Niacin (Vitamin B3)
Severe niacin deficiency causes pellagra: rash, diarrhoea, confusion and, untreated, death. It’s rare in Australia now. High-dose niacin causes its own problems, from flushing to liver damage.
Pellagra: the signs
- Skin: a rough, dark, sunburn-like rash on sun-exposed skin, often around the neck
- Gut: a bright red tongue, vomiting, diarrhoea or constipation
- Brain: low mood, apathy, headache, fatigue, memory loss, sometimes confusion or hallucinations
- Untreated, it can be fatal
Who’s at risk
- Heavy alcohol use and very poor diets
- Eating disorders, inflammatory bowel disease, cirrhosis
- Carcinoid syndrome and Hartnup disease (rare conditions that use up or lose tryptophan, which the body turns into niacin)
- Some medicines, such as long-term isoniazid for tuberculosis, without B6 supplements
Food sources
- Meat, chicken, fish, peanuts, legumes, wholegrains and fortified cereals.
- Your body also makes niacin from tryptophan in protein foods.
- Adults need about 14–16 mg a day (as niacin equivalents).
High doses
- Flushing: nicotinic acid from about 30–50 mg can cause hot, red, itchy skin. Unpleasant, not dangerous. Nicotinamide (another form) doesn’t flush.
- Liver damage and raised blood sugar can occur at 1,000–3,000 mg a day, especially with slow-release forms.
- Heart disease: two big trials (AIM-HIGH and HPS2-THRIVE, over 25,000 people) found adding niacin to a statin didn’t prevent heart attacks or strokes and caused more side effects. It’s no longer recommended for this.
- Nicotinamide is sometimes recommended by skin specialists to reduce new skin cancers in high-risk people. Ask your doctor before starting.
See your GP if
- You have a rash on sun-exposed skin with diarrhoea or memory problems
- You take high-dose niacin and develop nausea, yellow skin or tummy pain
- You’re considering high-dose B3 for cholesterol or skin cancer prevention
Weird history
- In the early 1900s, pellagra killed thousands in the US South, where people lived on corn. Doctor Joseph Goldberger showed it came from diet, not germs, partly by trying (and failing) to infect himself.
- In Mexico and Central America, corn has long been soaked in lime (nixtamalisation), which frees its niacin. That’s why corn-based diets there didn’t cause pellagra.
Common questions
What is pellagra?
Severe niacin deficiency, causing a sunburn-like rash on sun-exposed skin, gut symptoms such as diarrhoea, and brain symptoms such as low mood, confusion and memory loss. It is treatable with niacin.
Does niacin lower cholesterol and prevent heart attacks?
It changes cholesterol numbers, but large trials found adding it to a statin didn’t prevent heart attacks or strokes and caused more side effects. It isn’t recommended for this.
Why does niacin make my skin flush?
Nicotinic acid widens blood vessels in the skin, causing warmth, redness and itch. It’s harmless and fades. Nicotinamide doesn’t cause flushing.
Can niacin damage the liver?
Yes, at high doses (usually 1,000 mg a day or more), especially slow-release forms. Only take high doses under medical supervision.
Helpful resources
- Healthdirect: Vitamins and mineralsPlain-English Australian Government guide. Free.
- Dietitians AustraliaFind an Accredited Practising Dietitian near you.
Evidence and more information
- NIH Office of Dietary Supplements: Niacin
- Nutrient Reference Values for Australia and New Zealand (Eat for Health)
maladywise.com/niacin/