Vitamin B3 (Niacin / Nicotinic Acid & Nicotinamide)

Direct Answer

Vitamin B3 comprises nicotinic acid and nicotinamide, precursors to NAD+ and NADP+ coenzymes central to over 400 enzymatic cellular reactions and DNA repair by PARP enzymes. Adult RDA is 16 mg NE (men) / 14 mg NE (women), with a Tolerable Upper Limit of 35 mg/day.

Source: NIH ODS / EFSA · Last reviewed Aug 28, 2026

Specs

Nutrient Type	Water-Soluble Pyridine Vitamin
Adult RDA / RDI	16 mg NE / day (Men) / 14 mg NE / day (Women) (NE = Niacin Equivalents)
Tolerable Upper Limit (UL)	35 mg / day (Supplemental nicotinic acid; prevents prostaglandin flushing)
Chemical Forms	Nicotinamide (Niacinamide), Nicotinic Acid, Nicotinamide Riboside (NR), Nicotinamide Mononucleotide (NMN)
Primary Biological Function	NAD+/NADH redox electron carrier in glycolysis/TCA cycle, NADP+/NADPH reductive biosynthesis, PARP-1 DNA repair, Sirtuin activation
Deficiency Condition	Pellagra ('The 4 Ds': Diarrhea, Dermatitis on sun-exposed skin, Dementia, Death)
Top Whole Food Sources	Chicken Breast, Canned Tuna, Salmon, Beef, Turkey, Peanuts, Brown Rice, Shiitake Mushrooms
Tryptophan Biosynthesis Pathway	60 mg of dietary amino acid L-tryptophan converts endogenously into 1 mg of niacin (1 NE)

The Prostaglandin Niacin Flush

Doses of crystalline nicotinic acid >50mg stimulate Langerhans cell GPR109A receptors, releasing prostaglandin D2 and E2 which cause intense dermal capillary vasodilation, tingling heat, and skin redness lasting 30–60 minutes.