TX 551 
 .L2 
 Copy 1 
 
 \ 
 
 U. S. DEPARTMENT OF ACxRICULTURE, 
 
 OFFICE OF EXPERIMENT STATIONS, 
 A. C. TKT'E, I):RErTOR. 
 
 — ^i 
 
 THE NUTRITION INVESTIGATIONS OF 
 
 THE OFFICE OF EXPERIMENT STA 
 
 TIONS AND THEIR RESULTS. 
 
 By 
 C. F. LANGWORTHY, 
 
 III Ch<iriji' of Nutrition Jmrxtiijatimis. 
 
 [Reprint from Annual Report of the Office of Ex})eiinieut Stations for 
 the year ended June 30, PKXj.] 
 
 ^7 
 
 tlNGTON :COVERNMENT PRINTING OFTICE : 1907 
 
^7 
 
 CONTEXTS. 
 
 Pag-e. 
 
 Scope of the work 360 
 
 Distribution of the work 363 
 
 Some results of the nutrition investigations 364 
 
 Distribution of food materials in the diet 364 
 
 Dietary studies 366 
 
 Digestion experiments 367 
 
 Respiration calorimeter experiments 368 
 
 Special studies of cereals, legumes, meat, fruits, and nut:^ 370 
 
 Pedagogics of nutrition 371 
 
 Conclusion 372 
 
 II 
 
 SEP C 1907 
 D. ofD. 
 
THE NUTRITiOX INVESTIGATIONS OF THE OFFICE OF EXPERI- 
 ; MENT STATIONS AND THEIR RESULTS. 
 
 "^ By C. F. Langworthy, 
 
 In charge of Niitrition Tnrestiyations. 
 
 In recent years the experimental study of yarioiis prol)lems con- 
 nected with food and nutrition of man and domestic animals has been 
 actiyely followed in the United States. Some of the work has been 
 of a yery practical nature and some has been highly technical. 
 Though they are not commonly considered together, the studies of the 
 food of man and animals have much in common, for of course the 
 physiological laws which underlie the nutrition of the animal body 
 are essentially the same for all warm-blooded animals. Then, too, 
 many experimental methods are common to both classes of inves- 
 tigation, at least as regards the principles on which they are based, 
 though it is needless to say that the details and the manner of using 
 the methods are varied. A considerable part of this inquir}^ into 
 the various food problems has been carried on in connection with the 
 agricultural experiment stations which have been established in the 
 United States during the last thirty j^ears and are now in operation 
 in all the States and Territories of the Union with the exception of the 
 Philippines. In the earlier years of the experiment station movement 
 in this country investigations which had to do with food in a broad 
 sense were quite largely confined to work with domestic animals. 
 However, early in their history many of the experiment stations 
 studied the nutritive value of grains and other foods used by man as 
 well as various problems connected with the storage, handling, and 
 transportation of food products and related questions, and after a 
 time a number of them included studies of the food of man in their 
 regular work. 
 
 Studies of the nutritive value of different foods have been conducted 
 in the United States for a great many 3-ears, but the first systematic 
 attempt to investigate such problems dates from the investigations 
 carried on by Prof. W. O. Atwater for the Smithsonian Institution and 
 for the Massachusetts bureau of labor and statistics, and the nutri- 
 tion investigations of the Office of Experiment Stations are a natural 
 outgrowth of this enterprise, as Professor Atwater, who was the first 
 director of the Office of Experiment Stations, early sought to include 
 this work with the other lines followed. 
 
 In 1894-5 Congress provided a special appropriation which enabled 
 the Secretary of Agriculture to prosecute inquiries in this direction and 
 
 359 
 
360 
 
 KEFOET OF OFFICE OF EXPEEIMEISTT STATIONS. 
 
 tlie work was later assigned to the Office of Experiment Stations. 
 From the first the plan of cooperation with experiment stations, 
 agricultural colleges, and other educational institutions and with 
 philanthropic associations was followed in the belief that such a course, 
 in which each party was a contributor, would yield the most satis- 
 factory returns for a given investment. The sums which have been 
 appropriated by Congress for the nutrition investigations of the 
 Department of Agriculture have been since the beginning as follows : 
 
 ■ Appropriations for nutrition investigations. 
 
 
 
 I 
 
 iscn 
 
 1 year. 
 
 Amount. 
 
 
 Fiscal j-e?.r. 
 
 Amount. 
 
 IvO'- 
 
 ^_ 
 
 
 
 
 ?1 0,000 
 15, OtlJ 
 15,000 
 15, 000 
 15. 000 
 15.000 
 17, ,500 
 
 iOOl-2.... 
 J 902-3.... 
 
 
 S20.000 
 
 189.-)- 
 
 
 
 
 
 20,000 
 
 
 
 
 
 i90;i-4 
 
 1904-.T 
 
 20.000 
 
 
 
 
 
 
 20, 000 
 
 IVI^- 
 
 
 
 
 
 190,5-6 
 
 1906-7 
 
 20,000 
 
 IQOO- 
 
 
 
 
 
 20,000 
 
 -1901 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 
 These amounts have been increased by contributions from other 
 sources, some of which are not easily estimated in terms of money, 
 since they consist in large part of the use of laboratories, apparatus, 
 chemicals, and other facilities for research, the counsel and help of 
 experts, and similar services. Some of the States, notably Connecticut 
 and Illinois, have made special appropriations for the stud}^ of prob- 
 lems relating to the food and nutrition of man, and a considerable 
 number of the experiment stations, educational institutions, philan- 
 thropic associations, and private individuals have donated sums of 
 money to promote cooperative research. 
 
