"Niacin" redirects here. For the neo-fusion band, see Niacin (band).
Niacin (also known as vitamin B3, nicotinic acid and vitamin PP) is an organic compound with the formula C6H5NO2 and, depending on the definition used, one of the forty to eighty essential human nutrients.
Niacin is one of five vitamins associated with a pandemic deficiency disease: niacin deficiency (pellagra), vitamin C deficiency (scurvy), thiamin deficiency (beriberi), vitamin D deficiency (rickets), vitamin A deficiency (night blindness and other symptoms).
Niacin has been used to increase levels of HDL cholesterol in the blood and has been found to modestly decrease the risk of cardiovascular events in a number of controlled human trials. However, in a recent trial AIM-HIGH, a slow-release form of niacin was found to have no effect on cardiovascular event and stroke risk in a group of patients with LDL levels already well-controlled by a statin drug, and the trial was halted prematurely on evidence that niacin addition actually increased stroke risk in this group. The role of niacin in treating cardiovascular risk remains under debate.
This colorless, water-soluble solid is a derivative of pyridine, with a carboxyl group (COOH) at the 3-position. Other forms of vitamin B3 include the corresponding amide, nicotinamide ("niacinamide"), where the carboxyl group has been replaced by a carboxamide group (CONH2), as well as more complex amides and a variety of esters. The terms niacin, nicotinamide, and vitamin B3 are often used interchangeably to refer to any member of this family of compounds, since they have similar biochemical activity.
Niacin cannot be directly converted to nicotinamide, but both compounds could be converted to NAD and NADP in vivo. Although the two are identical in their vitamin activity, nicotinamide does not have the same pharmacological effects (lipid modifying effects) as niacin; these effects occur as side effects of niacin's conversion. Nicotinamide does not reduce cholesterol or cause flushing. Nicotinamide may be toxic to the liver at doses exceeding 3 g/day for adults. Niacin is a precursor to NAD+/NADH and NADP+/NADPH, which play essential metabolic roles in living cells. Niacin is involved in both DNA repair, and the production of steroid hormones in the adrenal gland.