Antioxidants don't prevent prostate cancer: study

A high intake of vitamin E, beta-carotene, and vitamin C does not prevent prostate cancer, results of a large study suggest. However, smokers may have a lower risk of advanced prostate cancer if their intake of vitamin E is high, and men with low dietary beta-carotene intake seem to benefit from supplemental beta-carotene.

Previous studies evaluating the associations between antioxidants and prostate cancer risk have yielded contradictory results.

So Dr. Richard B. Hayes, from the National Cancer Institute in Bethesda, Maryland, and colleagues looked at the effects of antioxidant intake on prostate cancer among 29,361 men enrolled in a large prostate cancer screening trial.

They report their findings in the Journal of the National Cancer Institute this week.

During average follow-up of 4.2 years, there were 1338 incident cases of prostate cancer, including 520 men diagnosed with advanced disease.

In the whole cohort, there was no association between vitamin E, vitamin C and beta-carotene consumption and prostate cancer incidence.

Overall, "our cohort findings, although based on relatively short follow-up, do not provide strong support for population-wide implementation of high-dose antioxidant supplementation for the prevention of prostate cancer," the study team concludes.

However, they report, among men with dietary beta-carotene below the median, supplemental beta-carotene intake of at least 2000 micrograms was associated with a reduced risk of prostate cancer.

Among current smokers and those who quit within the past 10 years, high-dose supplemental vitamin E intake was associated with a reduced risk of advanced prostate cancer. On the other hand, supplemental vitamin E tended to increase their risk of nonadvanced cancer.

The investigators offer that vitamin E "might mitigate smoking-induced genetic or hormonal changes that increase risk of advance prostate cancer." However, they caution that similar levels of vitamin E supplementation have been associated in some studies with increased health risk or mortality.

Even with the beneficial findings associated with vitamin E supplementation among smokers, Dr. I-Min Lee and colleagues at Harvard Medical School in Boston emphasize, "an important course of action for overall cancer prevention is to continue efforts to prevent the initiation of smoking and to promote the cessation of smoking among those who do smoke."

SOURCE: Journal of the National Cancer Institute, February 15, 2006.