 Until ill health prevented. Prof. W. O. Atwater was the chief of the 
 nutrition investigations and was responsible for the plans and general 
 oversight of the work. A large amount of experimental work was also 
 carried on under his immediate supervision in Professor Atwater's 
 laboratory in the chemical department of Wesleyan University, the 
 Connecticut (Storrs) Experiment Station being a generous contributor 
 to the enterprise. As time progressed and the correspondence and 
 other business arrangements connected with the nutrition investiga- 
 tions developed, it became evident that the enterprise as a whole should 
 be centered in Washington, and at the beginning of the fiscal year 
 1906-7 a division of nutrition investigations was established in the 
 Office of Experiment Stations. 
 
 SCOPE OF THE WORK. 
 
 In the earlier years of the nutrition investigations many analyses of 
 American food materials were made, as the data regarding the chem- 
 ical composition of such food materials were comparatively hmited. 
 Information along this line has, however, accumulated very rapidly 
 
NUTRITION INVESTIGATIONS AND THEIE RESULTS. 361 
 
 as a result of studies carried on by different investigators, and data 
 are now so abundant that studies of proximate composition of food 
 materials no longer constitute one of the lines of work followed in the 
 cooperative nutrition investigations of the Office. Dietary studies — 
 that is, studies of the kinds and amount of food purchased, eaten, and 
 wasted — were early recognized as of great importance, and a large 
 number have been made in private families, schools, colleges, public 
 institutions, and elsewhere under a variety of conditions and in widely 
 separated regions. , 
 
 No matter what its composition, food is of no use to the body 
 unless it is digested, and it is natural that experiments should have 
 been undertaken with a variety of food materials to leain how 
 thoroughly they were assimilated by the body and to ascertain the 
 effect of various methods of preparation and combination upon 
 thoroughness of digestion. Furthermore, it is supposable that the 
 occupation in which the subject is engaged, whether active or seden- 
 tary, may have an influence upon the work of the digestive tract, 
 and this question has also been studied. Many questions regarding 
 the thoroughness of assimilation may be investigated with the aid 
 of ferments under conditions which approximate those in the bod}', 
 and a large number of such artificial digestion experiments have been 
 carried on, particularly in studying ease and rapidity of digestion, a 
 question which is very different from thoroughness of digestion, 
 though the two are often confused in popular discussions of the 
 subject. 
 
 Variations in the excretion of nitrogen have long been regarded as 
 indications of changes taking place in the body, and it has been a 
 general custom of physiologists to study the balance of income and 
 outgo of nitrogen. Such studies have formed a part of the nutrition 
 investigations of the Department. Much more useful as a means 
 of studying the food requirements of the body and other questions 
 are determinations of the balance of carbon, oxygen, and hydrogen, 
 as well as nitrogen, and determinations of the balance of income and 
 outgo of energ}^. Such studies necessitate special apparatus, and a 
 respiration calorimeter has been devised which is admirably adapted 
 to the purpose for which it is designed and which, it seems fair to 
 say, is so far the most perfect instrument of its type. The respiration 
 calorimeter is of such a size that a man may remain in comparative 
 comfort in the respiration chamber for a number of hours or days, 
 and the measurements of income and outgo of matter and energy 
 may be made with great accuracy. The determination of energy 
 values of food and excretory products necessitates some special 
 apparatus for measuring the heat of combustion of these materials, 
 and in connection with the nutrition investigations a bomb calorimeter 
 has been perfected which has proved very satisfactory. 
 
362 REPORT OF OFFICE OF EXPERIMENT STATIONS. 
 
 Numerous studies have been undertaken of the changes brought 
 about and losses sustained when foods of different sorts are cooked 
 in different ways, the principal food materials included in this work 
 being bread, vegetables, and meat. Canning and preserving fruits 
 and vegetables may be regarded as special applications of cooking 
 processes and much experimental work has been done along these 
 lines with a view to the elaboration of satisfactory household methods. 
 In general, it may be said that in connection with the different lines 
 of work mentioned it has been necessary to devise and perfect experi- 
 mental methods, as at the time the investigations were first under- 
 taken the amount of work which had been done in the United States 
 and elsewhere along similar lines was not very considerable. 
 
 The same period which has witnessed the development of the 
 nutrition enterprise has seen a great interest aroused in the teaching 
 of home economics in schools and colleges, and nutrition is one of the 
 main divisions included in this subject? As the nutrition investiga- 
 tions have supplied a great deal of data which the teachers of home 
 economics must use and as the Office was already closely identified 
 with other educational enterprises, it was almost inevitable that the 
 pedagogics of nutrition should receive attention and become an 
 increasingly important part of the nutrition enterprise. 
 
 The preparation of reports of investigations and popular summaries 
 has also constituted an important feature of the work. 
 
 The following table shows in graphic form the character and 
 extent of the investigations which have been undertaken up to July 
 1,1906: 
 
 Cooperative nutrition investigations of the Office of Experiment Stations. 
 
