Niacin (vitamin B3) can be obtained from niacinamide, an amide of niacin that is typically well tolerated and not associated with causing a -flushing" reaction.
Niacin occurs in the body as two metabolically active coenzymes, NAD (nicotinamide adenine dinucleotide) and NADP (NAD phosphate). Niacin has pervasive roles in energy-related and biosynthetic metabolic processes. At least 200 enzymes depend on these niacin cofactors. The NAD-dependent enzymes are involved in mostly catabolic, oxidative reactions that release energy from carbohydrate, fat and protein, whereas the NADP-dependent enzymes more commonly function in biosynthetic pathways of compounds such as fatty acids.