THE ENERGY EQUATION. 409 



would be but slightly excessive, while the same would be true 

 of carbohydrates. The trouble is with the deficiency in fat. 

 Notice how easily this may be corrected. A pound and a half 

 of beans cooked with one-fourth pound of fat pork will yield 

 over 3000 Cal. and furnish a diet easily assimilated by men at 

 moderate work. What is said of the bean is practically true 

 of the pea; each one approaches in value a mixed meat and 

 cereal diet. 



Required Protein. A much debated question is that of 

 the actual protein requirement, supposing the other food ele- 

 ments sufficiently abundant. The standards given above have 

 not gone unchallenged. Several observers have described 

 metabolism tests in which less than one-half the 120 or more 

 grams of protein, usually considered necessary in the daily 

 food, appears to be sufficient for all needs and able to maintain 

 the body in nitrogen equilibrium. Most of these experiments 

 have been, however, too short to really prove much definitely. 



But recently very elaborate and long continued investiga- 

 tions on groups of men have been described by Chittenden in 

 which the evidence in favor of a low protein requirement is 

 put in an entirely new light, and in which it is also shown that 

 the 3000 large calories of energy in our food is more than 

 necessary for ordinary practical needs. In a group of five 

 professional men Chittenden found an average nitrogen libera- 

 tion corresponding to the metabolism of something over 46 

 gm. of protein daily and an average energy value in the whole 

 food of about 2300 calories through a period of six to nine 

 months. In a group of thirteen soldiers, taking abundant ex- 

 ercise, there was a daily consumption of food having an aver- 

 age value of about 2600 calories, and an average protein con- 

 sumption of about 56 gm. through five months, fall, winter 

 and early spring. In a group of seven student athletes a pro- 

 tein consumption of about 61.5 gm. daily with a total food 

 consumption equivalent to about 2575 calories was observed. 



In all these cases the tests were continued long enough to 

 bring the men into practical nitrogen equilibrium with good 



