Sucrose) Group- Ci2 Ho2 O,, Cane Sugar (Sucrose) Malt Sugar (Maltose) Milk Sugar (Lactose) G rape Suga r i or G lucose ) Group. Grape Sugar (Dextrose) Fruit Sugar (Levulose) That the second and third groups bear a definite Corn Starch. Rice Starch. (From Hygiene, by Parks.) chemical relation to the first may be seen by a com- parison of their formulae. Starch is the most important of the carbohydrates from the standpoint of food. It is familiar to us all as the fine, white, glistening powder of "corn starch" and of laundry starch. We may easily, by washing it, obtain it also from grated potatoes and from flour. Starch is found only in the vegetable kingdom, and is manufactured by green plants and stored in differ- ent parts of the plant in the form of tiny grains lying within the plant cells. starch 46 FOOD AND DIETETICS structure of Starch Starch Grains The structure of these grains has been very hard to determine because of their minuteness. It was thought for a long time that they were composed of a cellu- lose envelope enclosing the true starch, and that by the action of water and heat these grains swelled and the cellulose en- velope burst. A later theory was that the starch grain was built up in alternate layers of starch cellu- lose and starch granulose. The late work of a German botanist, Meyer, seems to show that the grains are in the form of sphero-crystals, each made up of many tiny particles. These radiate from a center, and at the same time are arranged in concentric layers. The particles are of two kinds called by Meyer alpha-amylose and beta-amylose. These may be compared to the starch cellulose and starch granulose of the older theory. Upon the appli- cation of heat and moisture the beta-amylose swells and becomes gelatinous, forming a solution. The alpha-amylose is affected only by a temperature much above the boiling point, or by long continued heating. The starch grains in different plants differ much in form, size and general appearance, as shown in the Bean Starch. FOOD PRINCIPLES A7 illustrations. The relation of the difference in struc- ture to digestibility is not well determined. Dextrin is a substance having the same general composition as starch, but unlike it in some of its properties. It is chiefly important to us in that it is an intermediate product of the change of starch into sugar. Glycogen is the form in which carbohydrate is stored in the body until it is needed for use. It is Dextrin Diagram Representing the Supposed Structure of a Sphero-Crystal of Starch, Showing Radial and Concentric Arrangement. From A. Meyer. found chiefly in the liver and is sometimes called ani- mal starch. Cellulose is so slightly digested that we do not put it in the list of human foods, yet it is important from two standpoints. First, it gives the necessary bulk to food ; and second, it so encloses the nutrients in vegetables and fruits that it must be definitely con- sidered in cookery. Cellulose 48 FOOD AND DIETETICS Composition Water and Mineral Matter Nutrient Ratio Allied to the gums are the pectose and pectin that are concerned in the making of jelly from fruit juice. The gelatinous substance obtained from Irish moss also belongs in this class. The sugars will be dis- cussed imder the special foods. FATS The fats, like the carbohydrates, are composed of carbon, hydrogen and oxygen, but with these elements in very different proportions from that in which they exist in the carbohydrates. There is a much larger proportion of carbon with less oxygen than in starcli and sugar, and this accounts for the readiness with which they burn and the intense heat that we get from them. They are of both animal and vegetable origin. Those which are liquid at ordinary temperature we often speak of as oils. In discussing the value of a food we commonly con- sider only the organic principles. Although water is absolutely necessary it is so easily supplied and so abundant that we do not have to consider whether or not it is present in our food as we purchase it. This is not true of mineral matter to so great an extent, but it is largely so, except in the case of growing children. The mineral matter will, as a rule, take care of itself if we provide the other substances needed. By food value or nutritive value we ordinarily mean the amount of organic nutrients present in the food. In determining the importance of any particular food, we consider not only the total amount of the nutrients FOOD PRINCIPLES 49 present, but the relation that the proteid bears to the other nutrients. This is often called the nutrient ratio. The nutrient ratio of potatoes, for example, containing two per cent of proteid and eighteen of starch, is i to 9. In reckoning this ratio, fat is changed into its starch equivalent, that is, one part of fat is considered equal to two and a quarter of starch. The following classification of the food principles classification may help to fix in the mind their relationship. Nutritive Ingredients (or Nutrients) of Food r I Protelds, e.g.. albumin, casein, gluten, etc. 1 Nitrogenous •< Gelatinoids, e.g., gelatine, etc. Organic. ■{ I Extractives. I Non-nitrogeneous-j gj^^o^yd^'^tes, e.g., sugar, starch. T„_„„-„^^ J Mineral matters. Inorganic. -I ^^^^^ of Foods Use of Food Principles in the Body Proteid.. ..Forms tissue eg , white (albumen) V of eggs, cvird (casein) J All serve as of milk, lean meat, / fuel to yield gluten of wheat, etc. V energy in the Fats Are used or stored as fat / forms of heat e.g., fat of meat, but- y and muscu* ter, olive oil, oils of 1 lar power corn and wheat, etc. j Carbohydrates. Are used or transformed into fat. e.g., siiffar. starch. etc. Mineral matters(ash) . . Share in forming bone, assist in digestion, etc e.g.. phosphates of lime, potash, soda, etc. Amount of Food Required Food for Different Ages DIETAEY STANDARDS In addition to a knowledge of food constituents, of the proportion of which these exist in our food, and of the use of food in the body, we need to know the amount of food necessary to supply our daily needs under different conditions. Many factors will influ- ence not only the total amount of food that we need, but also the proportions in which we shall use the pro- teids, the carbohydrates and the fats. The flesh weight of the body is important in deciding the amount of proteid (that is, the muscle weight, not the total weight of the body) since the greater the flesh weight the greater the nitrogenous waste. The shape of the person, whether tall or thin, or short and plump, in- fluences the amount of fuel food required, since the amount of surface exposed affects the loss of heat. The degree of activity has an important influence upon the amount of all the food principles. Variations in climate to a certain extent affect the amount of heat to be produced in the body, and occupation also has an important influence. The age of the individual is, within certain limits, one of the greatest factors. The growing child needs a large amount of building material, while the old person needs distinctly to lessen the tissue building foods. The accompanying diagram gives an idea of the way in which these proportions vary with different ages. It will be seen that the proportion of proteid is much greater in comparison with other food materials 60 DIETARY STANDARDS 51 in the case of the child than of the aduh. The total amount of food is also greater in proportion to body weight in the child than in the adult. Although not shown in the table, mineral salts are needed in large proportion in the child's diet, while they may well be cut down in the diet of the old. The amount of food needed increases rapidly from birth to about four Yaars of Age St 56 «0 <« it Ta 7«- 89 6 40 5 00 '4tO ! 4 > SB I 94 t 60 aac I 80 « 40 / ^ / '■^ 5s^ J ' s.'^i"-. / ^'L'- i r 1 ■V, K^ / "^ ^. / N / N / / t^ / ,0^ X "^ _Pfo[ nat ^ / — ^ -— n ■^^ ' 1 ■ .^^ ^ — —^ ■* — — — •**. — i 9 80 540 5 00* 4 6 4 t C> a • • 5 4 J soej J.o; 9 3 o ro 6 O Z Years of Age. M U Sa 56 40 4« 48 i» 9t> 60 64 68 7t 76 80 Diagram Showing the Varying Amounts of Food Principles Required at Different Ages. years of age, very slowly from four to about ten, with a rapid increase from this time to twenty-four. From ten to twenty-four the carbohydrates should increase in amount more rapidly than the other food principles. To put in terms of the nutrient ratio the difference between the diet of the child and that of the adult — in the adult diet the ratio is about 1 15.3 ; in the diet of the child, i :4.3. Nutrient Ratio 52 FOOD AND DIETETICS standard Dietaries Experimental Dietaries These statements are of course true only approxi- mately, yet one familiar with children must recognize in them a fair generalization from the facts. The proportions of the different food principles needed daily constitute the dietary, and dietary stand- ards have been made up taking into account as far as possible these different conditions. These dietaries are sometimes called experimental, and sometimes sta- tistical, according to the method used in formulating them. An experimental dietary is the result of care- ful observations of the effect of different proportions of food nutrients upon an individual under determined conditions. The statistical dietary is the outcome of the study of the actual ration of large numbers of peo- ple. Each of these has its drawbacks. In the first case it is difficult to decide how far the result is due to individual idiosyncrasy, and a large number of ex- periments must be tried before the personal factor can be eliminated. In the second case it is hard to determine whether some variation in the diet might not produce better results. An example of the first method of formulating die- taries is that of Professor Atwater's respiration calori- meter, sometimes called ''the man in a box," described in one of the government pamphlets. A small room was constructed in the laboratory with flues arranged to bring in fresh air and to carry off the products of respiration. Each of these flues was arranged so that the temperature and composition of the air entering DIETARY STANDARDS 53 and going out might be determined. A man lived in this room for several days at a time, his food being given to him by means of slides in a double wall. A sample of each food given was analyzed and a determi- nation of the number of calories yielded by it made by means of the bomb calorimeter. All food taken was carefully weighed, and the excreta of the body were analyzed so that an accurate estimate could be made of the total income and outgo of the body. See illus- tration on page 32. Many statistical dietaries have been taken, some of statistical the most valuable being those of the German army. Experiments have been made there as to the effect of the addition of certain articles of food to the diet, and the conclusions have been of much value. Similar dietary studies have been made at many schools and universities. From a careful comparison of dietaries made up in these two ways certain standards have been deter- mined upon. The American standards vary in some important points, notably in the amount of fat used, from those of Europe. Some of these dietaries are given here. 54 Chittenden's Experiments FOOD AND DIETETICS Standard Dietaries Voit o ce ^0 a ce u u 'a -5 M OC5 o ^ ^0 o Q Woman at moderate work (German) 92 118 145 119 156 185 80 100 125 150 44 56 100 51 71 71 80 100 125 150 400 500 450 531 568 568 300 360 450 500 536 674 095 701 795 824 460 560 700 800 2425 Man at moderate work (German) 3055 Man at hard work (German) 3370 Playfair, Man with moderate exercise (English) Active laborer (English) 3140 3630 Hard- worked laborer (English) 3750 Atwater. Woman with light Exercise (American) Man with light exercise (American) Man at moderate work (American) 2300 3815 3520 Man at hard work (American) 4060 There are twenty-eight and thirty-four hundredths grams (28.34) in one ounce. A man at moderate work requires, therefore, according to the American standard, about four and one-half ounces of proteid, four and one-half ounces of fat, and nearly a pound of carbohydrate daily. The dietary standards that we have been considering are those that have been accepted generally since work of this kind was first begun. Some late experiments conducted at Yale University by Professor Chittenden and others, indicate that a much smaller amount of food, especially of proteid, may better serve the pur- poses of the body, than the larger amounts indicated in these standards. The experiments were carried out upon men representing three different classes of in- dividuals. The first class was composed chiefly of DIETARY STANDARDS 55 professors and instructors. The second represented the moderate worker. The third class were trained athletes. The experiments covered a period of five months, and the proteid taken daily varied from about thirty-five to fifty grams per day, while the total num- ber of calories yielded was from twenty-five to twenty- eight hundred a day. The general conclusion drawn from these experiments is that under ordinary condi- tions of life, with an ordinary amount of work, bodily health and vigor are maintained as well, if not better, on a minimum proteid diet than on the amount given in the generally accepted standards. Some careful experiments and analyses recently made by the physiological chemist, Dr. Otto Folin, at the McLean Hospital, Waverly, Mass., indicate that about twenty grams of proteid represents the actual daily proteid wastes of an average sized man under ordinary conditions. That is, only about three-fourths of an ounce of proteid material is necessary per day in an adult to rebuild the nitrogenous tissue of the body that wears away through use.* Such radical differences from standards found by long experience to give good results in health and strength must be considered very carefully before be- ing accepted. But in this as in many other ways, we may be obliged to revolutionize our ideas of food. We must not fail to distinguish between the amount of proteid required and the amount of food containing proteid. If, for example, meat be supplied containing *See Report of the Lake Placid Conference on Home Economics, 1905, and American Journal of Physiology, March, 1905. Dr. Folin's Experiments Amount of Food to Furnish Required Proteid 56 FOOD AND DIETETICS Example for Practice Calculations Balanced Bation i8 per cent of proteid (a fair average), a little more than a pound and a half of the meat will be required to furnish the four and a half ounces of proteid. Bread containing" 9 per cent of proteid would be re- quired to the amount of three pounds. Nearly two pounds and a quarter of eggs, with 13.1 per cent of proteid, or about eighteen eggs, would be necessary to supply four and a half ounces of pure proteid. Taking the percentage composition from the accom- panying table, calculate the amount of milk that would be required daily to furnish four and a half ounces proteid. How much potato would be required ? How much corn meal? Calculations: From the table, milk is found to con- tain 3.3% of proteid or i oz. contains .033 oz. protein. To furnish 4.5 ozs. would require 4-5 -^ -033 = 136+ As a pound contains 16 ozs., 136 oz.=8^ lbs. A pint of milk weighs about i lb., so about 4j4 quarts would be required to provide 4.5 ozs. of proteid. Potatoes as purchased contain 1.8% proteid. 4.5 ^ .018 = 250 250 oz. = 15 lbs. (aprox.) A bushel of potatoes weighs about 60 lbs., conse- quently about one peck of potatoes would be required. Corn meal contains 8.9% proteid and by the same calculations 3 lbs. 2 ozs. will be found to contain 4.5 ozs. of proteid. It is by no means a matter of indifference whether the proteid be derived from any one of these food DIETARY STANDARDS 57 materials, or from a mixture of different ones. The other food ingredients present must be taken into account. For example, the three pounds of bread Composition of the Edible Portion of Some Common Foods a) u u < 5 63.2 63.7 55.0 82 5 88.3 84.6 75.3 3 3 1.0 25.9 13 4 19.0 20.3 18.7 19,3 27 3 16.7 6.0 0.4 1.3 4.0 85.0 33 7 10.5 19.1 13.6 17.5 16.3 0.3 0.3 1.3 0.5 0.6 5.0 "2.4" "3.3" 13.0 21 100.0 75.1 71.9 53.1 71.9 74.1 75.4 79.0 18.4 59.6 62.0 2.9 17.3 76.1 30.3 325 Butter 3,605 Cheese 1,950 Eggs 720 Beef (sirloin) 1,155 Beef (round) . . 950 Mutton (leg) Fowl 1.085 1.045 Cod (boneless salt) Cod (fresh) 490 325 Oysters 230 ApDles ; . . . 290 Bananas Sugar. 460 1,857 Flour (white) 6.5 1.0 1.1 1.8 1.3 1.0 0.4 1.0 3.5 2.9 0.9 2.0 2.3 2.2 i2.6 11.4 35.3 6.8 10.3 12 5 12.3 78.0 12.6 9.5 94.7 4.8 14.6 5.9 11 4 13.8 9.2 10.7 13.4 9.2 7.8 2.2 22.5 21.6 1.2 21.0 2.6 12.9 i.6 1.9 1.3 8.8 0.9 1.9 0.3 0.1 1.8 1.0 0.3 54.9 3.3 48.7 1.650 Flour (entire wheat) Bread 1,675 1,215 Crackers 1,905 Macaroni 1,665 Corn meal ..... 1,655 Rice 1,630 Potatoes Dried Beans Dried Peas . 385 1,605 1,6.55 Lettuce 90 Almonds 3,030 Raisins Chocolate. 1,605 2,860 (See pages 36 and 37 for charts giving graphic representa- tion of these foods.) would furnish also more than a pound and a half of carbohydrates, a great excess of the required amount. The meat would vary in fat, but estimating 58 FOOD AND DIETETICS the per cent as twenty, the pound and a half would yield four and eight-tenths ounces, more than would be required for the day. The quantities used of these different foods must then be so adjusted that the nu- trients will be in approximately the right proportion. The deciding upon these different quantities from the percentage composition of the food is the essential point in calculating dietaries. 'u°se*^of The question will probably come to each one — of le anes ^^^ much practical use for the everyday housekeeper is this study of dietaries. In the first place, it would mean the expenditure of a great deal of time if one should undertake to determine each day's rations in this way. In the next place, it is impossible to know the actual composition of the food that we eat, except in a few cases. We may be fairly sure of the com- position of the Qgg, but when meat varies in proteid from 12 per cent to 22 per cent as it does according to the Atwater analyses, how are we to determine the composition of the particular cut that we are using to-day? Moreover, even if our meal were prepared so that the exact proportions of nutrients were fur- nished, it is quite possible that one member of the family might eat too large a proportion of the pro- teids and another too much of the carbohydrates. Another element of uncertainty lies in the difference in composition between cooked and uncooked food. Rice, for example, according to the tables, contains 79 per cent of carbohydrate and 7.8 per cent of pro- DIETARY STANDARDS 59 teid. But if you will weigh a cup of rice before it is cooked, and the same rice after it is cooked, you will find that it has gained perhaps four times its original weight. In other words, a quarter of a pound of cooked rice will only furnish about a fourth as much nutrient as a quarter of a pound of rice without the added water. Often we can allow for this difference in the calculation of our dietary ; but sometimes we know too little about the changes which take place in cooking to do this. Finally, even if we know exactly what we eat we do not know what we assimi- late. Is there, then, any use in the dietary standard? In two ways it is of great service. In the first place, variation it is a standard by which we may test our diet if we ItaJdard extend our experiment over a sufficiently long period. At the beginning of a month let us take account of stock, estimate the amount of food materials on hand, and then keep careful account for a month of all food brought into the house ; at the end of the month we will again estimate what we have on hand and in this way ascertain the amount of raw material used. Table IV, with the details which follow, gives an example of a carefully calculated dietary. The com- position of the various foods was taken from Bulletin No. 28 of the office of Experiment Stations, U. S. De- partment of Agriculture.