Dietary supplements containing higher amounts of Vitamin E and selenium can increase prostate cancer risk in older men, a new study has shown. The study shows the risk associated with high-dose vitamin supplements, which have become popular in the last few years. "Many people think that dietary supplements are helpful or at the least innocuous. This is not true," said corresponding and first author Alan Kristal from Fred Hutchinson Cancer Research Center, according to a news release. "We know from several other studies that some high-dose dietary supplements - that is, supplements that provide far more than the daily recommended intakes of micronutrients - increase cancer risk. We knew this based on randomized, controlled, double-blinded studies for folate and beta carotene, and now we know it for vitamin E and selenium," Kristal added. The study was based on data from a trial called Selenium and Vitamin E Cancer Prevention Trial (SELECT), which was designed to find out whether higher doses of vitamin E and Selenium could reduce the risk of prostate cancer. Instead, researchers found that staying on high-doses of vitamins led to an increase in prostate cancer risk. For the study, researchers looked at information from 1,739 men diagnosed with prostate cancer and 3,117 men without the cancer. Researchers found that men taking vitamin E supplements had a 17 percent increased risk of prostate cancer. Also, selenium supplements increased the cancer risk by 91 percent in men who had high levels of selenium before the start of the study. "Men using these supplements should stop, period. Neither selenium nor vitamin E supplementation confers any known benefits - only risks," Kristal said. Nearly half of all adults living in the U.S use at least one dietary supplement. Research has shown that some of these supplements might be a waste of money. A recent study also showed that vitamin C and E supplements interfere with muscle development. According to the Food and Drug Administration, vitamins aren't harmful. However, taking large doses of vitamin supplements can be dangerous. People who take blood thinners must be careful about multivitamin intake. The National Cancer Institute funded the study.