An analysis of data from a large national study found that people who took a 200 microgram selenium supplement each day for almost eight years had an increased risk of developing type 2 diabetes than those who took a placebo or dummy pill. The data came from the Nutritional Prevention of Cancer Trial (NPC), a large randomized, multi-center, clinical trial from the eastern United States, designed to evaluate whether selenium supplements prevent skin cancer. In the current study, researchers selected 1,202 participants who did not have diabetes when they were enrolled in the NPC Trial. In the current study, 58 out of 600 participants in the selenium group and 39 out of 602 participants in the placebo group developed type 2 diabetes. After 7.7 years of follow-up, the relative risk rate was approximately 50 percent higher among those randomized to selenium than among those randomized to placebo. Selenium is a naturally occurring trace mineral present in soil and foods necessary in minute amounts to aid in metabolism.