* If, on calculating the food value of the different materials, we find that for the * "The Chemical Composition of American Food Materials" which may be obtained by sending five cents t«. com to the U. S. Department of Agriculture, Office of Experiment Stations, Washington, D. C. 6o FOOD AND DIETETICS number of persons served we have a distinct varia- tion from the standard diet, we can legitimately con- clude that there is something wrong. If, for ex- ample, we find that the amount of proteid calculated in our food materials is twice as much as that supposed to be required, we shall conclude that either our fami- lies must be using a much larger amount of proteid than would be conducive to the best health, or there must be much unnecessary waste, and in either case, an investigation would be needed. Errors in Another way in which the dietary standard is of Dietaries ^ ... . . especial service, is in enabling us to judge what error in diet is responsible for some particular weakness or peculiarity in any member of the family. A girl of fourteen may be unusually thin or may appear lan- guid and tired, and everything point to improper feed- ing as the cause. The first thing to do in this case would be to see whether the child's diet were deficient in any one of the three nutrients, and if so bring the diet up to the standard. In dealing with abnormal condi- tions, then, or with large masses of people, or with diet over an extended length of time, the dietary standards may be applied to great advantage. It is not necessary to apply it strictly to each individual at each meal. The calculation of a few dietaries is very useful in giving us a definite idea of the general composi- tion of foods, and so making it easier to estimate the amount of different nutrients which we are providing DIETARY STANDARDS 6i at ordinary meals, without the tediousness of reckon- ing each meal in detail. In such calculations the following factors are used to reduce the results to the standard of one man at moderate work. Factors used by the TJ. S. Department of Agriculture in Calculating Meals Consumed in Dietary Studies. Man at hard muscular work requires 1.2 the food of a man at moderately Factors active muscular work. Man with light muscular work and and boy 1.5-16 years old require 0.9 the food of a man at moderately active muscular work. Man at sedentary occupation, woman at moderately active work, boy 13-14, and girl 15-16 years old require 0.8 the food of a man at moderate- ly active muscular work. Woman at light work, boy 12, and girl 13-14 years old require 0.7 the food of a man at moderately active muscular work. Boy 10-11 and girl 10-12 years old require 0.6 the food of a man at moder- ately active muscular work. Child 6-9 years old requires 0.5 the food of a man at moderately active muscular work. Child 2-5 years old requires 0.4 the foM of a man at moderately active mitscular work. Child under 2 years old requires 0.3 the food of a man at moderately active muscular work. In making dietary studies all food used should be weighed, but the following data may be of use for approximate home calculation : I meastiring cup^^ pint. i6 tablespoons=i cup. 3 teaspoons^ I tablespoon. A cup of water weighs about 8.3 oz., of milk 8.6 oz., of cream 8.4 oz., of butter 8.4 oz., of lard 7.5 oz., of sugar 8 oz., and a tablespoonful of the foregoing weighs about 0.5 oz. A cup of meal weighs 5 oz., of sifted flour 4 oz., of oatmeal 2.7 oz., of cream of wheat 6 oz. A cubic inch of meat or butter weighs about 0.5 oz. An Q.^g without shell weighs 1.6 oz. A slice of bread lA in. thick weighs i oz., a heaping teaspoonful of sugar 0.4 oz. Home Studies FOOD AND DIETETICS PART I 1. What to-day is included in the food problem? 2. What factors affect the proportion of the income spent for food? 3. At current prices in your locality, give a list of foods you would provide for a day's ration at 15 cents per person for raw food material. At 25 cents. At 40 cents. 4. To what extent can waste in food be eliminated? 5. How do animal and vegetable foods compare in cost? 6. Which would be the cheaper source of proteid, beefsteak at 22 cents per pound, milk at 7 cents per quart, bread at 5 cents per pound, corn meal at 3 cents per pound? Give details of calculations. 7. With what two forms of energy are we chiefly concerned? What is meant by potential energy? 8. What is meant by calorie? By the mechanical equivalent of heat? 9. How does the amount of heat produced by pro- teid compare with that obtainable from an equal amount of starch? With that from an equal amount of fat? FOOD AND DIETETICS 10. What relation has digestibility to food value? 11. What are the five food principles? Give their functions. W'hich of the food principles is most important? 12. What is meant by proteid ? Name the most com- mon representatives of the class found in food. 13. If possible, perform the experiments in separat- ing some of the proteids as described and report. 14. How does gelatine dififer from the true proteids? How may it be obtained? 15. W'hat is the most important carbohydrate from the standpoint of food? Wliat is its source? 16. How do fats differ from carbohydrates? 17. What is meant by food value? By nutrient ratio? 18. How are dietary standards determined? 19. What factors affect the amount and proportion of food needed? 20. Of what practical value to the housekeeper are dietary standards? 21. Calculate the. amount of proteid, carbohydrate, and fat in your own diet for one day as nearly as you can. Give details of calculation. 22. What questions have come to you in the study of this lesson? Note. Question 21 is optional. After completing the test sign your full name. FOOD AND DIETETICS PART II SPECIAL FOOD STUFFS In the selection of foods one of the questions that will come up will be that of the relative value of ani- mal and vegetable foods. An increasing- number of people are confining their diet largely, if not exclu- sively, to vegetable products, while others add to these such animal substances as do not imply the taking of life, such as milk and eggs. Is a mixed diet essential for health? Or may we at will choose exclusively from the animal or the vegetable kingdom? Certain broad distinctions between animal and vege- table food will immediately present themselves. Speaking generally, animal foods are richer in nitrog- enous matter, while vegetable foods are the chief source of carbohydrates. This becomes much more evident if we compare the two in a dry condition. Milk, for instance, makes a poor showing in proteid as compared with dried peas and lentils, or even with rice. But if we take the total solids of the milk as a basis of comparison, eliminating the 87 per cent of water, the case is quite otherwise. This is the fair method, for the dried peas and rice absorb many times their weight of water in the process of cooking, so that the analysis of the raw material is quijte dififerent from that of the cooked food. Animal and Vegetable Food Stuffs Distinction 64 FOOD AXD DIETETICS Caiboliydrates Comparative Cost Hutchison gives the following composition of a few typical dried foods : One hundred parts of dried lean beef contain 8g parts of proteid. One hundred parts of dried fat beef contain 51 parts of proteid. One hundred parts of dried pea flour contain 27 parts of proteid. One hundred parts of dried wheat contain 16 parts of proteid. One hundred parts of dried rice contain 7 parts of proteid. To this we may add : One hundred parts of dried milk contain 25 parts of proteid. On the other hand we find our carbohydrates almost wholly in the vegetable kingdom. Milk is the only important exception to this. In milk, dried, we find 38 parts of carbohydrate to 100 of the total solids. Another difference between animal and vegetable food is found in their comparative cost. Animal food as a rule is much more expensive than vegetable. This is not difficult to understand when we remember that our animal food has been put through a further pro- cess of manufacture than the vegetable food. If the grain raised, instead of going directly to man as food, is used to feed cattle, and these in turn are slaughtered to furnish nourishment for human beings, the process necessarily adds to the cost of the food. This pro- cess, as well as the fact that plants are in general builders of material, while animals break dozen the complex compounds built up by the vegetables, is graphically shown by the accompanying diagram. SPECIAL FOODS The same intermediate process which adds to the cost of food increases also its digestibihty, though the less complete absorption by the system of vegetable ■nigestibility Animal ^/fg Cycle of Life > s ^n1!',^°^P»^^^''ve^^t'°'^''^^^ than of animal proteid seems to lie in the fact that in the plant the proteid is enclosed within cellulose walls and ordinary processes of cooking do not always free it, rather than in any difference in the proteids them- selves. In deciding from which kingdom we shall choose 66 FOOD AND DIETETICS Source of Proteid Vegetarian Diet Structure our diet, we consider almost wholly the proteid. As we have seen, carbohydrates must necessarily be ob- tained chiefly from vegetable sources, and it seems to be a matter of indifference whether the fat of the diet is of animal or vegetable origin. With the addi- tion of milk, butter, cheese, and eggs, it is not diffi- cult with care to provide a satisfactory dietary without the use of meat. The case is different when vegetables form the only source of food supplies. Because of the great excess of carbohydrates and the presence of indigestible mat- ter in the form of cellulose, a great bulk of food must be taken in order to get the necessary proteid. As a matter of fact, nearly all purely vegetarian diets are deficient in proteid. The extra cost of the animal pro- teid is justified by its availability since it may be ob- tained without an excess of other substances and since it is easily assimilated. MEAT In the ordinary famil^^ the greater part of the pro- teid diet is probably furnished by meat, so that a knowledge of the composition and nutritive value of this article of food is important. The structure of the meat may be best seen if one with a sharp knife scrapes a small piece of meat, thus separating the muscle fibre from the white connective tissue. Under the micro- scope the muscle fibre is seen to consist of bundles of smaller fibres held together by delicate connective tis- sue in which fat cells are imbedded. These muscle MEAT 67 fibres vary in length in different kinds of meat, and the length of fibre probably plays some part in the digestibility of the meat — the short fibre meats being the more digestible. The toughness or tenderness of meat depends partly upon the muscle fibres and partly upon the connective tissue, though as a rule the same conditions that have made the connective tissue tough and strong will have had a sim- ilar though less effect upon the muscle fibre. In general the muscles that are most used or most exposed to v^Ind and weather will be both tougher and richer in flavor than those not so ex- posed. The young animal will, of course, have more delicate tissues and less toughened fibres than the older or harder worked animal. The composition of different pieces of meat, even from the same animal, differs greatly, the proteid of beef, for instance, varying all the way from twelve per cent to twenty-one, according to the cut of meat and to the feeding of the animal from which it is obtained. The proteids of meat include a number of different substances, the chief of which are fibrin, myosin and albumin. After the animal is killed the myosin coagu- FIBRE OF MEAT. a Fibre b Fat c Connecting tissue Composition Proteids of Meat 68 FOOD AND DIETETICS Albumen Flavor Fat of Heat lates, thus causing the hardening of the muscle, known as rigor mortis. In this condition the meat is very tough, and the hanging of meat is practiced in order to give time for th^ disappearance of this rigor by the re-sokition of the myosin. The presence of albumin in the meat can be easily shown by soaking a small portion of the meat in water for a few minutes, and then heating this water. The albumin dissolves in the water and coagulates upon heating just as white of Qgg would do under similar conditions. The scum that forms in the water when a piece of meat is boiled, is largely this same albumin. Beside the true proteids, gelatine may be obtained from meat in varying quantities. The connective tis- sue upon boiling becom.es gelatine, and it is due to this as well as to the gelatine obtained from the bones that water in which meat has been cooked so often sets into a jelly. The color of meat is due largely to the same substance that gives the color to blogd, haemoglobin. Its flavor depends chiefly upon the nitrogenous substances called extractives, though the characteristic taste of pork and mutton is caused partly by the fats they contain. These extractives have no real food value, but act as stimulants. The fat in meat varies even more in amount than the proteid; beef, as purchased, containing from five and eight-tenths per cent to more than forty per cent. Even in meat that appears lean much fat is present lying between the muscle fibres. This may be seen MEAT 69 upon heating the meat in water, when globules of fat appear from even the leanest meat. The solidity of the fat is due chiefly to the stearin that is present. The amount of water in meat varies very much. A lean cut of beef may have as much as seventy-five per cent of water, while a fat piece might not conta'in more than fifty per cent. In general the more fat the less water there is present, so that in buying it is economy to select meat that is moderately fat. From the standpoint of digestibility, meat is an ex- cellent food. It is among the most easily digested of the proteid foods. As a rule raw meat is more digesti- ble than cooked, and rarely cooked meat more digesti- ble than that which is well done. The cooking of meat has its value not in adding to the digestibility but in developing flavor, so that the meat becomes more palatable ; and in rendering it more safe, by de- stroying certain parasites that are sometimes present in raw meat, particularly in pork, and bacteria that under certain circumstances may cause dangerous de- composition. There is much difference in the digestibility of dif- ferent meats. Pork is ranked among the less- digestible meats, since it requires a longer time for complete digestion than do other varieties. This is probably due to the large amount of fat closely combined with the muscle fibres. Bacon fat, on the other hand, from its different form, is generally found to be easily di- gested. Water Factors in Digestibility 70 FOOD AND DIETETICS Effects of Cooking Losses in Boiling Mutton and beef stand equally well in this respect. As has been suggested before, short fibred meats are in general more easily digested than long fibred ones, yet veal is an exception to this. Hutchison explains this by suggesting that the fibres of veal easily elude the teeth on mastication, and that the comparatively in- sipid character of the veal fails to excite a free flow of gastric juice. It would seem that tl:is absence of extractives would be the more important factor. How far the cooking of meat alters its chemical composition is not wholly determined. Some inter- esting experiments at the University of Illinois l:ave taught us much about the losses that take place in the cooking. It is shown that in whatever way meat is cooked, there is much loss of weight, amounting either in boiling or in roasting to a fourth or even a third of the original weight. This loss is partially proteid and fat, but consists still more largely of water. The loss of water appears to be caused partly, at least, by the hardening and consequent contraction of the muscle fibre, the water being mechanically forced out. An interesting experiment has been tried in regard to the effect of salt in preventing or accelerating the losses in meat. A salt solution was prepared, having the same density as that of the juices of the meat, and a piece of meat was boiled in this. It was found that a very small amount of the juices of the meat were lost in the water and practically none of the salt penetrated MEAT 71 into the interior of the meat. The conclusion drawn was that very Httle interchange of the water and the meat juices could take place unless the medium in which the meat was cooked was either less or more dense than the meat juices themselves. Meat does not form a cheap source of proteid food, but the cost can be lessened very much by care in selecting the cheaper cuts. As a rule these cheaper parts need longer cooking than the more expensive tender cuts, and, as has been suggested before, the fuel must be taken into account in estimating their cost. Where the cheapness of the meat is not counter- balanced by the additional expense of the fuel a great variety and a satisfactory diet may be obtained with only the occasional use of the more expensive portions. As has been said, the nutritive value of the cheaper parts is as great as that of the more tender portions. The nutritive value of meat soups, broths and ex- tracts has been much discussed. Often in estimating this value too little allowance has been made for the method used in preparation. A clear soup contains a very small amount of real food. Its value lies in the extractives that give it flavor, and in the small amount of gelatin that it contains, and in its power to stimu- late the flow of the gastric juices, and so whet the appetite rather than satisfy it. The meat from which such a soup has been made still contains a large por- tion of its nutritive value, and although because of its lack of flavor it cannot be used as it is, it may be Cost of Meat Soups and Broths Extractives y2 FOOD AND DIETETICS Extracts of Meat Beef Juice . Nutritive Value and Digestibility made palatable and attractive by the addition of spice or seasoning, or by its combination with a small por- tion of fresh meat. Unless large quantities of soup are made, it ought to be possible, in the ordinar}^ household, to utilize the soup meat in some way. The commercial extracts of meat are similar to clear soup in that they contain practically nothing but the extractives. A more nutritious broth may be made if the meat, cut in small pieces, is allowed to soak for some time in cold water and then is heated to a low temperature, not above i8o degrees Fahren- heit, and kept at this point for some hours.* Toward the end of the process the broth may be brought to the boiling point for a few minutes in order to dissolve all the gelatin possible. The brown flecks of albumin that form must be served in the broth and not be strained out. Even made in this way, the value of the broth is small compared with that of meat, but it is much greater than that of the clear soup. Raw beef juice is valuable as a food. If the beef be cut small, and thoroughly pressed, a much larger amount of proteid is obtained than by any other treat- ment. The round of beef, very slightly broiled and pressed, may yield as much as seven per cent of pro- teid and four per cent of extractives. FISH One of the most natural substitutes for meat is fish. Its nutritive value is much like that of meat, al- though it contains a somewhat smaller proportion of FISH 73 proteid. It also has the advantage of being as a rule easily digested, and so is particularly adapted to the needs of a person of sedentary habits. It is probably this fact that has given rise to the false idea that fish is a particularly good brain food. As a matter of fact, it is no more a brain food than meat or eggs or any other proteid food. The cost of fish is generally less than that of meat, so that it furnishes a cheap source of the necessary proteid. The value of fish depends, however, upon nearness to the source of sup- ply much more than does that of meat, since fish de- teriorates rapidly upon keeping. For food purposes we may divide fish into white classification and fat fish ; or we may take Hutchison's classification of, (i) fish with more than five per cent of fat, such as eels, salmon and herring; (2) fish with from two to five per cent of fat, as halibut and mackerel ; and (3) fish with less than two per cent, such as cod and haddock. Fish with a small amount of fat is more easily digested than the more oily variety. Be- side the proteid and fat in the fish, we obtain a certain amount of gelatine. The sturgeon furnishes isin- glass, a very pure variety of this substance. In estimating the cost of fish, allowance must be cost made for the large amount of waste so that the price per pound tells by no means the whole story of its value from an economic standpoint. The follow- ing analysis by Miss Williams shows the waste in of Fish Variety in Diet Shell Fish 74 FOOD AND DIETETICS cooked fish as served at the table, and also the amount of nutrient present. Composition of Fish Fish Part analyzed Per cent Waste. Bones, etc. Per cent Gelatin Per cent Water Per cent Nutrients Sardines . . Whole 4.91 5.99 8 33 11.66 10.51 15.99 6.13 35.10 21. 50 31.20 6.84 42.17 61 06 67.12 53.29 65.21 63.78 67.68 46 46 61 29 53.09 69 35 79.85 61.18 77.71 65.20 52 92 Salmon . . Section 0.53 0.55 1.09 0.35 0.43 0.33 80 0.86 0.59 0.03 33.02 Trout Eels. Mackerel . . Cod. Whole Head s removed. Whole Section 24.10 33.96 24.03 19 79 Salt cod Section 25.85 Haddock .. Whole 17.64 Whiting. .. Whole 16.35 Turbot Halibut. Anterior and head. . Section 15.12 23 78 Plaice Flesh. 20 14 Soles Oysters Smelts Whole Shell contents. .... 