The final analysis of the Selenium and Vitamin E Cancer Prevention Trial (SELECT) indicated that vitamin E increased the risk of developing prostate cancer in otherwise healthy men by 17% when compared to placebo. The results of the study were published in the Journal of the American Medical Association and presented at the 2012 Genitourinary Cancers Symposium.
Prostate cancer is the most commonly diagnosed type of cancer (other than skin cancer) in U.S. men. Although many prostate cancers are diagnosed at an early, curable stage, treatment of prostate cancer can cause urinary, sexual, and bowel problems that have a substantial impact on quality of life. Prevention of prostate cancer, therefore, continues to be an important research priority.
There is a great deal of interest in the relationship between diet and cancer, and some previous studies suggested that selenium and vitamin E may reduce the risk of certain types of cancer, including prostate cancer.
To further explore the relationship between selenium and vitamin E supplementation and risk of prostate cancer, researchers conducted SELECT, which was a randomized trial that enrolled more than 35,000 men from 400 study sites across the United States, Canada, and Puerto Rico. At the start of the study, all men had normal prostate-specific antigen (PSA) levels and a normal digital rectal examination. Study participants were assigned to one of four groups: selenium supplementation; vitamin E supplementation; selenium and vitamin E supplementation; or placebo.
In 2008, after approximately 5.5 years of follow-up, preliminary results indicated no benefit from supplementation and participants were instructed to stop taking the supplements. Researchers, however, continued to collect information from the men in order to continue to evaluate the long-term effects
After 7 years of follow-up (5.5 years of supplementation), researchers found that vitamin E supplementation was associated with a statistically significant increased risk of prostate cancer, whereas supplementation with selenium was not. Men in the vitamin E group were 17% more likely than men in the placebo group to be diagnosed with prostate cancer.
These results suggest that daily supplementation with vitamin E may increase the risk of prostate cancer among healthy men. It is always important to communicate with your physician about any supplements you may be taking so that you can discuss the risks and benefits.
 Klein EA, Thompson I, Tangen CM, et al: Vitamin E and the risk of prostate cancer: Updated results of the Selenium and Vitamin E Cancer Prevention Trial (SELECT). 2012 Genitourinary Cancers Symposium. Abstract 7. Presented February 2, 2012.
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