Niacin (Vitamin B3): The Evidence, Food Sources, and Supplement Guidance

Quick answer

Niacin, also called vitamin B3, is a water-soluble vitamin the body uses to turn food into energy and to keep the skin, nerves, and digestive system healthy. Severe deficiency causes pellagra, a disease with the classic pattern of dermatitis, diarrhea, and dementia, which is now rare and mostly limited to very restricted diets. The biggest myth around niacin is that high-dose supplements are a good way to improve cholesterol: large doses can lower LDL and triglycerides, but major trials found they did not reduce heart attacks or deaths, and they caused side effects, so they are no longer a routine cholesterol treatment. Food sources include poultry, fish, meat, peanuts, and fortified grains, and supplements should generally stay near the recommended amount.

What niacin does

Illustration of niacin foods including poultry, fish, peanuts and fortified cereal beside skin, nerve and energy icons — Illustration: niacin helps turn food into energy and supports the skin, nerves and digestion, and comes from poultry, fish, peanuts and fortified grains.

Niacin works through two related forms, nicotinic acid and nicotinamide:

Energy metabolism: niacin helps convert food into usable energy.
Skin, nerves, and digestion: niacin supports the health of the skin, the nervous system, and the digestive tract, which is why deficiency shows up there.
DNA repair: niacin is involved in processes that maintain and repair DNA.
Made from tryptophan: the body can convert the amino acid tryptophan into niacin, which is one reason deficiency is uncommon even when direct intake is modest.
Water-soluble: the body does not store much, so steady intake matters, and excess is excreted in urine.

The practical takeaway: niacin is an energy and tissue-support vitamin that the body can partly make on its own, and the honest news is that true deficiency is rare while high-dose supplements carry real risks.

The myth about niacin for cholesterol

Illustration comparing high-dose niacin flush and risk with niacin from food being enough — Illustration: high-dose niacin causes flushing and carries risks, while niacin from food supports normal health.

The long-standing claim is that high-dose niacin is a heart-healthy way to fix cholesterol. The evidence tells a more careful story:

It is true that large doses (far above the diet) can raise HDL and lower LDL and triglycerides, and niacin was used for years for that reason.
But major trials, including AIM-HIGH and HPS2-THRIVE, found that adding niacin to a statin did not reduce heart attacks, strokes, or deaths, and it increased side effects.
Common side effects include flushing (a hot, red, itchy face and chest), and less often high blood sugar, liver problems, and muscle issues.
The truth: food niacin supports normal health, but high-dose niacin is not a proven way to prevent heart disease, and it should not be self-prescribed for cholesterol.
What to do instead: manage cholesterol with a clinician and proven approaches, and get niacin from food.

The deficiency reality

Severe niacin deficiency causes pellagra, with the classic pattern of dermatitis (a rough, sun-sensitive rash), diarrhea, and dementia, and death if untreated.
Pellagra is now uncommon and is mostly limited to people living in poverty, refugees and displaced people, and people eating very limited diets low in niacin and protein.
It was historically common where diets relied heavily on untreated corn, because the niacin in corn is not well absorbed unless the corn is treated, as in traditional nixtamalization.
Other causes include alcohol use disorder, malabsorption, and some carcinoid tumors that divert tryptophan away from niacin production.
Early signs can include a bright red, sun-sensitive rash, a sore or smooth tongue, and digestive upset. These are reasons to see a doctor, not to self-diagnose.

Who is at risk

Illustration of niacin status levels from usually fine to higher risk to medical care — Illustration: niacin status levels, from a varied diet that is usually fine to higher-risk groups and medical care.

Niacin deficiency is uncommon, but some groups are at higher risk:

People with very limited or monotonous diets, including those living with food insecurity.
People with alcohol use disorder.
People with malabsorption conditions or prolonged poor intake.
People whose diets center on untreated corn without niacin-rich protein.
People with certain carcinoid tumors that change tryptophan use.

For everyone else, a varied diet with protein foods and fortified grains covers niacin needs comfortably, and the body’s ability to make niacin from tryptophan adds a buffer.

Niacin foods

Poultry and meat: chicken, turkey, and beef are rich sources.
Fish: tuna, salmon, and other fish are strong sources.
Peanuts and legumes: peanuts and legumes provide niacin.
Fortified cereals and grains: enriched breads and cereals are fortified with niacin.
Note on tryptophan: protein foods also supply tryptophan, which the body converts to niacin, so protein-rich diets protect against deficiency.

The simple rule: include poultry, fish, or legumes and choose fortified grains, and niacin intake is covered without supplements.

Supplements and the flush

The key warning: high-dose niacin, especially nicotinic acid, causes flushing in most people, and can also raise blood sugar, stress the liver, and interact with other medications.
The tolerable upper limit is 35 mg per day for adults from supplements, far below the doses once used for cholesterol.
Niacin in a standard multivitamin, usually well under the upper limit, is safe for most people.
Extended-release and high-dose forms carry greater liver risk, and the flush can be managed but not eliminated.
The honest position: get niacin from food, keep supplements near recommended amounts, and treat high-dose niacin as a medical decision, not a self-care choice.

FAQ

What does niacin (vitamin B3) do?

Niacin helps turn food into energy and supports the skin, nervous system, and digestive tract, and it plays a role in DNA repair. The body can also make niacin from the amino acid tryptophan.

What are the symptoms of niacin deficiency?

Severe deficiency causes pellagra, with dermatitis (a rough, sun-sensitive rash), diarrhea, and dementia. It is now rare and mostly limited to people with very restricted diets, alcohol use disorder, or malabsorption.

Does niacin lower cholesterol?

High doses can lower LDL and triglycerides and raise HDL, but major trials found no reduction in heart attacks, strokes, or deaths when added to a statin, and side effects were common. It is not a routine cholesterol treatment today.

Which foods are high in niacin?

Poultry, beef, fish such as tuna and salmon, peanuts and legumes, and fortified or enriched grains. Protein foods also supply tryptophan, which the body converts to niacin.

Can too much niacin be harmful?

Yes. High doses cause flushing, and can raise blood sugar, harm the liver, and interact with medications. The upper limit from supplements is 35 mg per day for adults, so high-dose niacin should only be used under medical guidance.

Sources

National Institutes of Health, Office of Dietary Supplements: Niacin, Health Professional Fact Sheet. https://ods.od.nih.gov/factsheets/Niacin-HealthProfessional/
National Institutes of Health, Office of Dietary Supplements: Niacin, Consumer Fact Sheet. https://ods.od.nih.gov/factsheets/Niacin-Consumer/
Harvard T.H. Chan School of Public Health, The Nutrition Source: Niacin, Vitamin B3. https://nutritionsource.hsph.harvard.edu/niacin-vitamin-b3/
National Academies, Dietary Reference Intakes: Niacin (chapter). https://www.ncbi.nlm.nih.gov/books/NBK114304/

Disclaimer

This article is for information only and is not medical advice. Always consult a qualified healthcare provider about your health.

Reviewed by the VI Editorial Team. Last reviewed: September 21, 2026