FOODS. 



117 



food principles which were calculated as necessary to replace the tissue and 

 food metabolized. 



COMPARISON OF THE INCOME AND OUTCOME. 



Other estimates as to the amounts of the organic food principles required 

 daily based on the amount of the excreted products are as follows: 



From the foregoing estimates it is assumed that for the maintenance 

 of nitrogen equilibrium an amount of protein, 100 grams or more, or about 

 1.5 to 1.7 grams for each kilogram of body weight must be consumed each 

 day; and that if the amount falls below this minimum the tissues will be 

 called upon to yield up a portion of their protein and thereby undergo 

 deterioration with a consequent loss of their efficiency. 



It has, however, been established that nitrogen equilibrium can be main- 

 tained without detriment to the body or its activities, for a variable period 

 of time, extending over months and years, on a diet much poorer in its 

 protein content than in any of the foregoing diets. Chittenden has demon- 

 strated by a long series of carefully conducted experiments on human 

 beings, that the protein intake can be reduced to 60 grams or 0.85 grams 

 for each kilogram of body weight without any impairment in the working 

 capacity of the tissues or of the individual. Even this amount is in actual 

 excess of the tissue needs as the protein metabolism according to Chittenden's 

 experiments probably does not amount to more than 0.75 grams for each 

 kilogram of body weight. 



The daily observations of some twenty-four individuals who were placed 

 on a diet in which the protein content was low for a period varying from 

 five to eighteen months revealed the fact that they not only maintained the 

 nitrogen equilibrum but that they gained in weight and strength as shown 

 by their capacity to meet successfully various endurance tests. These 

 experiments would therefore indicate that the consumption of 100 or more 

 grams of protein each day is unnecessary and that any amount beyond that 

 actually needed for tissue repair, approximately 60 grams or even less for 

 an individual weighing 70 kilograms is undesirable, for, as will be stated in 

 subsequent pages, all protein when metabolized yields a series of nitrogen- 

 holding bodies which must be subsequently eliminated by the kidneys and 



