Water and mineral salts do not yield heat, but are required to build tissue and to
keep the body in a healthy condition.
In addition, it is well to note that a well-balanced diet is one that contains all
of the five food substances in just the right proportion in which the individual
needs them to build up the body, repair it, and supply it with energy. What this
proportion should be, however, cannot be stated offhand, because the quantity and
kind of food substances necessarily vary with the size, age, and activity of each
person.
Every one of the five food substances just considered must be included in a person’s
diet; yet, with the exception of milk, no single food yields the right amounts of
material necessary for tissue building and repair and for heat and energy. Even milk
is in the right proportion, as far as its food substances are concerned, only for
babies and very young children.
It will thus be seen that to provide the body with the right foods, the diet must
be such as to include all the food substances. In food selection, therefore, the
characteristics of the various food substances must be considered well.
Fats yield the most heat, but are the most slowly digested. Proteins and carbohydrates
are more quickly digested than fats, but, in equal amounts, have less than half as
much food value.
