Some Antioxidant Supplements May Raise Death Risk

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"They included every trial under the sun," Shao said. "Some [studies] were a day long, some were several years long. The majority of trials involved very sick patients -- treatment trials that were very, very different from how antioxidant supplements are used by most consumers, which is to maintain health."

In fact, antioxidants were used to treat a variety of diseases in 47 of the trials used in the study. Those therapeutic trials included more than 68,000 participants. There were another 21 trials, involving more than 114,000 people, where people took antioxidants in hopes of preventing disease.

Even then, "overall, they didn't find a mortality effect," Shao said. "Only when they divided the trials up using their own criteria were they able to come up with this statistically significant effect."

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.