Niacin, or vitamin B3, is a B vitamin the body turns into NAD, a helper molecule that more than 400 enzymes need. Niacin is the name for nicotinic acid, nicotinamide (niacinamide) and related forms. This page is about nicotinic acid, the form that causes skin flushing and that, at prescription doses (Niaspan and generic niacin ER), was used for high cholesterol. Severe deficiency causes pellagra.
Also known as: nicotinic acid, Niaspan, niacin ER.
ODS lists a Recommended Dietary Allowance of 16 mg niacin equivalents (NE) a day for men and 14 mg NE for women 19 and older (18 mg NE in pregnancy, 17 mg NE while breastfeeding). The adult Tolerable Upper Intake Level from supplements and fortified foods is 35 mg a day. ODS says niacin is in multivitamins, B-complex products and niacin-only supplements, and some niacin-only products contain 500 mg or more per serving.
Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling. ODS says most people in the United States get more than the RDA from food (poultry, beef and fish provide about 5 to 10 mg per serving). Nicotinic acid above nutritional needs causes flushing: red, burning, tingling or itchy skin on the face, arms and chest. Nicotinamide does not cause flushing, and "flush-free" inositol hexanicotinate is absorbed less. See niacinamide for that form.
What studies show: two large trials tested high-dose extended-release nicotinic acid added to a statin. In AIM-HIGH (3,414 people with heart disease), 1,500 to 2,000 mg a day raised HDL and lowered triglycerides, but the trial was stopped early because heart events did not fall (16.4% vs 16.2% on placebo). In HPS2-THRIVE (25,673 adults with heart disease), 2 g a day with laropiprant improved blood fats but did not lower major heart events, and ODS notes it raised the risk of diabetes, gut problems, bleeding and skin problems. These are study protocols, not a recommendation.
Safety, per ODS: no harm has been reported from niacin in food. At 1,000 to 3,000 mg a day, nicotinic acid can cause low blood pressure (with a risk of falls), fatigue, higher blood sugar and insulin resistance, nausea, heartburn and belly pain, and blurred vision. Over months or years it can harm the liver, up to hepatitis and liver failure, and this is more likely with extended-release forms. ODS says doses this high are drug doses, taken only with medical approval and monitoring.
We could not find a single published half-life or time to peak for niacin that applies to a supplement dose, so we do not list one. ODS says all tissues turn absorbed niacin into NAD.
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