22.02 0.74 13.06 22 29 Whole "18.86 6.38 15.56 Fish, beside being an economical source of nitroge- nous substances, has much value in satisfying the demand for variety in food. Any lack in nutrients is frequently supplied by the sauces with which it is served, and by the fat used if it is fried. It would seem to be an error from the standpoint of food values to serve a rich sauce with a fish like salmon that already contains a high proportion of proteid and a large amount of fat, but an egg sauce served with a light fish like cod or haddock has its justification, not only in the additional flavor imparted, but in the addi- tional food value. Oysters may be taken as a good type of the various shell fish that we use. The analysis of oysters shows a composition somewhat similar to that of milk, FISH 75 although they are higher in nitrogen and lower in fat than milk. Average Composition of Oysters. (Langworthy.) (Exclusive of liquid.) Water 88.3 Nitrogenous substances 6 1 Fat 1.4 Carbohydrates 3 8 Salts 1.9 When milk is seven cents a quart and oysters are twenty-five, the amount of food material purchased for a given amount differs greatly in the two. When oys- ters are fifty cents a quart they must be distinctly re- garded as a luxury, used for the purpose of provid- ing variety, and not as a valuable source of food. Oysters are one of the few animal foods that contain a large amount of carbohydrates. These are present in the liver of the oyster in the ' form of glycogen. The oyster is especially easy of digestion, but this digestibility is lessened by cooking. This is particu- larly true when the oyster is overcooked. An object- tion to the use of the raw oyster is that during the so-called fattening of the oyster, that is done in shal- low water, it may become contaminated w^ith typhoid germs derived from sewage. Some noted epidemics have been traced to this source. This simply means that greater care should be taken in the supervision of such a food supply in order that it may be protected from such possible contamination. Of other shell fish commonly used, clams have a similar composition to that of oysters, but contain Comparative Cost Digestibility Clams Lobsters 7^ FOOD AND DIETETICS Dried and Smoked Fish Cooking a tougher muscle, while lobsters and crabs are gen- erally considered somewhat indigestible because of the firmness and compactness of their fibre. The dif- ficulty here seems partially at least to be the failure to properly masticate the flesh, as is true in so many other cases, and also the difficulty of obtaining the food in an absolutely fresh condition. Dried and smoked fish deserve a place in the diet for the sake of variety, and because, since the water has been eliminated, a large amount of food material is obtained for a small amount of money. The use of cer- tain varieties of canned fish has become general. Sal- mon is perhaps the most satisfactory of these. Special care should be taken in using canned fish to remove it immediately from the can after it is opened, and to use' it within a short time. Fish that has been frozen should be cooked immediately after thawing, since it decomposes much more rapidly than fish which has not been frozen. Fish, particularly some varieties, such as cod, occa- sionally contains parasites, but these are destroyed by thorough cooking. It is essential that all fish used should be thoroughly cooked, although this does not mean that it should be cooked at a high temperature. A temperature of from i8o to 200 degrees Fahrenheit continued long enough to coagulate the proteid and render the fish opaque instead of clear, gives far more satisfactory results than boiling. As in other cooking of flesh, this principle is appar- ently violated when fish is cooked in a hot oven, or FISH 77 fried, but as a matter of fact, the violation is only true so far as the outside layers are concerned, and this sacrifice is made in order to keep the shape of the fish and to develop the flavor. Comparative Costs of Protein and Energy as Furnished by a Number of Food Materials at Certain Prices Kind of Food Material. Codfish Codfish steaks Bluefish Halibut Cod, salt Mackeral, salt Salmon, canned Oysters, "solids" (30 cents per quart) Oysters, "solids" (60 cents per quart) Beef, sirloin Do Beef, round Beef, stew meat Beef, dried ' 'chipped" Mutton chops (loin) Mutton leg Pork roast (loin). ; Pork, smoked ham Milk (7 cents per quart) . . Milk (6 cents per quart) Lobster Wheat flour Corn meal Potatoes (90 cents per bushel) Potatoes (45 cents per bushel) Cabbage Corn, canned , Apples Bananas Strawberries From Fish as Food Cost of Price per protein pound. per pound. Cents. 10 fO.94 13 .71 n 1.23 18 1.18 7 .44 10 .68 12 .55 1.5 2.50 30 5 00 £5 1.53 20 1.23 11 .77 .5 .36 25 .97 20 1.54 22 1.48 1-3 .85 23 1.65 BV2 1.06 3 .91 18 3.05 3 .27 2 .33 • ry2 .88 K .44 ■ 2^ 1.79 10 3.57 i'A 5.00 7 8.75 7 7.00 Cost of energy per 1000 calories. $0.49 .36 .59 .38 .32 .11 .13 .65 1.30 .26 .21 .16 .07 .33 .14 .25 .09 .13 .11 .09 1.24 .02 .01 .05 .02 .20 .22 .07 •22 .38 EOOS One of the most general substitutes for meat is the egg. One would at first thought expect eggs to be of much the same composition as milk, since each fur- Composition 78 FOOD AND DIETETICS White and Yolk nishes food for the growing animal, but when the different conditions are considered, the reason for the variation in this respect is readily seen. The ^g^ must contain a large amount of nourishment in the most compact form. It must furnish all the materials nec- essary for growth, but it does not need to provide for activ- ity to the extent that milk does. Consequently we find the carbohydrates wholly ab- sent, and a much larger pro- portion of solid material than is present in milk. The solids are in the form of proteids, fourteen and eight-tenths per cent; fat, ten and a half per cent ; and mineral salts, one per cent. This refers to the edible part only. The white of the ^gg contains twelve per cent of proteid, Avith practically no fat and a small amount of mineral matter, while the yolk has sixteen and two- tenths per cent of proteid and almost thirty-two per cent of fat. The greater part of the mineral salts are also in the yolk, although the sulphur that causes the blackening of the silver spoon with which we eat our tgg is chieflv in the white. (After Hutchison.) Diagram showing Composi- tion of White and Yolk of an Egg. EGGS 79 While eggs form a valuable meat substitute, it is - difficult to use them wholly in the place of meat, since it takes so many eggs to equal a pound of meat. From eight to nine eggs constitute a pound. If the eggs have the composition given and meat contains eighteen per cent proteid, it would require about twelve eggs to furnish as much proteid as one pound of meat ; and one who would have no difficulty in eating half a pound of beefsteak at a meal, would not wish to eat an equal weight of eggs. Eggs like meat need to be supplemented by carbo- hydrate material. Bread and eggs furnish a satis- factory combination as well as bread and meat. Raw eggs are usually considered more easily digested than cooked eggs, although some experiments show that the cooked egg leaves the stomach in a shorter time than the uncooked. This is explained by the state- ment that the raw egg is digested largely in the in- testine. Its failure to excite the secretion of gastric juice in the stomach makes it possible to use raw eggs in the diet when the stomach requires rest. Hard cooked eggs take a longer time to digest than Digestibility those lightly cooked, but from recent government experiments they seem to differ little in the complete- ness with which they are digested, an egg boiled three minutes having 8.3 per cent of its nitrogen undigested at the end of five hours ; one boiled for five minutes having 3.9 per cent undigested, and one boiled for twenty minutes having 4.2 per cent remaining. Eggs 8o FOOD AND DIETETICS cooked at i8o degrees Fahrenheit for five and ten min- utes respectively were totally digested in five hours. Possibly the rapidity of the digestion of the hard ■ cooked ^gg may depend on the fineness of mastication. Cost Whether eggs are to be used freely depends largely upon their price. Eggs at fifteen cents a dozen may be so used, while at fifty cents a dozen they can not be regarded as an economical source of food. MILK Milk is often called a perfect food. This is true, however, only in a limited sense. Hutchison gives five tests of a perfect food. Tests of First, such a food must contain all the nutritive a Perfect . , - Food constituents required by the body ; proteids, fats, carbohydrates, mineral matter and water. Second^ it must contain these in their proper rela- tive proportions. Third, it must contain, in a moderate compass, the total amount of nourishment required daily. Fourth, the nutritive elements must be capable of easy absorption, and yet leave a certain bulk of un- absorbed matter to act as intestinal balance. Fifth, it must be obtainable at a moderate cost. Of these tests milk meets only the first perfectly. It contains the two proteids, casein and albumen. It contains the fat so familiar to us in the form of cream and butter. The carbohydrates are represented in it by milk sugar or lactose. The mineral salts are par- MILK 8i ticularly valuable, and consists chiefly of calcium compounds, including calcium phosphate. When we come to the second test, we find a differ- ent condition. An average sample of milk contains 87 per cent of water, three and three-tenths per cent proteid, four per cent fat, and five per cent carbohydrate, with seven-tenths of one per cent mineral matter. This pro- portion is of course right for the young animal, who de- mands a large proportion of muscle-building food, but it is far from a desirable propor- tion for the adult. Remembering that the nu- trient ratio is about one to five, or to put it in another form, that the adult requires approximately five times as much carbohydrate (or its equivalent) as proteid, we see that milk must be sup- plemented by some food containing a large proportion of carbohydrate before it can adequately supply the needs of the adult. As a matter of fact, experience has taught us to use with milk such a food as bread, thus supplying the needed starchy material. The third condition is not met better than the second. At least four quarts of milk a day would be necessary for the complete nutrition of a healthy man doing a (After Hutchison.) Composition of a Glass of Milk. Proportions of Nutrients Nutrient Ratio 82 FOOD AND DIETETICS moderate amount of muscular work. Milk also is lack- ing in the bulk of unabsorbed matter that it leaves. Cost The fifth condition may or may not be fulfilled. In the city the price of milk is too high for it to be an economical source of food if used exclusively. On the other hand in the country the price of milk is often so low that this condition might be fulfilled. A comparison of the food value obtained from one pound (a pint) of milk and from that of a similar weight of some common article of food, is given, with the cost of each at prices taken from two differ- ent sections of the country: Comparative Food Value of Milk lb. of milk fui'iiislies .033 lbs. proteid .01 lbs. fat .05 lbs. carbohydrate " " sirloin steak " .165 " " .161 " " no " " " eggs (8 eggs) " .131 " " .093 " " no " " bread " .093 " " .013 " " .5311bs. " " potatoes " .018 " •' .001 " " .147 " (one 60th bu.) From milk at (.01 per qt. or .02 per lb.) 1 lb. of proteid costs $ .60 " (.07 ' .035 '■ " " sirloin steak at .18 a lb. " .25 " eggs at (.15 per doz. or .10 per lb.) " (.36 " " " .21 " " ) " bread at .05 per lb. M .; .> 08 " " •' potatoes at .60 per bu. or .01 per lb. " " '• $1.20 " " " .02 " " In addition to the proteid, the money invested would have purchased, in the case of milk more than a pound of fat and of sugar ; in that of meat an equal amount of fat; in the case of bread more than five pounds of starch; in that of potatoes nearly seven pounds of 1 " " " 1.06 1.09 1.52 .76 J. 83 .51 .87 .56 1.11 MILK 83 starch ; while three-fourths of a pound of fat would be furnished by the eggs. Even at city prices milk might well be substituted to a certain extent for other proteid foods. The habit of many people of using milk simply as a beverage in addition to the food required, is perhaps responsible for the fact that many people find milk indigestible ; the difficulty lies not with the milk but with the over- abundance of food. An experiment was tried at the Maine Agricultural College on the effect of a limited and an unlimited amount of milk at the University boarding house. These experiments are reported in the Government Bulletin called Milk as Food, and the following conclusions are drawn : "First, the dietaries in which milk was more abun- dantly supplied w^as somewhat less costly than the others, and at the same time was fully as acceptable. Second, the increased consumption of milk had the effect of materially increasing the proportion of pro- tein in the diet. Third, the milk actually supplied the place of other food materials, and did not, as many suppose, simpl}^ furnish an additional amount of food without diminishing the quantity of other materials. Fourth, the results indicate that milk should not be re- garded as a luxury, but as an economical article of diet which families of moderate income may freely purchase as a probable means of improving the char- acter of the diet and of cheapening the cost of the supply of animal food." A Food Not a Beverage An Economical Food 84 FOOD AND DIETETICS Chart of the Pecuniary Economy of Milk and Other Foods at Given Prices Frotein- CarlMliyaraRs Fuel value. MILK 85 We may conclude that while it would not be econom- ical to obtain our total food supply from milk, it is good economy to use it freely in connection with other foods to furnish part of the proteid of the diet. The digestibility of milk varies very much with the method in which it is taken. If a small amount of liquid rennet or of the junket tablets so commonly found in the market, be added to a portion of warm milk, a thick clot forms. This is similar to the process that takes place in the stomach after milk has been swallowed. Milk properly, then, so far as its diges- tion is concerned, is a solid rather than a liquid food. Its digestibility depends largely upon the way in which this clot is formed. If the milk be swallowed rapidly, so that the rennin acts upon a large mass at once, one large clot is formed. If, on the other hand, the milk be sipped slowly, or eaten from a spoon, the action is slower and the curd is broken. The same result in a more marked degree is obtained by the addition of certain substances, such as lime- water, to the milk ; or by the mixing of the milk with bread, as is done in eating bread and milk. Some peo- ple who cannot use milk in its ordinary form have found that they could digest it without difficulty if a cracker were rolled into fine crumbs and stirred into the milk. The digestive juices that would act slowly upon a large mass of curd, act readily upon the same amount when it is broken into small clots. Boiled milk has generally been considered less diges- Digestibility Addition to Milk 86 FOOD AND DIETETICS Boiled Milk Buttermilk Koumiss Skim-milk tible than uncooked milk, but some experiments seem to contradict this. The experiment station bulletin states that when cow's milk has been boiled before it is taken into the stomach it is likely to be precipitated in a more floculent form. Hutchison says that it has been found in the case of infants and calves that ster- ilized milk which has been kept at or above the boil- ing point for more than an hour is absorbed quite as well as milk which has merely been boiled in the usual way, and he concludes that boiling does not appreciably diminish the digestibility of milk. On the other hand, the government bulletin states, after acknowledging that the results of experiments upon the subject are conflicting, that ''the more com- mon experience seems to indicate that cooking or heat- ing the milk makes the proteids somewhat more difficult for most persons to digest, but there are ex- ceptions to this rule, if it be a rule, for there are per- sons who cannot take fresh milk with comfort but with whom boiled milk agrees very well." In this case as in many others we must wait for a larger number of experiments to be made before we can make very dogmatic statements. Buttermilk is considered an especially digestible form of milk, while koumiss or fermented milk is of still greater value in this respect. Skim-milk deserves more general use than it has, since the proteid of the milk nearly all remains in this, and it is for the proteids MILK 87 that we especially value the milk. Where skim milk is sold at a low price, it is economy to use it freely in cooking, supplying the needed fat in a- less expensive form than cream. The Composition of Milk The composition of milk has already been stated in Casein a general way. If we examine it more in detail, we find that the proteids of milk consist chiefly of two: casein or, as it is sometimes called, caseinogen. This forms about three per cent of the total of the milk. It is held in solution more or less completely by the salts of lime present in the milk. When acid is added to the milk, or it becomes sour, this casein is precipitated. When rennet is added the casein is coagulated and is changed in chemical composition. The scum that forms upon heated milk is chiefly casein. The other proteid present in milk is lact-albumen. Lact This coagulates when the milk is heated for a long time. It is present in much smaller amount than the casein, forming only about one-seventh of the total proteid of the milk. The sugar of the milk, forming between four and five Milk per cent, is called lactose or milk sugar. It has two important characteristics. It lacks the sweetness usu- ally associated with the name of sugar, having only a very slight sweet flavor, and it is considered the most digestible form of sugar, apparently fermenting in the Albumen Sugar FOOD AND DIETETICS Fats Mineral Matter stomach or intestines with much less ease than do other sugars. For both of these reasons it is particu- larly suitable for the use of infants or invalids. The commercial article is obtained from milk, and is sold in the form of a fine white powder looking not unlike pulverized sugar. Aside from its use as a food it is extensively used in the preparation of pills. The fat of milk is present in the form of an emulsion. If one looks at a drop of milk through the microscope one s.ees a large num- ber of tiny fat globules. That the fat is so fine- ly divided is a factor in its digestibility, though fat derived from milk, either in the form of cream or butter, is also considered particularly digestible. The mineral matter of milk consists largely of potash and lime salts, and of these salts the phos- phates are the most abundant. These are important, not only in the building of bone tissue, but also, as has been suggested before, in holding the casein in solution. r^^ Fat Globules of Milk Magnified 200 Times. a Skim Milk. b Whole Milk. c Cream. MILK 89 Water forms about 87 per cent of milk, and its chief water use in this form is in holding other materials in solu- tion. To compare milk with other foods, we should properly think of the solid ingredients alone, since the water has no more food value than water in any other form. Milk readily undergoes many changes, some of them Souring harmless and some more or less harmful. The most common change is that of souring. Bacteria present in the milk act upon the sugar and change it into lactic acid. After a certain amount of this acid has been produced, the growth of the bacteria is stopped, and no further change in the sugar takes place, though undoubtedly certain other changes take place both in the fat and in the proteid. There is no evidence that sour milk is unwholesome, use of The objection to it seems to be chiefly one of taste. Its m°iJ use in cooking produces good results, and many pre- fer it for some purposes to sweet milk since it seems to produce a more tender product than does the sweet milk. On the other hand, milk may under the action of certain bacteria produce most harmful products, and poisoning from these ptomaines is not uncommon where milk has been handled in an uncleanly manner and has been poorly cared for. A more serious dan- ger from milk is that owing to the excellent food it furnishes for almost all bacteria, it is frequently a carrier of disease. Disease germs that in water would not multiply and would probably live only for a short 90 FOOD AND DIETETICS Pure Milk Care of Milk Condensed Milk time, multiply abundantly in milk. It is because of the possibility of the presence of these harmful bac- teria, rather than from any danger from sour milk, that we guard our milk supply carefully. Each hour that elapses between the milking of the cow and the use of the milk by the consumer, increases the num- ber of bacteria present. One cubic centimeter of milk frequently contains from 