 I Number ! Number 
 Line of work. 1 of inves- i of publi- 
 
 tigations.! cations. 
 
 Dietary studies 
 
 Digestion experiments. 
 
 Experiments on the effect of different circumstances on the income and outgo of 
 
 nitrogen 
 
 Eespiration calorimeter experiments 
 
 Experiments on efl'ects of cooking on meats 
 
 Experiments on losses in cool-ing vpgetatjles 
 
 Investigations on changes and losses in bread making 
 
 Special investigations , 
 
 Compilation of data 
 
 Preparation of popular summaries 
 
 (a) 
 
 a These investigations arc included in the publications reporting digestion experin-ents. 
 
 In addition to the popular summaries and the technical bulletins 
 included in the above table, a large number of briefer summaries 
 have been prepared which have appeared in the series of farmers' 
 bulletins entitled "Experiment Station Work," and for the last ten 
 years the subject of food and nutrition has constituted one of the 
 divisions of the Experiment Station Record, and abstracts of the 
 current literature of the subject have appeared regularly. 
 
NUTKITIUN INVESTIGATIONS AND THEIR RESULTS. 363 
 
 DISTEIBUTION OF THE WORK. 
 
 The cooperative investigations of the Office of Experiment Stations 
 have been carried on in a considerable number of institutions in 21 
 States and Territories. The following brief summary arranged alpha- 
 betically by States shows the localities in which the investigations 
 have been prosecuted and the names of the cooperating institutions: 
 
 Alabama. — Tuskes'ee Normal and Industrial Institute. 
 ......^ 
 
 California. — University of California and California Agricultural Experiment Station . 
 
 Connecticut. — Wesleyan University, Storrs Experiment Station, and Connecticut 
 Bible Normal College. 
 , Georgia. — University cf Georgia. 
 
 Hawaii. — Hawaii Agricultural Experiment Station. 
 
 Illinois. — Hull House, Chicago; Lewis Institute, Chicago; University of Illinois 
 and University of Chicago. 
 
 Indiana. — Purdue University. 
 
 Maine. — University of Maine and Maine Agricultural Experiment Station. 
 
 Maryland. — Baltimore Board of Charities and several public institutions in Balti- 
 more. 
 
 Massachusetts. — Massachusetts Institute of Technology, Boston; School of House- 
 keeping, Boston; Wellesley College, Harvard University, and Bible Normal College, 
 Springfield. 
 
 Minnesota. — University of Minnesota and Minnesota Agricultural Experiment 
 Station. 
 
 Missouri. — University of Missouri. 
 
 New Jersey. — New Jersey Agricultural Experiment Station. 
 
 New Mexico. — New Mexico College of Agriculture and Mechanic Arts and New 
 Mexico Agricultural Experiment Station. 
 
 Neiv York. — Cornell University, Ithaca; Association for the Improvement of the 
 Condition of the Poor, New York; New York Christian Alliance, New York, and 
 Columbia University, New York. 
 
 North Dakota. — North Dakota Agricultural College. 
 
 Ohio. — Lake Erie College. 
 
 Pennsylvania. — Philanthropic institutions, Philadelphia; Drexel Institute, Phila- 
 delphia, and Pennsylvania College for Women, Pittsburg. 
 
 Tennessee. — University of Tennessee. 
 
 Vermont. — Vermont Agricultural Experiment Station. 
 
 Virginia. — Hampton Normal and Agricultural Institute and LTniversity of Virginia, 
 Charlottesville. 
 
 Mention should also be made here of other investigations, which 
 though not strictly a part of the cooperative inquiry yet are so closely 
 related to it that they may be included in the summary. On behalf 
 of the New York State Commission in Lunacy an extended series of 
 dietary studies was undertaken in New York hospitals for the insane, 
 under Professor Atwater's direction, as were also studies at the 
 Elmira Reformatory, New York. For a number of years a sum of 
 money has been granted by the Carnegie Institution for nutrition 
 investigations at Middletown, Conn., and the work has been so 
 planned that it supplemented the investigations there carried on 
 under the auspices of this Department. 
 
3(34 REPORT OF OFFICE OF EXPKRIMFNT STATIOISrS. 
 
 SOME RESULTS OF THE NUTRITION INVESTIGATIONS. 
 
 It is difficult to measure the results of scientific investigations in the 
 usual units, particularl}" when the data sought are in a considerable 
 degree educational. When, as in the case of nutrition investigations, 
 the results have also a very decided practical value and are capable 
 of application on every farm and in every home, such an estimate of 
 values is even more difficult. An idea of the returns given for the 
 money invested may be gathered ftom the fact that since the institu- 
 tion of the investigations in 1894-95, the total sum appropriated for 
 this work has been $222,500. The total number of dietary studies 
 made has been 485, each study having covered from three to thirty 
 days. The total number of digestion experiments with men has been 
 675, and in general each experiment has covered three days. Supple- 
 menting this phase of the work 300 artificial digestion experiments 
 have also been made. The total number of metabolism experiments 
 has been 500, of which 88 have been experiments with the respiration 
 calorimeter. These latter experiments have covered a total of 270 
 experimental days. The total number of cooking experiments has 
 been nearly 200. 
 
 In addition to the above, a number of miscellaneous experiments 
 have been made for the study of special problems, and the studies of 
 pedagogical problems have likewise been numerous. 
 
