Vitamin B3 (niacin)

Niacin is a water soluble vitamin of the B complex group. It is a precursor to NAD+ and NADP+ and hence plays an essential metabolic role in cells.

Biosynthesis

• niacin is synthesised in the liver from the essential amino acid tryptophan

Causes of niacin deficiency

• Hartnup's disease: hereditary disorder which reduces absorption of tryptophan
• carcinoid syndrome: increased tryptophan metabolism to serotonin

Consequences of niacin deficiency:

• pellagra: dermatitis, diarrhoea, dementia