FOODS 121 



From the foregoing considerations it is essential that the constituents of 

 a normal diet should be present in certain amounts and should bear a certain 

 ratio one to another. Many attempts have been made to construct a suit- 

 able diet for a man weighing 70 kilos while doing light or moderate work. 

 The following are accepted estimates: 



Ranke. 



Grams. 



Protein 100 



Fat 100 



Starch 250 



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 apparent 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 gram 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 equilibrium, 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 

 perhaps the intestinal glands as well. This necessitates on the part of the 

 kidneys, the chief eliminating organs, the expenditure of a certain amount 

 of energy. The wear and tear of these organs will be proportional to the 

 amount of urea and other materials which they are called upon to excrete 

 and if the kidneys fail to excrete them, some may become deposited in the 

 tissues and give rise to certain nutritional disorders. Any unnecessary con- 

 sumption of proteins should therefore be avoided. 



It must be remembered, however, as protein yields energy when me- 

 tabolized, that the heat value of the excluded protein must be balanced by 

 an increase in the amount of either starch or fat or both, an increase the 

 will yield on oxidation an equivalent amount of heat. 



An advantage to the body which a high protein diet (100 to 125 grams) 



