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A TEXTBOOK OF PHYSIOLOGY 



A little one, 4,000 calories, is now the amount of the field service 

 ration of the British Army. 



A study of the different dietaries of the world, selected by the 

 people themselves, shows that the age and occupation markedly 

 influence the actual consumption of food, but that economic and other 

 conditions largely influence the diet chosen by men doing the same 

 type of work in different countries. In the following table (Lang- 

 worthy) the physiological availability of food ingested is taken into 

 account : 



These confirm the results of research as to, the amount of protein 

 required in a diet. It is apparent that, allowing for individual tastes 

 and characteristics, 100 to 120 grammes of protein should be con- 

 tained in the diet of an average individual. Allowance also must be 

 made for the fact that all proteins are not of equal nutritive value. 

 Reference has already been made to the great value of protein bodies, 

 like caseinogen, containing aromatic groupings such as tyrosin 

 and tryptophan, and to the inefficiency to support life of bodies like 

 gelatin, zein, hordein, which contain none or little of such groupings. 



Recently it has been suggested that a diet containing a minimum 

 of protein (about 40 to 50 grammes) daily is better. It is certain that 

 an excessive ingestion of protein is harmful, especially when taken with 

 lack of exercise, but the evidence adduced in favour of such a small 

 amount when the individual is healthy and energetic is by no means 

 convincing. It does not follow that a minimum diet is an optimum 

 diet, and since we must assume that the present races are the survivors 

 of the fittest, there is no reason to believe that the ingestion of 100 

 to 120 grammes of protein daily, as is common to all virile races of the 



