As many as 160 million people worldwide take antioxidant supplements to hopefully improve their health, but whether these supplements help or harm us is uncertain.

Now, Danish researchers warn that beta carotene, vitamin A and vitamin E supplements won't prolong your life and may actually increase slightly your risk of dying.

"Our findings contradict studies claiming that antioxidants improve health," said scientists at Copenhagen University Hospital's Center for Clinical Intervention Research. "Considering that 10 percent to 20 percent of the adult population in North America and Europe may consume the supplements, the public health consequences may be substantial."

According to their article in the latest Journal of the American Medical Association, the researchers analyzed 68 studies involving more than 232,000 adults to examine the effects of beta carotene, vitamins A, C and E, and selenium.

In 47 out of the 68 studies, the antioxidant supplements were linked to increased death rates ranging from 4 percent for vitamin E to 16 percent for vitamin A. Vitamin C and selenium had no higher death risk, according to the findings.

In many of the studies, people took doses far above their recommended daily level for the supplements. Dr. Christian Gluud, one of the researchers from Copenhagen University Hospital, said the studies don't say why the people died, but he speculated that heart attacks, strokes, clogging and hardening of the arteries, and other conditions killed them.

He said antioxidant supplements may screw up the body's own defenses for warding off chronic diseases.

"We have had this huge industry really wanting to demonstrate an intervention effect that has gone to lengths to do so," Gluud said. "Sadly enough for the industry, and for us as consumers, it has failed to do so."

More hits for supplements

This makes the second time in less than a week that antioxidant supplements have taken a big hit. Last week, the American Heart Association said that antioxidant supplements vitamin E, C and beta-carotene - and even folic acid - should not be used to ward off or treat cardiovascular disease.

The comments came when the association announced new guidelines for the treatment of heart attacks, strokes and other cardiovascular maladies in women.

"The American Heart Association doesn't recommend using antioxidant vitamin supplements until more complete data are available," the group's leaders say, on the association's Web site. "Eating a variety of foods low in saturated fat, trans fat and cholestereol will provide a natural source of these vitamins, minerals, and fiber."

The association's statements echo sentiments from many health experts, who believe antioxidants work better at bringing you health benefits if you get them from food, such as fruits and vegetables, rather than from a bunch of pills.

Don't throw out the pills

Still, health experts said, you shouldn't throw out out your pills quite yet.  Some scientists say antioxidants help thwart the damage to your DNA caused by "free radicals" that can ultimately lead to heart disease and cancer.

Doctors sometimes prescribe the nutrients in supplement form for patients who don't have enough of them in their blood.

But health experts also said that moderation is the key and some of the vitamins carry potential side effects. For example, vitamin E can thin your blood and increase your chances of bleeding, while large doses of vitamins A, D, E and K can lead to toxic buildup in the liver, brain and heart.

Keith Ayoob, a pediatrics expert at New York City's Albert Einstein College of Medicine in New York, told ABC News that a complete multivitamin with 100 percent of the recommended dietary allowance is all you need to take.

'Generalized conclusions'

As for the slightly higher death rates cited in the Danish analysis, some health experts and officials with the supplement industry said the research contains too many holes to get them worked up about mortality.

For example, many people in the studies analyzed by the Danes were sick with life-threatening conditions anyway. In addition,  the projects were so varied in characteristics that they could not be used for general conclusions.

Andrew Shao, a scientist with the Council for Responsible Nutrition, which represents the supplement industry, said the  Danish project creates "generalized conclusions that may inappropriately confuse and alarm consumers who can benefit from supplementing with antioxidants.

"Healthy consumers can feel confident in continuing to take antioxidants for the benefits they provide. This meta-analysis does nothing to change those facts," Shao said. "There is plenty of studies out there that show supplements do provide health benefits." 

Meanwhile, Daniel Fabricant, a vice president with the Natural Products Association, another supplement trade group, said the Danish research "stands in stark contrast to large actual clinical studies that have not demonstrated any increased risks" of death.

"Just yesterday, a group of Swedish researchers concluded that vitamin A may help reduce some risks of stomach cancer," he said. "And ironically, this same medical journal has released a stream of studies suggesting the health benefits of antioxidants, from reduced risk of Alzheimer's disease and macular degeneration to helping improve immune functioning in patients with HIV."

For more information

•  Mayo Foundation for Medical Education and Research

•  Are Too Many Vitamins Bad for Your Health?

•  Separating Supplement Facts from Fiction

•  U.S. Office of Dietary Supplements

Source: American Medical Association
Reference: Journal of the American Medical Association

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