healthy individual.

Some of the food-stuffs, such as water and table salt, come to the
body separate from the others; but generally the different types
reach us intimately mingled in the various articles of food in common
use. Foods vary greatly, however, in the amount of the different
food-stuffs they contain. The meats, for example, have a relatively
large protein content; in the vegetables starch, which is one of the
carbohydrates, predominates. As to the choice of food and the amount
that is necessary for the average person, generally the appetite is a
safe guide; but the accurate observations of physiologists have gone
so far as to determine the exact requirements of the body. Not the
least important principle taught by these investigations is to avoid
dietary fads, for in arranging a satisfactory diet the problem to be
solved is not, What is it possible to live on? but, What serves best
as nourishment? The experience of countless generations has taught us
that we thrive best on a diet which includes all five food-stuffs.

_Water_ constitutes nearly two-thirds of the weight of the body.
As water is constantly being given up in the life process, health
demands an abundant supply of liquids to replace the waste. The
average daily loss has been found to be between two and three quarts.
Of this amount the urine constitutes nearly two-thirds; and the
remaining third is eliminated through the skin, the lungs, and the
bowels. Although the deficiency thus created is met in part by the
water in our solid food, the greater part of the loss is made up by
the liquids we drink, and we are warned, in a measure, by the
sensation of thirst that they are needed.

_Mineral material_ is of the greatest importance as a