Proteins constitute the chief material of which our bodily
tissues are built; this material is present in all living cells of the
human, animal, and plant body. Nothing else can take its place in
building new body tissues or in replacing losses of body tissues, worn
out through usage. Aside from their importance in building the living
cells of the body itself, proteins have other important functions in
nutrition in that certain hormones and enzymes used in regulating body
functions are composed in part or in their entirety of protein
substances, and hence we must obtain this type of nutrient in the diet
in order to build these accessory materials, as well as the structure of
the body itself.
During exercise, the contraction and expansion of the muscles
produce lactic acid in considerable quantities from carbohydrates, and
the proteins in the muscles combine with this lactic acid in such a way
as to prevent acidity from building up to a harmful degree. This
protective, or buffer action, of proteins is an important function which
is shared by some other nutrients as well, particularly certain
Proteins provide some energy to the body, since, during the
normal course of bodily activity, protein tissues undergo destruction
with a liberation of chemical energy. In times of starvation, the
oxidation of the protein tissues themselves serves as the chief source
of body energy as long as they hold out, although under normal
circumstances carbohydrates and fats are the body's primary and
secondary supplies of energy, respectively.
An intake of protein insufficient for purposes of building the
new body tissues of growing children will lead to subnormal growth.
Deficiencies of protein of a severe and prolonged type may lead to a
tendency to form abnormal accumulations of water in the tissue spaces,
particularly in the extremities. In this deficiency disease edema—
excessive swelling accompanied by extreme weakness and the wasting away
of the muscles—characterizes the disorder.
Protein deficiency may result from causes other than too low an
amount of protein in the dietary. Gastrointestinal disorders may
interfere with proper protein digestion, and certain diseases may be
associated with heavy losses of protein from the body. These cases
require the personal care of a physician.
Rich food sources of proteins are lean meat including poultry and
fish, eggs, milk, and some vegetables, particularly peas, beans, nuts,
and the germ of cereal grains. The proteins from vegetable sources
should be supplemented by a liberal supply of meat, milk, and eggs.
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Handbook of the
Victory Garden Committee
War Services, Pennsylvania
State Council of Defense
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