The US government is stopping a major study of whether vitamin E and selenium prevent prostate cancer – because the supplements aren’t working. More than 35,000 men age 50 and older have been taking one or both supplements or dummy pills as part of a study called the SELECT trial. But the National Cancer Institute announced Monday that they will be getting letters in the next few days telling them to quit the pills. An early review of the data shows neither supplement, taken alone or together, is preventing prostate cancer. Of more concern, slightly more users of vitamin E alone were getting prostate cancer – and slightly more selenium-only users were getting diabetes.