 As a result of the work 30 farmers' bulletins and 50 technical bulle- 
 tins have been published, as well as numerous short popular summaries. 
 
 In earlier statements " which have been published, attention has 
 been called to some of the important results of nutrition investigations 
 and at this time reference will be made to some of the later work. 
 
 DISTRIBUTION OF FOOD MATERIALS IN THE DIET. 
 
 Food habits vary greatly in different regions of the United States, 
 and firticles of diet which are popular in one region are almost unknown 
 in another. There are certain staple foods, however, such as meat and 
 bread, which are obviously common to all regions, and it is generally 
 conceded that such staple foods are the principal sources of nutritive 
 material in the diet. The proportion of nutrients and energy which 
 different classes of food materials supply in the diet of the average 
 American family is a matter of considerable interest, and the table 
 which follows and which is based on the results of 376 dietarj^ studies 
 gives results which may be regarded as fairlj^ conclusive. 
 
 « Some Results of Dietary Studies in the United States. Reprinted from U. S Dept. 
 Agr. Yearbook, 1898. 
 
 Scope and Results of the Nutrition Investigations of the Office of Experiment Sta- 
 tions. Reprinted from'U. S. Dept. Agr., Office of Experiment Stations Ann. Rpt. 
 1901. 
 
 Investigations on the Nutrition of Man in the United States. U. S. Dept. Agr., 
 Doc. No. 713. 
 
NUTRITION INVESTIGATIONS AND THEIR RESULTS. 
 
 365 
 
 Proportion of nutrients furnished by different food materials in average of 376 American 
 
 dietary studies. 
 
 Food materials. 
 
 Total 
 
 food 
 
 material. 
 
 Protein. 
 
 Fat. 
 
 Carbo- 
 hydrates. 
 
 ANIMAL FOODS. 
 
 Beef and veal 
 
 Per cent. 
 7.2 
 
 .9 
 7.2 
 
 .7 
 
 Per cent. 
 16.7 
 2.1 
 9.3 
 1.6 
 
 Per cent. 
 
 13.2 
 
 2.6 
 
 42.1 
 
 .9 
 
 Per cent. 
 
 Lamb and mutton 
 
 
 Pork, including lard 
 
 
 Poultry 
 
 
 
 
 Total meats 
 
 16.0 
 
 29.7 
 
 58.8 
 
 
 
 
 Fish 
 
 1.8 
 2.1 
 
 3.5 
 4.1 
 
 1.0 
 2.9 
 
 
 Eggs 
 
 
 
 
 Butter 
 
 1.6 
 .3 
 
 16.5 
 
 .3 
 1.0 
 
 S.7 
 
 16.6 
 1.1 
 8.0 
 
 
 Cheese 
 
 
 Milk and cream 
 
 3 6 
 
 
 
 Total dairy products 
 
 18.4 
 .2 
 
 10.0 
 .2 
 
 25.7 
 .2 
 
 3 
 
 
 3 
 
 
 
 
 38.5 
 
 47.5 
 
 88.6 
 
 3 9 
 
 
 
 Wheat flour, patent 
 
 12.2 
 .1 
 
 .1 
 .3 
 
 5.8 
 
 19.4 
 .1 
 
 !5 
 8.1 
 
 1.5 
 
 25.6 
 
 
 2 
 
 Wheat flour, graham 
 
 .2 
 
 
 .1 
 1.6 
 
 1 
 
 Wheat ijread, patent . . . : 
 
 12.4 
 
 
 1 
 
 
 .1 
 .3 
 .6 
 
 8.7 
 .2 
 .5 
 .3 
 
 1.3 
 .1 
 
 .1 
 .5 
 .8 
 10.1 
 .2 
 
 1.0 
 .3 
 
 1.6 
 .1 
 
 
 .2 
 
 Crackers 
 
 .5 
 .9 
 3.8 
 .1 
 . 5 
 
 1 
 
 
 1.4 
 
 
 13.7 
 
 
 .4 
 
 Oatmeal and preparations 
 
 1.1 
 
 
 .9 
 
 Rye 
 
 .1 
 
 3.1 
 
 
 .5 
 
 
 
 
 30.6 
 
 43.0 
 
 9.1 
 
 , 61.8 
 
 
 
 
 5.4 
 
 
 17.5 
 
 
 
 .1 
 
 
 
 
 
 
 1.0 
 
 .6 
 
 12.5 
 
 6.2 
 
 2.9 
 
 .4 
 
 3.8 
 
 1.6 
 
 .2 
 
 :z 
 
 .5 
 
 1.7 
 
 
 .3 
 
 
 8.3 
 
 
 1.7 
 
 
 
 
 20.3 
 
 8.7 
 
 1.0 
 
 12.0 
 
 
 
 
 3.8 
 .6 
 
 .3 
 .2 
 
 .3 
 .1 
 
 2.5 
 
 
 1.2 
 
 
 
 Total fruits 
 
 4.4 
 
 .5 
 
 .4 
 
 3.7 
 
 
 
 Nuts . 
 