400,000 to several million bacteria. Efforts to guard the milk supply have been directed in two ways. The sterilization or pasteurization of all milk is often recommended; but a more satisfactory method would seem to be the insuring of cleanly con- ditions upon the dairy farm where the milk is pro- duced. The next essential after cleanliness is that the milk should be cooled rapidly when first milked, since the lower temperature makes the fluid less favorable for the growth of germs. In the household milk should be kept in perfectly clean vessels, and should be loosely, not tightly, cov- ered, in order that there may be access of air to it, since the absence of fresh air favors the growth of certain putrefactive organisms. The entirely open vessel is only allowable in perfectly clean surround- ings, not only free from dust, but with no strong flavoring substance near from which odors could be absorbed. One form in which we often get milk is that of evaporated or condensed milk. This is simply milk MILK 91 from which most of the water has been removed, and which has been made sterile by heating to a high tem- perature. It has usually been sweetened, and the sugar acts as a preservative. \Miile it is a convenient form for use when fresh milk is not obtainable, its large amount of sugar renders it somewhat undesirable as a common article of diet, and also makes it unfit for many cooking purposes. There is being put upon the market now milk powder that seems to consist chiefly of the curd of the milk dried and ground. \Mth the addition of water it forms a very fair substitute for milk. Milk is perhaps more often adulterated than any other common article of diet. The most common form of adulteration is that of skimming or removing part of the cream. This can easily be detected, because it increases the specific gravity of the milk. To coun- terbalance this, water, which is slightly lighter than milk, is added in such proportion that the twice adul- terated milk gives the same test as if it had not been tampered with at all. Another adulteration that is sometimes practiced is that of adding coloring matter to the milk. This is usually done in order to conceal the blueness of the milk, when it has been watered. Preservatives are frequently used. Of these boric acid is probably the least harmful, though some au- thorities contend that formaldehyde in the minute quantities in which it is used has no physiological Milk Powder Adulteration Preservatives 92 FOOD AND DIETETICS effect. A milk that will stand in a warm place for some hours and show no tendency to sour is open to the suspicion of having* been treated in some such way. Ordinary cooking soda is sometimes added to neutralize the acidity that may be present because of the age of the milk. Salicylic and benzoic acids are sometimes found, while formaldehyde is used most of all. MILK phoducts Butter The importance of milk is hardly greater than that of its two chief products, butter and cheese. Butter consists chiefly of the fat of the milk with a small amount of water, of casein and of salt, with sometimes a little milk sugar. The average amount of fat con- tained is 82 per cent. The fats which are present may be put into two classes : Those derived from the so- called ''fixed" fatty acids, and those from the volatile fatty acids. The fixed fatty acids are present in the form of stearin, the chief ingredient in beef fat, and of palmitin and olein. The amount of the volatile acids present differentiate butter from most of the other fats that we commonly use as food. The flavor of butter is produced apparently by the action of bacteria upon the cream, the different flavor of butter at different times of the year coming largely from differences in the kind and amount of bacteria that find their way into the milk. The "ripening" of the cream is often induced by artificial cultures of the proper bacteria. Many buttermakers abroad and in BUTTER 93 some sections of our own country, depend entirely upon these bacterial cultures for the production of their butter flavor. The rancidity of butter may be produced by changes taking place in the casein that is present, or from a decomposition of the fats themselves. Cooking les- sens the digestibility of butter as it does that o-f other ^ats, probably because of the decomposition that takes place when fats are subjected to a high temperature, and the consequent freeing of irritating fatty acids. The adulteration of butter consists chiefly in a sub- stitution of other substances, either in whole or in part, for the butter fat, or of an inferior and ''doc- tored" article. The coloring of butter is almost univer- sal, but it is so generally accepted that it can hardly be classed as an adulteration, although it surely shows a false standard in foods when we insist upon buying a deep yellow compound colored with annatto or some other foreign m.aterial instead of the delicate straw- colored substance that most natural uncolored butter is. The substitutions spoken of are chiefly either what is called renovated butter, or oleomargarine. Reno- vated butter is made by taking different lots of stale or rancid butter, melting it, allowing the curd to settle, and re-churning the fat with a small amount of milk. The product is certainly better than the rancid butter, but it cannot compare in flavor and in wholesomeness with fresh butter, and certainly should not be sold as such. Changes Adulteration Renovated Butter 94 FOOD AND DIETETICS Butterine Oleomargarine, or biitterine, is made by clarifying the fat of beef and churning it in milk. It differs from butter in its composition in that it contains practically no curd, and is lacking in the volatile fatty acids that are present in the butter and character- istic of it. It is a cheaper product than butter, and the temptation to put it upon the market under the name of butter has consequently been great. There is absolutely no reason, however, why, sold under its own name, it should not be a very general article of use. There seems nothing to show that it is materially less digestible than butter itself; it does not grow rancid with the ease that butter does, and it is made in a perfectly cleanly and wholesome way, certainly so far as the best quality of it is concerned. Even if it is artificially colored, this is no worse than is true of butter. The difference in taste between it and butter is rather in an absence of the aroma that we find in the best butter, than in any disagreeable flavor present. Indeed, although each person thinks to the contrary in regard to himself, few people are able to distin- guish it from butter by taste. It may be used in almost every way as a butter substitute. It is perfectly satis- factory to use in the making of sauces or upon vege- tables or meat. It does not make so light a cake as butter, and is not satisfactory for this purpose, except that in a plain cake it may be substituted for part of the butter ; and it cannot be used in candy making as, for some reason, it fails to combine with the other CHEESE 95 materials and always separates out upon cooling. ^ Since it is so much cheaper than butter it would be well to use it as a substitute for part of the more ex- pensive material. The present law in regard to it has lessened its sale to a great extent since it can no longer be artifi- cially colored, but.it is certainly only prejudice that prevents our accepting a pure white fat instead of a bright yellow one. Cheese, so far as nutritive value is concerned, stands cheese almost at the head of our list of foods. Since it is made from the curd of the milk, and the water has largely been disposed of in the whey, while the fat is carried down with the curd, we have the most im- portant part of the milk solids in a condensed form. The composition of the different varieties of cheese varies to quite an extent, but in a rough way w^e may say that cheese is one-third proteid, one-third fat and one-third water. Alineral salts are abundant as well, while a small amount of milk sugar is sometimes present. Cheese is prepared by the addition of rennet to cheese milk. Coloring matter is generally added, and salt. Makmg After the curd has set, it is cut in small pieces and the whey allowed to drain off. The curd is then put into a press and allowed to remain for a few hours. After this the real curing or ripening of the cheese begins, and this process is allowed to go on for months in order to develop the flavor. This flavor is produced 96 FOOD AND DIETETICS Digestibility Effects of Cooking by the action of bacteria, different varieties of bac- teria giving us the different flavors of the various kinds of cheese. While there is no question as to the nutritive value of cheese, there is more doubt as to its digestibility. In many countries cheese is used largely as a substi- tute for meat, and wherever it can be digested this is certainly a rational thing. Some people who have delicate digestions have no difficulty in digesting cheese, while others find it an extremely indigestible food. One difficulty seems to be that the cheese is frequently not chewed enough, and the digestive organs have to cope with lumps of the material. Cheese generally proves more digestible if it is finely divided and mixed with some starchy material like bread crumbs or macaroni. Another factor in its digestibility is the temperature at which it is cooked. Like all proteid foods, it is toughened and hardened by a high temperature. This is very evident in the case of such a dish as a Welsh rarebit, where over-cooking produces a tough, stringy, most indigestible mass. In combining cheese with such a dish as macaroni it is well not to allow the cheese to be at the bottom or the top of the dish, but to protect it from the high tem- perature by putting it between the layers of starchy material. Matthieu Williams, in his chemistry of cookery, suggests the use of a little bicarbonate of potash, the old-fashioned salaratus, to make the cheese more CHEESE 97 soluble and therefore more digestible. Sometimes after the cheese has become tough from the action of too high a temperature, it may be again made soft by the addition of this substance, or of baking soda. Hutchison suggests that the disagreeable effect that cheese has upon some people may be due to small quantities of fatty acids produced in the process of ripening. The philosophy of the use of cheese at the end of a dinner seems to be that the cheese in small quantities aids the digestion of other foods, even though it is not always easily digested itself. Wher- ever, then, cheese can be used and digested without difficulty, it forms an excellent article of food, one that should be used more freely than is done at present. 98 FOOD AND DIETETICS Importance CEREALS AND THEIR PRODUCTS The most important of all our vegetable foods are without doubt cereals. Not only do they contain a large amount of nutriment, chiefly, but by no means wholly, in the form of carbohydrates, but their areas of growth are widely distributed, and their power of adaptation to different climates and conditions is usu- ally great. This alone would render them exceedingly Bar PROBABLE NATIVE HOME OF THE GRAINS. (From Corn Plants By Fredric LeRoy Sargent.) important as food for the human race. Of them all wheat is undoubtedly the most important from its wide distribution and its power of adaptation to different conditions. Rice follows closely in importance, while corn, oats, rye, barley and millet each have an impor- tant place in the food of the world. The home of the CEREALS 99 cereals seems for the most part to have been Central Asia, nearly all, except rice and corn, originating there. Corn is supposed to have originated in Mex- ico. From these centers their production has spread through all parts of the vi'orld. A comparison of the composition of some of the different cereals in forms commonly used is given in the following table: Composition of Cereals. Wheat flour (entire) . . Cornmeal Oatmeal Rye flour Barley meal and flour Barley (pearled) Rice. Per Cent Per Cent Per Cent of of of Carbo- Water. Proteid. hydrate. 11.4 13.8 71.9 ' 12 5 9.2 75 4 7.3 16.1 67.5 12.9 6 8 78.7 11.9 10 5 72.8 11.5 8.5 77.8 12.3 8. 79. Wheat derives its special importance from the fact that it will grow in so many different climates and under so many varying conditions. It may be sown either in the fall or in the spring, and receives its name of winter or spring wheat, according to the time of the planting. Many varieties are found, such as red wheat and white wheat, hard and soTt w^heat. The hard wheats contain a larger proportion of gluten, and therefore a smaller proportion of starch than do the soft wheats. Wheat from which macaroni is manufactured, is an exceedingly hard variety. Suc- cessful attempts have been made within a few years to grow macaroni wheats in this country, and much of it is now produced in Dakota. Though hard wheat is Composition Wheat Varieties LOFC THE PRINCIPAL GRAINS. (Redrawn from Coi'n Plants.) CEREALS lOI used chiefly for making pastes like macaroni, excellent bread can be made from it also, as is shown by ex- periments made at the So, Dakota Agricultural Col- lege. Winter wheats as a rule are softer than spring wheats. So- called pastry flour is made from the softer wheats. Much of our bread flour is now made from mixtures of winter and spring wheat, and great care is exercised in the combining of these in order to keep an even standard. The process of manufacturing flour is carried out differently by different manufacturers, so far as its details are concerned, but the main features are the same. The wheat as it comes to the mill is first of all cleaned, by screening to get rid of any large foreign substances that may be present in it, and by "scouring" to get rid of the fine dirt that may adhere. The next process is that known as breaking. The wheat is cut by corrugated iron rollers provided for the purpose. There are generally five breaks in all. Each ''break" is put through a number of siftings. The meshes of the bolting cloth through which this sifting is done are graduated in size, and the products accordingly vary in Section of a Grain of Wheat. From a Maine Exp. Station Bulletin. Flour Bolting 102 FOOD AND DIETETICS Scalping Mixing and Testing fineness. The finest particles are calbd the dustings, the coarsest are the scalpmgs, while between these are the middlings, — germ, medium and fine. The scalpings from the first break undergo a second breaking and are again separated by sifting as in the first break, SECTIONS OF A WHEAT GRAIN SHOWING THE STRUCTURE AND DIFFERENT PARTS. (From Original Drawings.) and this process continues through all the breaks. The flours on the market are made from mixtures of the products of the different breaks. When a flour is mixed it is tested by making a portion of it into a small loaf and baking it, and comparing this loaf with that made from some standard flour. The scalpings from the last break constitute the bran. This is al- CEREALS ro3 most wholly cellulose and is therefore not digestible by human beings, but much of the so-called graham flour on the market is simply a mixture of white flour with some of this bran. Whole wheat flour is made by grinding the entire kernel of wheat. The outer coating of cellulose is thus divided into exceedingly small particles, so that it is less irritating to the digestive organs than when used in the form of large pieces of bran. There is little difficulty today in obtaining good flour, but the diflferent brands vary in composition, and so do different lots of the same brand, in spite of the effort to keep them constant. This means that a different treatment must be used. It is well, then, in the household, to experiment a few times with a new lot of flour before condemning it as poor and return- ing it. Some false standards have been set up in regard to flour. The best bread flour is not pure white, but yellowish in tint. It readily retains the impression of the fingers, if a little is pressed together in the hand. It always has a slightly gritty feeling, while pastry flour is much smoother and more velvety to the touch. Within a few years the use of cereals as breakfast foods has become general. W'e have now not only the standard meals, which have been used for a long time, but a multitude of patent preparations as well. The Maine agricultural experiment station found that of fifty varieties of cereals purchased in the market, only Whole Wheat Flour Standard Ereatfast Foods IG4 FOOD AND DIETETICS about twenty had been on sale for more than three years. ]\Iany of these are only new in name, or differ very slightly from those before used. Within a short time there has been added to our list of breakfast cereals many that claim to be predigested foods, and some that make absurd claims with regard to their wonderful food value, while others stand for what they are, without pretence. Probably there is comparatively little to choose be- tween different preparations of the same grain, so far as their chemical composition goes. The analysis of the uncooked food, however, by no means represents the composition of the cereal as we eat it. An analysis of boiled oatmeal, for instance, gave: Water, 84.5 per cent ; protein, 2.8 per cent ; carbohydrate, 1 1.5 per cent ; fat, 5 per cent. Comparing this with the analysis of oatmeal given on p. 99, we find only about one-sixth the per cent of nutritive material, with a correspond- ing increase of water. A cereal that would absorb a greater weight of water would show still greater varia- tion. Dipestitiiity The digestibility of the cereals is influenced by the of Cereals coarseness of the particles. The coarser foods are highly desirable in many cases, especially where a slug- gishness of the intestines exists, and in other cases are very irritating to the delicate lining of stomach and intestine. Individual needs must determine the use of each. Most of the cereals, even those that are steam CEREALS 105 cooked, need much more cooking than is ordinarily coSing^ given them in order to sufficiently hydrate the starch. Of the foods supposed to be ready to eat, it is difficult to speak definitely, for lack of careful experimentation. In most of them a certain proportion of the starch has been converted into dextrin and sugar. Two questions arise in regard to this. Has the starch been sufficiently changed so that it no longer is indigestible as uncooked starch ; and is it desirable to have the starch digested? There seems to be a tendency in our modern life to depend too largely upon predigested foods, particularly in the case of children. This means a tendency toward the lessening of the power to digest. It is certainly a question whether it is not best to take our starch undigested but in such a form that it can be easily acted upon by the digestive juices, rather than to have the work done outside the body. io6 FOOD AND DIETETICS History Kinds of Bread BREAD Bread was one of the earliest foods of man. That it was used long before history was written, the discover- ies of modern times have shown us. In Switzerland, in the lake dwelling's of prehistoric times, there have been found not only stones for grinding meal and bak- ing bread, but even bread itself, in the form of round cakes. The first mention of bread in literature is in Genesis, in the words of Abraham to the angels, 'T will fetch a morsel of bread." The Egyptians knew the art of breadmaking, and baked loaves and cakes in great variety of form and flavor. One ancient Greek writer names sixty-two kinds of bread in use ; and in Rome there were many bakeries, where not only was the baking of bread done, but the grain was pounded and sifted, to prepare it for use. In our own day bread is found in a great variety of forms, many of them characteristic of certain nations; familiar examples are the black bread of Germany, the oat cakes of Scotland, the hard rye cakes of northern Sweden, baked only twice in the year, and the passover cakes or unleavened bread of the Jews. Bread forms the staple food of a large section of the human race, and is often the only means of subsistence of the very poor. Mr. Goodfellow, in some investiga- tions made in London, found that in the worst districts fifteen per cent of the children ate only bread for the BREAD 107 twenty-one meals of the week, while forty per cent ^ more had other food only two or three times a week. It is essential that so universal a food should be nu- %°ll^ tritious, palatable, and digestible. To fulfil these con- ditions, the flour used must be rich in nutriment; the bread must be light and pOx'ous, that as large a surface as possible may be exposed to the digestive juices; and the cooking must develop the flavor, and render the food materials assimilable to the greatest possible extent. The necessary ingredients of bread are flour of some variety and liquid for moistening it. Salt for