Other name(s):

vitamin B-3 ₃, niacinamide, nicotinamide, nicotinic acid, nicotinic acid amide

General description

Niacin is a member of the B family of vitamins (B complex). It’s a water-soluble vitamin. Excess amounts come out in the urine. Like the other B vitamins, niacin helps make energy in your body. It helps your body use carbohydrates, fatty acids, and proteins.

It is found in many plant and animal foods, such as yeast, meats (especially liver), grains, legumes, corn treated with alkali (such as corn used in tortillas), and seeds. Niacin can be made by the liver from the amino acid tryptophan.

Niacin works in two enzyme systems (NAD and NADP). They affect all the tissues of the body. These enzyme systems help move hydrogen within a cell and make it available for biosynthesis, or the making of new compounds. These two enzymes also work closely with the energy molecule adenosine triphosphate.

Medically valid uses

Nicotinic acid or niacinamide are used to treat and prevent pellagra. This is a disease caused by niacin deficiency. Niacin is also used to treat high cholesterol. In some cases, niacin taken with colestipol can work as well as colestipol and a statin medicine.

Unsubstantiated claims

There may be benefits that have not yet been proven through research.

Niacin may improve the health of the skin. It may also improve thyroid function and keep your digestive system healthy. It may also treat:

• Schizophrenia

• Alcohol dependence

• Hallucinations due to medicines

• Leprosy

• Motion sickness

• Peripheral vascular disease

Recommended intake

How much niacin you need depends on how many calories you eat. You need about 4.4 mg to 6.6 mg of niacin for every 1,000 calories you eat.

Niacin is noted in milligrams (mg). The RDA is the recommended dietary allowance.

*Adequate intake. This is based off the average intake in healthy, breastfed infants.

Take niacin with food. This can help reduce upset stomach. Don’t crush or open time-release forms.

The amino acid tryptophan can be converted into niacin. Foods high in tryptophan may prevent niacin deficiency. Examples of these foods include milk and eggs.

Niacin is stable in heat. It doesn’t need to be refrigerated. Only small amounts are lost in cooking.

You need more niacin if you have certain cancers, such as carcinoid. You may also need more if you have chronic diarrhea or if you drink a lot of alcohol.

Isoniazid is a medicine used to treat tuberculosis. It can cause pellagra (a niacin deficiency). If you’re taking this medicine, you’ll likely need to take niacin supplements.

Cereals and grains have very little niacin. Because of this, diets mainly based on corn and corn flour (and low in tryptophan) may lead to pellagra.

Symptoms of pellagra include:

• Dark red, even-shaped blotches on the skin, more likely on skin exposed to sunlight and air

• Skin that is dry and cracked, with a brownish color

• Inflammation of the lining of the mucous membranes (nose, mouth, throat, and vagina)

• Inflammation of the intestinal tract

• Bloody diarrhea

• Confusion, delirium, and hallucinations

Side effects, toxicity, and interactions

Niacin dilates the blood vessels in the skin, especially in the upper body. A dose of 100 mg taken on an empty stomach may cause flushing of the skin. This may also cause intense itching or burning. A sustained-release form doesn’t prevent flushing. It only delays it. Niacinamide doesn’t cause this effect. Niacinamide doesn’t affect the cardiovascular system or change lipid levels.

Niacin can cause liver damage when taken long-term at high doses over a long time. This is more of a risk with the sustained-release form.

Some forms of niacin contain tartrazine. If you’re allergic to aspirin, you may be sensitive to tartrazine. You should stay away from forms that contain it. Don't take niacin without talking to your healthcare provider if you have liver problems or an active peptic ulcer.

If you’re pregnant, don’t take niacin supplements.

Nicotinic acid may keep medicines from working well. Some examples are medicines that slow blood clotting, lower cholesterol, and treat gout. If you take any medicines, talk with your healthcare provider before taking a niacin supplement.