HOW FOODS ARE PREPARED FOR USE IN BODY 99 



The food requirements of the body. For some time 

 chemists have had a standard of measurement for heat 

 given off when substances are burned. This heat unit 

 is called a calorie. A calorie is the amount of heat 

 required to raise the temperature of one pound of water 

 from zero to four degrees, Fahrenheit. The burning value 

 of foods may be determined and measured in calories. 

 Professor Atwater and others, by means of a series of in- 

 teresting experiments, endeavored to show how much 

 fuel is needed by our bodies each day, as well as the amount 

 of building material. It has been found, for instance, 

 that the human body needs from three to a little over five 

 ounces of protein each day, and enough fuel food to furnish 

 the body with from two thousand to six thousand calories. 

 We may adopt as our standard proportion of nutrients 

 i (protein): i (fat): 4 (carbohydrate). Stated in another 

 way this is about a quarter of a pound of protein, a quarter 

 of a pound of fats, and a pound of carbohydrates each 

 day for a person doing moderate work. More food would 

 be needed if hard work had to be done. 



How foods are prepared for use in the body. We all use 

 foods, but the body does not use them in the condition in 

 which we buy them . If we think for a moment, we will remem- 

 ber that food, in order to become a part of the body, has to 

 pass through the wall of the food tube and get into the blood, 

 and from there be carried to the place where it is to be used. 

 You cannot pass a solid material through a thick wall. Ob- 

 viously, the food tube has in some way to change the materi- 

 als from solids into liquids so that they can get through this 

 thick wall. This process of changing foods into a liquid con- 

 dition which enables them to pass through the walls of the 

 food tube and become part of the blood is called digestion. 



