Niacin or nicotinic acid is essential for the metabolism of the carbohydrate, fat and protein. It is also essential for the normal functioning of the skin, intestinal and nervous systems. This vitamin differs from the other vitamins of the B-complex group in that an essential amino acid, tryptophan serves as its precursor. Another characteristic of niacin is that it is not excreted in urine as such, but is metabolized to at least 2 major methylated derivatives N-methyl-nicotinamide and N-methyl pyridones.

Casal of Spain first described pellagra in 1735. Dr. Goldberger and his associates studied it between the years 1874 and 1929 and showed that food rich in vitamin B cured pellagra. In 1926 Smith and Hendrick identified that vitamin B contains heat labile and heat stable factors. The latter one cured pellagra. Dr. Goldberger named it as P-P factor.

Who is likely to be deficient?
Pellagra, the disease caused by a vitamin B3 deficiency, is rare in Western societies. Symptoms include loss of appetite, skin rash, diarrhea, mental changes, beefy tongue, and digestive and emotional disturbance.

How much is usually taken?
In part because it is added to white flour, most people generally get enough vitamin B3 from their diets to prevent a deficiency. However, 10–25 mg of the vitamin can be taken as part of a B-complex or multivitamin supplement. Larger amounts are used for the treatment of various health conditions.

It is essential for growth. It takes essential part in metabolism and tissue oxidation. Helps in the formation of fats from carbohydrates. Niacin may reduce the plasma lipid concentration in certain cases of hyperlipaemia, the process is not known.

It prevents pellagra. It has a stimulating effect on central nervous system.

In therapeutic doses, niacin produces the pronounced transient vasodilatation with flushing of the face. This is accompanied by an increase in peripheral blood flow and skin temperature.

Niacin also helps in the functions of the nervous and digestive system. It plays a role in food metabolism and in the formation of red blood cells and skin. NAD and NADP are coenzymes that are part of the energy production system of the body. This system works by means of oxidation and reduction (redox) reactions.

Niacin is suspected to decrease the susceptibility of certain type of cancer such as leukaemia, as a result of increase levels of DNA-repairing coenzymes (NAD).

It is a useful preparation for burn treatment.

People who are taking antituberculaosis drugs such as isoniazid may result in niacin deficiencies. Therefore they need more niacin in diet as compare to others.

Women who take oestrogen contraceptives have a larger requirement for niacin resulting from increased niacin synthesis in their bodies.

People suffering from HIV may be given extra niacin to postpone symptoms and elongate their life.

Niacin can also be useful for alcohol addicts and people with high cholesterol, mental problems, and severe stress problems or hyperthyroid, for athletes and for elderly people.

The requirement for niacin increases in increased calorie intake or expenditure in acute illness, after severe infection, injury etc.