124 A STUDY OF FOODS AND DIETARIES 



What we should eat. — It is evident from what has abeady 

 been learned that our daily dietary should include all of the organic 

 nutrients, in proper proportions. We must eat to work as well as 

 to grow or to repair our bodies. Our food must contain plenty 

 of water, and we must be sure that we have a supply of certain 

 mineral salts. And perhaps most important of all, we must have 

 a supply of vitamins, in order that nutrition and growth may 

 take place. 



Common Foods contain the Nutrients. — We have already 

 found in our study that various plant foods are rich in different 

 nutrients. Carbohydrates form the chief nutrient in the foods we 

 call cereals, bread, cake, fleshy fruits, sugars, jellies, and the like. 

 Fats and oils are most largely found in nuts and some grains. 

 Proteins are abundant, as we should expect, in those plants which 

 are richly supplied with nitrogen : peas and beans, and in grains 

 and nuts. Animal foods, however, are our chief supply of protein. 

 White of egg and lean meat are almost pure protein and water. 

 Animal foods also supply much fat ; for example, butter, lard, and 

 the fat in meats. 



Water. — Water is, as we have seen, a valuable part of food. 

 It makes up a very high percentage of fresh fruits and vegetables ; 

 it is also present in large proportion in milk and eggs, is less abun- 

 dant in meats, and is lowest in dried foods and nuts. The amount 

 of water in a given food is often a decided factor in its cost, as can 

 easily be seen by reference to the tables on pages 125 and 131. 



Refuse. — Some foods bought in the market may contain a 

 certain unusable portion. This we call refuse. Examples of 

 refuse are bones in meat, shells of eggs or of shellfish, the covering 

 of plant ceUs which form the skins of potatoes, and other vegetables. 

 Part of this refuse, called roughage, is important in our dietary as 

 it stimulates the muscles of the bowels to move and thus aids in 

 preventing constipation. The amount of refuse present also 

 plays an important part in the values of foods. The table ^ on 

 page 125 gives the percentages of organic nutrients, water, and 

 refuse present in some common foods. Similar information is 

 given by the diagrams on pages 126, 127, and 128. 



1 W. O. Atwater, Principles of Nutrition and Nutritive Value of Food, U. S. De- 

 partment of Agriculture, 1902. 



