Niacin from foods, such as chicken, salmon, tuna, turkey, unfortified breakfast cereal, avocado, beef, lentils, lima beans, pasta, peanuts, potatoes and whole-wheat bread, is unlikely to cause toxicity symptoms. However, you can get too much niacin through supplements, so you shouldn't take more than the tolerable upper intake level, which is 35 mg per day for adults, unless you are under a doctor's supervision.
Types
The two types of niacin supplements, nicotinamide and nicotinic acid, have different toxicity risks and effects. Doctors sometimes prescribe high amounts of nicotinic acid. These supplements come in both immediate-release and sustained-release versions, and niacin toxicity is more likely with the sustained-release version. Don't substitute sustained-release nicotinic acid for immediate-release nicotinic acid, because the dose differs depending on the type of niacin supplement the doctor prescribes.
Toxicity Effects
Nicotinamide toxicity symptoms include jaundice, nausea, vomiting, increased insulin sensitivity and elevated liver enzymes, and it is likely to occur at doses of 3 g per day or higher. Nicotinic acid toxicity symptoms include flushing, dry skin, rash, headache, abdominal discomfort, blurred vision, jaundice, increased insulin sensitivity and liver toxicity, and may start at doses as low as 750 mg per day, but usually occurs at doses of 1.5 g to 9 g per day. Rarely, niacin toxicity may have similar symptoms to cancer, according to an article published in the the journal "Age and Aging" in 2006.
Benefits of High Doses
High doses of nicotinic acid can lower both LDL cholesterol -- the bad cholesterol -- and triglyceride levels while increasing beneficial HDL cholesterol. Doses of 1,000 mg per day or above can lower LDL levels by up to 20 percent and increase HDL levels by up to 30 percent, according to the "Merck Manuals." Such a dose also may help prevent certain types of cancers and insulin-dependent diabetes, and slow the progression of HIV/AIDS.
Safety
If you are an alcoholic or suffer from diabetes, liver problems, cardiac arrhythmia, inflammatory bowel disease, migraines, gout or peptic ulcer disease, you are more likely to experience side effects from niacin supplements. Get your recommended dietary allowance, which is 16 mg per day for adult men and 14 mg per day for adult women, from foods, and only take niacin supplements under your doctor's supervision.
References
- Merck Manuals; Niacin; Larry E. Johnson, MD, PhD; April 2007
- Tufts New England Medical Center; Niacin; Mary Calvagna, MS, et al.; June 2010
- "Age and Aging"; Niacin Toxicity: A Rare Presentation Mimicking Malignancy; Abraham Joseph, et al.; July 2006
- Linus Pauling Institute; Niacin; Jane Higdon, Ph.D., et al.; June 2007
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