86 MAINE AGRICULTURAL EXPERIMENT STATION. 



consumed in the body increases to some extent with the amount 

 of external work done. From observation in the respiration 

 calorimeter in feeding experiments and in dietary studies, 

 Atwater estimates that a man at medium work uses daily about 

 45^ ounces of protein (.28 pounds or 125 grams). 



The energy of the body is derived from the potential energy 

 of its food, which can conveniently be measured by its fuel value. 

 The calorie is the unit and is the amount of heat necessary to 

 raise one kilogram of water 1° of the centigrade scale. This is 

 very nearly the same as the amount of heat required to raise 4 

 pounds of water 1° Fahrenheit. The fuel value of foods can be 

 very accurately determined by means of an apparatus termed 

 the calorimeter. For example, the fuel value of a pound of 

 shelled almonds, as given in the table on page 87, is 3,030 calories. 

 This means that if a pound of this substance were burned, the 

 heat given off would be capable of warming four times that 

 number or 12,120 pounds of water 1° F. 



The protein, fats and carbohydrates of the food are burned in 

 the body and their value for this purpose can be best expressed 

 in calories. A person remaining quiet in a temperature near 

 that of the body would theoretically only use sufficient energy to 

 perform necessary vital processes, such as digestion and assimila- 

 tion of food, circulation of the blood, etc. If the temperature 

 of the air is much below that of the body, more nutrients would 

 need to be burned in order to keep the body warm, and if at the 

 same time, exercise were taken or work of any kind done, added 

 potential energy of the food would be needed to perform this. 

 Atwater estimates that a man at medium work uses daily about 

 3,500 calories of potential energy which must be supplied by the 

 food. The .28 of a pound of protein in the daily ration would 

 furnish about 500 calories of energy; the remaining 3,000 

 calories must be furnished in the food in the form of fats and 

 carbohydrates. 



The food for a day's ration for a man at medium work should, 

 therefore, supply about .28 pounds of protein and 3,500 calories 

 of energy, or at the rate of 125 calories for each .01 pound of 

 protein. The above facts and estimates make it easier to under- 

 stand the nutritive value of different food materials and will help 

 in discussing the place of nuts as food. 