flavoring is required by almost every one, and to most of us the term bread implies some agent for light- ening the dough. Wheat is the flour most commonly employed not wheat only because of its widespread growth but because of the presence in it of the proteid called gluten, or morj strictly speaking, of the proteids that upon the addition of water form gluten. Gluten is an important aid in the making of bread light in that being an elastic tena- cious substance it retains the gas as it is formed in the dough. In the process of cooking, the gluten hardens and thus enables the loaf to retain its shape. This function of gluten may be compared to that of soap in the water from which soap bubbles are blown. If some gluten be prepared from flour, as in the ex- periment on page 41, and baked, the value of this sub- stance in lightening the dough will be appreciated. Bread io8 FOOD AND DIETETICS other Breads Of the other cereals, rye makes the lightest bread as its proteids form with water a sticky substance not so elastic or tenacious as the gluten of the wheat, but sufficiently so as to retain much gas. Corn flour, however, makes only a flat and crumbly loaf unless tgg be added to increase the elasticity of the dough. The most desirable bread flour is one rich in gluten. Leavening Agents DIAGRAM SHOWING COMPOSITION OF A LOAF OF BREAD. (After Hutchison.) Even very hard macaroni wheat may be made into excellent bread as has been shown at the South Dakota Agricultural Experiment Station. If a flour poor in gluten and rich in starch is to be used a stiffer dough must be made than with the opposite conditions. In spite of the efforts of the manufacturers to maintain a constant standard in flour each barrel varies somewhat, and slightly different treatment may be needed. Many different agents for lightening the dough have been used at various times. The ancient leaven was made by allowing flour and water to stand in a warm BREAD log place till it fermented. Part of this dough was used to start the fermentation in a new mixture of flour and water. In some sections of our own country "salt rising" bread is commonly used. In England aerated bread, made by forcing carbon dioxide under pressure into the dough, has been advocated and used to some extent. The most common method of lightening the loaf, in Yeast 1 • 1-1 r -xr Bread this country at least, is by means of yeast. Yeast comes into the household in three forms, that of liquid yeast, compressed, and dried yeast. The last is most often used by those too far from the source of supply to obtain compressed yeast in good condition. It makes satisfactory bread, but the process is a long one, as time must be allowed for the dry yeast to take up water and renew its life processes. Liquid, or home brewed yeast, prepared usually from potato with the water from a few hops, frequently with the addition of sugar and flour, and the whole fermented by means of the addition of a "pitching" yeast, is much less used than formerly. Aside from the trouble of preparation, it is open to the disadvantage of usually containing many bacteria and wild yeasts. Many think, however, that the fine texture and delicious flavor of old fash- ioned home made bread was due in part to the use of this yeast. Compressed yeast is a by product of the distillery or compressed the brewery. It is skimmed from the top of the fer- Yeast no FOOD AND DIETETICS Chemical Process Methods of Making meriting liquor, is washed, strained, mixed with a small amount of starch and pressed into large cakes. At the distributing centers it is cut and wrapped in foil and sold for one or two cents, according to locality. It is, on the whole, the most satisfactory yeast to use in bread making, though it is rarely, if ever, free from the bac- teria that cause the souring of bread when conditions are right for their growth. The changes that take place in the process of bread- making are largely those of fermentation. Some of the starch of the flour is changed to sugar, and the sugar is broken up into alcohol and carbon dioxide. If the fermentation goes too far the alcohol is changed to acetic and other acids and the bread becomes sour. Yeast is not the sole agent working; bacteria and not yeast are responsible for the souring, while the change of starch into sugar is probably accomplished by bac- teria or some enzyme (ferment) present in the flour. Chemical changes, such as the change of some of the starch into dextrin and some of the sugar into cara- mel, which takes place especially in the crust of the bread, are caused by the heat of the oven, while the same agent is responsible for the driving off of the alcohol and carbon dioxide present. A few years ago bread was almost invariably made by what is called the long process. A small amount of yeast was used and the bread was allowed to rise over night. Now more often the bread is set in the morning and the whole process is carried through in six hours. BREAD III The advantage of the latter method is that it makes it possible to watch the process and regulate the temper- ature more carefully than can be done if the bread is set at night. As temperature is an important factor in the growth of the yeast, too low a temperature hinder- ing its growth, and too high a temperature favoring the growth of the acid producing bacteria, this is a distinct advantage. The most favorable range of temperature is from 75 degrees to 90 degrees F. On the other hand, the long process produces a loaf of a texture preferred by many, and some ex- periments tend to shov^ that it may be slightly more digestible. There has been- discussion for many years over the Graham comparative value of graham, whole wheat and white wheat Sr^ead bread. Several years ago graham bread was urged upon every one as the only satisfactory bread. After a time the conclusion was reached that the coarse par- ticles of the graham flour were too irritating to the in- testinal wall, and its use was discouraged except where this very irritation was desirable, as in case of consti- pation. Then came the era of whole wheat bread, show- ing like the graham a high percent of nutriment. At one time it seemed to be considered almost a crime to use any other bread than this. The presence of phos- phates in larger amount than in white flour and the higher proportion of proteid seemed a sufficient reason for encouraging its use by every one. The latest government investigations have proved 112 FOOD AND DIETETICS White Bread More Nutritious Combinations with Bread that this was a false assumption. While from the chem- ical standpoint it is true, from the physiological one it is not. Less of the material of whole wheat bread is available for use in the body, or in other words, a larger proportion is excreted in the feces than in white bread, so that whole wheat is not superior to white bread in real nutritive value. It is hurried through the intestines more quickly and thus given less chance for absorption than is true of the white bread. The phosphates are so closely attached to the outer cellulose wall that they probably do not furnish any more ma- terial to the body than is obtained from bread made of white flour. Although bread contains a fair proportion of proteid, about 9.2 per cent, it has too little proteid, too little fat, and too large an amount of starch to form in itself a perfect food. Instinctively we supplement it with these lacking ingredients. We use butter on our bread, we eat bread with meat, or we combine it with milk. In either case we are supplementing it admirably. Eggs, too, contain the lacking fat and proteid. Nuts eaten with bread and cheese so much used in many countries have scientific sanction. Good bread is one of the cheapest, most nutritious, most easily and completely digested of all foods and well deserves its title the ''Stafif of Life." SUGAR 113 SUGAR AS FOOD ]\Irs, Abel, in the government pamphlet Sugar as Food, calls attention to the fact that the consumption of sugar is everywhere increasing. In England eighty-six pounds per capita and in the United States sixt3'-four pounds per capita were consumed in the year 1895. This means simply the sugar that is manu- factured in this form, and does not include that taken in the form of various fruits and vegetables. The desire for sugar seems to be universal, and the fact that children always crave it would seem to be an indication that it is needed in their diet. On the rther hand, we must remember that the manufacture of sugar is comparatively a late matter, and that earlier, a hundred years or so ago, people got along without it except as naturally present in their foods. in using sugar it must be remembered that it is a highly concentrated food, and that it is therefore not to be used in such large quantities as would be right m the case of foods containing a large amount of w^ater. It seems best fitted for assimilation by the body when it is diluted or used with other foods that give it the necessary bulk. It is also an error to use sugar, as is so often done, w^ith other foods in such a way or in so large an amount as to disguise the natural flavor of these foods. One of the advantages of sugar is that it passes quickly into the circulation, so that the energy obtained Consumption Concentrated Food 114 FOOD AND DIETETICS Sources of Sugar Glucose from it is available in a very short period. It is par- ticularly fitted for food in cases of exhaustion. The bad effects of sugar are ascribed by Mrs. Abel to its use in too great quantity. Three or four ounces a day can be disposed of by the healthy adult with impunity. It has generally been thought that sugar is injurious to the teeth, but this also is denied. Any bad effects of this kind are due not to sugar in the diet, but to the allowing particles of sweet food to re- fer acid fermentation and possible injury to the teeth. The source of most of the sugar used until a few years ago was the sugar cane. Now over half of the sugar used in the world is obtained from the sugar beet. In 1904, only about 10 per cent of the sugar used in the United States came from the sugar beet. There has been an impression that beet root sugar is less satisfactory for many purposes than the cane sugar, but it is identical chemically. It may be true in some cases that the beet root sugar has not been completely purified, and that these impurities give an odor to the sugar upon boiling, and possibly affect some of its uses ; but the properly prepared sugar may be used in every way that sugar from the sugar cane may ; indeed, it is impossible to distinguish between them. Another sugar of which we hear a good deal is glucose. This has been made much of as an adul- terant, particularly of candy. There is, however, no reason to think that glucose is less digestible or less SUGAR II easily assimilated than cane sugar. Indeed, it is more nearly ready for assimilation. When we boil sugar for any length of time in the presence of an acid, we change a certain amount of the sugar into glucose. Candy that will stretch we may be sure contains at least some of its sugar in this form. If glucose is pure and properly prepared there is no reason to fear it as an adulterant of candv. The cheap coloring matter and flavors that are used in some of the cheap candies are more to be feared, since some of them are harmful. It is possible that since glucose goes so rapidly into circulation it may overload the system more readily than would plain sugar, and it is more easily fer- mented. Maple sugar, regarded as a delicacy, is simply cane sugar plus the flavoring matters found in the maple tree. ]\Iilk sugar is generally considered, the most easily digested form of sugar and it less easily under- goes fermentation. Cane sugar is on the market in various forms. Ordinary powdered sugar is, of course, the same sub- stance as granulated sugar, but more finely ground. This is often considered adulterated because it is less sweet than the granulated form, but the lack of sweet- ness is due to the finely divided condition. A very simple test will serve to show the presence of adulter ants since these would probably be either some form of porcelain clay, or starch. If the sugar dissolves in water neither of these can be present. Maple Sugar Powdered Sugar ii6 FOOD AND DIETETICS Molasses Effect on Diet of Use of Sugar The brown sugars that we use are simply cane sugar that has not been decolorized, or has been only par- tially so treated. Molasses formerly was obtained as a bi-product in the manufacture of sugar, and was the part of the sugar-cane juice that would not crystallize, containing a large per cent of glucose. With modern methods of work and with the coming in of beet sugar, whose molasses has such a strong flavor that it cannot be put upon the market, a manufactured molasses came into use. The commercial molasses of the present day is frequently glucose, prepared from starch, colored and flavored with a small amount of molasses from the sugar factories. Sometimes the light molasses has been bleached, and the bleaching agents, unless completely removed, may be injurious. Sorghum molasses is also used in some sections. One comparison in regard to the addition of sugar to the diet may be interesting. In the case of milk, it has been found that an addition of this in any large amount to the diet means a corresponding decrease in the amount of other foods used. This seems not to be true of sugar. When sugar is furnished freely in abundance, it does not decrease the use of other foods, but sometimes by adding to the flavor of these actually increases thier consumption. On the other hand, the desire for sugar often marks an inadequate diet. TEST QUESTIONS The following questions constitute the "written reci- tation" which the regular members of the A. S. H. E. answer in writing and send in for the correction and comment of the instructor. They are intended to emphasize and fix in the memory the most important points in the lesson. FOOD AND DIETETICS PART II Read Carefully. The following- U. S. Government Bul- letins should be read in connection with this lesson: No. 34, Meat Composition and Cooking-; No. 85, Fish as Food; No. 128, Eg-g-s and their Use as Food; No. 74, Milk as Food; No. 112, Bread and the Principles of Bread Making-; No. 93, Sug-ar as Food, These may be obtained free by addressing the Department of Ag-riculture, Washing-ton, D. C. Place your name and address on the first sheet of the test. Iveave space between answers. Make your answers full and complete. 1. What is the relative value of animal and vege- table foods? 2. What are the chief nutrient ingredients of meat? How may the presence of some of these be shown? What reasons are there for cooking meat? 3. Compare clear soup, beef broth, and beef juice as to their nutritive value. 4. What meat substitutes may be used in the daily diet, and how does their value compare with that of meat? 5. In what ways does milk satisfy the require- ments of a perfect food? How does it fail? 6. What is the approximate composition of milk? Under what conditions is its free use econom- ical? 7. Give the composition of butter. How does cooking affect its digestibility? 8. What is renovated butter? How may oleomar- garine be used and how does it compare with butter in wholesomeness? 9. Describe the process of cheese making. POOD AND DIETETICS 10. What is the food vahie of cheese? With what foods should it be combined? 11. \M'iat can you say of the value of the cereals as" food? 12. If scales are available weigh out a portion of rice (about ^ cup), boil, and weigh again. If the scales are not at hand, measure the rice carefully, before and after cooking. How does the composition of the cooked rice differ from that of the uncooked? Repeat the experiment with a potato and compare results. 13. Why is wheat so extensively used? What is its especial value in bread making? 14. What are the chief steps in the manufacture of flour? 15. What are the tests for a good flour? Why is a flour high in gluten desirable for bread? 16. AMiat are the characteristics of good bread? 17. Compare the nutritive value of whole wheat and white bread. When is graham bread valu- able? 18. What kinds of yeast are in common use ? What are the advantages and disadvantages of each? 19. State the chief changes that take place in the process of bread making and baking. 20. W^hat is the value of sugar as food? How does beet sugar differ from that obtained from the cane? What can you say of the adulteration of sugar? 21. Ask one or more questions on this lesson. Note. — After completing' the test, sign your full name. FOOD AND DIETETICS PART HI VEGETABLES An increasing importance is coming to be attached to the use of vegetables and fruits in the diet. Not only vegetarians but many others have found from experience that it is possible to live largely upon vege- table food, while those who use meat freely lay great stress upon the vegetable accompaniments whether in the form of salads or of cooked vegetables. A study of vegetables - from the standpoint of bot- any would implv their classification according to the parts of the plant used ; whether leaf, as in the case of lettuce, cabbage, spinach ; stem, as in celer}' , aspara- gus, potato (a tuber, or underground stem) ; root, as in beet, carrot and sweet potato ; flower, as cauli- flower; or fruit, as squash, cucumber, tomato. From the standpoint of cookery the most important classification is that of strong flavored and szvcct flavored vegetables, since this modifies our method of cooking ; right methods leading us to retain all the juices of the latter as far as possible, while we legiti- mately discard part of the extract of the former. For example, green peas and string beans, young carrots, and squash, should be cooked in a small amount of water, or have the water in which they are cooked concentrated at the end so that it may all be served 119 Botannical Classification Flavor Classification 120 FOOD AND DIETETICS Nutritive Classification Cellulose of Vegetables with the vegetable ; while in the case of onions we may well use a large portion of water, and throw it away. It is true that in this latter case we may lose valuable salts and some nutriment, but these we sac- rifice for the sake of improved flavor. From the standpoint of diet a better classification would be into nutritive vegetables and flavor vegeta- bles. With the latter we should include those that contain mineral salts, but have little food value. Of this class, lettuce, spinach, cabbage, tomato and cucum- ber are types ; while rice, potatoes, peas, beans and lentils furnish examples of the former. Many vege- tables will be on the border line between the two. The composition of vegetables varies in general from that of animal foods in that here we have the carbo- hydrates largely represented. The chief carbohy- drates of vegetables are starch, sugar, and cellulose of various types. The fact that cellulose forms the framework of the plant and that it is within cellulose walls that the starch as well as the proteid of the plant are con- tained, is important in two ways. While cellulose is only slightly digested by human beings (only so little of it in young and tender plants really serving as a food that the amount may be neglected), it does have a more or less important function in furnishing the required bulk of food. If one undertakes to live wholly upon a vegetable diet, this bulk generally be- comes too great; on the other hand, one of the objec- VEGETABLES 121 tions to an exclusively animal diet is in the absence of bulk. Since the digestive juices do not act upon cellulose to any extent, and the nutritive portions of the vegetables are enclosed within walls of this sub- STARCH OF A POTATO ENCLOSED IN CELUL.OSE CELLS. stance, the province of cooking is to so change the cell wall that the nutritive materials may be set free, or the digestive juices penetrate to them. We usually speak of softening the cellulose by means of cooking. i\pparently what we really do is to dis- solve the intercellular substances that bind the walls together, and thus make it possible for the cell walls Effect of Cooking on Cellulose 122 FOOD AND DIETETICS to be mechanically ruptured, either in the process of cookery or by the pressure exerted in the mouth. Part at least of this intercellular substance belongs to the pectin group that causes the jelling of fruit juices. SWELLING OF THE STARCH. Hydration The first process in rendering the starch of the vege- table digestible is one of hydration. It is important, therefore, that an abundance of water be present when starch is cooked. Some vegetables like the potato contain so much water, that the necessary amount for the starch is supplied within the vegetable itself. The VEGETABLES 123 grains and other dry vegetables need to have a large amount supplied. The swelling^ of the starch grains upon hydration is probably an important agent