High-dose vitamin E supplements increase the risk of prostate cancer, results of a large clinical trial show.
The study’s findings, published Oct. 12, 2011, in the Journal of the American Medical Association, are based on an updated review of data from the Selenium and Vitamin E Cancer Prevention Trial (SELECT). More than 35,000 men age 50 and older were enrolled in the study to determine whether selenium and vitamin E, either alone or in combination, can lower a man’s risk for prostate cancer.
Among the men who took high-dose vitamin E daily, the researchers found a 17 percent increase in prostate cancer, compared with men who took a placebo.
“It’s very clear that high-dose vitamin E does not lower the risk of prostate cancer and, in fact, carries real risks for some men,” says Gerald Andriole, MD, the Robert K. Royce Distinguished Professor and chief of urologic surgery at the Siteman Cancer Center at Washington University School of Medicine in St. Louis and Barnes-Jewish Hospital. “For these reasons, men in the general population should not take high doses of vitamin E to promote prostate health.”
At the School of Medicine, about 110 men were enrolled in the trial, which was led by Robert Grubb III, MD, assistant professor of surgery. The patients are being notified of the study’s results and should continue to see their primary-care physician or urologist and bring these results to their attention for further consideration, Andriole says.
The SELECT trial ended in 2008, when a review of the data showed that the dietary supplements did not reduce the risk of prostate cancer. At that time, there was a small increase in the risk of prostate cancer among men taking vitamin E, but it was not statistically significant. The newly published study takes into account three additional years of follow-up.
Men in the study were randomly assigned to take one of four sets of supplements or placebos, with more than 8,000 men in each group. One group took both selenium and vitamin E; one took selenium and a placebo; one took vitamin E and a placebo; and the final group received placebos of both supplements. Men who took selenium alone or vitamin E and selenium together were also more likely to develop prostate cancer than men who took a placebo, but those increases were small and possibly due to chance.
The dose being studied was 200 micrograms of selenium and 400 international units of vitamin E. By comparison, most multivitamins contain about 50 micrograms of selenium and 30 to 200 international units of vitamin E.
The data show that, per 1,000 men, there were 76 prostate cancers in men who took only vitamin E supplements, compared to 65 in men who took a placebo over a seven-year period, or 11 more cases of prostate cancer per 1,000 men. This difference is statistically significant and not likely due to chance.
The SELECT trial was carried out at more than 400 clinical sites in the United States, Puerto Rico and Canada. It began in 2001 based on earlier research suggesting that selenium and vitamin E might reduce the risk of developing prostate cancer. After the independent safety monitoring review in 2008, participants were told to stop taking their study supplements because the data showed no benefit in using the supplements to prevent prostate cancer.
When the trial was halted, more than half of the participants consented to have their health monitored via mail questionnaires. Now, because of this latest finding, researchers are encouraging all participants to consider taking part in long-term study follow-up so investigators can continue to track outcomes.
Researchers involved in the SELECT trial are now measuring the amount of vitamin E, selenium and other nutrients in the blood of participants when they joined the trial to see if the effect of the supplements depended upon this baseline level of micronutrient. Other researchers are looking at single base changes in patients’ DNA to see if they affect cancer risk or perhaps increase a man’s risk of developing prostate cancer while taking vitamin E.
Except for skin cancer, prostate cancer is the most common type of cancer in men in the United States. The current lifetime risk of prostate cancer for American men is 16 percent. In 2011, there will be an estimated 240,890 new cases of prostate cancer and 33,720 deaths from this disease in the United States.
The research is funded by the National Cancer Institute; the National Center for Complementary and Alternative Medicine; the National Heart, Lung, and Blood Institute; the National Institute of Aging; and the National Eye Institute, all at the National Institutes of Health (NIH).
Publication: EA Klein, IM Thompson, CM Tangen, JJ Crowley, MS Lucia, PJ Goodman, L Minasian, LG Ford, HL Parnes, JM Gaziano, DD Karp, MM Lieber, PJ Walther, L Klotz, JK Parsons, JL Chin, A Darke, SM Lippman, GE Goodman, FL Meyskens, and LH Baker. Vitamin E and the Risk of Prostate Cancer: Results of The Selenium and Vitamin E Cancer Prevention Trial (SELECT). Journal of the American Medical Association. October 12, 2011.