A clinical trial testing the effects of vitamin E and selenium supplementation on prostate cancer shows a statistically significant increase in cancer risk with vitamin E supplementation, according to the latest analysis.
The Selenium and Vitamin E Cancer Prevention Trial (SELECT) was started in 2001 with much enthusiasm and was funded by the National Cancer Institute. Two previous cancer trials (for other forms of the disease) had suggested that people who supplemented with vitamin E and selenium had reduced risk of prostate cancer. This was the first trial designed to specifically test the benefits of these nutrients on prostate cancer, either alone or when administered together.
There were four conditions in the trial. In one condition participants were given a pill of 400 IU of vitamin E (oil based capsules) and another pill of 200 mg selenium (pressed tablets) to take daily. In another condition men were given the vitamin E pill and a placebo pill that looked like selenium. In the third condition participants were given the real selenium pill and a placebo that looked like vitamin E. And in the final condition both pills were placebo.
Researchers hoped they could achieve a 25% reduction in prostate cancer risk with vitamin E or selenium, but in 2008 researchers detected slightly more prostate cancer in men who were taking the vitamin E supplement alone. Though at that time the increase was not significant, the Data and Safety Monitoring Committee terminated the trial since it was obvious that the 25% reduction would not be met.