Vitamin C is also
known as ascorbic acid. It has antioxidant
properties and protects foods from oxidation, and it is required for all cell
metabolism. It is read-ily destroyed by heat, air, and alkalies, and it is
easily lost in cooking water.
Functions.Vitamin C is known to preventscurvy.This is a disease
char-acterized by gingivitis (soft, bleeding gums and loose teeth); flesh that
is easily bruised; tiny, pinpoint hemorrhages of the skin; poor wound healing;
sore joints and muscles; and weight loss. In extreme cases, scurvy can result
in death. Scurvy used to be common among sailors, who lived for months on
bread, fish, and salted meat, with no fresh fruits or vegetables. During the
middle of the eighteenth century, it was discovered that the addition of limes
or lemons to their diets prevented this disease.
Vitamin C also has an
important role in the formation of collagen, a pro-tein substance
that holds body cells together, making it necessary for wound healing.
Therefore, the requirement for vitamin C is increased during trauma, fever, and
periods of growth. Tiny, pinpoint hemorrhages are symptoms of the breakdown of
Vitamin C aids in the
absorption of nonheme iron (from plant and
ani-mal sources and less easily absorbed than heme
iron) in the small intestine when both nutrients are ingested at the
same time. Because of this, it is called an iron enhancer.
Vitamin C also appears
to have several other functions in the human body that are not well understood.
For example, it may be involved with the forma-tion or functioning of
norepinephrine (a neurotransmitter and vasoconstrictor that helps the body cope
with stressful conditions), some amino acids, folate, leukocytes (white blood
cells), the immune system, and allergic reactions.
It is believed to reduce
the severity of colds because it is a natural antihista-mine, and it can reduce
cancer risk in some cases by reducing nitrites in foods.
Vitamin C is absorbed
in the small intestine.
Sources.The best sources of vitamin C are citrus
fruits, melon, strawber-ries, tomatoes, potatoes, red and green peppers,
cabbage, and broccoli.
Requirements.Vitamin C is measured in milligrams. Under
normal cir-cumstances, an average female adult in the United States requires 75
mg a day and an average male 90 mg. In times of stress, the need is increased.
Regular cigarette smokers are advised to ingest 125 mg or more a day.
It is generally
considered nontoxic, but this has not been confirmed. An excess can cause
diarrhea, nausea, cramps, an excessive absorption of food iron, rebound scurvy
(when megadoses are stopped abruptly), and possibly oxalate kidney stones.
Deficiency.Deficiencies of vitamin C are indicated by
bleeding gums, looseteeth, tendency to bruise easily, poor wound healing, and,