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DIETETICS been considerable investigation in some Asiatic countries, notably Japan, but the most active inquiry during the past few years has been in the United States. N'ot all the studies of dietaries are made with sufficient completeness to furnish accurate data. Those which are being made at the present time are probably more trustworthy than most of the older ones. The total number of studies of dietaries which have been reported is difficult to determine. The number which are sufficiently accurate to be included in statistical averages may perhaps be roughly estimated at 700 to 800, of which over 300 have been made within the past ten years in the United States, and more are rapidly accumulating. The number of persons in the individual studies has varied from 1 to 100 or more. The data thus accumulated may be regarded as the beginning of the study of the comparative nutrition of mankind, but are not yet sufficient to warrant the definite generalizations which are to be desired. The figures of the following table will serve as illustrations :— Quantities of Available Nutrients and Energy in Actual Daily Food Consumjition of Persons in Different Circumstances. {Quantities per Man per Day unless othenvise stated.)

Persons with active work English Royal Engineers Prussian machinists, Krupp gun works .... American college athletes Swedish mechanics American machinist’s family ton, Mass. Bavarian lumbermen Persons with ordinary work. Bavarian mechanics Russian peasants Bavarian farm labourers Prussian prisoners. Swedish mechanics. American mechanics’ families American farmers’ families. Professional men. Japanese professional man German physicians. Swedish medical students Danish physician. American professional men’ families .... Japanese students. American college students. Persons with little or no exercise. Men (German) in respiration appa ratus Old men and women1 in house of refuge .... Men (American) in respiration calorimeter .... Prussian prisoners without work Persons in destitute circumstances German factory girls1 Gennan labourer’s family Italian mechanics. American day-labourers’ families Pittsburg, Pa. Prussian farm labourers Miscellaneous. Inhabitants of Java village, World’s Fair, Chicago Bohemians in Chicago. Italians in Chicago Russian Jews in Chicago American negroes .... Mexican families, New Mexico German army ration, peace footing German army ration, war footing. German army ration, extraordinary war ration Italian army ration, peace footing United States army ration, peace footing. ... . 1

800 100 5 2 3

130 874 2 477 3

5 46 12 51 114 18

Grams. Grams. Grams Calories. 132 79 612 3835 129 107 657 4265 157 205 468 4540 174 105 693 4595 167 241 598 5450 120 277 702 6010 112 119 126 117 123 95

32 31 52 28 75 143 124

553 571 526 620 507 390 453

3060 3155 3200 3320 3325 3360 3415

113 120 117 124 96 106 98

20 91 108 133 119 29 141

404 317 291 242 410 616 445

2340 2685 2725 2790 3220 3265 3580

261 377 319 457

2310 2410 2445 3025

222 278 384 299 556

1590 1635 2220 2400 2765

115 94 98 100

61 106 95 128 78 86 105 123 144 105

Quantities per person per day.

18 96 105 98 138 67 37 55 271 13

246 349 379 405 427 595 466 474 321 574 440

1445 2800 2960 3135 3390 3460 2720 3000 4495 2935 3725

7. Hygienic Economy of Food.—For people in good health and with good digestion there are two important rules to be observed in the regulation of the diet. The first is to choose the things which “ agree ” with them, and to avoid those which they cannot digest and assimilate without harm. The second is to use such kinds and amounts of food as will supply the nutrients the body needs, and at the same time to avoid burdening it with superfluous material, to be disposed of at the cost of health and strength. There are people who, because of some peculiarity of the alimentary system, are debarred from using foods which for people in general are most wholesome and nutritious. Some persons cannot endure eggs, others suffer if they take milk, others have to avoid certain kinds of meat, and others experience great discomfort if they eat fruits. But these cases are exceptions. In the processes of cleavage which the compounds of the food undergo in the body, substances are often formed which may be in one way or another injurious. In this sense it is literally true that “what is one man’s meat is another man’s poison.” But for the great majority of people in health proper combinations of the ordinary standard wholesome foods make a healthful diet. On the other hand, some foods have at times a great value over and above their use for nourishment. Fruits and garden vegetables often benefit people greatly, not as nutriment merely, for they may have very little of actual nutrients, but because of the vegetable acids or other substances which they contain, and which sometimes serve a most useful purpose. 8. Quantities of Nutrients Needed.—Various standards have been proposed by physiological chemists to represent the amounts of nutrients needed by people of different age, sex, and occupation for daily sustenance. The problem is this. How much protein, fats, and carbohydrates, or, more simply, what amounts of protein and energy, are required, under varying circumstances, to build and repair muscular and other nitrogenous materials, tissues, &c., and to supply the demand for internal and external muscular work, heat, or other forms of kinetic energy 1 Unfortunately, experimental data are still insufficient for entirely trustworthy averages. Two classes of data are employed for the estimates—dietary studies with considerable numbers of people, and metabolism experiments with individuals in which the income and expenditure of the body are studied by quantitative methods. The standards herewith are not to be considered as exact and final, but merely as tentative estimates of the amounts of nutrients and energy required. As the chief function of the fats and carbohydrates is to serve as fuel, their exact proportion in the diet is of less account than their total fuel-value. In the standards proposed by the present writer, therefore, no proportions of fats and carbohydrates are indicated, the Standards for Dietaries. Available Nutrients and Energy. Carbohydrates. Man at hard work (Voit). . ... Man at moderate work (Voit) Man with very hard muscular work (Atwater) Man with hard muscular work (Atwater). Man with moderately active muscular work (Atwater) Man with light muscular work (Atwater). Man at “sedentary” or woman with moderately active work (Atwater). Woman with light muscular work, or man without muscular exercise (Atwater) 2 3

Grams.2 Grams. Grams. Calories, 3270 437 133 95 485 2965 109 53 5500 161 4150 138 3400 115 3050 103 2700 92 2450 83

One ounce equals 28 "35 grams. Fats and carbohydrates sufficient, with the protein, to furnish the required energy.