Back
to Main Page
Niacin
Recommended Daily Allowance
| America |
Australia |
UK |
Men: 19 mg
Women: 15 mg |
Men: 19 mg
Women: 13 mg |
Men: 17 mg
Women: 13 mg |
Uses and Facts
Replacement for niacin lost due to inadequate
diet. Treatment for vertigo (dizziness) and ringing in ears. Prevention
of premenstrual headache. Reduction of blood levels of cholesterol and
triglycerides. Treatment for pellagra.
Niacin, which is also known as vitamin
B3, is the common name for both nicotinic acid and nicotinamide (or niacinamide).
It is a water soluble white powder and is more resistant to destruction
than other B complex vitamins. The body can convert the amino acid tryptophan
into niacin.
METABOLISM
Like other B vitamins niacin is essential
for the manufacture of enzymes that provide cells with energy through tissue
respiration and carbohydrate, protein and fat metabolism. Niacin is involved
in over 50 enzyme reactions and is essential for healthy skin, tongue and
digestive tract tissues and the formation of red blood cells.
HORMONES
Niacin is essential for the synthesis of various
hormones including sex hormones, cortisone, thyroxin and insulin. It is
also part of the glucose tolerance factor, a compound which enhances the
body's response to insulin (the hormone responsible for transporting glucose
into cells and storing it in the liver and muscles).
PROTECTION OF GENETIC MATERIAL
The repair of the genetic damage that occurs
when cells are exposed to viruses or dangerous drugs may require niacin.
NERVOUS SYSTEM
Niacin is essential for the normal functioning
of the brain and nervous system.
Absorption
Niacin is absorbed in the small intestine.
As it is water soluble, excess is excreted in the urine although small
amounts may be stored in the liver.
The amino acid tryptophan is converted
to niacin in the body if sufficient thiamin, riboflavin and B6 are present.
More than half the RDA for niacin can be obtained through the conversion
of tryptophan.
Deficiency
Severe niacin deficiency causes the disease
known as pellagra. Symptoms include a reddish skin rash on the face, hands
and feet which becomes rough and dark when exposed to sunlight. Other symptoms
include diarrhea, weakness, loss of appetite, lethargy, a sore mouth and
tongue, inflamed membranes in the intestinal tract and diarrhea. Nervous
system effects include dementia, tremors, irritability, anxiety, confusion
and depression. Pellagra may actually be a complex disorder involving thiamin,
riboflavin and other nutrients. Niacin deficiency was originally observed
in cultures whose diets relied heavily on corn prepared in a way which
left the niacin unavailable for absorption.
Large amounts of tryptophan can overcome
a niacin poor diet. Niacin deficiency is usually seen in those whose diets
are low in niacin and protein. Those at risk of deficiency include those
with absorption difficulties, alcoholics, the elderly who neglect their
diet, some infants and pregnant women.
Sources
Plentiful in meats, niacin is also formed
in the body from protein in eggs and milk. What's more, it's added to the
flour in breads, pastas, and other products--so most Americans get plenty.
The richest sources of niacin and tryptophan
are chicken, fish, cooked dried beans and peas, brewer's yeast, wheat bran,
peanuts, beef and whole grain wheat products. Fruits, vegetables and dairy
products all contain some niacin as do dates, figs and prunes. Flour is
enriched with niacin as processing of grains removes most of their niacin
content.
Niacin is relatively stable to heat and
light, and little is lost during cooking.
Supplements
Niacin supplements are available in nicotinic
acid and niacinamide forms. These have different applications.
Sustained release niacin supplements are
available and although these may reduce the skin flushing reaction caused
by large doses of niacin, they may be more toxic to the liver.
Interactions
Niacin works with other B vitamins.
Niacin may reduce the toxic side effects
on heart tissue of the anticancer drug adriamycin without reducing its
effectiveness in the treatment of cancer. It may also enhance the effectiveness
of anticonvulsant drugs such as phenobarbital.
The amino acid leucine competes with tryptophan
for absorption. Diets low in niacin and high in leucine may lead to niacin
deficiency disease.
Antibiotics may cause niacin flushes to
become more severe.
Alcohol may increase niacin needs.
Back
to Main Page