High-dose supplementation with both the trace element selenium and vitamin E increase the risk of high-grade prostate cancer. But importantly, this risk depends upon a man’s selenium status before taking the supplements. "Men using these supplements should stop, period. Neither selenium nor vitamin E supplementation confers any known benefits -- only risks," the lead author stated. "While there appear to be no risks from taking a standard multivitamin, the effects of high-dose single supplements are unpredictable, complex and often harmful. There are optimal levels, and these are often the levels obtained from a healthful diet, but either below or above the levels there are risks."

Source: Selenium, vitamin E supplements can increase risk of prostate cancer in some men