POODS AND DIETARIES 331 



be flesh-forming foods. They are, however, oxidized to release 

 energy if occasion requires it. 



, Fats and Oils. — Fats and oils, both animal and vegetable, 

 are the materials from which the body derives part of its energy. 

 The chemical formula of a fat shows that, compared with other 

 food substances, there is very little oxygen present; hence the 

 greater capacity of this substance for uniting with oxygen. The 

 rapid burning of fat compared with the slower combustion of a 

 piece of meat or a piece of bread illustrates this. A pound of butter 

 releases over twice as much energy to the body as does a pound of 

 sugar or a pound of steak. Human fatty tissue is formed in part 

 from fat eaten, but carbohydrate or even proteid food may be 

 changed and stored in the body as fat. 



\J Carbohydrates. — AYe see that the carbohydrates, like the fats, 

 contain carbon, hydrogen, and oxygen. Here, however, the 

 oxygen and hydrogen are united in the molecule in the same 

 proportion as are hydrogen and oxygen in water. Carbohydrates 

 are essentially energy-producing foods. They are, however, of use 

 in building up or repairing tissue. It is certainly true that in both 

 plants and animals, such foods pass directly, together with foods 

 containing nitrogen, to repair waste in tissues, thus giving the 

 needed proportion of carbon, oxygen, and hydrogen to unite 

 with the nitrogen in forming the protoplasm of the body. 



Inorganic Foods. — ^Vater forms a large part of almost every 

 food substance. The__hum^n body, by weight, is composed of 

 about 60 per cent water. It is used to make the blood, and a 

 sufficient quantity is most essential to health. When we drink 

 water, we take with it some of the inorganic salts used by the body 

 in the making of bone and in the formation of protoplasm. Sodium 

 chloride (table salt), an important part of the blood, is taken in 

 as a flavoring upon our meats and vegetables. Phosphate of 

 lime and potash are important factors in the formation of bone. 



Phosphorus is a necessary substance for the making of living matter, 

 milk, eggs, meat, whole wheat, and dried peas and beans containing small 

 amounts of it. Iron also is an extremely important mineral, for it is used 

 in the building of red blood cells. Meats, eggs, peas and beans, spinach 

 and prunes, are foods containing some iron. 



Some other salts, compounds of calcium, magnesium, potassium, and 



