Supplements that millions of Americans take to stave off disease and slow the aging process do not boost longevity and appear to actually increase the risk of dying, according to the most comprehensive study of whether popular "antioxidants" help users live longer.

The analysis, which pooled data from 68 studies involving more than 232,000 people, found no evidence that taking beta carotene, Vitamin A or Vitamin E extends life span and, in fact, indicated that the supplements increase the likelihood of dying by about 5 percent. Vitamin C and selenium appeared to have no impact -- either way -- on longevity.
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"There's a large body of data that shows that antioxidant supplementation is beneficial," said Andrew Shao of the Council for Responsible Nutrition, an industry group. "The message to the average consumer is: Don't pay attention to this. This doesn't apply to you. You can go ahead and continue taking your antioxidant supplements in addition to the other things you do in your life to stay healthy."

But Gluud and his colleagues defended the findings, saying that the study used careful methods developed by the internationally respected Cochrane Collaboration, an independent nonprofit effort to methodically assess medical claims. The analysis included many large studies involving healthy people, and the increased risk was clear after accounting for factors that could confuse the findings, Gluud said.