 
 
 .1 
 .2 
 
 
 
 .5 
 61.2 
 
 .1 
 
 .6 
 
 
 
 
 52.3 
 
 10.8 
 
 95.7 
 
 
 
 
 .3 
 
 .2 
 
 .6 
 
 .4 
 
 
 
 
 100.0 
 
 100.0 
 
 100.0 
 
 100.0 
 
 
 
 As will be seen from the above table, meats and poultry furnish 
 not quite twice as much protein as all other animal foods together, 
 and of the meats beef and veal together furnish in round numbers 
 half of the protein supplied by the group of total meats. As sources 
 of fat, meats furnish a little over twice as much as is supplied by all 
 the other animal foods, pork being the most important of the meats 
 in this respect. Dahy products are the most important animal 
 
366 REPURT OF OFFICE OF EXPERIMENT STATIONS. 
 
 foods aside from meats, milk and cream together furnishing 10 per 
 cent of the total protein and 26 per cent of the total fat of the diet. 
 The animal foods furnish less than 5 per cent of the total carbohy- 
 drates of the diet, this important food constituent being supplied 
 almost exclusively by the cereals and other vegetable foods. It will 
 be seen that the animal and vegetable foods are about equal in rank 
 as sources of protein, some 52 per cent of the total protein being sup- 
 plied by the vegetable foods, and the cereals furnishing 43 per cent 
 are the most important members of the group. Little fat is furnished 
 by vegetable foods, the group as a whole supplying only 11 per cent 
 of the total amount in the diet. 
 
 DIETAHY STUDIES. 
 
 As a result of the numerous dietary studies and kindred investi- 
 gations, wdiich form a part of the nutrition investigations, dietary 
 standards have been proposed which experience has shown are satis- 
 factory guides for the purchase of food supplies for families and 
 institutions. These so-called standards have been reported and dis- 
 cussed in earlier publications^ and need not be referred to further. 
 How far these so-called standards represent the physiological demands 
 of the body is a question which needs further investigation. 
 
 In the case of actual energy requirements it is obvious that the 
 amount required can not be less than the total quantity given off 
 by a fasting man performing no external muscular work. This 
 question and similar pliases of the subject have been studied with 
 the respiration calorimeter and the results are referred to on 
 page 368. As regards actual protein requirements, it seems very 
 probable that the quantity varies with different physiological con- 
 ditions and other circumstances and further investigations are needed 
 before final deductions are warranted. 
 
 The dietary studies have furnished a number of factors showing 
 the amounts of food required by children of different ages and by 
 women as compared with a man at moderate muscular work. These 
 factors have been referred to in detail elsewhere." 
 
 In earlier work no account was taken of the variations in food 
 requii-ements in old age as compared with middle life. A number 
 of the more recent dietary studies have been made in old-age homes 
 and similar institutions, and as a result of this work the conclusion 
 has been reached that the energ}^ requirements of men and women 
 past middle life are practically the same per kilogram, body weight, 
 and that such persons require nine-tenths as much food as an adult 
 man in full vigor who is engaged in moderate muscular work. 
 
 aJJ. S. Dept. Agr., Farmers' Bui. 142. 
 
KUTKITION INVESTIGATIONS AND THEIR RESULTS. 367 
 
 One of the most obvious applications of the results of the nutrition 
 investigations is found in the commissary department of large public 
 institutions and in general in the feeding of large groups. Available 
 data and experimental methods make it possible to examine the diet 
 under such conditions and pass upon its adequacy and real value, as 
 related to its cost, in much the same wdj that an expert accountant 
 can pass upon the financial condition of any business enterprise. It 
 is often possible to point out ways of checking waste and diminishing 
 cost, or of improving the character of the food without additional 
 expense. 
 
 ♦ As an illustration of the importance of nutrition investigations in 
 ]3ublic institutions it may be said that as a result of studies carried 
 on for several years in large institutions in one of the Eastern States 
 very considerable savings were affected, while the diet as a whole 
 was improved. An examination of the accounts of one of these 
 institutions showed a per capita saving of 13.7 per cent in the second 
 year of the work over the per capita expenditure for the first year, 
 and this reduction is all the more striking in view of the fact that 
 during the year in which it was made the price of a large number of 
 the food materials used had advanced very materially. A similar 
 saving was effected in a number of institutions, and it seems fau* to 
 conclude that the results were applicable to all the public institu- 
 tions in the State. The total cost of the food supplied to all the 
 institutions in the State at the time the studies were made was con- 
 siderabl}' over $1,000,000, and if a similar saving had been made in 
 all these institutions the total saving would have been more than 
 $150,000 per year. 
 
 In general, it may be said that the importance of appljdng the 
 results of the nutrition investigations in the providing of food for 
 public institutions, in the provisioning of camps and expeditions, in 
 regulating the commissary department of the Army and Navy, and 
 in determining the diet in schools and colleges, as well as in the home, 
 is becoming more generally recognized each year as is shown by the 
 man}' applications made to the Department for information along 
 these lines and the numerous requests for aid in carrying on experi- 
 mental dietary studies and other investigations. 
 
 DIGESTION EXPERIMENTS. 
 
