Vitamin B3

Vitamin B3 is a water-soluble vitamin that is also known as niacin. It has some antioxidant effects and exists in two forms: nicotinic acid and nicotinamide. Vitamin B3 can be made in small amounts in the body from the essential amino acid, tryptophan (60mg tryptophan produces 1mg niacin). Because of this, many foods and supplements may describe their vitamin B3 content in the form of 'niacin equivalents', which are equal to the amount of nicotinamide and nicotinic acid they contain plus one-sixtieth of their tryptophan content. Eggs and cheese are some of the richest dietary sources of tryptophan.

Why you need it

Niacin is important for healthy growth and development. Like other B group vitamins, niacin plays an important role in metabolism, enzyme function and energy production. It is essential for releasing energy from muscle sugar stores (glycogen) and for the uptake and use of oxygen in cells.

Because niacin is important for the processing of fatty acids released from body fat stores, it is used medicinally to lower abnormally high cholesterol and triglyceride levels. Niacin works together with vitamins B1 (thiamin) and B2 (riboflavin) for these task, and also works on its own to maintain healthy skin, nerves, intestines and intellectual function.

Niacin also combines with the mineral, chromium, to form the Glucose Tolerance Factor (GTF). This is essential for the action of the hormone, insulin, in controlling the way glucose is taken up into body cells. Lack of either chromium or niacin is associated with impaired glucose tolerance which may lead to diabetes.

Research

Vitamin B3 is a fast-acting aphrodisiac in pure form. It widens blood vessels and produces a so-called niacin flush similar to the sexual flush. It improves blood flow to the penis and also stimulates secretion of histamine - a chemical that naturally helps to intensify sensations during orgasm. It should not be taken in high doses however, as this can cause toxic side effects.

High dose niacin is used medically to treat raised cholesterol levels and reduce the risk of coronary heart disease. It lowers levels of harmful LDL-cholesterol, while raising levels of beneficial HDL-cholesterol and has been shown to reduce the risk of both non-fatal and fatal heart attacks.

Niacin has been shown to reduce blood levels of thyroid hormones without causing symptoms of underactivity. This finding is under further investigation. It is also undergoing further studies to investigate its ability to improve glucose control and reduce the risk of insulin-dependent (Type 1) diabetes, and it investigate a possible protective role against cancer.

Niacin has been shown to increase absorption of dietary zinc and iron from the gut.

How much you need

The EC RDA for niacin is 18mg. People who are physically active need more niacin than those with a sedentary lifestyle.

Children who eat fortified cereals for breakfast are more likely to have adequate intakes of niacin than those who do not eat cereals for breakfast.

High doses of niacin (300mg to 600mg daily) are prescribed medically to lower high cholesterol levels. Excess niacin produces a red flush and warming of the skin similar to blushing. People who blush easily seem to be more sensitive to this effect. For those who are very sensitive, a low dose of aspirin (75mg to 300mg) taken half an hour before the dose of niacin can reduce this effect.

Symptoms of niacin toxicity can occur at very high doses, including thickening and darkening of patches of skin (acanthosis nigricans), palpitations, worsening of pre-existing conditions such as diabetes and peptic ulceration and can also trigger gout and liver inflammation (hepatitis). Therapeutic use of high dose niacin to lower abnormal blood fat levels should therefore only occur under medical supervision.

Lack of vitamin B3 produces a rare deficiency disease known as pellagra. This occurs in parts of Africa where the diet contains large quantities of maize whose niacin is in a non-useable form of niacytin. In central America, maize for cooking tortillas is soaked overnight in calcium hydroxide which releases the niacin content.

Symptoms that may be due to vitamin B3 deficiency include

loss of appetite
headache
nausea
difficulty sleeping
poor memory
irritability
difficulty coping with stress
depression
weakness
fatigue
dry, scaly skin in areas exposed to light
premature wrinkles
sore, fissured tongue
mouth ulcers
inflamed gut and diarrhoea
indigestion
impaired glucose tolerance

Severe deficiency (Pellagra) classically produces symptoms of dermatitis, diarrhoea and dementia.

Foods containing vitamin B3 include

yeast extract
whole grains, brown rice, wholemeal bread and wheat bran
nuts
meat and poultry
oily fish
cheese
dried fruit
eggs
milk

Vitamin B3

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