According to the recent Selenium and Vitamin E Cancer Prevention Trial (SELECT), published in the Journal of the American Medical Association, vitamin E significantly increased the incidence of prostate cancer in healthy men. More than 35,000 relatively healthy men, aged 50 or older, from the United States, Canada, and Puerto Rico were divided randomly into four treatment groups to receive daily doses of selenium (200 micrograms from L-selenomethionine), vitamin E (400 international units [IU] of all rac-α-tocopheryl acetate), both selenium and vitamin E, or a placebo.
Initially, the report stated that selenium and vitamin E taken alone or together did not prevent prostate cancer. Because of these findings, 2008 participants were instructed to discontinue their study supplements. At that time, researchers found that men who took vitamin E had a slight increase in prostate cancer but the increase was not statistically significant. At a 7-year follow up, researchers noted an increase in prostate cancer of 17% in men who received the vitamin E supplement alone compared with those who received a placebo. No increase in prostate cancer was noted in the group that took vitamin E and selenium together.
The researchers noted there was no apparent biological explanation for the increased incidence of prostate cancer in the vitamin E group, but that the increased incidence was evident only after a longer period of monitoring. The researchers suggest that the effects from these supplements may continue long after treatment has ended. They also suggest that these findings underscore the importance of consumer education about the health claims of supplements where there is no strong evidence of health benefits from clinical trials.
Klein EA, Thompson IM Jr, Tangen CM, et al. Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). Journal of the American Medical Association. 2011;306(14), 1549–1556.
National Center for Complementary and Alternative Medicine (NCCAM). Vitamin E supplements increase incidence of prostate cancer, according to SELECT study. Retrieved December 22, 2011 from http://nccam.nih.gov/research/results/spotlight/101111.htm