Vitamin B3 (Niacin)

What it does

Vitamin B3, or niacin, is required to make two of the most heavily used coenzymes in the body: NAD and NADP. These molecules shuttle electrons through hundreds of reactions, making niacin fundamental to how cells release energy from food and how they build fats, cholesterol and other essential molecules. Few nutrients are involved in as many metabolic steps.

NAD also has a role beyond simple energy metabolism. It is consumed by enzymes that repair DNA and help regulate how cells respond to stress and ageing. Because of this, adequate niacin supports the maintenance and repair of tissues throughout the body, as well as normal function of the nervous system and the digestive tract.

Niacin comes ready-made from meat, fish, wholegrains and fortified foods, and the body can also make a small amount from the amino acid tryptophan found in protein. A severe, prolonged deficiency causes pellagra, classically described by the "three Ds" — dermatitis, diarrhoea and dementia. At the high doses sometimes used in medicine, niacin can affect blood fats, but such doses are a treatment rather than a nutritional need and can cause flushing and other effects.