Some Antioxidant Supplements May Raise Death Risk

That effect -- an increase of 7 percent in death risk associated with beta carotene supplements, a 16 percent rise associated with vitamin A use, and 4 percent increased risk associated with vitamin E -- was found in trials described as "low-bias," meaning that they met Bjelakovic group's criteria for careful scientific controls.

Blumberg offered some technical criticisms of the study, as well.

The antioxidants in the study have widely different modes of action, he noted. "It's like putting two very different drugs together and drawing one conclusion," Blumberg explained.

In addition, he said, "they do not mention anywhere in the report what people are dying of," so that it is difficult to attribute the deaths to the supplements.

"You don't see people dropping dead right and left from overdoses of antioxidant supplements," Blumberg said. "It is just not happening. You have to explain to me how some essential nutrients kill you in a couple of years."

Antioxidant supplements "have been shown in a number of studies to have no adverse effects," Blumberg said. "They are not toxic, but evidence that they prevent heart disease and cancer is equivocal."

So, in his opinion, it remains "perfectly reasonable" to take a multivitamin. "Whether you take an additional antioxidant depends on how you feel about the evidence," he said.

Both the American Heart Association and the American Cancer Society have said that the evidence for the benefits of antioxidant supplements is inconclusive. Both recommend getting antioxidants from a diet rich in fruits and vegetables.

But some studies have hinted at benefits for specific conditions, Blumberg said. For example, there is some evidence that taking antioxidant supplements may slow the development of neurological problems such as Alzheimer's disease in older people, he said.

The research center that Blumberg heads receives no funding from the supplement industry, Blumberg noted. About 85 percent of its money comes from federal agencies, with the rest given by producers of products such as California oranges.

More information

There's more on antioxidants at the American Heart Association.

SOURCES: Andrew Shao, Ph.D., vice president, science and regulatory affairs, Council for Responsible Nutrition, Washington, D.C.,; Jeffrey Blumberg, Ph.D., director, Antioxidants Research Laboratory, Jean Mayer USDA Human Nutrition Center on Aging, Tufts University, Boston; Feb. 28, 2007,Journal of the American Medical Association