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 (when lacking in human diet) 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 for over 50 years to increase levels of HDL in the blood and has been found to modestly decrease the risk of cardiovascular events in a number of controlled human trials .
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 Other forms of vitamin B3 include the corresponding amide, nicotinamide ("niacinamide"), where the carboxyl group has been replaced by a carboxamide group (CONH2), as well as more complex amides and a variety of esters.
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. 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.
Read more about Niacin: Dietary Needs, Deficiency, Lipid-modifying Effects, Toxicity, Nicotinamide, Inositol Hexanicotinate, Biosynthesis and Chemical Synthesis, Receptor, Food Sources, History, Research