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Niacin (B3 - Niacinamide/Nicotinic Acid)
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).
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:
Recommended Daily Allowance = 18mg
N.B. Only nicotinic acid (NOT niacinamide) can lower blood fat levels.
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.
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:
The main sources of niacin in the diet are meat and meat products, potatoes, bread and fortified breakfast cereals.
1. "Handbook of Dietary Supplements", Pamela Mason, Blackwell Science, 1995.