Nearly 50 nutrients; including amino-acids (the constituents
of proteins), carbohydrates, vitamins, and minerals are now known to be
essential for health. A balanced diet is one that can supply all the
essentials. It is almost certain that as time passes still other essential
elements in foods will be isolated. This is added reason why a balanced and varied
diet makes sense; if it is balanced and varied, it can supply all known
requirements and others still unknown.
The currently known essential nutrients
have their specific functions. Briefly, because muscles, heart, liver, kidney,
and other organs are composed chiefly of proteins, proteins are needed for
development and growth of these organs during childhood and adolescence. After
growth is over, body tissues, which are continually being worn out, must be replaced by new materials, So ample dietary
protein is essential at all times.
Meat, fish, milk, and eggs are among the
main sources of protein. Bones are composed chiefly of mineral substances such
as calcium and phosphorus which are required both for original bone formation
and for maintenance. Milk-fresh, canned, dried, skim, or whole-is a major
source. Calcium also is supplied by American and Swiss cheese, molasses, turnip
tops, dandelion greens.
And cereals, meat, and fish contain phosphorus.
The fuel of
life-what the body burns for energy-is sugar. Carbohydrates, which include both
sugars and starches, provide the fuel most readily, for in the body starches
are quickly converted to sugar. Fats and proteins also supply the fuel for
metabolism-not as quickly, but they can be stored by the body as reserves, for
use as needed. Vitamins help to convert foodstuffs into body tissues-skin,
bones, muscles, nerves. Although required only in minute amounts, their role is
obviously vital, and it is suspected that trace elements and perhaps still
other materials yet to be isolated may perform similar functions.
A well-balanced diet-for young and old, active or sedentary,
tall or short-can be supplied daily from four basic food groups: Milk and milk
products- 2 servings for adults; 3 to 4 for children; 4 or more for teen-agers.
One serving equals an 8-oz. glass of whole or skimmed milk; 1 oz . (1 slice) of hard
cheese; or 1/2 cup of cottage cheese.
