KINDS OF FOOD 349 



changed to protoplasm by the cell, and are used especially 

 for the building up and repairing of the body tissues. 

 Proteids give off some energy when, oxidized, but other 

 nutrients are better for this purpose. 



Gelatine is extracted from bones when they are boiled with water. 

 Like the proteids, it contains nitrogen, and like them gives off some 

 energy when oxidized, but it is not a true proteid, for it cannot be used 

 in the building of body tissues. Substances like gelatine are called 

 albuminoids, meaning, "like the albumins." 



Carbohydrates include the starches and sugars. 

 Starches come from corn, wheat, potatoes, and other 

 plants; sugars come from sugar cane, sugar beets, honey, 

 fruits, etc. Carbohydrates contain carbon, hydrogen, 

 and oxygen only (cf. 123) ; no nitrogen. They are used 

 by the body for the energy (heat) that they furnish. The 

 body seems to be unable to use starch and cane sugar 

 directly. Starch must first be changed to maltose (malt 

 sugar), and this to dextrose (also called glucose, or "grape 

 sugar "). Cane sugar must be changed to dextrose and 

 levulose (fruit sugar). 



Fats and oils contain carbon, hydrogen, and oxygen, 

 just as carbohydrates do (cf. 224). They are present in 

 such food materials as milk, butter, lard, olive oil, and the 

 fat of meat, as well as in eggs, corn, peanuts, etc. Fats 

 and oils, like carbohydrates, furnish heat and energy to 

 the body, but cannot build up protoplasm. The student 

 will see at once that we get these three nutrients (proteids, 

 carbohydrates,. and fats) by eating the bodies or products 

 of animals and plants. 



Our chief mineral food is salt; this is needed for important digestive 

 processes (cf. 364). Salt is present in many foods, and is used to 



