REQUISITES OF A NORMAL DIET 



475 



The chief diet-scales which have in the past been drawn up with the 

 object of supplying the proximate principles in the required proportions 

 are given in the table below: 



STANDARD DIETARIES. 



The basis of computation for these diets is to supply the necessary pro- 

 tein nitrogen consumed by the tissues of the body first of all, and then 

 to supply enough potential energy to balance the energy expended per 

 day. 



The amount of the excreted carbon and nitrogen is not always the same. 

 It has been proven possible, for example, to subsist on a diet containing 

 9 or 10 grams of protein nitrogen and 200 grams of carbon in the form of 

 carbohydrates and fats per diem, the ordinary diet for needle-women in 

 London, and the average of the cotton operatives in Lancashire during the 

 famine of 1862. The amount of these elements excreted falls to figures cor- 

 responding to such an income. Of course, upon such a diet the metabolism 

 is low, and persistent physical weakness must be the result, probably from 

 insufficient carbon. The 9 or 10 grams of nitrogen in such a semi-starva- 

 tion diet would be equivalent to 58.5 to 65 grams of protein, whereas the 

 amount of protein in some diets may be as high as 1 50 and more grams per 

 day. Chittenden's nutritional experiments, so often referred to in these 

 pages, have proven that adult men can subsist in nitrogenous equilibrium 

 and do vigorous work and maintain good health, on a protein diet below 

 that given in the above example, i.e., on 6 to 10 grams of nitrogen. In such 

 diets a plentiful supply of carbohydrates is permitted, but the caloric 

 value of the diet is less than those in the table above. 



Not only the proteins but also the fats may vary. The amount may be 

 as low as 35 grams and as high as 125 grams The carbohydrates may 

 vary from 200 grams to 500 grams and upward. Sometimes, with a small 

 proportion of fats, the carbohydrates may be correspondingly increased 

 to make up the necessary quantity of available potential energy. 



