A study undermining the benefits of antioxidant supplements ignores the large body of scientific evidence supporting the benefits of antioxidants, says the Canadian Health Food Association.

"A growing number of evidence-based studies continue to show the health benefits of antioxidants and cannot be discounted. They need to be considered when drawing conclusions from this meta-analysis," says Anne Wilkie, Vice-President and Head of Regulatory Affairs, Canadian Health Food Association.

"The study only serves to confuse healthy consumers who may take antioxidants," she says.

Danish researchers, authors of a new study published in the February 28, 2007 issue of the Journal of the American Medical Association, themselves acknowledge their analysis of previous studies has several limitations.

They combined studies where participants were vastly different from each other, including sick people. Dosages in the studies varied significantly and the length of time of taking the supplements and the follow-up differed among the trials. In addition to that, the use of
varying definitions of "all-cause" mortality in the trials.

"Healthy consumers should continue to rely on antioxidant supplements for the benefits they confer," says Wilkie. "This meta-analysis does not provide convincing scientific evidence that antioxidant supplements do not provide potential health benefits."

Danish researchers reported in the Journal of the American Medical Association that three popular antioxidant supplements - vitamins A and E and beta carotene - appear to increase death rates.

The Copenhagen team found that when taken separately, beta carotene increased death rates by 7 per cent, vitamin A by 16 per cent, and vitamin E by 4 per cent.

Gluud and his colleagues searched the scientific literature for every study about antioxidants published since 1990. Subjects in those studies were randomly assigned to get real vitamins or placebos.

When they analyzed that data, the researchers found that those taking any antioxidants were 5 percent more likely to die than those who were not. The causes of death were various.

The study has many gaps, experts comment. Researchers failed to specify, though, whether the death was caused by vitamins and their negative effects or by other factors. The studies included people who were already sick, while most people tend to take vitamins to stay healthy.

The study does not address the question of multivitamins, either. At least 150 million Americans regularly take dietary supplements that often include antioxidants. Researchers only focused on megadoses of antioxidants.

The team, headed by Goran Bjelakovic of Copenhagen University, also reported that vitamin C and selenium appeared to have no impact — either way — on longevity, suggesting that money spent on vitamin supplements is wasted.

"The message is: We shouldn't be putting anything in our mouths until we know whether it works," said Christian Gluud of the Copenhagen University Hospital in Denmark, who led the study which results are not independent but based on compilated data from previous studies. "It appears as if these substances may be harmful."

Other researchers, while noting that supplements are useful for people who have nutritional deficiencies, said the findings should prompt people to reconsider whether to continue taking megadoses in an effort to live longer. Some nutrients may be harmful at high doses or could interfere with the body's natural defenses, the researchers said.