THE UTILIZATION OF FOOD IN ANIMALS 345 



353. Proper balance of foods. We should eat every day 

 something made from cereals (Food Group I) either break- 

 fast food or bread or rice or macaroni. Fruit (Food Group III) 

 and vegetables (Food Group IV) should each be eaten at 

 least once a day. Most young people like fruit, but many do 

 not like vegetables and refuse to eat: them. Fruit and vege- 

 tables are important because they help to keep the alimentary 

 canal in good condition, and also because they contain a num- 

 ber of substances very important for growth, such as lime, 

 phosphorus, and iron. Everybody needs some fat. If milk is 

 used, a good deal of fat is furnished; some meats contain 

 much fat, but most people, especially thin people, need to eat 

 some fat (Food Group II) in addition to that from these 

 sources. Fat gives more energy than any other food when it 

 is burned in the body, and most people who need a good deal 

 of fuel, such as soldiers, lumbermen, etc., eat large quantities 

 of fat. We should eat daily some food rich in protein, such as 

 milk, cheese, meat, fish, eggs, peas, or beans (Food Groups IV 

 and V). In addition to its protein, milk contains so many 

 substances important for growth that it should be used every 

 day by growing children. The milk which is used in cook- 

 ing is just as valuable as if it were taken from a glass. 



All foods furnish more or less fuel fat the most, sugar 

 next, and watery fruits and vegetables least of all. An emi- 

 nent scientist thinks that some day we shall buy our food the 

 way a manufacturer buys coal according to its fuel value. 

 If we have to economize on food it is important to know 

 what foods in each group give the most fuel for the money, 

 but we must not omit any important kind of food. If we 

 remember that we should have cereal, protein food, fruit, 

 vegetables, and fat, we shall be able to choose in each group 

 those foods which we can afford. We must also remember 

 that milk is essential for growing children. 



354. Tea and coffee. Tea and coffee have not been men- 

 tioned so far in our discussion of food. The reason for this 



