Niacin, also known as vitamin B-3 or nicotinic acid, is a water-soluble micronutrient found in a wide variety of foods. Your body converts niacin into chemicals that support the function of hundreds of enzymes involved in a broad array of metabolic functions. In addition to its nutritional role, prescription-strength niacin is used to correct abnormal blood fat levels. The safe dosage of niacin depends on how it is used.
Niacin participates in redox reactions, a term you may recall from high school chemistry. Niacin derivatives produced by your body can either donate or accept electrons from other chemicals. This function proves essential for the metabolism of carbohydrates, proteins, fats and alcohol, and the production of certain chemicals manufactured by your cells.
The recommended daily intake for niacin is 14 mg for women. Foods that provide you with niacin include meat, fish, poultry, eggs, dairy products, nuts and vitamin-fortified cereals and grain products. Unless your doctor prescribes a higher dosage, your daily intake of supplemental niacin should not exceed 35 mg, according to the Institute of Medicine.
Your doctor may prescribe prescription-strength niacin if you have abnormal blood cholesterol and triglyceride levels. In high doses, niacin can reduce your triglyceride, total cholesterol and LDL, or "bad" cholesterol, levels. It also increases your level of HDL, or "good" cholesterol. You typically begin treatment with a low dose of niacin, often 250 mg daily. Your dosage is gradually increased over several weeks to 1 to 2 g daily for an extended-release formulation or 1.5 to 3 g daily for immediate-release medication, according to the National Cholesterol Education Program. If your blood fat levels remain abnormal on this dosage, your doctor may slowly increase your daily dose to up to 6 g daily, although this is uncommon.
Too much supplemental or prescription-strength niacin may cause side effects. You may experience nausea and vomiting, which is most common when you take doses of 3 g per day or more. Headaches and skin flushing, accompanied by a burning sensation and itching, may occur with high doses of niacin. These side effects occur because high-dose niacin can cause dilation of your blood vessels. High doses of niacin may adversely affect your liver, especially if you consume large amounts of alcohol.
Do not take over-the-counter niacin supplements in dosages greater than 35 mg daily unless your doctor advises you to do so. Do not attempt high-dose niacin therapy on your own; it is important to work with a health-care professional for this form of niacin treatment. Talk with your doctor before taking niacin or any other nutritional supplement to be sure it is safe for you.
- Oregon State University Linus Pauling Institute; Niacin; Jane Higdon, Ph.D.; 2002
- "Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline"; Institute of Medicine of the National Academies, Food and Nutrition Board; 1998
- MedlinePlus; Niacin; Alison Evert, M.S., R.D.; February 2011
- National Cholesterol Education Program: Adult Treatment Panel III At-a-Glance
- Drugs.com: Niacor FDA Monograph
- Comstock/Comstock/Getty Images
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