590 METABOLISM 



with men the percentage that should be allowed for women and children. 

 The figures are as follows: 



Man 100 



Woman 83 



Boy over 16 92 



Boy 14-16 81 



Girl 14-16 74 



Child 10-13 64 



Child 6-9 49 



Child 2-5 36 



Child under 2 23 



In calculating the calorie requirement of the population as a whole, 

 the necessity of making allowance for the varying needs of men, women, 

 and children would obviously make the calculations far too complicated 

 for practical purposes. It is necessary to have a factor by which we 

 may multiply the total population in order to determine its "man value." 

 This factor is based on the relative proportion of men to women and 

 children, and it amounts very nearly to 0.75, i. e., three-quarters of the 

 total population gives "the man value." Knowing the total population, 

 say, of a city, we must therefore multiply this by 0.75 in order to ascer- 

 tain for how many men doing moderate muscular work (3000 C.) food 

 has to be provided. 



THE PROTEIN REQUIREMENT 



The facts considered in the previous two chapters lead to the question: 

 To what extent may the proportion of protein in the diet be reduced 

 with safety? It is evident that there must be a minimum below which 

 every one of the necessary building materials of protein could not be 

 supplied in adequate amount to reconstruct the worn-out tissue protein. 



The extent to which the protein content of the diet of man can be 

 lowered with safety depends on several factors, of which the most im- 

 portant are: first, the nature of the protein; second, the number of non- 

 protein calories ; and third, the extent of tissue activity. Where so many 

 factors must be taken into consideration, the only method by which the 

 actual minimum can be determined consists in what may be called "cut 

 and try experiments." Of the many investigations of such a nature, 

 probably the best one for us to consider, is that recently published from 

 the Nutrition Laboratory of Copenhagen. The subject, an intelligent 

 laboratory servant, lived a perfectly normal and active life for a period 

 of five months on a diet of potatoes cooked with margarine and a little 

 onion, and containing 4000 C., with a total protein content of 29 grams. 

 During another period he did outdoor work as a mason and laborer, and 

 took 5000 C. daily, and 35 grams of protein. 



