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Vitamin B Niacin (Vitamin-B3).
Niacin (nicotinic acid) and its derivative niacinamide (nicotinamide or nicotinic acid amide) are two forms of a water-soluble vitamin referred to as vitamin B3. (Note that the name "niacin" is often used in the generic sense to refer to both nicotinic acid and its nicotinamide derivative.) Both compounds are precursors for the active forms of important enzyme cofactors (coenzymes) that assist in catalyzing oxidation-reduction reactions in the cell. These coenzymes are nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP).
Niacin is also a structural component of Glucose Tolerance Factor (GTF), an organo-chromium complex that potentiates insulin by improving its binding to cell surface receptors.
Deficiencies in niacin and niacinamide cause pellagra, a disorder with broad-spectrum symptoms including inflammation of the skin and mucous membranes, diarrhea, and neurological dysfunction (confusion, disorientation, anxiety, and insomnia). In the early 1900s, pellagra was endemic in the southern United States among children fed low-grade, starchy diets. It was first treated by supplementing those diets with meat, eggs, and milk. It was later successfully treated with niacin supplements.
Niacin has been used for many years in combination with other drugs to lower cholesterol levels. However, the levels used for this purpose (over 500 mg) should not be self-administered as a dietary supplement due to possible liver toxicity. Under the care and monitoring of a physician it can be used safely as part of an effective therapy to improve cholesterol levels.
Niacin is widely distributed in plant and animal foods. Good sources include meats, cereals, legumes and seeds. Milk, green leafy vegetables, and fish are also good sources.
Dietary niacin intakes below 500 mg are essentially non-toxic.
For additional information (including a list of references), please refer to the niacin technical bulletin at
http://www.usana.com/dotCom/company/science/components.
Additional Resources:
Niacin - U.S. National Library of Medicine Niacin and cholesterol - Mayo Clinic Niacin as a drug (not a supplement) - Drugs.com Niacin - Wikipedia