THE PROTEIN REQUIREMENTS OF MANKIND 101 



ing at least 100 grammes of protein daily, despite variations in 

 race, country, climate, and dietetic habits, is very significant, 

 and has been acknowledged by most observers as conclusive 

 evidence of the need of at least this amount of protein. This 

 argument is all the more forcible and convincing in view of the 

 fact that all the world over protein, particularly animal protein, 

 is one of the most expensive constituents of the food, often 

 involving a good deal of labour and sacrifice to procure. 



On the data furnished by freely chosen diets in different parts 

 of the world have been founded the standard dietaries which 

 have been given in detail in a former chapter. The most popular 

 and widely accepted of these is, perhaps, that laid down by 

 Voit, which provides 118 grammes of assimilable protein for an 

 energetic man doing a moderate amount of work. Up to com- 

 paratively recent times the approximate correctness of these 

 standards has never been called in question. They were regarded 

 as the minimal quantities that should enter into any well- 

 balanced diet, but not as bounds beyond which it was dangerous 

 to exceed. 



It has been objected to these standards, based on the dietetic 

 customs and habits of mankind, that, although the consumption 

 of over 100 grammes of protein daily is almost universal, it 

 does not necessarily follow that it is to the welfare of the body. 

 It has been pointed out that " habits and cravings are certainly 

 very unreliable indices of true physiological requirements ;" that 

 " dietetic requirements and standard dietaries are not to be 

 founded upon the so-called cravings of appetite and the in- 

 stinctive demands for food, but upon reason and intelligence, 

 reinforced by definite knowledge of the real necessities of the 

 bodily machinery." Chittenden even goes so far as to say : 

 " Standards which have been adopted more or less generally 

 throughout the civilized world, based primarily on the assump- 

 tion that man instinctively and independently selects a diet 

 which is best adopted to his individual needs, are open to grave 

 suspicion. The true food requirements of the body, under any 

 conditions, cannot be ascertained with any degree of accuracy 

 by observations of what people are in the habit of eating.' 

 Mankind, according to Chittenden, is guided by blind instinct 

 or the leadings of a capricious appetite, and eats as much of the 

 higher and more expensive protein food materials as he can 

 afford. Certainly, the only people who fail to attain the ordinary 