 It has long been a custom with physiologists to calculate the 
 digestibility of food of various kinds with the aid of average factors 
 when it was not ])ossible to determine digestibility by actual experi- 
 ments. Since it is the food digested and not the food eaten which 
 is of special importance to the body, it is very often desirable in 
 discussing ihe results of dietary studies to consider digestible nutri- 
 ents rather than total nutrients, and the data desii-ed may be readdly 
 
368 
 
 REPORT OF OFFICE OF EXPERIMENT STATIONS. 
 
 calculated by the use of factors. The following table shows the 
 factors for calculating the digestibility and fuel value of nutrients in 
 a number of single foods and groups of food materials, which have 
 been deduced from the large number of digestion experiments carried 
 on in connection with the nutrition investigations of the Office. xV 
 comparison of calculated results with data obtained from natural 
 digestion experiments has shown that these factors are reasonably 
 accurate, and it seems fau' to say that they are more satisfactory 
 than any which have been hitherto proposed. 
 
 Factors for calculating digestibility and fuel value of nutrients in food ynatcrials. 
 
 
 Protein. Fat. Carbohydrates. 
 
 En- 
 
 
 Pro- 
 por- 
 tion 
 of 
 total 
 
 in 
 mix- 
 ed 
 diet. 
 
 Di- 
 
 gest- 
 ibil- 
 ity. 
 
 Fuel value 
 per gram. 
 
 Pro- 
 por- 
 tion 
 of 
 total 
 
 in 
 mix- 
 ed 
 diet. 
 
 Di- 
 gest- 
 ibil- 
 ity. 
 
 Fuel value 
 per gram. 
 
 Pro- 
 por- 
 tion 
 of 
 total 
 
 in 
 mix- 
 ed 
 diet. 
 
 Di- 
 
 gest- 
 ibil- 
 ity. 
 
 Fuel value 
 per gram. 
 
 pro- 
 por- 
 
 Classes of food 
 materials. 
 
 To- 
 tal 
 nu- 
 tri- 
 ents. 
 
 Di- 
 gest- 
 ible 
 nu- 
 tri- 
 ents. 
 
 To- 
 tal 
 nu- 
 tri- 
 ents. 
 
 Di- 
 gest- 
 ible 
 nu- 
 tri- 
 ents. 
 
 To- 
 tal 
 nu- 
 tri- 
 ents. 
 
 Di- 
 gest- 
 ible 
 nu- 
 tri- 
 ents. 
 
 of 
 total 
 
 ac- 
 tually 
 
 avail- 
 able. 
 
 Meat and fish 
 
 P.ct. 
 33 
 
 4 
 10 
 
 P.ct. 
 97 
 
 97 
 97 
 
 Cals. 
 4.27 
 4.37 
 4.27 
 
 Cals. 
 4.40 
 4.50 
 4.40 
 
 P.ct. 
 1 63 
 
 P.ct. 
 95 
 
 Cals. 
 9.03 
 8.79 
 
 Cals. 
 9.50 
 9.25 
 
 P.ct. 
 4 
 
 P.ct. 
 
 98 
 
 Cals. 
 3.82 
 
 Cals. 
 3.90 
 
 P.ct. 
 
 f 87 
 \ 89 
 
 Dairy products 
 
 26 95 
 
 [ 93 
 
 Annual food (of 
 mixed diet) 
 
 47 
 
 97 
 
 4.27 
 
 4.40 
 
 89 
 
 95 
 
 8.93 ' 9.40 
 
 4 
 
 98 
 
 3.82 
 
 3.90 
 
 89 
 
 
 43 
 3 
 
 85 3. 87 
 
 4.55 1 
 
 if 62 
 
 98 1 4.11 
 
 97 1 4.07 
 
 98 3.87 
 
 4.20 
 4.20 
 3.95 
 4.20 
 4.20 
 4.00 
 
 91 
 
 Legumes (dried) 
 
 78 
 
 3.47 
 
 4.45 
 
 ■ 11 
 
 90 
 
 ! 2 
 
 83 
 98 
 
 Starches . . . 
 
 
 
 
 
 8-37| 9-"50 ■..^:. 98i4.n 
 10 1 95 ; 3.99 
 
 98 
 
 Vegetables 
 
 6 
 1 
 
 83 
 85 
 
 3.11 
 3.36 
 
 3.75 
 3.95 
 
 91 
 
 Fruit 
 
 4 
 
 90 
 
 3.60 
 
 88 
 
 
 
 
 Vegetable food (of 
 mixed diet) 
 
 .53 
 
 85 
 
 3.74 
 
 4.40 
 
 1 
 11 ; 90 
 
 8.37 9.30 96 
 
 97 
 
 4.03 
 
 4.15 
 
 92 
 
 Total food (of 
 mixed diet).. 
 
 103 
 
 92 
 
 4.05 
 
 4.40 
 
 100 
 
 95 
 
 8.93 
 
 9.40 
 
 100 
 
 97 
 
 4.03 
 
 4.15 
 
 91 
 
 The table shows that the different food materials and groups of food 
 materials vary greatly in the thoroughness with which they are assim- 
 ilated. Meats of different sorts, as ordinarily prepared for the table, 
 and indeed animal foods as a whole, are more completely digested 
 than the common vegetable foods. Considering foods as a whole, 
 96 per cent of the total organic material is digested and 91 per cent of 
 the energy is available. In other words, on an average the body 
 rejects only about 4 per cent of the nutrients and about 9 per cent of 
 the energy supplied by the food. 
 
 RESPIRATION CALORIMETER EXPERIMENTS. 
 
