Harvard Men's Health Watch

On call: Selenium and vitamin E for prostate cancer

On call

Selenium and vitamin E for prostate cancer

Q. I have been taking selenium in the hope that it would prevent me from getting prostate cancer. But I heard on the radio that the National Cancer Institute is advising men to stop taking selenium. Should I stop it?

A. Many of us shared the hope that selenium might reduce the risk of prostate cancer. The optimism stemmed from a 1996 report from the Nutritional Prevention of Cancer Trial, which found that 200 micrograms (mcg) of selenium a day reduced the risk of prostate cancer by a startling 63%. A series of observational studies followed; although the results were mixed, many suggested that selenium might help.

When results are mixed or surprising, the next step is a careful randomized clinical trial. Beginning in 2001, the National Cancer Institute recruited over 35,000 men age 50 and above to test the effects of selenium and vitamin E, which had also shown mixed results against prostate cancer. The men were randomly assigned to take 200 mcg of selenium, 400 international units (IU) of vitamin E, both selenium and vitamin E, or a placebo every day.

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