Food Values 355 



Food Substances or Nutrients. There .are six food sub- 

 stances : proteins, carbohydrates (starch and sugar), fats and oils, 

 mineral matter, water, and vitamins. All of these substances enter 

 into the composition of the human body. 



Proteins. Proteins form an essential part of protoplasm and 

 are therefore absolutely necessary for the growth and the repair 

 of all living tissues. They also produce energy when oxidized 

 in the body. The most important foods containing proteins are 

 lean meat, milk, cheese, fish, white of eggs, or albumen, and cer- 

 tain seeds, such as beans and peas. 



The chemical elements that enter into the composition of 

 proteins are nitrogen, hydrogen, oxygen, carbon, and sulphur. 

 Animal proteins emit an offensive odor when they decompose. 

 The most important element in all proteins is nitrogen. Proteins 

 are often called nitrogenous or albuminous foods. 



Fats, Oils, and Carbohydrates. Just as proteins provide the 

 material for the growth and repair of tissue, so fats, oils, and car- 

 bohydrates furnish most of the material which, when oxidized, 

 supplies the energy necessary for the body. The most important 

 foods containing fat are butter and meats. All meat foods contain 

 some fat. Milk, cheese, the yolk of eggs, and many seeds, such 

 as cotton seed and flax seed, and nuts yield fat and oil. The most 

 important carbohydrates are starch and sugar. All carbohy- 

 drates are of vegetable origin and are found in fruits, grains, 

 seeds, roots, tubers and, to some extent, in other parts of plants. 

 All fats, oils, and carbohydrates are made up of various combina- 

 tions of carbon, oxygen, and hydrogen. 



Mineral Matter. The most important mineral substances 

 needed by the body are phosphates, carbonates, sulphates, and 

 nitrates, used in the making of protoplasm, bones, and teeth. 

 These substances form a part of green vegetables and grain 

 cereals. Common salt also is important, since it is needed in the 

 digestive fluids and renders food more palatable, or pleasing to 

 the taste. 



Vitamins. Vitamins is a word which has recently come into 

 use to designate various unknown substances in foods that appear 

 to be necessary to the maintenance of perfect health in the body. 



