198 PHYSIOLOGICAL CHEMISTRY 



example. In this case the individual will be excreting less nitro- 

 gen than he receives in his foods. He is said to be in positive 

 nitrogen balance since he is laying up nitrogen compounds. In 

 wasting disease, in starvation, or on insufficient protein diet the 

 loss of nitrogen may be greater than the intake in the food. This 

 condition is known as negative nitrogen balance. 



It is a curious fact that nitrogen balance may be maintained 

 on widely varying levels without any apparent inconvenience. 

 The problem of the necessary amount of protein in the diet thus 

 resolves itself into the problem, on what amount of protein can 

 an individual be kept in nitrogen equilibrium; a further phase 

 of the question will be to determine whether minimum protein 

 is desirable from a physiologic and general p.oint of view. 



If a man is consuming a diet containing 10 grams of protein 

 nitrogen, and is on nitrogen equilibrium at that level, suppose 

 his protein ration to be doubled, so that he will be taking 20 

 grams of protein nitrogen, and that he continue on this diet. 

 The first day he will excrete considerably more than 10 grams 

 of nitrogen, but not the entire 20 grams. The second day he will 

 excrete still more, and on the third or fourth day he again will 

 be in nitrogen equilibrium, but now on 20 grams nitrogen. If 

 this is now cut to 10 grams, the process is reversed, and in three 

 or four days he will be in equilibrium again at the lower level. 



An ardent advocate of a low protein diet was Horace 

 Fletcher, an American who long suffered from ill health. He 

 greatly reduced both the total quantity of food taken, and the 

 amount of protein which it contained. The results were so satis- 

 factory that a study of the problem was undertaken by various 

 investigators. Chittenden carried out a long series of metabolism 

 experiments on several men. Folin's report of the case of Dr. 

 van Sommeren indicated the effects on the quantitative composi- 

 tion of the urine of a low protein diet. (Folin's "30 Normal 

 Urines," an analysis of 30 24-hour specimens was the first com- 

 plete study of the 24-hour output of normal urine constituents. 

 This furnishes a standard for comparison.) These results al- 

 ready have been referred to. Folin himself lived on a starch 