in the rupturing of the cellulose cell wall already referred to. THE CELL WALLS RUPTURED. Sugar is the soluble carbohydrate of the vegetable, as starch is the insoluble form in which this nutri- ment is stored. Some vegetables, such as carrots, show large amounts of sugar, while starch is absent from this part of the plant. Other typical vegetables containing a large amount of sugar are beets, pars- Sugar in Vegetables Starchy- Vegetables 124 FOOD AND DIETETICS nips, artichokes, sweet potato. Onions, cabbage, and some varieties of peas, string beans, squash and sweet corn all contain a fair amount. Veg-etables containing a large amount of starch are Proteid of Vegetables COMPOSITION OF THE CARROT AND TURNIP. ( After Hutchison ) represented by potato, sweet potato, rice, peas, beans and lentils. Some vegetables containing large amount of cellulose are squash, potato, beet, celery, cabbage. As a rule, we do not look to the vegetable world for our main supply of proteid, yet some of our vege- tables,' notably the legumes, do contain an abundant VEGETABLES 125 supply of this food principle. Whether this is as avail- able for use in the body as the proteid in meat is often questioned. With ordinary cooking processes it evidently is not, but with long continued heat the matter is different. That there is no inherent differ- ence betv^een vegetable and animal proteid, so far as eo.TboKydrcv.te Ccduloie Mm Mat ExtvACt. COMPOSITION OF THE CABBAGE. Blackened portions represent amount dissolved in cooking. its digestibility is concerned, would seem to be indi- cated by the fact that when the vegetable is finely di- vided, as in the case of some of the vegetable meals, it is absorbed to a greater extent than in its ordinary form. It is said, for instance, that when lentils are soaked and boiled until soft, 60 per cent of their pro- teid is absorbed, while in the lentil meal 90 per cent is utilized by the body. No careful experiments have been made to see what proportion of the boiled lentils would have been absorbed if the cooking had been continued for several hours. There is every reason, Digestibility of Vegetable Proteid 126 FOOD AND DIETETICS however, to think that the percentage would be in- creased. Anyone who has compared dry peas or beans cooked two hours, or until they have just become soft, with those cooked from eight to twelve hours will realize the difference in the result. The Potato Salts of Vegetables TAT ^^aj^ CRUDE FIBER -^/^ PROTEID ASH COMPOSITION OF THE POTATO. Among the vegetables, the potato, in this country at least, is the most generally used. It has of late been decried as having no food value. This is far from true. It has, of course, a small amount of pro- teid, some of which is lost in the process of cooking. Its mineral salts are less in amount than in many vege- tables, and are partially lost in the cooking. Its chief value as food lies in the starch it contains, and in the fact that its very absence of strong flavor makes it acceptable day after day. Vegetables should be in our diet not only for their food value but for their mineral salts as well. The bad efifect of the failure to use a certain proportion of vegetables and fruits, has long been known. Scurvy has usually been attributed to this error in diet, while it is quite possible that some minor disorders of the VEGETABLES 127 digestion are attributable to the same cause. Cabbage, lettuce, celery, onion, spinach and the different leaves used as greens find their value almost wholly in the presence of mineral salts. Alushrooms have often been considered of great value, from the proteid they contain, but it seems cer- tain now that this value has been much exaggerated, Mushrooms SECTION OF A POTATO. a — Outer Skin, d — Inner Skin or Fibro-vascular Layer. d — Inner Flesh. -Flesh. and that the reason for using them as articles of food lies in their pleasant flavor and the variety they give, rather than in the amount of nutriment they furnish the system. The digestibility of different vegetables must always be difficult to ascertain, so far as any one individual is concerned. Not only the presence of cellulose, but Digestihility of Vegetables 128 FOOD AND DIETETICS of acids, as in the tomato, of nitrogeneous substances, such as asparagin found in asparagus, and of vola- tile flavors, as in the onion, all affect this question. There has been within a few years a great gain in the abundance and variety of vegetables available. Formerly in winter choice was confined to cabbage. COMPOSITION OF THE CUCUMBER. turnip, squash, onions and a few others. Now a visit to the market of a large city, even at the least promis- ing time of year, shows an overwhelming variety of fresh vegetables. If we add to these the numerous canned vegetables of excellent quality available (and these are increasing in variety constantly) and the dried vegetables, like the peas, beans and mushrooms even, that are obtainable, we have no excuse for limit- ing our diet so far as vegetables are concerned. True economy will consist not in cutting down the supply but in choosing fresh vegetables at the time when each is most abundant and therefore cheapest, and presumably at its best, and in supplementing these by the judicious use of the canned or dried product, not forgetting the ordinary winter vegetables. VEGETABLES Average Composition of Vegetables 129 Name Beans, dried.... Beans, string.. .. Peas, dried Peas, green Potatoes Sweet Potatoes. Sweet Corn Parsnips Carrots Beets Turnips Onions Cabbage Spinach Squash Tomatoes Lettuce Celery Cucumbers Percentage Composition of Edible Portion pi o u 03 o 7.0 45.0 20.0 20.0 61.0 20.0 20.0 20.0 30.0 10.0 15.0 50.0 15.0 20.0 15.0 12.6 89.2 9.5 74.6 78.3 69.0 75.4 83.0 88.2 87.5 89.6 87.6 91.5 92.3 88.3 94.3 94.7 94.5 95.4 55.2 5.5 57.5 15.2 18.0 26.1 19.2 11.0 8.2 8.8 6.8 9.1 4.5 2.3 8.2 3.3 2.2 2.3 2.4 P^ 4.4 1.9 4.5 1.7 .4 1.3 .5 2.5 1.1 .9 1.3 1.1 .9 .9 1.0 .5 22.5 2.3 24.6 7.0 2.2 1.8 3.1 1.6 1.1 1.6 1.3 1.6 1.6 2.1 1.4 .9 1.2 1.1 .8 1.8 3.5 .3 .8 1.0 2.9 .5 1.0 .1 1.0 .7 1.1 1.1 .7 .5 1.4 .4 1.0 .1 1.1 .8 .3 .6 .3 1.0 .3 2.1 .5 .8 .4 .5 .3 .7 .1 1.0 2 .7 1,605 195 1,655 465 385 570 470 300 210 215 185 225 145 110 215 105 90 85 80 *Not including fiber. tincluding fiber and thus higher than fuel value available in the body. The substances grouped under carbohydrates in the above table are chiefly starch, sugar and pectose bodies. Church states that turnips contain no starch or sugar, only pectose, but one of the analyses of the Department of Agriculture showed one sample to contain over 4% of sugar. The carrot contains sugar and pectose, but no starch; parsnips, sugar, starch and pectose. The nitrogenous matter is only in part proteid ; in potatoes about 57% ; in carrots, onions, cabbage, cucumbers, lettuce, about one-half. FRUITS Classiflcation of Fruits Dietetic Value Nutritive Value Fruits may, like vegetables, be classified as flavor fruits and food fruits, and again these two classes will run together so that we shall have difficulty in decid- ing where certain ones belong. The apple, the orange, the strawberry, although all having a certain food value, are used so largely for their flavor and to give variety, that these may well be put under the head of the flavor fruits. Bananas form, perhaps, the best common example of the food fruits. Bread fruit, so largely used in the tropics, is another representative of this class. From a dietetic standpoint the most important func- tion of fruits is that of furnishing mineral salts and or- ganic acids to the body. The potash salts are consid- ered especially important. Some fruits, Hke the pine- apple, contain ferments that are said to be aids to digestion. Fruits are generally laxative in effect, — apples, figs, prunes, peaches and berries are particu- larly effective in this respect, especially if taken be- tween meals or at the beginning of a meal. Their chief nutritive value is given to fruits by the carbohydrate group. This is largely in the form of sugar, while the remainder consists chiefly of vege- table gums, among which may be included the ''pectin bodies" that give to fruits their power to form jelly. Starch may be present in unripe fruits, but disappears as the fruit ripens. Bananas, as we use them, contain a small amount of starch. Of fresh fruits very few contain more than one per cent of nitrogenous maX- ter, not all of which is proteid. 130 FRUITS 131 Dried fruits may be without question put under the food fruits, dates containing sixty-six per cent of carbohydrate, prunes approximately the same amount, figs about sixty-three per cent, while raisins furnish seventy-five per cent. Raisins in this respect stand almost at the head of the list of concentrated foods since thev furnish so much nutriment in so small a Dried Fruits WATER PROTEIO FAT. CARBOMVORATE MIN. MAT. ACIOS CELLULOSE COMPOSITION OF AN APPLE. (, After Hutchison. J bulk. When fresh fruits are not obtainable dried fruits may well take their place. These are usually less expensive than fresh fruits, and properly cooked go far to make up for the absence of the fresh varie- ties. Canned fruits are increasingly used, and many who formerly thought it necessary to put up large amounts of fruit at home, are now purchasing those canned on a commercial scale. \Miether this is a wise thing or Canned Fruits Varieties 132 FOOD AND DIETETICS not depends on the amount of fruit available for the housekeeper at a low cost, the price of sugar, and the time and strength at her disposal. Often the fruit commercially canned is really superior to that pre- pared at home for the reason that the canning is done where the fruit is easily obtainable in its freshest and most perfect condition. When canned fruit is as rea- sonable in cost as it is at present, the housekeeper should certainly be very sure that her time cannot be used to better advantage before she undertakes to prepare quantities of fruit at home. Perhaps no article of diet has increased in use dur- ing the last few years so rapidly as fruits. Not only the most hardy, but the more perishable varieties, in- cluding berries, are by improved methods of transpor- tation, by the use of refrigerator cars and by increased areas of cultivation made available through a longer season, and at greater distances from the source of supply than ever before. The fruit industries, includ- ing the cultivation of the fruit, the great canning and drying establishments, and the transportation of the product, have become of immense importance in the commercial world, jj-g^ New varieties of fruit produced by careful selection and cross fertilization are constantly appearing. Some of the most important changes that have been induced by cultivation have been the lessening of the proportion of cellulose, the production of seedless varieties, the increase in size and the development of fine flavors. FRUITS 133 As in the case of vegetables, the digestibihty of fruits is largely an individual matter. Bananas may be eaten freely by many, even by children, while oth- ers fail to digest even a small portion. Strav^berries, generally considered easily digested, are actual poison to some people. The chief benefit of a table of digesti- bility is as a guide for experimentation. In feeding a child, for instance, one would try first the fruits con- sidered most digestible. Aside from the personal equation, ease in mastica- Digestibility tion is one of the important elements in the digestion of fruits, as in the case of other foods. The banana, for instance, easily slips down the throat in large pieces ; the blueberry can be swallowed whole, while such a fruit as the apple is naturally more thoroughly masticated, for ease in sw^allowing^ and the orange almost falls apart of itself. The difference in the digestibility of ripe and unripe fruits is generally attributed to the larger proportion of cellulose in the latter ; this and the excess of acids in unripe varieties is held responsible for their ill effects. Gilman Thomson gives among the commoner fruits easy of digestion : grapes, oranges, lemons, cooked apples, figs, peaches, strawberries and raspberries ; while he classifies as somewhat less digestible : melons, prunes, raw apples, pears, apricots, bananas and fresh currants. Dried currants and citron he considers "wholly indigestible," while he gives as the most use- 134 FOOD AND DIETETICS ful fruits for invalids : lemons, oranges, baked apples, stewed prunes, grapes, banana meal. Young children and those of delicate digestion should avoid all skin and seeds of fruit. Average Composition of Fruits Percentage Composition of tfi Edible Portion to «4-l T3 O O * 13 u tn en < o Bananas 35. 75.3 21.0 1.0 1.3 .6 .8 460 Grapes 25. 77.4 14.9 4.3 1.3 1 6 .5 450 Plums 5. 5. 78.4 80.9 20.1 16.5 V 9 1.0 1.0 .5 .6 395 Cherries 8 365 Huckle berries 81.9 16.6 V .6 6 .3 345 Apples 25. 84.6 13.0 1.2 .4 5 .3 290 Pears 10. 84.4 11.4 2.7 .6 5 .4 295 Black berries 86.3 8.4 2.5 1.3 1 .5 270 Apricots Peaches 6. 85 13.4 9 1.1 .5 270 6. 27. 85.0 86.9 10.5 11.6 9 .5 .8 .6 .5 Oranges 2 240 Raspberries (red) Cranberries ? 85.8 9.7 2.9 1.0 .6 255 30"."" 88.9 89.3 89.3 8.4 7.4 9.3 1.5 1.1 .4 .4 1.0 .4 6 7 3 .2 .5 3 215 Lemons 205 Pineapple 200 Muskmellon 50. 5. 89.5 90.4 7.2 6.0 2.1 1.4 .6 1.0 .6 .6 185 Strawberries 6 180 Watermelon 60. 92.4 6.7 'i .4 ') .3 140 * Not including fiber, t Including fiber. The carbohydrates of fruits are chiefly in the form of sugar. Nearly all contain pectin bodies and these are most abundant in unripe fruit. The acids of the fruits are here included un- der the carbohydrates . Apples, pears and peaches contain malic acid; lemons and oranges, citric acid; grapes, tartaric acid ; rhubarb, oxalic acid, etc. FRUITS Average Composition of Dried Fruits 135 Dates.. .. Raisins.. Currants Figs Prunes .. Apples. . . Apricots. tf 10.0 10.0 15.0 Percentage Composition of Edible Portion 15 4 14.6 17.2 18.8 22.3 28.1 29.4 © -u Cfi 03 t3 S >> 0} -t.3 xi ^ tc a en .a f^ < cfl Ih; 78.4 2.1 2.8 1.3 76.1 2.6 3.3 3.4 74.2 2.4 1.7 4.5 74.2 4.3 .3 2.4 73.3 2.1 2.3 66.1 1.6 2.2 2.1 62.5 4.7 1.0 2.4 1,615 1,605 1.495 1,475 1,400 1,350 1,290 * Including fiber. NUTS Nutritive Value The form of fruits that we know as nuts has a very different place in diet from that of the ordinary fruit. We find here foods having a nutritive value that com- pares favorably with that of the most nutritious sub- stances. Almond kernels for instance contain twenty- one per cent of proteid, fifty-four of fat, and seventeen PFtOTElD f^AT 74r4^ ,,,//6ARB0HyDFfATS ■ Va^^ MIN. MAT. X&LUUUOdE. COMPOSITION OF AN ENGLISH WALNUT. of carbohydrates, while peanuts are richer still in pro- teid and also contain a large amount of fat. Indeed, nuts often may well be substituted for meat, and have the advantage that they supply at the same time a certain amount of carbohydrates. Some nuts, as chest- nuts, are very rich in the latter. The table given is taken from the experiment station bulletin. Nuts as Food, and shows the composition of some of the most common nuts. ise NUTS Average Composition of Nuts 137 S ^ ^ Percentage Composition Edible Portion OF 0) a o u Hi en 03 'O >> M XI c8 u en -2 tn .2 13 o Almonds Brazil Nut s Filberts Hickory Nuts 64.8 49.6 52.1 62.2 49.7 58.0 16.1 86.4 48.8 4.8 2.7 3.7 1.4 2.9 2.8 31.0 .6 7.2 3.5 4.2 9.3 1.6 2.0 21.0 8.6 15.6 5.8 10.3 16.7 5.7 3.8 2.9 6.3 22.6 27.9 30.5 29.3 51.9 33.6 65.3 25.5 70.8 64.4 6.7 8.3 25.9 57.3 54.5 42.0 49.2 46.6 17.3 3.5 13.0 4.3 14.3 14.8 39.0 .5 14.3 31.6 15.6 18.7 16.2 17.1 2.0 2.0 2.4 .8 1.7 1.3 1.5 .4 .9 1.3 3.1 2.1 2.5 5.0 3030 1545 3290 1265 Pecans Walnuts 3445 3305 Chestnuts Butternuts Cocoanuts Cocoanuts. shredded Pistachio 1115 430 1415 3125 3010 Peanut.^ Roasted Peanuts Peanut Butter 26.4 32.6 2640 2955 2830 Much has been said about the indigestibility of nuts, but this probably comes largely from the fact that nuts are most usually eaten at the end of a hearty meal after the appetite has been completely satisfied. If nuts were more often taken as a substitute for a part of the meat of the meal, there would probably be less difficulty with regard to their digestion. An- other important factor in their digestibility as in the case of other foods, is that of their finely divided con- dition ; often they are insufficiently masticated. Some of the nut meals and pastes on the market are valuable because of their fine division, and their use as a meat substitute certainly has a rational basis. Peanut but- ter is the most common of these preparations. Digestibility of Nuts TEA, COFFEE AND COCOA The common beverages, tea, cofTee and cocoa, are in such- general use today that it is difficult to realize that two of them were not introduced into Europe until the seventeenth century, and the other only a hundred years earlier, though other nations had known them long before. Tea drinking began in Japan in 692 A. D., while coffee, though not known to the Greeks and Romans, had been used in Abyssinia and Ethiopia from time immemorial. Varieties The tea plant seems to be a native of Assam, a prov- of T6& ince of Burmah, but it has been grown in China and Japan for fifteen hundred years. Two different types of the plant are illustrated by the Assamese and Chi- nese varieties. The tea of Assam grows luxuriantly, but is sensitive to drought, cold or winds. Its leaves are of bright green, sometimes reaching a size of nine inches in length and three in width, while the young leaf is of soft texture and golden color.. It may pro- duce as many as twenty "flushes," or successive crops of young leaf during each picking season. The Chi- nese plant is tough and hardy, able to endure severi- ties of climate, and to grow in poor soil with deficient moisture. The leaf is smaller, tougher and darker than that of the Assam tea plant. Between these two extremes exist all varieties of tea. Most varieties produce three or four crops a year. The tea plant produces small white flowers which eventually yield the seed from which cultivated tea is 138 TEA 139 raised. In cultivating the plant an effort is made to produce abundant young leaf, since good tea is made from this alone. Pekoe tea is the choicest variety. The undeveloped bud at the end of a young shoot is Pekoe Tea TEA LEAVES. a — Flowery Pekoe. 6 — Orange Pekoe, c— Pekoe. -is 16 7 2 5 .6 II. 9 i.o .1-6 3-3 7 9 22.3 12.9 ■9 9-8 23 9 .1 0835 07S 018 595 013 216 231 02Q 446 043 036 012 434 001 036 3 268 •^ O 1- XI ^ CJ 66 51 22 5 76 30 ico 3 73 U 331 135 255 575 344 350 286 lOI 000 156 091 02s 280 8.929 fe Oh flH .0365 •S55 .003 .015 1. 168 .270 .280 .005 .572 .162 .C16 .011 .612 .002 .250 .024 SI Total Amount of Food Consumed During the Day Proteid Carbohydrate 3 268 ounces 8.929 ounces or or 92.615 grams 253.019 grams There are 28.34 grams (28'/3) in an ounce. Fat 3.901 ounces or 112.821 grams Fuel and Energy Value of Food Consumed Calories 92.615 grams proteid X 4.1= 379-7 253.019 grams carbohydrate X 4.1 = 1,037.3 114.821 grams fat X 9.3 = 1,049.0 Total 2,466.0 Of course this involves a great deal of calculation, and no one would think of undertaking so much extra work often. As stated on page 60, the chief value of calculating a few dietaries is in giving a definite 194 FOOD AND DIETETICS idea of the composition of food. It is not expected or necessary that each day's ration should conform to any standard. It is only when the diet is calcu- lated for a considerable period of time that it be- comes of much use for comparison. The method of studying the diet for a month is described on page 59. When this is done, there is in reality less calculation involved, for then the figures are based on the amount of raw materials used and the composition of each individual dish need not be calculated. That is, the total weight of flour, butter, milk, eggs, and sugar is known and there only remains the allowance to be made for waste. The whole subject of standard dietaries is in a somewhat chaotic state at present. Professor Chit- tenden's experiments have shown that it is possible to maintain health and strength on about half the amount of proteid recommended in the standard dietaries. If Dr. Folin's theory is correct (see fol- lowing article), any ordinary diet contains more than sufficient proteid for the physiological needs of the body. Nearly all dietetians agree that, from the phy- siological standpoint, it is immaterial whether the body obtains its supply of heat and energy from fats, carbohydrates, or proteids. But all this does not mean that a proper balance between the food materials is not necessary for health. Digestibility, bulk, personal taste and habit must NOTES ON THE QUESTIONS 195 be considered. The problem, then, of the balanced ration becomes an individual one, to be solved ac- cording to the conditions and experience of each individual person. To make the best selection of foods it is necessary to know as much as possible about the composition of all ordinary foods. Then proper cooking and serving and especially the man- ner of eating and the amount eaten are fully as important as the composition. So there is no royal road to the selection of a best diet, but experience based on knowledge should give good judgment. — M. Le Bosquet. PROTEIN METABOLISM IN ITS RELATION TO DIETARY STANDARDS* Otto Folin, Ph. D, McLean Hospital, Waverly, Mass. Present views concerning the role of fats, carbohy- drates, and proteins in the animal organism are not essentially different from views that prevailed a generation ago. An earlier theory, brilliant but untenable in the light of later more exact experi- ments, was advanced by Liebig about the middle of the 19th century. This theory held that the protein taken with the food constitutes the sole source of muscular energy and that fats and carbohydrates serve only to maintam the body tem.perature. LIEBIG'S THEORY Voit, in the course of experiments undertaken to test the validity of Liebig's theory, established the remarkable fact that severe physical work is not accompanied by any material increase in the destruction of protein within the animal organism, as of course would be the case if protein were the sole or even the chief source of muscular energy. The destruction of Liebig's erroneous but definite theory of metabolism naturally led to renewed investigations concerning the function of fats, carbohydrates, and *Paper read at the Lake Placid Conference on Home Economics, June, 1905. 