Vitamin E may increase risk of prostate cancer

Daily supplementation with vitamin E increases the risk of prostate cancer, according to a study released online today by the Journal of the American Medical Association.

Researchers at the Cleveland Clinic and elsewhere randomly assigned 34,887 relatively healthy men at average risk of prostate cancer to one of four treatment groups: about a quarter got 400 international units of vitamin E per day, another quarter received 200 micrograms per day of the mineral selenium, a third took both nutrients, and the final group took a placebo.

After about seven years, the team halted the trial when they detected a statistically non-significant, but still worrisome, increased risk of prostate cancer in the men who took vitamin E alone. After another three years of follow-up, when the men had stopped taking the pills, that risk became even greater: 620 developed prostate cancer compared with 529 men in the placebo group, a statistically significant 17 percent increase in risk. Those who received vitamin E plus selenium supplements had no increased risk of prostate cancer. The investigators suggest that selenium might have dampened the increased risk associated with vitamin E alone. But men in the trial who took selenium alone did not have a reduced risk of prostate cancer.

Bottom line: The investigators could not explain how vitamin E supplementation might increase prostate cancer risk. But they warn that the implications of their findings are substantial given that more than half of people 60 or older take supplements containing vitamin E. Moreover, 23 percent of them take at least 400 IU per day, as in the study, despite a recommended daily dietary allowance of only 22.4 IU for adult men. Other research has failed to find any benefit from vitamin E supplements in preventing other forms of cancer or heart disease, in men or women. However, a diet rich in vitamins and minerals, including vitamin E, clearly is beneficial. Read more about who needs supplemental vitamins and minerals.

Source
Vitamin E and the Risk of Prostate Cancer: The Selenium and Vitamin E Cancer Prevention Trial (SELECT) [Journal of the American Medical Association]

—Doug Podolsky