Vitamin B3

Niacin, which the body can also make in small amounts from the amino acid tryptophan. A long shortage produces pellagra, historically described by its dermatitis, diarrhoea and dementia.

Forms NAD and NADP, the coenzymes that drive several hundred metabolic reactions. Also involved in DNA repair.

• Meat, poultry and fish
• Peanuts
• Whole grains
• Mushrooms
• Fortified cereals

The body can make a little from tryptophan, which is why protein intake affects requirements.

16 mg NE (men) · 14 mg NE (women) for most adults. The upper limit, past which harm becomes likely, is 35 mg from supplements.

Reference intakes are population figures. Pregnancy, illness, age and medication all move an individual’s needs, which is one of several reasons this page is information rather than advice.

A sustained shortage has a name here: Pellagra. That is worth pausing on — nutrients whose deficiency earned a name are the ones where the consequences were severe enough, historically, to be described as a disease.

Most at risk: Heavy alcohol use, severe malnutrition, and some rare metabolic disorders.

Diets dominated by untreated maize, alcohol dependence, malabsorption, and Hartnup disease. Also carcinoid syndrome and isoniazid treatment, both of which divert tryptophan.

The classic four Ds — dermatitis on sun-exposed skin, diarrhoea, dementia and, untreated, death. Historically endemic where maize was the staple, because its niacin is bound and unavailable unless treated with lime.

Every sign here has other, often likelier, explanations. A list of symptoms is a reason to look into something, never a diagnosis.

Urinary metabolites can be measured but rarely are. The diagnosis is usually clinical, supported by the response to treatment.

Meat, fish, poultry, peanuts, wholegrains and fortified cereals. Traditional nixtamalisation of maize with lime releases the bound niacin, which is why the practice matters.

Nicotinic acid at high doses causes a pronounced flush and, used as a lipid treatment, requires liver monitoring. Nicotinamide does not flush. Neither belongs in high-dose self-treatment.

Nicotinic acid causes intense flushing, itching and headache above about 50 mg. Sustained high doses can damage the liver. The doses once used for cholesterol are prescription territory, not self-treatment.

Interactions: High doses affect blood sugar and uric acid.