Niacin
(B3 - Niacinamide/Nicotinic Acid)
DESCRIPTION:
Two related compounds - nicotinic
acid and niacinamide (nicotinamide) are both called niacin.
Niacin is also commonly known as vitamin B3, the water-soluble
vitamin that prevents the deficiency disease pellagra.
Niacin may also be made in the body
from the essential amino acid tryptophan. Sixty molecules of
tryptophan are needed to make one molecule of niacin. (The
exception is pregnant women, where the conversion is twice as
efficient).
The conversion of tryptophan to
niacin also requires the presence of other nutrients - such as Thiamin,
Pyridoxine
(vitamin B6)
and Biotin.
Niacin is one of the most stable B
vitamins, being unaffected by light, air or alkalis. The only
appreciable loss of niacin occurs when it leaches into cooking
water.
Niacin forms two coenzymes in the
body, namely nicotinamide adenine dinucleotide (NAD) and
nicotinamide adenine dinucleotide phosphate (NADP). These
coenzymes, like the ones formed by thiamin and Riboflavin,
are involved in the release of energy from food.
Symptoms of minor niacin deficiency
are tiredness, Depression
and loss of memory. The disease pellagra results from a severe
deficiency of niacin, and is characterised by the three D’s - Diarrhoea,
Dermatitis
and dementia. Niacin deficiency is common in certain
maize-eating populations because the niacin in maize (and other
cereal grains) is bound in such a way as to make it unavailable
to the body. To compound this problem, maize is also a
relatively poor source of tryptophan.
Upper safe level for daily
supplementation:
(niacinamide) = 450 mg
(nicotinic acid) = 150 mg
Recommended Daily Allowance = 18mg
Alcoholics:
Alcoholics are commonly deficient in niacin and often need to be
given a supplement of this vitamin (1) - preferably along with
other members of the B complex.
High Cholesterol:
Niacin (as nicotinic acid) has been used to very good effect in
the lowering of cholesterol (2) . However "megadoses"
(usually grams per day) need to be used for this purpose and any
such supplementation should therefore only be done under full
medical supervision.
N.B. Only nicotinic acid (NOT
niacinamide) can lower blood fat levels.
Mental Health:
High levels of niacin have been advocated in certain
schizophrenic conditions (1) and although the information on
this subject is conflicting, there are reported cases of quite
remarkable recoveries using niacin.
Arthritis:
Osteoarthritis and other painful joint conditions may also
respond to niacin treatment (as niacinamide) (1).
Very high doses of nicotinic acid
(3-6 g per day) may cause changes in liver structure, with the
timed release form of the vitamin seeming more likely to be
implicated in this respect. However, safety data on niacinamide
confirms that this form of niacin may be taken at higher
supplement levels than nicotinic acid.
INTERACTIONS
AND CONTRA-INDICATIONS
At levels above 20 mg, nicotinic
acid (NOT niacinamide) may cause dilation of blood vessels in
the skin with resultant skin flushing. This effect usually wears
off after days of repeated administration and occurs to a much
lesser degree if the nicotinic acid is taken with food.
Supplements of nicotinic acid should
not be taken by people suffering from the following conditions:
- Gout
- Diabetes
- Stomach Ulcers
- Liver disease
Food (mg/100g)
Rice bran 18.5
Tuna 11.6
Chicken liver 9.3
Chicken, light meat 8.1
Wheatgerm
5.6
Brown rice 4.7
Broccoli 0.8
Dried figs 0.4
The main sources of niacin in the
diet are meat and meat products, potatoes, bread and fortified
breakfast cereals.
REFERENCES:
1. "Handbook of Dietary
Supplements", Pamela Mason, Blackwell Science, 1995.
2. Crouse JR 3rd, New developments in the use of niacin for
treatment of hyperlipidaemia: new considerations in the use of
an old drug. Coron Artery Dis, 1996,7;4:321-326.
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