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Can antioxidants cause cancer?

For years, scientists believed carotenoids and retinoids, such as the antioxidant vitamin A, might help prevent two major causes of death in the United States – lung cancer and cardiovascular disease. But a 1995 landmark study found the combination supplementation of beta-carotene and vitamin A may actually increase your risk of developing or dying from lung cancer or cardiovascular disease.

This multi-center, randomized, double-blind, placebo-controlled trial funded by the National Cancer Institute followed 18,314 smokers, former smokers and workers exposed to asbestos, who received 30 mg of beta carotene and 25,000 IU of vitamin A (in the form of retinyl palmitate) a day for an average of four years. During the study, 388 new cases of lung cancer were diagnosed, and 254 of those patients died. Participants receiving supplementation were at a 28 percent higher risk of developing lung cancer than the placebo group; the overall mortality rate was 17 percent higher than the placebo group; and the overall rate of death from cardiovascular causes was 26 percent higher than the placebo group.

The study had been initiated to test the hypothesis that beta-carotene and vitamin A could reduce the risk of lung cancer in these high-risk populations, but researchers stopped the study 21 months earlier than planned because of these unexpected, adverse results. Researchers are now calling for randomized prevention trials to test the effects of increased intake of beta-carotene or vitamin A individually.

 

References

1.  Omenn GS, Goodman GE, Thornquist MD, et al. Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med. 1996 May 2;334(18):1150-5.


Date Published: 08/02/2007
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