Vitamin B3

Also indexed as: Inositol Hexaniacinate, Niacin, Niacinamide, Nicotinamide, Nicotinic Acid

What is it?

The body uses the water-soluble vitamin B3 in the process of releasing energy from carbohydrates. It is needed to form fat from carbohydrates and to process alcohol. The niacin form of vitamin B3 also regulates cholesterol, though niacinamide does not.

Vitamin B3 comes in two basic forms—niacin (also called nicotinic acid) and niacinamide (also called nicotinamide). A variation on niacin, called inositol hexaniacinate, is also available in supplements. Since it has not been linked with any of the usual niacin toxicity in scientific research, some doctors recommend inositol hexaniacinate for people who need large amounts of niacin.

Where is it found?

The best food sources of vitamin B3 are peanuts, brewer’s yeast, fish, and meat. Some vitamin B3 is also found in whole grains.

Vitamin B3 has been used in connection with the following conditions (refer to the individual health concern for complete information):

Science Ratings	Health Concerns
	Acne (topical niacinamide) High cholesterol High triglycerides (niacin) Intermittent claudication (niacin–inositol hexaniacinate) Osteoarthritis (niacinamide)
	Dysmenorrhoea (painful menstruation) (niacin) High cholesterol (inositol hexaniacinate) High triglycerides (inositol hexaniacinate) Peripheral vascular disease (inositol hexaniacinate) Raynaud’s disease (niacin–inositol hexaniacinate) Schizophrenia Type 1 diabetes
	Alcohol withdrawal support (niacinamide) Anxiety (niacinamide) Cataracts (niacinamide) Dermatitis herpetiformis (nicotinamide, when combined with tetracycline) HIV support Hypoglycaemia (niacinamide) Hypothyroidism (niacin) Multiple sclerosis (niacin) Photosensitivity (niacinamide) Tardive dyskinesia (niacin or niacinamide) Type 2 diabetes (niacinamide)
Reliable and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit. For a herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

Who is likely to be deficient?

Pellagra, the disease caused by a vitamin B3 deficiency, is rare in Western societies. Symptoms include loss of appetite, skin rash, diarrhoea, mental changes, beefy tongue, and digestive and emotional disturbance.

How much is usually taken?

In part because it is added to white flour, most people generally get enough vitamin B3 from their diets to prevent a deficiency. However, 10–25 mg of the vitamin can be taken as part of a B-complex or multivitamin supplement. Larger amounts are used for the treatment of various health conditions.

Are there any side effects or interactions?

Niacinamide is almost always safe to take, though rare liver problems have occurred at amounts in excess of 1,000 mg per day. Niacin, in amounts as low as 50–100 mg, may cause flushing, headache, and stomachache in some people. Doctors sometimes prescribe very high amounts of niacin (as much as 3,000 mg per day or more) for certain health problems. These large amounts can cause liver damage, diabetes, gastritis, damage to eyes, and elevated blood levels of uric acid (which can cause gout). Symptoms caused by niacin supplements, such as flushing, have been reduced with sustained-release (also called ‘time-release’) niacin products. However, sustained-release forms of niacin have caused significant liver toxicity and, rarely, liver failure.¹ ² ³ ⁴ ⁵ One partial time-release (intermediate-release) niacin product has demonstrated clinical efficacy without flushing, and also without the liver function abnormalities typically associated with sustained-release niacin formulations.⁶ However, this form of niacin is available by prescription only.

In a controlled clinical trial, 1,000 mg or more per day of niacin raised blood levels of homocysteine, a substance associated with increased risk of heart disease.⁷ Since other actions of niacin lower heart disease risk,⁸ ⁹ the importance of this finding is unclear. Nonetheless, for all of the reasons discussed above, large amounts of niacin should never be taken without consulting a doctor.

The inositol hexaniacinate form of niacin has not been linked with the side effects associated with niacin supplementation. In a group of people being treated alternatively with niacin and inositol hexaniacinate for skin problems, niacin supplementation (50–100 mg per day) was associated with numerous side effects, including skin flushing, nausea, vomiting and agitation.¹⁰ In contrast, people taking inositol hexaniacinate experienced no complaints whatsoever, even at amounts two to five times higher than the previously used amounts of niacin. However, the amount of research studying the safety of inositol hexaniacinate remains quite limited. Therefore, people taking this supplement in large amounts (2,000 mg or more per day) should be under the care of a doctor.

Vitamin B3 works with vitamin B1 and vitamin B2 to release energy from carbohydrates. Therefore, these vitamins are often taken together in a B-complex or multivitamin supplement (although most B3 research uses niacin or niacinamide alone).

Are there any drug interactions?
Certain medicines may interact with vitamin B3. Refer to drug interactions for a list of those medicines.

References
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1. 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 1994;271:672–7.

2. Knopp RH, Ginsberg J, Albers JJ, et al. Contrasting effects of unmodified and time-release forms of niacin on lipoproteins in hyperlipidemic subjects: clues to mechanism of action of niacin. Metabolism 1985;34:642–50.

3. Gray DR, Morgan T, Chretien SD, Kashyap ML. Efficacy and safety of controlled-release niacin in dyslipoproteinemic veterans. Ann Intern Med 1994;121:252–8.

4. Rader JI, Calvert RJ, Hathcock JN. Hepatic toxicity of unmodified and time-release preparations of niacin. Am J Med 1992;92:77–81 [Review].

5. Knopp RH. Niacin and hepatic failure. Ann Intern Med 1989;111:769 [letter].

6. Goldberg A, Alagona P Jr, Capuzzi DM, et al. Multiple-dose efficacy and safety of an extended-release form of niacin in the management of hyperlipidemia. Am J Cardiol 2000;85:1100–5.

7. Garg R, Malinow M, Pettinger M, Upson B, Hunninghake D. Niacin treatment increases plasma homocyst(e)ine levels. Am Heart J 1999;138:1082–7.

8. Brown WV. Niacin for lipid disorders. Postgrad Med 1995;98:185–93 [review].

9. Guyton JR. Effect of niacin on atherosclerotic cardiovascular disease. Am J Cardiol 1998;82(12A):18U–23U [review].

10. Welsh AL, Ede M. Inositol hexanicotinate for improved nicotinic acid therapy. Int Record Med 1961;174:9–15.

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or chemist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires March 2007.

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