120 A. I. RIXGER 



His children, who were brought up on this low protein diet, measured and 

 weighed as much as others two years older, and possessed great endurance. 



In another series of experiments his assistant lived for a period of 

 178 days on a diet consisting of 30.75 grains of protein (4.76 grams of 

 nitrogen) with a total food supply of 3500 calories per day. Throughout 

 the entire period he enjoyed excellent health and maintained his hody 

 weight. 



During Jhe period of the World War opportunity was afforded to study 

 this problem on a large scale because of the forced reduction in protein in- 

 gestion by most of the people of the Central European empires. 



Thus Lichtwitz (1917) reports the maintenance of nitrogenous equilib- 

 rium by citizens of Gottingen, living on 2400 calories and 64.9 grams of 

 protein per day and weighing 70 kg. 



Jansen (1917 (a)) carried on a series of experiments on thirteen indi- 

 viduals for periods of several months (March to May, 1917). They 

 were engaged in light work and received 60.5 grams of protein, with car- 

 }x)hydrates and fats to make up a total energy supply of 1600 calories per 

 day. On this diet they were unable to maintain either nitrogenous equilib- 

 rium or body weight. 



The average loss per day was 0.28 kg. of body weight and 11.77 grains 

 of protein (1.9 grams nitrogen). He then increased the carbohydrate 

 and fat in the diet to the extent of 500 calories, i. e., they received the 

 same amount of protein, but a total energy supply of 2100 calories. Doing 

 the same amount of work, they were able to maintain nitrogenous equilib- 

 rium and body weight. The average weight of his subjects was 62.1 kg., 

 the nitrogen ingested was 9.68 grams; hence the amount of nitrogen per 

 kg. was 0.156 gram, or slightly above Chittenden's figures. 



These experiments by Jansen prove definitely that it was not the low 

 protein in the diet that was responsible for the loss in body weight and 

 negative nitrogen balance, but the low caloric supply. 



The question of optimum versus minimum protein supply in the diet 

 of man cannot be answered on the basis of physiological experiments alone. 

 In a great many instances, it is purely an economic question, and at the 

 same time psychological factors and the influence of habit play a tre- 

 mendous role. 



Advocates of a low protein diet describe in glowing terms the psychic 

 state of well-being when on a low protein diet, whereas the man accustomed 

 to a full protein diet complains bitterly when forced to live on a restricted 

 protein diet. ' 



The consensus of opinion of most workers in this field seems to be 

 that for a normal individual the ingest ion of Yoit's quota of 118 grains 

 of protein per day (19 grams of nitrogen or 0.271 gram per kg. of body 

 weight) is not objectionable, but offers no special advantage. Man can 



