Study: Vitamin E Raises Prostate Cancer Risk

If you’re an older man who takes vitamin E supplements, you may be putting yourself at an increased risk of prostate cancer.

A large study of about 35,000 men age 50 and older found that those taking vitamin E daily had a 17 percent higher risk of developing prostate cancer. The study will be published Wednesday in the Journal of the American Medical Association.

“Taking high doses, 400 IU (international units), of vitamin E seemed to increase the risk of prostate cancer,” lead author Dr. Eric A. Klein of the Cleveland Clinic said in a statement. “We have to not look at these (supplements) as inert substance; they actually have a pharmacologic effect and that’s important so you have to be careful about what you take.”

This latest finding is from a follow-up study of the Selenium and Vitamin E Cancer Prevention Trial (SELECT) published in 2008. That initial research found no reduction of prostate cancer risk from taking selenium and vitamin E supplements and a “statistically nonsignificant” increase in prostate cancer risk associated with taking vitamin E. Researchers then called for longer follow-up study.

For SELECT, 34,887 healthy men between August 2001 and June 2004 were randomly assigned to one of four daily treatments: 8,752 received 200 micrograms of selenium; 8,737 received 400 IU of vitamin E; 8,702 received both; and 8,696 were given a placebo.

Scientists reported that a total of 521 additional prostate cancers were diagnosed: 113 in the placebo group, 147 in the vitamin E group, 143 in the selenium group, and 118 in the combination group.

Researchers found that the rate of prostate cancer detection was greater in all groups when compared with placebo, but was statistically significant only in the vitamin E alone group, which showed a 17 percent increased rate of prostate cancer.

“Given that more than 50 percent of individuals 60 years or older are taking supplements containing vitamin E, and that 23 percent of them are taking at least 400 IU/daily despite a recommended daily dietary allowance of only 22.4 IU for adult men, the implications of our observations are substantial,” the authors wrote.

The researchers said the findings suggests that vitamin E can increase prostate cancer risk long after supplementation has ended.

Prostate cancer is a relatively common disease — about one in six men will be diagnosed with it, according to the American Cancer Society. However, it has a mortality rate of only 3 percent.

What confounds doctors is determining who is at greater risk of dying from prostate cancer once it is discovered. Many tumors are slow growing and aggressive treatment such as surgery and radiation can leave men impotent and incontinent.

A government panel sparked controversy recently by issuing new guidelines that the commonly administered PSA test for prostate cancer no longer be given to healthy men. Experts advise men to consult their doctors and consider their personal risk factors when making decisions about testing and treatment.