HEAT VALUES OF FOOD 311 



the body to accomplish the various actions essential 

 to the life of the individual. 



Heat Dissipation. Heat is given off by warming 

 the food and liquids consumed, to the temperature of 

 the body; in warming the air we breathe to the body 

 temperature; in the evaporation of water from the 

 lungs and skin ; in the skin it is given off by the pro- 

 cesses of radiation and conduction. 



The quantity of heat essential to the maintenance 

 of the body temperature and the quantity liberated 

 is determined experimentally by a study of the heat 

 values of different foods; another method is by 

 means of an apparatus called a colorimeter, in which 

 is collected and measured the heat given off as a 

 result of oxidation of the food within and given off 

 from the body daily. 



Heat Values of Food. By the first method 1 gram 

 of food is burned, the hydrogen and carbon of the 

 food is chemically converted into carbon dioxide and 

 water as a result of oxidation, and during this change 

 heat is given off and collected which the experiment has 

 proved will raise the temperature of a given amount 

 (1 kilogram) of water. The amount of heat evolved 

 is expressed in gram or kilogram, degrees or calories. 



A calorie is the amount of heat necessary to raise 

 1 gram of water 1 C. It has been demonstrated 

 that certain foods produce far more heat than others 

 (expressed in calories), and hence more or less heat 

 will be dissipated, and an increase or decrease in 

 energy will be apparent, dependent upon whether 

 the diet is rich in proteins, carbohydrates, or fats. 

 The carbohydrates and fats are reduced, after being 

 absorbed to carbon dioxide and water, the proteins 

 are changed to a compound urea with the liberation 

 of heat, expressed in calories as follows: 



1 gram of protein 4.1 calories 



1 gram of fat 9.3 calories 



1 gram of carbohydrates -.4.1 calories 



