Vitamins, Minerals and Dietary Supplements

What is niacin (vitamin B3)?

Niacin, a white crystalline substance, belongs to the B-vitamin group. A water-soluble vitamin, it is absorbed in the intestines and carried throughout the body in the bloodstream. After the body uses what it needs, any excess niacin is excreted in urine.

Why do we need it?

Niacin helps break down blood sugar for energy. It also acts as a vasodilator, widening blood vessels and helping increase blood flow. Some health experts have prescribed niacin supplements for helping people lower high cholesterol or triglyceride levels; it thus plays a major role in protecting against cardiovascular disease.

How much niacin should I take?

According to the National Academy of Sciences, the recommended daily allowance (RDA) for niacin is as follows:

• Adult men: 19 milligrams/day
• Adult women: 15 milligrams/day
• Children aged 7-10: 13 milligrams/day
• Infants: 6 milligrams/day
• Pregnant/lactating women: 19 milligrams/day.

What are some good sources of niacin?

One of the best sources of niacin is fish, particularly mackerel and swordfish. Niacin can also be found in chicken, veal, pork, salmon, milk, eggs, fortified cereals, avocados, and some nuts.

What can happen if I don't get enough niacin?

Niacin deficiency causes pellagra, a chronic disease characterized by skin eruptions, digestive and nervous disturbances and mental deterioration. The condition can usually be reversed by taking niacin supplements.

Anemia may also occur as a result of low niacin levels, although this is usually due to an accompanying deficiency in folic acid.

What can happen if I take too much?

Niacin toxicity can lead to a variety of conditions. Even mildly high doses can cause a dilation of the blood vessels and lead to a potentially painfully tingling about the face and shoulders called the "niacin flush," as well as headaches, itchiness and stomach problems. Larger doses may cause diarrhea, nausea, ulcers, gout, diabetes and in rare cases, liver damage. Most of these conditions (with the exception of liver damage) can usually be reversed by discontinuation of high doses.

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References

• DSHP therapeutic position statement on the safe use of niacin in the management of dyslipidemias. American Society of Health System Pharmacists. Am J Health Syst Pharm Dec. 15, 1997;54(24):2815-9.
• Guyton JR. Effect of niacin on atherosclerotic cardiovascular disease. Am J Cardiol Dec. 17, 1998;82(12A):18U-23U.
• McKenney JM, Proctor JD, Harris S, Chinchili VM.A comparison of the efficacy and toxic effects of sustained vs. immediate release niacin in hypercholesterolemic patients. JAMA March 2, 1994;271(9):672-7.
• Recommended Dietary Allowances, 10th ed. Washington, D.C.: National Academy Press.
• Brown BG, et al. Moderate dose, three-drug therapy with niacin, lovastatin, and colestipol to reduce low-density lipoprotein cholesterol <100 mg/dl in patients with hyperlipidemia and coronary artery disease. Am J Cardiol July 15, 1997;80(2):111-5.