About D2d

The Vitamin D and type 2 diabetes (D2d) study is a large multi-center clinical trial conducted in twenty-two cities around the United States. The goal of D2d is to determine whether vitamin D supplementation is safe and effective in delaying the onset of type 2 diabetes in people at risk for the disease and to gain a better understanding of how vitamin D affects glucose metabolism. D2d met its enrollment target in December 2016. 2,398 participants who are at risk of developing diabetes were randomly assigned to receive either vitamin D or placebo and will be followed for an average of 4 years for development of diabetes.

“The D2d study aims to definitively answer that question, can vitamin D reduce the risk of developing type 2 diabetes?” says Myrlene Staten, M.D., D2d Project Officer at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of NIH. “Vitamin D use has risen sharply in the U.S. in the last 15 years, since it has been suggested as a remedy for a variety of conditions, including prevention of type 2 diabetes. But we need rigorous testing to determine if vitamin D will help prevent diabetes. That’s what D2d will do.”

There are over 86 million Americans who are at increased risk for developing type 2 diabetes. Lifestyle changes, such as healthy eating, exercise and weight loss, can decrease the chances of developing diabetes. However, many people still develop diabetes despite efforts at changing their lifestyle.  Therefore, there is a need for interventions that are safe, inexpensive and easy to implement to prevent type 2 diabetes and decrease disease burden. Based on recently published studies, vitamin D has emerged as a potential determinant of type 2 diabetes risk. However, according to reports by the Institute of Medicine and the Endocrine Society, the evidence to support vitamin D supplementation for prevention of diabetes is inconclusive and D2d is expected to be the definitive study to answer this question. 

Study Sponsors

Primary Sponsor


Other Sponsors