In America, dietary standards have been discussed chiefly by Atwater, Chittenden, and Langworthy. Atwater, in his later writings,* ceasing to make distinction between fats and carbohydrates as sources of energy in ordinary dietaries, but making allowances for different degrees of muscular activity, recommended the following standards:

That these standards were not intended simply as expressions of the actual needs of the body is plainly shown by the allowance of 150 grams of protein for a man at hard work, as against 100 grams for a sedentary man. By his own experiments with men at rest and at work in the respiration calorimeter Atwater had demonstrated that muscular work need not increase protein metabolism, if a sufficient amount of fuel be provided in the form of carbohydrates and fats. Hence, when, in providing for muscular work, he proposes to increase the protein in practically the same ratio as the calories, the idea evidently is not that such an increase is necessary, but simply that it was considered advisable on general grounds not to alter very greatly the nature of the diet in increasing its amount.

* Farmers' Bulletin No. 142, U. S. Department of Agriculture. Also Fifteenth Annual Report Agricultural Experiment Station, Storrs, Conn., 1903.

Langworthy's Compilation Of Results Of Dietary Studies

* In calculating these results it is assumed that women consume 0.8 as much food as men, and children of different ages from 0.3 to 0.8 as much as the man of the family.

In explanation of the liberality of his standards Atwater suggested that "the standard must vary not only with the conditions of activity and environment, but also with the nutritive plane at which the body is to be maintained. A man may live and work and maintain bodily equilibrium on either a higher or a lower nitrogen level, or energy level. One essential question is, What level is most advantageous? The answer to this must be sought, not simply in metabolism experiments and dietary studies, but also in broader observations regarding bodily and mental efficiency and general health, strength, and welfare."

Langworthy, maintaining a similar point of view, has collected the data of large numbers of dietaries believed to be fairly representative of the food habits of people of different occupations in the United States and other countries, and stated them in terms of protein and calories per man per day with the results shown on the preceding page.

Langworthy concludes that the results obtained, the world over, for persons of moderate activity," do not differ very markedly from a general average of 100 grams of protein and 3000 Calories of energy, and that it is fair to say that, although foods may differ very decidedly, the nutritive value of the diet in different regions and under different circumstances is very much the same for a like amount of muscular work." He also points out that in some cases this may not be apparent until allowance is made for differences in body weight. Thus he estimates the average weight of the Japanese professional and business men at 105 pounds, so that their food consumption of 87 grams protein and 2190 Calories corresponds to 105 grams protein and 3120 Calories for a man of 150 pounds, which agrees well with the American average for similar employment.

As a standard for men with more muscular activity, such as mechanics at moderately active work, Langworthy suggests 3500 Calories including 105 grams of protein.

Chittenden differs from those whose standards have been quoted in giving almost no weight to the results of dietary studies, holding that these serve chiefly as a measure of self-indulgence, and that the true measure of what the body will most profitably use is to be found in the results of experiments upon the protein metabolism, such as have been described in Chapter VIII (Factors Determining The Protein Requirement). On the basis of these experiments he proposes as a standard allowance for the man of 70 kilograms body weight, 60 grams of protein and 2800 Calories per day. For business and professional men such as Chittenden evidently has in mind, the allowance of 2800 Calories is in substantial agreement with earlier estimates. Sixty grams of protein for a man of 70 kilograms is, however, decidedly lower than any standard previously current.