Niacin in Red Bull

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. 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 Other forms of vitamin B₃ include the corresponding amide, nicotinamide ("niacinamide"), where the carboxyl group has been replaced by a carboxamide group (CONH₂), as well as more complex amides and a variety of esters.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 the same 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 as niacin, which occur as side effects of niacin's conversion. Nicotinamide does not reduce cholesterol or cause flushing.^[1] Nicotinamide may be toxic to the liver at doses exceeding 3 g/day for adults.^[2] Niacin is a precursor to NAD+/NADH and NADP+/NADPH, which play essential metabolic roles in living cells.^[3] Niacin is involved in both DNA repair, and the production of steroid hormones in the adrenal gland.

Niacin is one of five vitamins associated with a pandemic deficiency disease:

• niacin deficiency (pellagra)