 In conducting experiments of various kinds it is often very desirable 
 to Iviiow every requirement of a subject engaged in mi scular work. 
 The exact measurement of energy expenditure is time consuming and 
 requires special apparatus, but with the aid of the factors deduced 
 from the large number of experiments which have been made with 
 
NUTRnrON INVESTIGATIONS AND THEIR RESULTS. 369 
 
 the respiration calorimeter the desired data may be calcuhited approx- 
 imately. In the experiments referred to all grades of muscular 
 activity have been tested, from the quiet of a fasting subject in deep 
 sleep to the excessive muscular work of a professional bicycle rider 
 whose powers were taxed to the utmost. When muscular work was 
 performed other than that involved in the ordinary motions essential 
 to eating and drinking and moving about in the respiration chamber, 
 the muscular exercise consisted in operating a bicycle-like apparatus. 
 The ease with which the wheel turned, and hence the severity of the 
 work could be regulated, and the total amount of work performed 
 could be accurately measured. 
 
 It will be remembered that in discussions of body energy the amount 
 of work is measured in terms of heat, the calorie being the commonly 
 accepted heat unit. It should also be said that under usual conditions 
 the total heat output during a given period affords an indication of 
 the muscular activity of the body. When the body is quiet the heat 
 output is small and when it is active the heat output is correspond- 
 ingly larger, and the same is true of the carbon dioxid output. The 
 average results of the experiments showing the output of carbon 
 dioxid and heat for the body under the different conditions indicated 
 are summarized in the table following, and with the aid of such data 
 the total carbon dioxid and heat output, and hence the total energy 
 output of the body, may be calculated. 
 
 Average normal output of carbon dioxid and heat from the body. 
 
 Conditions of muscular activity. 
 
 Man a t rest, sleeping 
 
 Man at rest, a waive, sitting up 
 
 Man at light muscular exercise 
 
 Man at moderately active muscular exercise. 
 
 Man at severe muscular exercise 
 
 Man at very severe muscular exercise 
 
 Average quantities 
 
 per hour. 
 
 Carbon 
 dioxid. 
 
 Heat. 
 
 Grams. 
 
 Calories.. 
 
 25 
 
 t'5 
 
 35 
 
 leo' 
 
 55 
 
 170 
 
 100 
 
 2,0 
 
 liO 
 
 4;'0 
 
 210 
 
 (00 
 
 It will be seen that the output not only of heat but also of carbon 
 dioxid is very nearly proportional to the amount of muscular work. 
 As an example of the way in which the data included in the table may 
 be used for calculating the carbon dioxid and heat output under 
 varying degrees of muscular activity the following may be cited: 
 
 If a man sleeps eight hours per day, we may say that the carbon 
 dioxid output during this period is approximately eight times the 
 hourly amount eliminated during sleep by the average subject, or 
 8 by 25 = 200. If he is at very severe muscular labor for eight hours, 
 the carbon dioxid output would correspond to eight times the hourly 
 amount for verv severe work, that is, 8 by 210= 1,680. And if the 
 
370 REPORT OF OFFICE OF EXPERIMENT STATIONS. 
 
 remaining eight hours of the day were devoted to going to and from 
 workj eating, sitting, etc., corresponding, say, to six hours of rest and 
 two hours at hght muscular exercise, the carbon dioxid output will 
 be six times the average amount eliminated per hour at rest, that is, 
 6 by 35 = 210 grams, and two times the amount given off at light 
 work, 2 by 55=110 grams. The total for the twenty-four hours 
 would obviously be the sum of the quantities mentioned above, or 
 2,200 grams. The heat eliminated in the twenty-four hours by men 
 at very severe work may be likewise calculated by multiplying the 
 time devoted to sleep, work, etc., by the average hourl}' output. In 
 eight hours at sleep he would eliminate 520 calories (S by 65 = 520); 
 in eight hours at work, 4,800 calories (8 by 600 = 4,800); in six hours 
 of rest, 600 calories (6 by 100 = 600); and in two hours at light exer- 
 cise, 340 calories (2 by 170 = 340); makuig a total for the twenty-four 
 hours of 6,260 calories. 
 
 The investigations made in connection with the respiration calorim- 
 eter have furnished the most accurate records jet available of the 
 normal diurnal variations in body temperature. A summary of this 
 work and a discussion of the results which apply to problems of 
 ventilation and other topics have been included in a recent publica- 
 tion of the Department.'' 
 
 SPECIAL STUDIES OF CEREALS, LEGUMES, MEAT, FRUIT, AND 
 
 NUTS. 
 
 As regards the results of special investigations, particular interest 
 attaches to the studies of the digestibility ajid nutritive value of cereal 
 products. The extensive investigations which have been made with 
 different grades of flour have shown that when ground from the same 
 lot of wheat the standard patent flour furnishes slightly less protein 
 and mineral matter than the coarser flours but surpasses them in 
 digestibility, and so may be fairly said to have a somewhat higher 
 nutritive value pound for pound. The coarser flours have a somewhat 
 laxative effect, which is commonly attributed to their bran content, 
 and are useful in the diet in this way and for the variety which they 
 give. In general, it may be said that flours of all sorts are nutritious 
 and wholesome and among the most iinportant constituents of the 
 diet. 
 
 The investigations with cereal breakfast foods have shown that 
 this class of goods so much used at the present time may constitute 
 an important source of nutritive material, and that although the 
 individual products differ less among themselves in nutritive material 
 than is commonly supposed, as a whole the}^ are nutritious and 
 directly comparable with flours of various tj^pes. The breakfast 
 foods in which the coarser part of the grain has been removed have 
 
 a\J. S. Dept. Agr. Yearbook, 1904, p. 205. 
 
