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Antioxidant Supplements Up Death Risk

Study Shows No Benefit, Slightly Higher Death Risk for Antioxidant Supplements
By
WebMD Health News
Reviewed by Louise Chang, MD

Feb. 27, 2007 – Use of the popular antioxidant supplements beta-carotene, vitamin E, or vitamin A slightly increases a person's risk of death, an overview of human studies shows.

The study also shows no benefit -- and no harm -- for vitamin C supplements. Selenium supplements tended to very slightly reduce risk of death.

Oxidative stress -- caused by highly reactive "free radical" compounds circulating in the blood -- is a factor in most diseases.

Antioxidants sweep up these free radicals. It seems to be a no-brainer that taking antioxidant supplements would protect your health. But it may not be that simple.

A new, detailed analysis of human studies of beta-carotene, vitamin A, and vitamin E shows that people who take these antioxidant supplements don't live any longer than those who don't take them. In fact, those who take the supplements have an increased risk of death.

The finding, reported in TheJournal of the American Medical Association, comes from Goran Bjelakovic, MD, DrMedSci, of the University of Nis in Serbia; Christian Gluud, MD, DrMedSci, of Copenhagen University Hospital in Denmark; and colleagues.

"Our findings have already changed the way I counsel my patients about antioxidant supplements," Bjelakovic tells WebMD in an email interview. "According to our findings, beta-carotene, vitamin A, and vitamin E cannot be recommended. I am telling them that they should stop using these supplements."

"There is no reason to take anything that hasn't been proven beneficial. And these antioxidant supplements do not seem beneficial at all," Gluud tells WebMD.

Not everyone agrees. Nutritionist Andrew Shao, PhD, is vice president for scientific and regulatory affairs at the Council for Responsible Nutrition, a supplement-industry trade group.

"Consumers can feel confident in relying on their antioxidant supplements as they always have," Shao tells WebMD. "They can continue to take them knowing they will provide the same benefits -- and this article does not change that."

Antioxidant Supplements and Death Risk

Bjelakovic, Gluud, and colleagues analyzed data from 68 randomized clinical trials of antioxidant supplements that included 232,606 people. When they looked at all the trials together, they found that the supplements offered no benefit but did no harm.

However, some of the trials were more exactly controlled than others. There were 21 trials that had a "high bias risk." These trials had one or more problems with randomizing study participants to the supplement or placebo groups, with blinding both the participants and the investigators to whether participants received supplements or placebos, and/or with following up on all participants until the end of the study.

So the researchers looked only at the 47 "low-bias-risk" studies -- which included nearly 181,000 participants and which did not include people taking selenium. They found that:

  • Taking vitamin A supplements increased the risk of death by 16%.
  • Taking beta-carotene supplements increased the risk of death by 7%.
  • Taking vitamin E supplements increased the risk of death by 4%.
  • Taking vitamin C supplements did not have any effect on risk of death.

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