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Niacin for cholesterol

Q. I hope you can clear up some family confusion. My doctor gave me a prescription for Niaspan, but my wife found the same medication, niacin, at the supermarket at a much lower price. Is it a drug or a vitamin?

A. Niacin is a natural substance "" in fact, it's vitamin B₃. Like other vitamins, it's required to keep the metabolism working properly. But the recommended dietary allowance (RDA) for B₃ is only 18 mg a day, far less than the amount needed to improve cholesterol levels. Still, any dose of niacin can be sold as a "dietary supplement" without a doctor's prescription and without FDA oversight.