366 REPORT 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 1 1 per cent 

 of the total amount in the diet. 



DIETARY STUDIES. 



As a result of the numerous dietary studies and kindred investi- 

 gations, which form a part of the nutrition investigations, dietary 

 standards have been proposed which experience has sho^\^l 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 requu-ements 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 phases 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 phj'siological con- 

 ditions and other circumstances and further investigations are needed 

 before final dechictions are warranted. 



The dietary studies have furnished a lumiber 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 

 requirements 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 energy requirements of men and women 

 past middle life are practically the same per kilogi'am body weight, 

 and that such persons require nine-tenths as mucii food as an adult 

 man in full vigor who is engaged in moderate muscular work. 



aU. S. Dept. Agr., Farmers' Bui. 142. 