NUTRITIOlSr INVESTIGATIONS AND THEIR RESULTS. 371 
 
 much the same digestibilitv and total nutritive value pound for 
 pound as the finer ifours, while those which retain the outer portions 
 of the grain are more directly comparable with whole wheat and 
 graham flours. 
 
 Studies of the nutritive value of dried legumes have formed an 
 important part of the nutrition investigations and have shown that 
 in general these foods are well assimilated and may be made very 
 important and economical sources of proteia-in the diet. Particular 
 interest attaches to the results obtained with cowpeas, an important 
 crop in the Southern States but little known in other regions. This 
 legume, which possesses a distinctive and palatable flavor and may 
 be cooked in a variety of ways, has been shown to closely resemble 
 the more common beans and peas in digestibility and nutritive mate- 
 rial, and is well worthy of general use. 
 
 The investigations with fruits and nuts have demonstrated that 
 these materials may be fairly regarded as economical sources of nutri- 
 ents and energy, even when used in fairl}^ large amounts, and indicate 
 that an appreciation of their real food value will greatly increase the 
 amounts consumed. 
 
 The extended investigations which have to do with the losses 
 sustained when meat is cooked in various w^ays have showai that 
 the loss is smaller in boiling than in roasting or frying. In general, 
 the principal constituent lost in cooking is water, though when meat 
 is boiled the amount of total substance which is removed may be as 
 great as 20 per cent. Generally speaking, the smaller the cut the 
 greater the percentage loss in cooking. The investigations have also 
 shown that it is possible to control temperature and other factors so 
 that uniform results may be obtained in the preparation of meat in 
 the household or where it is cooked in larger ciuantities. 
 
 PEDAGOGICS OF NUTRITION. 
 
 An examination in detail of the courses in home economics given 
 at the fifty or more agricultural colleges and other institutions receiv- 
 ins: Government aid will show that the instruction in nutrition is very 
 largely based on the results of the food investigations which have been 
 carried on under the auspices of this Department. The same is true 
 of the courses of instruction along this line given in high schools, 
 universities, medical colleges, and other American educational insti- 
 tutions. The number of text-books on food and nutrition has been 
 comparatively limited, and at present a large proportion of teachers 
 criving instruction in these subjects depend on Department publica- 
 tions to supply this need. It is worthy of note that the newer text- 
 books and handbooks of nutrition and physiological chemistry draw 
 very largely upon the data furnished by these nutrition investigations, 
 anci that the authors almost uniformly acknowledge their indebted- 
 ness to the Department work and their appreciation of it. A similar 
 
LIBRARY OF CONGRESS 
 872 REPORT OF OFFICE OF EXPERIME^ 11 
 
 use is made in other countries of the results c n 014 339 773 7 
 
 gations, and as an instance maybe cited the i ^^..^ 
 
 of a considerable proportion of the nutrition publications in connection 
 with the general movement for the dissemination of information 
 ' regarding food and nutrition in that country. 
 
 As a part of the nutrition enterprise special attention is being paid 
 to the collection of data of use to teachers and its arrangement in peda- 
 gogical form, the work being carried on along the lines which have 
 proved so successful in formulating courses in other branches of agri- 
 cultural education. 
 
 CONCLUSION. 
 
 Attention has been directed in the foregoing pages to the lines 
 which have been especially followed in carrying on the nutrition 
 investigations of the Office of Experiment Stations, and some of the 
 results of this important agricultural enterprise have been pointed out. 
 
 As regards their origin, all foods, both animal and vegetable, are 
 agricultural products. In the past the farmer was very commonly 
 the distributor of his products, and the foods passed directly from the 
 farm to the consumer. At the present day this is much less common, 
 and most of the foodstuffs become articles of commerce before they 
 reach the housewife, and in many cases are manufactured products, 
 as they must pass through the mill, the dairy, the packing house, or 
 other manufacturing institution before they are ready for use. 
 
 Briefly stated, the chief object of the nutrition investigations is to 
 secure the better utilization of these varied food products, and it 
 seems fair to say that much has already been accomplished along 
 this line. The housewife in the farm home or in the town has at her 
 disposal a large amount of data regarding the composition, digesti- 
 bility, and nutritive value of foods and their relative economy as 
 sources of nutrients and energy, which will aid her in making a good 
 use of her available food supply, and will help her to prepare for her 
 family a diet which is rational and suited to their physical needs. At 
 the same time, the investigations have demonstrated the importance 
 of having the daily fare palatable, well cooked, and attractive, and 
 have shown how such requirements ma}^ be met without undue cost. 
 The manufacturer and the distributer of food products are likewise 
 helped by the dissemination of knowledge concerning food materials 
 and their preparation, for such knowledge means a greater develop- 
 ment of the important commercial enterprises in which they are 
 interested. And finally, the farmer, the cattle raiser, the dairyman, 
 the market gardener, and all who are direct producers of food supplies 
 are benefited, as a knowledge of the important facts regarding the 
 comparative value of different foods can not fail to bring about 
 improved standards of living, and hence a greater demand for the 
 foodstuffs which they alone can supply. 
 
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