66 FOOD 



63. The Proteids. The proteids are the building foods, 

 furnishing muscle, bone, skin cells, etc., and supplying blood 



and other bodily fluids. The 

 best-known proteids are white 

 of egg, and lean of fish and 

 meat ; peas and beans have 

 ~r^ also an abundant supply of this 



FIG. 27. _ is the amount of fat neces- Substance. This class of foods 

 sary to make one calorie; b is the contains Carbon, Oxygen, and 

 amount of sugar or proteid necessary to . , - . -,-,.. 



make one calorie. hydrogen, and in addition, two 



substances not found in carbo- 

 hydrates or fats namely, nitrogen and sulphur. Since the 

 proteids contain all the elements found in the two other 

 classes of foods, they are able to contribute, if necessary, to 

 the store of bodily energy ; but their main function is up- 

 building, and the diet should be chosen so that the pro- 

 teids do not have a double task. 



For an average man four ounces of dry proteid matter 

 daily will suffice to keep the body cells in normal condition. 



It has been estimated that 300,000,000 blood cells alone 

 need daily repair or renewal. When we consider that the 

 blood is but one part of the body, and that all organs and 

 fluids have corresponding requirements, we realize how vast 

 is the work to be done by the food which we eat. 



64. Mistakes in Buying. The body demands a daily ration 

 of the three classes of food stuffs, but it is for us to determine 

 from what meats, vegetables, fruits, cereals, etc., this supply 

 shall be obtained (Figs. 28 and 29). 



Generally speaking, meats are the most expensive foods we 

 can purchase, and hence should be bought seldom and in 

 small quantities. Their place can be taken by beans, peas, 

 potatoes, etc., and at less than a quarter of the cost. The 

 average American family eats meat three times a day, while 



