480 FOOD [CH. XXX. 



and heat being the chief being simultaneously liberated. During 

 muscular exercise the output of carbon greatly increases ; the increased 

 excretion of nitrogen is not noticeable. Taking, then, the state of 

 moderate exercise, it is necessary that the waste should be replaced 

 by fresh material in the form of food ; and the proportion of carbon 

 to nitrogen should be the same as in the excretions : 250 to 15, or 

 16 '6 to 1. The proportion of carbon to nitrogen in protein is, how- 

 ever, 53 to 15, or 3 "5 to 1. The extra supply of carbon must come 

 from non-nitrogenous food viz., fat and carbohydrate. 

 Voit gives the following daily diet : 



Protein 120 grras. 



Fat 100 



Carbohydrate 333 



Kanke's diet closely resembles Voit's ; it is 



Protein 100 grms. 



Fat . . . 100 



Carbohydrate 250 



Such typical diets as these must not be considered as more than 

 rough averages of what is necessary for a man in the course of the 

 day. Actual experience shows that in the diets of different nations 

 there are considerable variations from this standard without the 

 production of ill effects. Age, and the amount of work done, also 

 influence the amount of food necessary ; growing children, for instance, 

 require a relatively rich diet ; thus, milk, the diet of the infant, is 

 proportionally twice as rich in proteins, and half as rich again in 

 fats, as the normal diet given above. During work more food is 

 necessary than during inactivity. 



Attention has recently been devoted to the question whether as 

 much protein as 100 to 120 grammes daily is really necessary, and 

 by far the most convincing of the experiments published in favour 

 of a reduction are those carried out by Chittenden en himself, his 

 colleagues, his students, and on soldiers and athletes, over compara- 

 tively long periods of time. The protein intake was reduced to half 

 and sometimes to less than half the quantity hitherto regarded as 

 necessary. The deprivation was followed by no untoward results ; 

 bodily equilibrium was maintained ; the health remained perfect or 

 improved; the muscular force in athletes was increased; mental 

 acuity was undiminished, and desire for richer food soon disappeared. 



It may be freely admitted that the majority of well-to-do people 

 eat too much protein; there are not many who limit themselves 

 even to Voit's minimum, and in those who are prone to digestive and 

 uric acid diseases, one cannot but feel that improvement in body and 

 mind would be the result of more temperate habits. 



But if we were all to permanently reduce our diet to the 

 Chittenden level, we might be living perilously near the margin; 



