Supplements containing antioxidants -- purported fighters of cancer and age-related cell damage -- may do little to prolong the lives of people who take them, according to a new review of published studies.
But critics of the analysis, released Tuesday by The Cochrane Library, call the review flawed, adding that antioxidants have health benefits that are not recognized by this new research.
In the review, researchers at Copenhagen University Hospital in Denmark looked at data from 67 studies on antioxidant supplements.
"We could find no evidence to support taking antioxidant supplements to reduce the risk of dying earlier in healthy people of patients with various diseases," said lead study author Goran Bjelakovic in a press release.
"The findings of our review show that if anything, people in trial groups given the antioxidants beta-carotene, vitamin A and vitamin E showed increased rates of mortality."
Bjelakovic added that there was no indication that the antioxidants vitamin C and selenium had any effect on life expectancy.
Some diet experts said the results are not surprising in light of previous findings.
"There's no good evidence that antioxidant supplements prolong life, prevent disease, etc., and this review fits with the results of the reviews of other groups," said Dr. Paul Shekelle, director of the Southern California Evidence-Based Practice Center for the RAND Corp.
But others maintained that the study took the wrong approach, possibly oversimplifying the potential effects of these vitamins.
"Lumping all antioxidants together is not fruitful from a scientific or medical perspective," said Dr. Meir Stampfer, professor of epidemiology and nutrition at the Harvard School of Public Health in Boston. "Antioxidant is a relative chemical property, and all these highly disparate nutrients have lots of different effects."
Though health experts continue to argue over the benefits of antioxidant supplements, Americans are downing vitamin pills in ever-larger numbers.
Data from the National Health and Nutrition Examination Survey suggest that about 52 percent of Americans -- about 150 million in all -- take dietary supplements on a regular basis. More than one-third take multivitamins, and nearly one in eight take antioxidant supplements like vitamin C and vitamin E.
The upshot of this popularity is a multibillion-dollar industry that has left its mark on pharmacy and grocery shelves across the country.
In recent years, however, a number of studies and reports have chiseled away at the healthy reputation of vitamin supplements.
In May 2006, the National Institutes of Health released a conference statement in which it suggested that more information would be necessary before it could recommend that Americans take multivitamins -- and, by extension, antioxidant supplements.
But more damning was a series of reviews suggesting that some antioxidant supplements could actually hasten death.
"The vitamin E review on mortality that was in the Annals of Internal Medicine in 2005 … actually concluded vitamin E was associated with increased mortality," Shekelle said. "One can argue whether or not this association was true, but at the very least the association was not the other way, towards decreased mortality."