Niacin, also known as Vitamin B3, plays a key role in metabolism by assisting in the breakdown and utilization of carbohydrates, fats, and proteins for energy. Nicotinic acid and nicotinamide are the two forms of niacin in the human body. Nicotinic acid is a well accepted treatment for high cholesterol and heart disease prevention. Large doses (more than 1,000mg) have been shown to reduce triglycerides, total cholesterol and LDL ("bad") cholesterol, while increasing HDL ("good") cholesterol. Dietary supplements are not regulated by the U.S. Food and Drug Administration (FDA) and should not be taken without consulting a physician. While niacin from naturally occurring food sources has no adverse effects, large doses of niacin from supplement, pharmaceuticals and fortified foods are associated with detrimental side effects.
Flushing
One common and first-noticed complaints following a large dose of niacin either from a prescription form or a supplement is face and/or body flushing lasting about 15 to 30 minutes. You may also experience itching. Taking niacin with a meal or aspirin and breaking the dose into several smaller doses throughout the day may help reduce or eliminating flushing. Time-released products are also available.
Gastrointestinal Discomfort
Indigestion, vomiting and nausea may also be caused by large doses of niacin. As with flushing, dividing up the amounts and consuming with food may help reduce any gastrointestinal discomfort. Niacin should not be used by individuals with active ulcers, gastroesophageal reflux (GERD) or alcohol abuse.
Elevated Blood Sugar
High doses of nicotinamide has been associated with elevated blood sugar levels and poor control of diabetes, insulin resistance and pre-diabetes.
Liver Toxicity
In large doses, nicotinic acid can harm liver function and cause abnormal liver function tests. If left untreated, liver toxicity, damage and failure can result. Individuals with liver disease should not consume supplemental forms of niacin.
Elevated Uric Acid
Levels of uric acid in the blood may increase due to high doses of niacin. This may exacerbate gout symptoms and cause red, hot and tender joints.
Birth Defects
The Recommended Dietary Allowances (RDA) produced by the Institute of Medicine (IOM) recommend pregnant women consume 18mg of niacin daily. Due to the risk of birth defects, pregnant women should not take niacin supplements that provide more than 18mg a day.
Death
Niacin at extremely high doses can cause tissue and organ toxicity leading to death. Unless you are under a physician care, the IOM does not recommended consuming more than the Tolerable Upper Intake Level (UL) of 35mg a day.
References
- "Popular Dietary Supplements;" Allison Fragakis, M.S., R.D. and Cynthia Thomson, Ph.D., R.D.; 2007
- Institute of Medicine
- American Heart Association
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