An NIH-funded trialexternal link disclaimer has found that taking vitamin D supplements does not prevent type 2 diabetes in people at high risk of the disease. In this study, which was co-sponsored by the Office of Dietary Supplements, 2,423 U.S. adults at high risk of developing type 2 diabetes received either 4,000 international units (IU) per day of vitamin D3 or placebo for about 2.5 years. At the end of the study, there was no meaningful difference in the risk of type 2 diabetes between those who took vitamin D3 and those who took the placebo. The lead researcher, Dr. Anastassios G. Pittas from Tufts Medical Center, said that the strengths of the study included a large number of participants as well as racial and ethnic diversity. In addition, the dose of vitamin D3 was high enough to produce a large difference in vitamin D blood levels between groups, while still being safe.