Little evidence that multivitamins do any good

updated 7:49 p.m. ET May 17, 2006

WASHINGTON - Over half of U.S. adults use multivitamins, mostly the pretty healthy people who also eat nutrient-fortified foods. Yet there's little evidence that most of the pills do any good — and concern that some people may even get a risky vitamin overload, advisers to the government said Wednesday.

Worried about bottles that promise 53 times the recommended daily consumption of certain nutrients, specialists convened by the National Institutes of Health called Wednesday for strengthened federal oversight of the $23 billion dietary supplement industry — especially efforts to pin down side effects.

For the average healthy American, there's simply not enough evidence to tell if taking vitamins is a good or bad idea, said Dr. J. Michael McGinnis of the Institute of Medicine, who led the NIH panel's review.

"We don't know a great deal," he said, calling for more rigorous research.

Moreover, McGinnis added, "The product with which we're dealing is virtually unregulated," meaning there are even questions about how the bottles' labels convey what's really inside.

Vitamins and minerals, often packaged together, are the most-used dietary supplements, and widely assumed to be safe. After all, vitamins naturally occur in some of the healthiest foods, and vitamin deficiencies have been known to be dangerous since scurvy's link to a lack of fruits and vegetables was discovered centuries ago.

Ironically, the NIH panel concluded, the people most likely to have nutrient deficiencies are the least likely to use multivitamins.

Yet among the generally healthy and affluent, use of vitamin supplements — along with fortification of foods with extra vitamins — has skyrocketed in recent years as scientists speculated that high doses of certain nutrients might prevent cancer or other diseases.

That's where safety questions arise, because too much of certain nutrients can be bad.

Few proven supplements
There are only a few proven disease-preventing supplements, the NIH panel concluded:

• Women of childbearing age should take folic acid supplements to prevent spina bifida and related birth defects.
• Calcium and vitamin D together can help protect the bones of postmenopausal women.
• Antioxidants and zinc may slow the worsening of the blinding disease called age-related macular degeneration.

On the other hand, smokers should avoid taking beta-carotene supplements, because the pills can increase their risk of lung cancer, the report stresses.

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