PROBLEMS IN NUTRITION 331 



can even be decreased by muscular activity, for the larger total of 

 nutriment consumed prevents the decomposition of the proteids of 

 the body. 



The total amount of nutriment of a man is almost exclusively 

 determined by the muscular work he performs. The mental work 

 has nothing to do with nutrition; whether the brain is used in- 

 tensely, or whether it is retained as inactive as is possible, as far as 

 we know to-day, does not seem to affect the requirement of energy 

 by the body, nor its requirement of food. The amount of energy 

 required by the individual to sustain his bodily temperature differs 

 but slightly, for the differences in external temperature are nearly 

 compensated by the wonderfully acting heat regulation of our bodies, 

 and the artificial heat regulation by our clothes and dwellings. The 

 influence of muscular activity is very much greater. A man resting 

 quietly in a warm room requires from 1500-1700 calories per day; 

 while one working in the laboratory, or sitting, produces from 2100- 

 2400 calories. For light hand labor this is increased to 2800, while 

 for laborers, Liebig and others have observed from 4000-6000 calories, 

 and Atwater and Wood found up to 8000 calories for the lumbermen 

 of Maine. As the average of all his experiments, Atwater found 2270 

 calories for quiescent, and 4550 calories for hard-working people, i. e., 

 exactly double the value. 



Although the total number of calories varies according to the work, 

 the amount of proteids for all men remains approximately equal, 

 and from this we can draw an important conclusion. The food of 

 those not doing physical work must be relatively richer in proteids, 

 for an equal absolute amount of proteids must be contained in a 

 smaller total amount of food. The foods richest in proteids are meat 

 and the other products of the animal kingdom, and it is evident that 

 the diet must be the richer in meat, the less physical work done 

 by the person. An illustrative example will make this quite clear. 

 A laborer does hard physical work, and consequently requires a diet 

 which produces 5000 calories per day. Consuming only bread, pota- 

 toes, and other vegetable products, he would obtain 100 gr. of pro- 

 teids and even more without trouble. Let us assume that he moves to 

 a city and changes his occupation, living a sedentary life. For this he 

 would require but 2500 calories, and retaining the quality of his diet- 

 ary he would have to do one of two things. Either he must eat the 

 previous quantity, which would be impossible for any length of time, 

 for the body could not use such an excessive amount, or he must 

 decrease it to one half, whereby he would obtain the requisite number 

 of calories, but with them only 50 gr. of proteids. To nourish himself 

 properly, then, he will have to decrease his allowance of food to one 

 half, and add to it 50 gr. of proteids, i. e., about 250 gr. of meat. This 

 example, of course, is extreme, and will not often be observed with 



