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RESULTS OF FOOD INVESTIGATIONS. 169 
Edible portion.—As the flesh of meat and fish, the white and yolk of eggs, 
wheat flour, etc. The edible portion consists of water and nutritive ingredients 
or nutrients. The principal kinds of nutritive ingredients are prodein, fats, 
carbohydrates, and mineral matters. 
The water, refuse, and salt of salted meat and fish are called non-nutrients. 
In comparing the values of different food materials for nourishment they are left 
out of account. 
Food supplies the wants of the body in several ways. It either— 
Is used to form the tissues and fluids of the body; 
Is used to repair the wastes of tissues; 
Is stored in the body for future consumption; 
Is consumed as fuel, its potential energy being transformed into heat or 
muscular energy, or other forms of energy required by the body; or, 
In being consumed protects tissues or other food from consumption. 
The fuel value of food.—Heat and muscular power are forms of force or 
energy. The energy is developed as the food is consumed in the body. The 
unit commonly used in this measurement is the calorie, the amount of heat 
which would raise the temperature of a pound of water about 4° F. 
The following general estimate has been made for the average amount of 
energy available in 1 pound of each of the classes of nutrients: 
Calories. 
In 1 pound of protein, - - - - - - - - 1,860 
In 1 pound of fats, - - - - - - - - - 4,220 
In 1 pound of carbohydrates, - - - - - - - 1,860 
In other words, when we compare the nutrients in respect to their fuel values, 
their capacities for yielding heat and mechanical power, a pound of protein of 
lean meat or albumen of egg is just about equivalent to a pound of sugar or 
starch, and a little over two pounds of either would be required to equal a pound 
of the fat of meat or butter or the body fat. 
When an intelligent and economical housewife goes to the 
market to make her purchases, she is thinking of meat and 
flour and potatoes; what they cost, and how they will be 
relished. But in fact, though she does not realize it, she is 
buying certain nutritive substances in the food—tissue formers 
and fuel ingredients, which she and her husband need to 
repair the wastes of their bodies and to give them strength for 
their daily toil, and which their children must have for healthy 
growth and work and play. Her real problem, though she 
does not understand it, is to get the most and the best nutri- 
ment for her money. ‘The members of the family need, as 
essential for the day’s diet, certain amounts of protein to make 
blood and anuscle, bone and brain, and corresponding quantities 
of fat, starch, sugar, and the like, to be consumed in their 
bodies, and thus to serve as fuel to keep them warm and to 
