ter. But meat and eggs are not the
only foods high in protein. In fact, most ordinary foods contain more or
less protein. The chief exceptions are butter, oleomargarine, oil, lard,
and cream--which consist of fat (and water)--and sugar, sirups, and
starch, which consist of carbohydrate (and water).

[Sidenote: Proportion of Protein]

Foods should be so selected as to give to the ration the right amount of
protein, or repair-foods, on the one hand, and of fats and
carbohydrates, or fuel-foods, on the other. A certain amount of protein
is absolutely essential. While, for a few days, protein may be reduced
to little or nothing without harm, if the body be long deprived of the
needed protein it will waste away and ultimately death will result.
Therefore, too little protein would be a worse mistake than too much.

The right proportion of protein has been the subject of much
controversy. According to what are regarded as the best investigations,
it is generally about 10 per cent. of the total number of heat-units
consumed. This does not, of course, mean 10 per cent. of the total
weight nor 10 per cent. of the total bulk, but 10 per cent. of the total
nutriment, that is, 10 calories of protein out of every 100 calories of
food.

[Sidenote: Human Milk]

Most persons in America eat much more protein than this. But that
10 calories out of 100 is not too small an allowance is evidenced by the
analysis of human milk. The growing infant needs the maximum proportion
of protein. In the dietary of the domestic animals, the infant's food,
the mother's milk, is richer in protein than the food of the grown
animal. Consequently an analysis of human mother's milk affords a clue
to the maximum protein suitable for human beings. Of this milk
7 calories out of every 100 calories are protein. If all protein were as
thoroughly utilized as milk-protein or meat-protein, 7 calories out of
100 would be ample, but all vegetable proteins are not so completely
available. Making proper allowance for this fact, we reach the
conclusion that 10 calories out of every 100 are sufficient.

[Sidenote: Excessive Use of High-Protein Foods]

A chief and common error of diet consists, then, in using too much
protein. Instead of 10 calories out of every 100, many people in America
use something like 20 to 30. That is, they use more than double what is
known to be ample. This excessive proportion of protein is usually due
to the extensive use of meat and egg