Little evidence that multivitamins do any good

For other vitamins, concern arises mainly with super-doses that exceed the government's "recommended daily amount," or RDA. Between 1 percent and 11 percent of supplement users may be exceeding the upper limits set for certain nutrients, if they add together their doses from pills and their diets, said Cornell University nutritionist Patsy Brannon.

Leading her list: Too much niacin can damage the liver. Among other examples, too much vitamin A can cause birth defects, and too much vitamin E can cause bleeding problems.

Aghast at the super-doses on some bottles, panelist William Vaughan of Consumer's Union asked, "Why would I take 53 times what people tell me is the RDA?"

If you choose to take vitamins, use those labeled with 100 percent of the RDA or "daily value," advised Brannon. Together with a good diet, that would provide most people plenty without getting near the upper limit.

Dangerous interactions
Some vitamins also can interact dangerously with medications, and doctors should ask their patients what they take, the panel said.

Congress limited the Food and Drug Administration's oversight of vitamins and other dietary supplements in 1994. Unlike most medications, most supplements sold today never had to be proven safe, much less proven to bring any health benefit.

The NIH panel marks the fourth scientific report in recent years urging more FDA authority over supplements, urging the agency to, among other things, mandate that manufacturers report customer side effects just like medication makers do.

Legislation that would do that has languished in Congress since 2004; the industry's Council for Responsible Nutrition said Wednesday it supported that call.

But "for millions of Americans who struggle with diet and nutrition, a daily multivitamin provides a safe, affordable, and reliable means of filling nutrition gaps and promoting overall good health," added council president Steven Mister.

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