60 SCIENCE OF HOME AND COMMUNITY 



Uses of nutrients. The only kind of nutrient which can 

 build tissue is protein, hence a certain amount of this 

 kind of food is absolutely necessary for the maintenance of 

 the Ixxiy ; but the amount needed is less than was formerly 

 considered necessary. Proteins also serve as fuel in the 

 body, but it is better that most of this fuel be obtained from 

 other foods. Carbohydrates and fats cannot build tissues, 

 but they serve the purpose of foods in yielding fuel to keep 

 the body warm and to furnish energy for the muscles. 

 Mineral matters aid in forming bone and other tissues and 

 help to regulate some of the activities of the body. Water 

 supplies the body tissues with fluid and carries nutrients in 

 solution. 



Vitamines. Recent studies of foods have shown that in 

 addition to the five nutrients mentioned above there are 

 other substances, called vitamines, that are important for 

 a proper diet. These substances serve a very important 

 purpose in regulating some essential body processes, such 

 as the contraction of the muscles and the absorption of 

 food from the intestines. When these vitamines are lack- 

 ing in the diet serious results to health follow. It' is known 

 that there are two classes of these substances, one of which 

 is soluble in water and the other in fat. The one soluble in 

 water is found in many foods, including milk, eggs, meat, 

 the bran and germ of cereals, succulent vegetables, legumes, 

 and probably in all fruits. The one soluble in fat is found 

 less widely distributed and more care is necessary in plan- 

 ning the diet to see that it is included. This is found in 

 green leaves, such as lettuce, in eggs, liver, and the fat of 

 milk. It is found to a lesser extent in meats, especially in 

 the organs of the body and the fat near them. 



Digestion of food. Before the nutrients can be used in 

 the body they must go through the process of digestion, 

 the purpose of which is to change foods into a soluble form 

 so that they can be absorbed into the blood and used by 