196 PROTEIN METABOLISM • 197 protein; and in this necessary constructive work, Voit became the recognized leader. From his labor- atory came investigations and deductions which have since been almost universally accepted as final. Voit's dietary standards, the practical outcome of all this work, are intended to represent a few fundamental facts. A man of average size gives off in a day a certain quantity of energy (in the form of work and heat). This energy can be measured and often has been measured, with a fair degree of ac- curacy. The more physical work a man does the more energy both in the form of work and of heat is given off, and the increase in energy consumption due to work or exercise has also been measured. The daily consumption of energy in the animal organism is obtained at the expense of food. And since it is known just how much energy can be obtained from burning a given quantity of fat, starch, or protein, it becomes theoreti- cally simple, and practically quite possible, to calculate the amount of food that a given individual doing a certain work must consume in order to main- tain the equilibrium of the intake and outgo of energy. Such calculations are based on the assumption that food materials when oxidized within the animal organism liberate the same amount of energy as when burned in ordinary air or oxygen, and there' is no reason to doubt the correctness of this assumption. igS FOOD AND DIETETICS VOIT'S DIETARY STANDARDS In so far as Voit's dietary standards prescribe the amount of dry food material, of available energy- giving material necessary under given conditions, they have undoubtedly been of very great service. The dietary standards, however, prescribe not only how much available energy the daily food must con- tain, but also how much of that energy can be most profitably supplied in the form of protein and how much in the form of fats and carbohydrates. Voit's well known average diet, for example, calls for 56 gm. fat, 500 gm. carbohydrates, and 118 gm. protein. The justification and probable value of such more specific standards of diet is the subject of this paper, and it is a subject on which I think there is room for differences of opinion. It should, however, at once be stated that such differences of opinion do not concern the non-nitrogenous part of the dietary standards. Voit, and with him all competent to have an opinion, are agreed that the fats and carbo- hydrates need not at all be provided in the ratio of 56 to 500. PROPORTION OF FATS TO CARBOHYDRATES It is a well-known fact that if more fat than the animal organism can advantageously oxidize is sup- plied, such fat, in so far as it is absorbed, is stored as fat in the body. If an excess of carbohydrates is taken, such excess is also converted into fat and is PROTEIN METABOLISM 199 likewise stored as fat for future use. Further Pfliiger has recently advanced the not improbable hypothesis that fats are not completely oxidized as such within the animal organism, but are first converted into carbohydrates. The animal organism is then able to convert carbohydrates into fat and fat into car- bohydrates according to its needs, and the logical conclusion therefore is quite in harmony with the accepted view that it is theoretically a matter of relatively small importance what ratio is selected for the fats and carbohydrates. The two taken together must of necessity furnish the greater part of the fuel value of the food, but upon individual peculiarities, relative cost, and a number of other accidental factors depends what ratio between the two may be most suitable in any given case. PROTEIN IN THE DIETARY With regard to the protein prescribed by the die- tary standards the case is different. The animal or human organism, while able to convert carbohydrates into fat and probably also fat into carbohydrates, can effect no such transformation of non-nitrogenous food into the highly nitrogenous proteins. It may be able to produce carbohydrates, and therefore also fat, out of protein, but it certainly can not produce protein out of fat or carbohydrates. The protein of the food not only furnishes energy and heat, as do the fats and carbohydrates, but it, and it alone, 200 FOOD AND DIETETICS furnishes the material which replaces the constant loss of living protoplasm. It is therefore clearly necessary that the daily food should contain enough protein to protect the organism against loss of body tissue. On the other hand, it is generally believed that instead of being advantageous it is probably detrimental to the full-grown organism to have to take care of more protein than is needed for the re- placement of lost tissue material. An excess of fat or carbohydrates, the human organism can to a very great extent take care of by adding it to its store of body fat, but it has not the power similarly to in- crease its supply of reserve protein. Any excess of nitrogenous material supplied with the food leads at once to a correspondingly increased destruction of protein. And the formation of excessive quantities of nitrogenous katabolism products within the body is supposed to be more or less a source of danger. I think all are agreed that gout at least is largely the result of "high living." MINIMUM PROTEIN The important question then is, How much pro- tein must the diet of normal persons contain ? Voit came to the difinite conclusion that ii8 grams are needed for a man weighing 70 kilos (150 lbs.), and for more than a generation this figure has been gen- erally accepted as substantially correct. But is it? Since the publication in 1881 of Voit's great mono- PROTEIN METABOLISM 201 graph on metabolism it has been shown by Hirsch- feld, Klemperer, Pechsel, and Siven that the daily protein destruction in men of average size can be reduced to 40 grams or less, and that nitrogen equi- librium can be maintained by furnishing such small amounts of protein with the food. The experiments by means of which Voit secured the almost universal acceptance of his standard minimum protein re- quirement are essentially similar and in no way superior to these more modem experiments which seem to prove that 40 grams of protein, or less, are enough to maintain nitrogen equilibrium. One might therefore suppose that the later experiments would have been accepted as proving the erroneous- ness of Voit's figures, or that they would at least have been deemed sufficiently important to lead to a gen- eral reopening of the whole question. But the earlier conclusions and generalizations of Voit had in the meantime, so to speak, survived the probation period, and had become the accepted doctrine, not to say tradition, of the scientific public. In addition, it must be remembered that Voit's standard comes much nearer the average common usage. The widespread and earnest acceptance of Voit's figure is undoubtedly in a great measure due to the fact that it agrees tolerably well with the protein consumption actually prevailing among the people, specially among those not too poor to procure the more expensive articles of food. 202 FOOD AND DIETETICS AVERAGE CONSUMPTION It has frequently been asserted that the people at large do as a matter of fact consume on the average about ii8 grams of protein per 70 kilos of weight. But I venture to insist that the question of average protein consumption has little or nothing to do with the problem before us. To argue that the customary or the average consumption of pro- tein is the necessary consumption suggests that the necessary potein consumption is after all far more flexible than is indicated by the standard diets. It also implies that the people have solved the problem without the aid of science, and further that their average health and vigor is now all that we can hope for in so far as the protein contents of the food have anything to do with it. Voit, himself, remained, I think, somewhat under the strong influence of Liebig's teachings concerning the peculiar value of protein as a food. It is diffi- cult to see how he could otherwise have failed to find that it is possible to maintain nitrogen equili- brium on a comparatively small fraction of the pro- tein which he declared to be the minimum. It was right and natural that Voit should not put the nec- essary protein requirement at too low a figure; its great practical import demanded cautiousness. But the minimum protein requirement for man could of course not be found except by studying the meta- bolism of man under the influence of smaller and PROTEIN METABOLISM 203 smaller quantities of protein. This is clearly demon- strated by the results of the modem low nitrogen equilibrium experiments. The disciples of Voit can not and do not question the accuracy of the results recorded from the low protein feeding experiments. But it is now rightly enough held that to prove that a person can main- tain nitrogen equilibrium for a limited length of time, as for a few days, on a very small amount of protein does not at all prove that he can permanently do so with advantage or even with impunity. The correctness of this position must be granted, and it is, in fact, the position taken by the more conserva- tive experimenters on low nitrogen equilibrium, as for example by Siven. But while freely admitting this, it must, in my opinon, be insisted that the low protein experiments of even such short duration, as a few days, have completely destroyed the scien- tific basis on which the protein prescriptions of Voit and his disciples are supposed to rest. LOW PROTEIN EQUILIBRIUM As far as we yet know there is no reason for assum- ing that a diet capable of maintaining nitrogen equi- librium for a week should fail to do so at the end of a month or any other time. In fact, investigations of the last three or four years clearly indicate that nitro- gen equilibrium can be maintained for long as well as for short periods on very small quantities of protein. 204 FOOD AND DIETETICS In 1902 Dr. R. O. Neumann, privatdocent in the Hygiene Institute at Kiel, published an account of metabolism experiments with himself covering a period of over two years. The average composition of his diet during that time corresponded to 117 grams fat, 213 grams carbohydrates, and 74.2 grams protein per 70 kilos of body weight. Neumann's ex- periments covering such a long period would cer- tainly seem to constitute definite proof that Voit's so-called minimum protein requirement is at least half again as large as is really necessary for the per- manent maintenance of nitrogen equilibrium, physi- cal vigor, and efficiency. More striking still are the metabolism records pub- ^lished last year, by Professor Chittenden. I shall not go into details of this work, as Mrs. Richards is on the program for a report on it. But I must cite the fact that Chittenden maintained a body weight of 57 kilos as well as nitrogen equilibrium from July, 1903, until the publication of his book in the fall of 1904, on an average protein consumption of less than 35 grams a day. DR. FOLIN'S STUDIES My own studies of protein metabolism in man, though pursued in a different way and for a different purpose, have a direct bearing on the problem of the necessary minimum protein consumption. The specific waste products formed from the destruction PROTEIN METABOLISM 205 of protein within the human organism are ehminated in soluble form- with the urine. They are therefore easily available for detailed chemical investigations, and as the result of innumerable studies much exact knowledge has been gained concerning the normal katabolism products of protein. My investigations lie within this field. The views that have till recently prevailed con- cerning the chemistry of urine, in so far as it relates to the problem of protein metabolism, may be con- cisely stated as follows: All the nitrogen of the protein destroyed in the body is eliminated with the urine, and almost 90% of it appears in the form of urea. From 95% to 98% of the nitrogen is eliminated as urea, kreatinin, ammonia, and uric acid. The absolute amount of each of these nitrogenous products depends upon the amount of protein katabolized, but changes in the amount of protein destroyed affect them all equally, thus leaving them always in about the same proportion to each other and to the total nitrogen. This fact, if correct, is very important, because it clearly indicates a certain unity in the chemical pro- cesses concerned with the use and destruction of protein within the body. It indicates that the pro- tein of the food and the protein of the living tissues are essentially alike and in the same condition with reference to the organism at the time of their final destruction. The two rival theories concerning this subject accordingly agree in assuming the essen- 2o6 FOOD AND DIETETICS tial unity of the chemical processes involved in pro- tein katabolism, and the only point of difference between the two is that one, the theory of Voit, holds that the protein must be in solution and dead before being oxidized and destroyed, while the other, that of Pfliiger, assumes that it is only actually liv- ing protoplasm that is destroyed. It would be useless in this connection to go into a detailed discussion of these two theories, because I think it can be shown that the fundamental pre- mise of both, namely, the supposed constancy in the relative distribution of the urinary nitrogenous products, is no longer tenable. RELATIVE PROPORTION OF NITROGEN WASTE PRODUCTS The fact that the relative proportions of the vari- ous nitrogenous constituents of normal human urine have so long been supposed to be approximately constant is in a measure directly the result of Voit's teachings concerning the minimum protein requirement. The destruction of loo grams pro- tein or more within the organism, as demanded by the dietary standards, rendered it well nigh impos- sible to discover the laws that govern the formation and elimination of each product. About a year and a half ago I discovered accidentally that the urine corresponding to a very low protein katabolism has a chemical composition which is very different from that of urine derived from the standard diets. This PROTEIN METABOLISM 207 led to numerous attempts to reduce the daily pro- tein destruction in normal persons to the lowest pos- sible level. Nearly all preceding attempts to reduce the pro- tein katabolism have also been attempts to main- tain at the same time nitrogen equilibrium. In mine the question of nitrogen equilibrium, or loss of protein, was not considered, and I have as a matter of fact used a diet containing almost no protein. I have kept several normal persons for a week or more, two or three persons for two weeks, and one for 17 days on a diet consisting exclusively of pure arrow root starch and 300 cc. of cream. In this way the daily protein katabolism has repeatedly been reduced to about 20 grams a day. Detailed chemical studies of the urines correspond- ing to such greatly reduced protein katabolism have shown that the relative proportion which the nitro- genous products bear to each other and to the total nitrogen does change and very greatly. For ex- ample, the kreatinin elimination is entirely inde- pendent of the total amount of protein katabolized. It is just as great on a diet containing no protein as on one containing 118 grams of protein. In the one case it represents from 17% to 20% of the total nitro- gen, in the other from 3% to 4%. The urea, on the other hand, is peculiarly a product of excessive protein katabolism. When the urinary nitrogen represents a katabolism of 100 grams of protein, 90% of that 2o8 FOOD AND DIETETICS nitrogen is present as urea, while when the protein katabolism has been reduced to 20 grams, only from 50% to 60% of its nitrogen appears in the form of urea. DIFFERENT KINDS OF PROTEIN METABOLISM These facts concerning urea and kreatinin suffice to show how entirely erroneous has been the assump- tion that the nitrogen of katabolized protein is always distributed in the same proportion among the different waste products. It may therefore be superflous now to go into further details concerning the laws that govern the formation and elimination of the different products. The fact that these laws are widely different for different products, as for urea and kreatinin, demonstrates with a fair degree of certainty that protein metabolism is not all of one kind. The true minimum katabolism or protein, as ob- tained in my feeding experiments with starch and fats, is clearly very different from the katabolism of the large quantities of protein demanded by the dietary standards. The former converts not over 60% of the protein nitrogen into urea, and is the source of all the kreatinin eliminated with the urine. The katabolism of that food protein which is not absolutely needed for the maintenance of nitrogen equilibrium, on the other hand, yields probably at least 95% of its nitrogen in the form of urea and yields no kreatinin whatever. The katabolism PROTEIN METABOLISM 209 which yields the kreatinin clearly tends to be con- stant and independent of the food protein; it can therefore fairly be said to represent the tissue meta- bolism. The katabolism which yields chiefly urea is the katabolism of the excessive food protein, and its amount depends directly upon the amount of protein contained in the food. This I have called the exogenous metabolism. EXOGENOUS METABOLISM Since the exogenous metabolism seems to have nothing to do with the tissue metabolism, and since it increases immediately with every increase of pro- tein furnished with the food and in porportion to such increase, it represents nothing else than the effort of the organism to get rid of nitrogen that it does not need and can not use. The remarkable ability of the human organism to establish nitrogen equilibrium on almost any quantity of protein does therefore not mean, as has been believed, that the organism uses protein by preference instead of fats and carbohydrates. This phenojnenon is merely the result of our habitual consumption of more pro- tein than can be used in the tissue metabolism. Being always supplied with an excess, we have al- ways with us the maximum amount of reserve pro- tein that we can advantageously carry, and any further increase in the supply simply leads to an in- creased elimination. 