198 GENERAL SCIENCE 



of Calories consumed. If a great amount of protein is eaten, waste 

 matter, such as uric acid, and other poisonous substances are formed. 

 Most foods contain protein. There are a few exceptions, such as 

 butter, oleomargarine, oil, lard and cream, which consist of fat and 

 water; and sugar syrups and starch, which consist of carbohydrates 

 and water. Such foods as meat and eggs are very high in protein 

 values. Cheap sources of proteins are beans, peanuts, skim milk 

 and cheese. 



Protein as Fuel for the Body. The protein compounds are not 

 only used for building and repairing tissue but are also burned 

 directly in the body, like the carbohydrates, thus rendering impor- 

 tant service as fuel. The protein can be so changed in the body 

 as to yield fats and carbohydrates, and such changes actually occur 

 to some extent. In this and in other ways they supply the body 

 with fuel. 



A dog can live on lean meat. He can convert its material into 

 muscle and its energy into heat and muscular power. Man can do the 

 same; but such a one-sided diet would not be best for the dog, and it 

 would be still worse for man. The natural food for carnivorous 

 animals like the dog supplies fats and some carbohydrates, and that 

 for omnivorous animals like man furnishes fats and carbohydrates in 

 liberal amounts, along with protein. Herbivorous animals, like 

 horses, cattle, and sheep, naturally require large proportions of 

 carbohydrates. 



Fat. Fats contain no nitrogen, but have a great deal of carbon 

 and hydrogen which are easily oxidized, producing more energy than 

 protein or carbohydrates. 



A proper proportion of fats in food is about 30 per cent. Oils 

 and fats have a good laxative tendency, but they cannot be taken in 

 too large quantities without destroying the appetite. Cheap sources 

 of fats are oleomargarine and cotton seed oil. 



Carbohydrates. Carbohydrate food is chiefly produced from 

 plants, except milk. Candies, sugars, starches, molasses, honey, etc., 

 are some of the best examples of carbohydrates. The chief sources 

 of carbohydrates are sugar, starch, bread, potatoes, glucose, bananas, 

 etc. These are great fat-producing as well as heat-producing 

 foods. 



