FOODS AND THEIR USES 61 



is about the amount eaten by a man of average appetite. 

 In order to secure a heathful diet, the general principles 

 stated in the following paragraphs should be borne in mind, 

 by an adult or by a growing boy or girl. 



73. Necessity for a mixed diet. A sufficient variety 

 of foods should be eaten at each meal to obtain all the 

 nutrients needed. In 69 we learned that in none of the 

 foods on the chart are the nutrients in the right proportions. 

 Cow's milk comes the nearest to being a perfect food, but 

 its percentage of carbohydrates is too small. If we were 

 to feed on meat alone, we should get too large an amount of 

 proteins; while most of the vegetable foods are lacking in 

 fats. Hence, a well-balanced diet should consist of a mixture 

 of many kinds of foods. Such a diet will supply not only 

 the proteins, fats, and carbohydrates, but also the mineral 

 matters so necessary in the development of the bones and 

 teeth, and in the making of living substance. In fact, some 

 foods, such as spinach, are valuable chiefly on account of 

 the mineral matters which they contain. If the appetite 

 is normal, one is fairly sure to secure the nutrients in ap- 

 proximately the right proportions. 1 



tein for each day is considerably more than the body really needs. 

 Dr. Chittenden experimented on five of the Yale University pro- 

 fessors, on thirteen soldiers of the United States army, and on five 

 of the best athletes at Yale ; he found that all agreed that they 

 could do better physical and mental work, and do it without any loss 

 of weight, when they had become accustomed to taking less than half 

 their ordinary amount of proteins. In several instances rheuma- 

 tism, biliousness, and other derangements of the body were cured by 

 this restricted diet. "There is no question, in view of our results," 

 says Professor Chittenden, " that people ordinarily consume much 

 more protein food than there is any real physiological necessity for, 

 and it is more than probable that this excess of food is in the long 

 run detrimental to health, weakening rather than strengthening the 

 body, and defeating the very objects aimed at." 



1 It is desirable that pupils prepare a list of the kinds of foods and 

 beverages, stating quantity of each, that formed their diet on the 



