GENERAL METHODS HISTORY OF PROTEID FOOD. 789 



important, from a scientific and from an economic standpoint, to 

 determine the low limit for this equilibrium and to ascertain whether, 

 for the purposes of the best as well as the most economical nutrition, 

 this low limit is as good as or preferable to a higher amount of pro- 

 teid in the diet. Examination of the dietaries of civilized races 

 shows that, on the average, 100 to 120 gms. of proteid are used 

 daily by an adult man. Voit gives 118 gms. of proteid as the average 

 daily consumption. A variable portion of this amount passes into 

 the feces in undigested form, but we may assume that about 105 

 gms. are absorbed and actually metabolized in the body. Experi- 

 ments show, however, that a man may exist in good health upon 

 a much smaller amount per day, as little as 20 to 40 gms.,* provided 

 the non-proteid portion of the diet is increased. The question is 

 whether the large excess of proteid above what is actually necessary 

 for nitrogen equilibrium is beneficial to the body or is harmful, or 

 lastly is merely a waste, or as the older physiologists called it, a 

 luxus consumption. The facts at our command at present are in- 

 sufficient to give a final answer to this question. On the one side, 

 we have the following facts: Some observers (Munk, Rosenheim), 

 from experiments made upon dogs, state that when a low proteid 

 diet is maintained for some time the animals show a marked dis- 

 turbance in digestion and absorption, which may terminate in 

 death. The fact that mankind universally under the guidance of 

 the self-regulating appetite has adopted a high level of proteid food 

 must also be allowed to have considerable weight. With our im- 

 perfect knowledge of all the conditions it is dangerous to assert 

 that this outcome of the processes of natural selection is without 

 important significance. There is also the fact that in the modern 

 treatment of tuberculosis high feeding with proteids constitutes a 

 factor to which much importance is attributed. The inference seems 

 to be that such a diet increases the power of resistance of the tissues 

 toward invading micro-organisms. On the other side, we have the 

 evidence of numerous investigators who have experimented upon 

 themselves that a proteid diet much smaller than that ordinarily 

 used suffices to maintain normal nutrition. Chittenden, especially, 

 in the careful work already referred to, has shown that men in various 

 walks in life, students, athletes, soldiers, may be well nourished, 

 without loss of strength or impairment of the feeling of well-being, 

 on a diet containing 30 to 50 gms. of proteid instead of 118 gms. 

 These observers believe that the excess of proteid usually employed 

 is undesirable in that it increases the amount of injurious nitrog- 

 enous waste products, that it throws an unnecessary amount of 

 labor upon the excretory organs, and that it increases the pos- 



* Consult Chittenden, " Physiological Economy in Nutrition," New York, 

 1905, for discussion and literature. 