2IO FOOD AND DIETETICS CONCLUSIONS Such, in brief, are the conclusions which I have drawn from detailed studies of the waste products of protein katabolism. To recapitulate: We have learned from Voit that protein is not needed to supply energy ; and the work of more recent investigators has demonstrated that nothing like loo grams of protein is needed to maintain nitrogen equilibrium in a man of average size. Further, from detailed analytic studies, we have learned that some waste products, like kreatinin, represent tissue metabolism, and others, like urea, the metabolism of that food protein which is destroyed as rapidly as it is taken in. The two kinds of meta- bolism are independent. The tissue metabolism is for each individual a constant quantity, irrespec- tive of the amount of protein contained in the food. Obviously, therefore, there is a constant minimum protein requirement to prevent loss of tissue material. The amount of protein needed for this purpose is very small, probably not over 25 grams a day. It does, however, not necessarily follow that 25 grams protein should be prescribed instead of 118 grams. The prevailing idea that consumption of more than the minimum amount of protein is detrimental to health may not be true. The minimum may not be the optimum. But what has been considered the minimum, 118 grams, may be beyond the opti- mum, possibly even above the maximum amount of protein that any normal person should consume. PROTEIN METABOLISM 2ii DISCUSSION Mrs. Abel — I should like to ask Dr. Folin if he would recommend for tuberculosis patients a great deal of milk and eggs. Dr. Folin — Any opinion I give must simply be my own. I should be inclined to think it unneces- sary to prescribe any quantity of protein whatever. By that I do not mean to say how much should be consumed, because in our food products, say bread and butter, there is enough to meet all requirements as shown by these investigations, but at the same time the experience of past generations shows that we can at least, without any noticeable disadvan- tage, consume considerable quantities of protein. For instance, I should not advise stopping all use of meat. I should be inclined to take the same atti- tude toward protein as toward fats and carbohy- drates. We must have enough food to maintain the energy that is consumed, and I think the same liberty can be taken toward protein as toward the other two. We do not quite know just what is the effect of compelling the system to eliminate large quantities, and so long as we do not know I do not believe we can take a very definite standpoint on the question. It is generally believed that such diseases as gout are more or less directly due to high living, but we can not prove it, and moreover it is a question whether protein consumption and meat eating are at all identical. Such products as uric 212 FOOD AND DIETETICS acid are formed in large quantities by meat eaters, but they are not formed when such products as milk and eggs are taken; consequently, I should say that we do not know. In regard to such disease as consumption, I have no personal experience, but if the point is merely to build them up and give them a large amount of reserve material, we can see that it is entirely unneces- sary to feed large quantities of milk and eggs, be- cause the nutrition of milk and eggs is at once eliminated, and presumably the rest of that food is stored as fat and carbohydrates, and so I should be inclined at least to consider it worth while to try whether fat and carbohydrates would not produce just as good results. Mrs. Abel — There are several here I think who have to do with feeding people in hospitals, and one lady with tuberculosis patients, and I should like very much for my own information to know whether these patients take and digest and seem to flourish under this high feeding of eggs and milk. I myself have to visit a poorhouse where there are loo tuber- culosis patients. Eggs are 40 cents a dozen in winter, and the state must pay for them. Still the prescrip- tion is 3 and 4 eggs a day and a large quantity of milk. If it is not necessary, it is of immense im- portance to the whole country to know it, for other patients need the money which now goes for this purpose. PROTEIN METABOLISM 213 Miss Fraser — I am trying to feed consumptive patients as economically as possible, to give them the things they like and must have and to do it all on a certain sum. Our patients are fed in the fol- lowing way. They have breakfast at 7.30. We expect them to take half an hour for that meal, and they may stay as much longer as they like. At 10.30 they have their lunch of milk and eggs, no limit to the quantity of milk and eggs or egg nog. At 12.30 we have dinner. A number of patients at that meal take a raw egg and m.ilk. At 3.30 they are called to lunch, milk and eggs. At 5.45 supper, milk and eggs again and just as much as they can eat besides. At 8.30 milk and eggs again. Some of those patients during the night take milk and eggs. We give them cereal twice a day, for breakfast and supper, cooked eight hours in a double boiler. They are very fond of that, but we find that if they know there is steak they do not take so much. The same at dinner with soups. I find they do not take as much, for they think they must save space for roast beef. Vegetables they are fond of. I try to give them as much as they can eat. They seem to have an idea that they must eat plenty of rare beef and milk and eggs. I have heard patients" who have been cured, come back and say to the others "Now eat all the meat and milk and eggs that you can and never mind the other things.' ' Farther than that I cannot tell. The patients look healthy and no 214 FOOD AND DIETETICS one would have any idea that they were a lot of sick people. Miss Bevier — Would Dr. Folin say that we can not help getting from any food as much protein as the system needs and so there is no such thing as balanced rations? Dr. Folin. — If you eat enough bread and butter to give 2500 calories, I believe you would get enough protein. Be sparing of the butter if fat is too great. It is exceedingly difficult to get any diet that does not contain nutrition that is equal to the metabo- lism. The one point that you would need to consider would be fuel value and in regard to that there is now perhaps a little difference of opinion. The work done by the department of agriculture is prob- ably the safest guide at present. Dr. Langworthy — Dr. Folin's is the most impor- tant contribution to the subject made in a long time. It clears up some matters, throws light on others, and I think when work has gone on for a time longer we shall know a great deal more about this subject. I like his attitude in not drawing frenzied conclusions from so many and interesting results. I never want to forget that whenever we find a race living on a small amount of food, or largely on vege- table diet, it is not a capable race. The Italian peasants who live on com meal and a little fish do little work, yet bring them to this country and give PROTEIN METABOLISM 215 them better diet and they do a great deal more and better work in a day. The second and third gener- ation develops a larger man than his father or grand- father. We find that the Japanese eat just about the same amount of protein as the standard covers. ^ ^ ^j :^< :Jc Mrs. Richards — One point which every one has very carefully left out of this discussion is the food of the child. All these experiments in lowering the food protein must be practiced on our own and not on the children's diet at present. SUPPLEMENTAL PROGRAM ARRANGED FOR CLASS STUDY ON FOOD AND DIETETICS MEETING I (Study pages i - 29) The Food Problem Food materials and their Adulteration, by Ellen H. Richards. Chapter L ($1.00, postage loc.) Cost of Food, by Ellen H. Richards. Pages 1-7. ($1.00, postage I2C.) Sanitary and Economic Cooking, by Mary Hinman Abel. Pages 1-5. (40c., postage loc.) Cost of Food Cost of Food, by Ellen H. Richards. Chapters XI-XIV. Bulletin No. 129 (Office of the Experiment Station.s), Dietary Studies in Boston, Springfield, Philadelphia, and Chicago. Price IOC. (coin), of the. Supt. of Documents, Washington, D. C. Sanitary and Economic Cooking — Some Cheap Dishes. Pages 25-33. Ru,mford Kitchen Leaflets — Good food for little Money, by Ellen H. Richards. ($1.00, postage loc.) Principles of Nutrition and the Nutritive Value of Food. Farmers' Bulletin No. 142. (Free of Dept. of Agriculture, Washington, D. C.) Topic: Food in Relation to National Character. MEETING II (Study pages 30-49.) Food and the Body Principles of Nutrition and Nutritive Value of Food. Farm- ers ' Bulletin No. 142. Food and Dietetics, by Hutchison. Chapter I. ($3,00, postage 30c.) 217 2i8 FOOD AND DIETETICS Food Principles Make experiments on proteids described on pages 41 and 42. Clean and grate a small potato under slowly running water, pour through muslin to collect fibers, let starch settle. Exhibit: Make up an exhibit showing quantities of food hav- ing the same fuel and energy value — say 800 calories, which is a little over one-third the daily requirement for a woman at moderate work according to dietary standards. Show bread, meat, butter, milk, eggs, sugar, potatoes, apples, etc., and label each food with the weight in ounces and cost. Calculation. Bread furnishes about 1650 calories per pound; to furnish 800 calories would require 800 divided by 1650; which multiplied by 16, equals 7.75 oz. — about half a loaf. Milk furnishes 325 calories per pound. 800 divided by 325 and multiplied by 16 equals about 40 oz., or a quart and half a pint, and so on. Exhibit: Make an exhibit of foods containing 1.126 oz., of proteid, — one-third the daily ration for a woman — labeling each with the weight and cost. MEETING III (Study pages 50-61) Dietary Standards Food and Dietetics, by Hutchison. Chapters II and III. ($3.00, postage 26c.) Dietary Computer, by Ellen H. Richards. ($1.50, postage I2C.) Bulletin No. 28, American Food Materials. Price 5 cents (coin), of the Supt. of Documents, Washington, D. C. Physiological Economy in Nutrition, by Chittenden. In- troduction, Chapters IV, V, and Conclusion. ($3.00, postage 20c.) Article in Century Magazine, February, 1905, by Chittenden. PROGRAM 219 Protein Metabolism in Relation to Dietary Standards, by Folin. See Supplement, pages 196-215. See " Notes on the Questions," piages 191-195. Send to the Battle Creek Sanitarium, Battle Creek, Mich., for some of their menus giving fuel value of food served. See articles in Good Housekeeping, — August, 1906, '.' Fletch- erism as Household Economy," and October, 1906, " Sense and Science in Dietetics," by Dr. Stedman. Exhibit: Make up exhibits showing a standard day 's ration for a woman with light exercise — 80 grams (about 3 oz.) of proteid — with sufficient fats and carbohydrates to bring the total fuel value up to 2300 calories. See Bulletin No. 28, American Food Materials, for composi- tion of any foods not given in the lesson books. (Select answers to Test Questions on Part I and send them to the School and report on exhibits and supplemental work.) MEETING IV (Study pages 63-116) Special Foods Food and Dietetics, by Hutchison, and other standard books. Food Products of the World, by Green. ($1.50, postage 14c.) Meat and Fish Meats, Composition and Cooking. Farmers' Bulletin No. 34. Fish as Food. Farmers' Bulletin No. 85. Poultry as Food. Farmers' Bulletin No. 182. Meat on the Farm, Butchering, Keeping, Curing. Farmers' Bulletin No. 183. Roasting of Beef, Circular 71, University of Illinois. Isabel Bevier. (Postage 2c.) 220 FOOD AND DIETETICS Eggs, Milk, and Milk Products Eggs and their use as Food. Farmers' Bulletin No. 128. Milk as Food. Farmers' Bulletin No. 74. Facts about Milk. Farmers' Bulletin No. 42. Food Value of Cheese, in Farmers' Bulletin No. 244. Milk Supply of Two Hundred Cities and Towns. Bulletin No. 46. Price 10 cents (coin), of the Supt. of Documents, Washington, D. C. Milk and its Products, by Wing. ($1.00, postage loc.) Cereals and Cereal Products Bread and the Principles of Bread Making. Farmers' Bul- letin No. 112. Wheat, Flour, and Bread. Extract No. 324. Macaroni Wheat. Extract No. 326. Studies in Bread and Bread Making. Bulletin No. loi. Price 5 cents (coin), of Supt. of Documents, Washington, D. C. Cereal Breakfast Foods. Farmers' Bulletin No. 249. Cereal Breakfast Foods. Bulletin No. 84 and 118, Maine Agricultural Experiment Station, Orono, Maine. Pop Corn, in Farmers' Bulletin No. 202. Corn Plants, by Sargent. (75c., postage oc.) Story of Grain of Wheat, by Edgar. ($1 . 00, postage loc.) Sugar Sugar as Food. Farmers' Bulletin No. 93. Maple Syrup and Sugar, in Farmers' Bulletin No 124. (Select answers to Test Questions on Part II and report on supplemental work.) MEETING V (Study pages 119-157) Vegetables, Fruits, and Nuts Beans, Peas, and other Legumes as Food. Farmers' Bul- letin No. 121. PROGRAM 221 Sweet Potatoes. Farmers' Bulletin No. 127. Peanuts: Culture and Uses. Farmers' Bulletin No. 25. Value of Potatoes as Food. Extract from Year Book, 1900. Losses in the Cooking of Vegetables. Farmers' Bulletin No. 73. Mushrooms as Food, in Farmers' BuHetin No. 79. Banana Flour; Canned Tomatoes, in Farmers' Bulletin No. 119 Chestnuts, in Farmers' Bulletin No. 114. CofTee Substitutes, in Farmers' Bulletin No. 122. Food Value of Beans, in Farmers' Bulletin No. 169. Nuts as Food. Bulletin No. 54, Maine Agricultural Experi- ment Station, Orono, Maine. Coffee Substitutes. Bulletin No. 65, Maine Agricultural Experiment Station, Orono, Me. Nutrition Investigations among Fruitarians and Chinese, Bulletin No. 107. Price 5 cents (coin,) of the Supt. of Documents, Washington, D. C. Further Investigations among Fruitarians, Bulletin No. 132. Price 5 cents (coin), of the Supt. of Documents, Washing- ton, D. C. Food and Dietetics, by Hutchison. Chapters XIV and XVIII. Cocoa and Chocolate. Walter Baker Co., Dorchester, Mass. (Postage 6c.) MEETING VI (Study pages 158 - 180) Adulteration of Food See Articles on "Safe Food" in the Delineator, January to July, 1906, by Mary Hinman Abel. Food Materials and their Adulterations, by Ellen H. Richards. ($1. 00, postage loc.) Standards of Purity for Food Products. Circular No. 17. 222 FOOD AND DIETETICS Use and Abuse of Food Preservatives. Extract No. 221. Some forms of Food Adulteration and Simple Methods for their Detection. Bulletin No. 800, Bureau of Chemistry. Price 10 cents (coin), of the Supt. of Documents, Washing- ton, D. C. Make some of the tests described, in the text and above bulletins. Officials Charged with Enforcement of Food Laws. Circular No. 16. The food laws of your own state. Write to the officer given in Circular No. 16 for them and send for the part of bulletin of Bureau of Chemistry containing them. Topics: Laws, if any, in your own town. Are they en- forced ? The Local Milk Supply, — investigate. Condition of the Local Slaughter Houses. Special Diet Food and Dietetics, by Hutchison. Diet in Disease, Chap- ter xxvn. Diet in Obesity and Fattening Diet. Chapter XXVIIL Food as a Factor in Student Life, by Richards and Talbot. (25c., postage 2C.) Diet in Relation to Age and Activity, by Thompson. ($1.00, postage 8c.) A, B and Z of our own Nutrition, by Fletcher. ($1.00, postage IOC.) Vegetarianism, by Kellogg. (Select answers to Test Questions on Part III and report on supplemental work.) INDEX Adulteration of butter, 93 of coffee, 147 of food, 158 of milk, 91 of tea, 142 Albumin, 68 Albuminoids, 43 Animal food, 63 Apple, composition of, 131 Atwater's experiments, 52 Bacon, digestibility of, 69 Bacteria in butter, 92 in cheese, 96 in milk, 89 Balanced ration, 56, 194, 214 Beef, 70 digestibility of, 70 juice, 72 Bibliography, 181 Bomb calorimeter, 35 Borax experiment, 165 Boric acid, 91 Bread, 106 corn, 108 graham, 1 1 1 inaking, no nutritive value of, 112 rye, 108 white, 112 whole wheat, in yeast, 109 Breakfast foods, 103 Broth, nutritious, 72 Butter, 92 adulteration of, 93 effect of cooking, 93 rancid, 93 Butter, renovated, 93 Butterine, 94 Buttermilk, 86 Cabbage, composition of, 125 Caffeine, 155 Calculations of dietaries, 56, 191 Caloric, 34 Calorimeter, bomb, 35 respiration, 32, 52 Carbohydrates, 64 classification of, 45 composition of, 44 in nuts, 136 in vegetables, 120 Carrots, composition of, 124 Casein, 41, 87 Cellulose, 47 effect of cooking on, 121 in vegetables, 120 Cereal coffee, 156 Cereals, 98 composition of, 99 cooking of, 105 digestibility of, 104 Chart, composition of foods, .28,37 division of income, 8 heat and energy, 36 of economy of foods 29, 84 Cheese, 95 digestibility of, 96 effects of cooking on, 96 Children, food for, 174 Children's parties, 175 Chittenden's experiments, 54 Chocolate, 153 Clams, 75 • 223 224 INDEX Coal tar dyes, 164 Cocoa, 148 digestibility of, i5g food value of, 154 nibs, 152 physiological effects of , 155 shells, 152 Coffee, 143 adulterants, 147 .cereals, 156 composition of, 144 physiological effects of, 155 tests, 147 Collagen, 43 Coloring matters, 163 Composition of apple, 131 of carbohydrates, 44 of cereals, 99 of coffee, 144 of eggs,. 77 of fats, 48 of fish, 74 of food, 28, 30 of meat, 67 of milk, 81,87 of nuts, 136 of potato, 126 or proteids, 42 of tea, 141 of the body, 31 of vegetables, 120 Condensed milk, 90 Cookery, economical, 13 Cooking, cost of, 10 effect on meat, 70 Cost of cooking, 10 of eggs, 80 of fish, 73 of food, 7,25 of labor, 1 1 of meat, 71 Cucumber, composition of , 1 28 Dextrin, 47 Diet, 173 for children, 174 for old age, 179 students', 178 to reduce fat, 179 Dietaries, 50, 52 calculations of, 56, 191 estimating, 59, 173 experimental, 52 standard, 50, 52, 54, 194, 197, 214 • Dietaries, statistical, 53 use of, 58 Digestibility, 36, 65 of cereals, 104 of cheese, 96 of eggs, 79 of fruits, 133 of meat, 69 of milk, 85 of nuts, 137 of vegetables, 65, 127 Dyes in food, 164 Eating between meals, 177 manner of, 175 Economy, food, 26, 29 in cookery, 13 Eggs, 77 composition of, 77 cost of, 80 digestibility of, 79 Energy, 33" kinetic, 34 potential, T^Ti source of, 2)Z unit of, 34 Engel's laws, 7 Extractives, 43, 71 Extracts of meat, 72 Factors in dietarv calculations, 61 Fats, 48 INDEX 225 Pats, in child's diet, 176 in milk, 88 Fibrin, 67 Fish, 72 cooking of, 76 cost of, 73 digestibility of, 72 dried, 76 shell, 74 smoked, 76 Flour, 10 1 bolting, 10 1 scalpings of, 102 standard, 103 testing of, 102 Folin's experiments, 55 studies, 204 Food, 30 adulteration of, 158 . amount required, 50 animal, 63 building, 31 classification of, 49 composition of, 30 cost of, 7, 64 digestibility of, 36, 38 economy, 10 energy in, 32 for children, 174 for different ages, 50 fuel value, 32 functions of, 30 nutrients of, 49 preservatives, 161 principles, 41, 49 vegetable, 63 waste of, 12 Formaldehyde, 91 Fruits, 130 canned, 131 digestibility of, 133 dried, 131 unripe, 133 Fuel foods, 39 Gelatine, 43 test, 172 Gelatinoids, 43 Glucose, 114, 160 Gluten, 41, 107 Glycogen, 47 Government bulletins, 182 . Heat, 32 in body, 32 mechanical equivalent of, 35 unit of, 34 Hydration of starch, 122 Income chart, 8 Kinetic energy, 34 Koumiss, 86 Labelling, correct, 162 Labor, cost of, 1 1 Lact-albumin, 87 Lactic acid, 89 Lactose, 87 Leavening agents, 108 Legumin, 42 . • Liebig's theory, 196 Lobsters, 75 Meat, 66 cost of, 71 digestibility of, 69 effect of cooking, 70 extracts of, 72 fat of, 68 flavor of, 68 losses in boiling, 70 proteids of, 67 Mechanical equivalent of heat, 35 Menus, 24 Metabolism, 196 exogenous, 209 protein, 196 226 INDEX Milk, 80 adulteration of, 91 boiled, 86 composition of, 81, 87 condensed, 90 cost of, 82 digestibility of, 85 fats, 88 mineral matter in, 88 powder, 91 preservatives, 91 products, 92 pure, 90 sour, 89 sugar, 87 Mineral matter, 48 Molasses, 116 Mushrooms, 127 Mutton, digestibility of, 70 Myosin, 42, 67 Nutrient ratio, 48, 51, 81 Nutrients of food, 49 Nuts, 136 Oleomargarine, 94 Omnivorous tastes, 176 Ossein, 43 Oysters, 75 Pectin, 48, 130 Pectose, 48 Pork, digestibility of, 69 Potato, composition of, 126 Potential energy, 33 Preservatives, 165 milk, 91 Program for supplemental study, 216 Proteids, 41 composition of, 42 equilibrium, 203 in nuts, 136 minimum, 200 Proteids, nomenclature of, 43 of meat, 67 requirements in the body. 55 requirements for children, 174, 215 source of, 66 Protein, 43 metabolism in relation to dietary standards, 196, 215 Pure food, 158 food bulletins, 186 Ration, balanced, 56, 194, 214 Renovated butter, 93 Respiration calorimeter, 32 Salts, 48 of vegetables, 126 Serving, dainty, 26 Shell-fish, 74 Skimmed milk, 86 Soup meat, nutritive value of, 71 Soups, 71 nutritive value of, 7 1 Sour milk, use of, 89 Special diet, 173 food stuffs, 63 Standard dietaries, 52, 54, 194, 197, 214 Starch, 45 com, 45 hydration of, 122 in fruits, 130 structure of, 46 Starchy vegetables, 1 24 Students' diet, 178 Sugar, 113 beet, 114 cane, 115 ' digestibility of, 114 effect on diet, 116 granulated, 115 INDEX 227 Sugar, in vegetables, 123 maple, 115 powdered, 115 test of, 115 value as food, 113 Table of comparative diges- tibility, 39 of comparative food value of milk, 82 Table of composition of cere- als, 99 of cocoa, 153 of cofifee, 146 of common foods, 57 of dried fruits, 135 of fish, 74 of fruits, 134 of m.eats, 5 7 of nuts, 137 of oysters, 75 of soup, 20 of starches, 22 of sugars, 22 of tea, 146 of vegetables, 23, 129 Table of cost of food, 17, 19, 27. 77 of digestibility, 38 of nutritive value, 15 Tannic acid, 156 Tea, 138 adulteration of, 142 composition of, 141 names of, 140 Tea, physiological effects, 155 tests, 142 varieties of, 138 Tests for aniline colors, 171 for butter, 168 home, 168 Theobromine, 153 Turnip, composition of, 124 Veal, 70 Vegetable dyes, 164 foods, 63 Vegetables, 119 cellulose of, 1 20 classification of, 119 composition of, 1 20 digestibility of, 127 proteids of, 124 salts of, 126 starchy, 124 sugar in, 123 Vegetarian diet, 66 Voit's dietary standards, 197 Waste of food, 12 Water, 48 in meat, 69 Wheat, 99 varieties of, 99 whole, 103 winter, 10 1 Work, external, 7^2> internal, 2>2> Yeast, kinds of, 109 i.fB^'Q ^y^^