Vitamin B3, commonly known as niacin or nicotinic acid, is one of the B complex of water soluble vitamins needed by the body every day.

In its derivative form of nicotinamide, niacin is required by the body for the production of coenzymes known as, if you'll forgive the jargon, nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP).

The importance of NAD and NADP may be shown by the fact that over 200 of the body's other enzymes are dependent on an interaction with them for an almost infinite variety of vital functions.

The antioxidant enzymes, superoxide dismutase, catalase and glutathione, for example, are the body's first line of defence against highly damaging superoxide free radicals and work in a closely complementary fashion. Each of these anti-oxidant enzymes is formed by the body from the amino acids in the proteins in your diet, and each is needed for the others to function correctly.

This holistic functioning of the body is also reflected in the dietary requirements for the successful production of the enzymes. As well as a good supply of first-class protein, ie that containing each of the essential amino acids, a wide variety of vitamins and minerals are required to allow optimal levels of enzyme manufacture.

So for example, vitamin E cannot do its work in the absence of an adequate supply of active vitamin C. In its turn, vitamin C cannot remain active without the presence of glutathione. And although it is the most prevalent anti-oxidant enzyme in the body, glutathione cannot act effectively in the absence of the trace mineral, selenium, and vitamins of the B complex, including B3 and B6.

In addition to its importance in assisting with the manufacture of anti-oxidant enzymes, there is also some evidence that levels of niacin above those required for the avoidance of deficiency may have some protective effect against the DNA cell damage that may be a precursor to the development of cancer.

Intense attention has also been paid to the apparent effectiveness of niacin (or nicotinic acid) in reducing blood levels of Low Density Lipids (LDLs), the so-called "bad" cholesterol, an effect recognised since 1955. It has also been demonstrated by numerous research reports that levels of High Density Lipids (HDLs), or "good" cholesterol may be raised by niacin. This has given rise to extravagant claims for niacin as a natural alternative to conventional heart drugs, including statins. But it has to be stressed that the beneficial effects appear to require pharmacological doses of several grams a day, which should only be taken under medical supervision.

In fact the recommended upper safe level of niacin intake has been set by the Food and Nutrition Board at 35 mg a day to avoid the unpleasant flushing of the face and body which is a common side effect of high doses. At the other end of the scale, the most important extreme deficiency disease relating to vitamin B3 is known as pellagra.

Symptoms of pellagra affect the skin, the digestive system and the brain, so sufferers may develop a heavily pigmented rash on areas of the skin exposed to sunlight; they may experience vomiting and diarrhea and symptoms similar to the early signs of dementia. In the most extreme cases pellagra can even be fatal if allowed to progress untreated.

Fortunately, however, as little as 11 mg of niacin a day has been shown to be sufficient for the prevention of pellagra, and the disease should never now be seen in affluent Western societies. But the Recommended Dietary Allowance (RDA) has been set at a slightly higher, safety, level of 16 mg for men and 14 mg for women To put this in perspective, a small 3oz serving of lean chicken or turkey will provide between 5 and 7 mg, beef 3 mg; and salmon or tuna (a particularly rich source) between 8 and 11 mg. An unfortified cup of cereal may provide 5 mg, fortified perhaps as much 20 mg or more.

Milk, nuts, beans and leafy green vegetables may be useful secondary sources, but it should be noted, however, that unrefined grains such as corn or wheat (even in the form of wholemeal bread) are relatively poor sources because the niacin they contain is not easily absorbed by the human digestive system.

The RDA of 16mg should be easily achieved through a normally well balanced daily diet, and should be enough to prevent deficiency disease, but as always in nutrition, mere absence of disease is not at all the same thing as optimal health. So the sensible approach to supplementation, and the one recommended by numerous authorities to ensure maximum benefits, appears to be to take a multi-vitamin or B complex supplement sufficient to raise niacin intake to around 20 mg a day.