Niacin

Other name(s):

vitamin B₃, niacinamide, nicotinamide, nicotinic acid, nicotinic acid amide

General description

Niacin is a member of the B family of vitamins (B Complex). Niacin is a water-soluble vitamin and excess amounts are excreted through the kidneys. Like the other B vitamins, niacin plays an important role in energy production.

Niacin functions in two important enzyme systems (NAD and NADP) that affect all the tissues of the body. These enzyme systems help transport hydrogen within the cell and make it available for biosynthesis. These two enzymes also function closely with the energy molecule adenosine triphosphate (ATP).

Medically valid uses

Nicotinic acid or niacinamide are used to treat and prevent pellagra (a disease caused by niacin deficiency). Niacin is also used to treat elevated cholesterol. In some cases niacin, in conjunction with colestipol, can be as effective as a combination of colestipol and one of the "statin" drugs (e.g., lovastatin, pravastatin, or simvastatin) to treat elevated blood cholesterol (hyperlipidemia).

Unsubstantiated claims

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Niacin is claimed to improve the health of the skin, improve thyroid function, and maintain the digestive system.

Other claims include treating schizophrenia, alcohol dependence, drug-induced hallucinations, leprosy, motion sickness, and peripheral vascular disease. Again, these claims are not supported in scientific research findings.

Recommended intake

The specific requirements for niacin are dependent on the total number of calories consumed. Approximately 4.4 to 6.6 mg of niacin are required for every 1,000 calories consumed.

As indicated below, niacin is supplied in milligrams. It is not currently supplied in International Units. The RDA is the Recommended Dietary Allowance.

To reduce the possibility of stomach upset, take niacin products with food. Do not crush or open time-release formulations.

The amino acid tryptophan can be converted into niacin. Therefore, foods high in tryptophan (such as milk and eggs) may prevent niacin deficiencies.

Niacin is relatively stable in heat (and does not therefore need to be refrigerated). Only small amounts are lost in the cooking process.

There is an increased need for niacin if you have certain cancers (typically carcinoid), chronic diarrhea, or if you consume moderate to large amounts of alcohol.

Isoniazid (INH), a drug used in the treatment of tuberculosis, can cause pellagra. Niacin supplements are therefore recommended during isoniazid treatment.

Pellagra is the deficiency disease associated with lack of niacin in the diet. Because cereals and grains have very little niacin, diets based on corn and corn flour (also low in tryptophan) and little else may lead to pellagra.

Symptoms of pellagra include dark red, symmetrical blotches on the skin, especially on those areas exposed to sunlight and open air. The skin ultimately becomes dry and cracked, with a brownish discoloration. Other symptoms include inflammation of the lining of the mucous membranes (nose, mouth, throat, vagina) and the intestinal tract, bloody diarrhea, and emotional changes (confusion, delirium, hallucinations).

Side effects, toxicity, and interactions

Niacin (not niacinamide) produces dilation of the blood vessels in the skin, particularly in the upper body. As a result, a dose of 100 mg taken on an empty stomach may produce flushing of the skin with intense itching or burning. A sustained-release form does not prevent the flushing, only delays it. Niacinamide does not produce this effect. Niacinamide does not affect the cardiovascular system or alter lipid levels.

Taken in high doses for prolonged periods of time, niacin has been implicated in liver damage and changes in liver function. This is especially true for the sustained-release form.

Some niacin preparations contain tartrazine. If you are allergic to aspirin, you may be sensitive to tartrazine, and should avoid preparations that contain it. Do not take niacin without consulting a physician if you have liver problems or an active peptic ulcer.

If you are pregnant, do not take niacin supplements in addition to your regular prenatal vitamins.

Although a severe interaction between niacin and lovastatin has been reported, this interaction has not been reproduced in a controlled study. Nevertheless, the association between using niacin and lovastatin and the development of myolysis and myositis is strong. Avoid the combination of these medications.

Nicotinic acid may decrease the ability of sulfinpyrazone to decrease the uric acid levels. Additionally, a side effect of niacin may be to increase uric acid levels. Use caution if you have an elevated uric acid level or gout and need to take a niacin supplement.

Additional information

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