Keck Medicine of USC clinician researchers seek volunteers to take part in the first definitive, large-scale clinical trial to investigate if a vitamin D supplement helps prevent or delay Type 2 diabetes in adults who have prediabetes, which places people at high risk for Type 2 diabetes. Funded by the National Institutes of Health (NIH), the study is taking place at about 20 study sites across the United States.

The multiyear Vitamin D and Type 2 Diabetes (D2d) study will include approximately 2,500 people. The aim is to learn if vitamin D — specifically D3 (cholecalciferol) — will prevent or delay Type 2 diabetes in adults aged 30 or older with prediabetes. People with prediabetes have blood glucose levels that are higher than normal but not high enough to be called diabetes.

“This study aims to definitively answer the question: Can vitamin D reduce the risk of developing Type 2 diabetes?” said Myrlene Staten, 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.”

D2d is the first study to directly examine if a daily dose of 4,000 International Units (IUs) of vitamin D helps keep people with prediabetes from getting Type 2 diabetes. The dosage is higher than a typical adult’s intake of 600-800 IUs a day, but within limits judged appropriate for clinical research by the Institute of Medicine. Based on observations from earlier studies, researchers speculated that vitamin D could reduce the diabetes risk by 25 percent. The study will also examine if gender, age or race affect the potential of vitamin D to reduce diabetes risk.

“Although the study is open to all interested patients, our site will have a focus on the Latino population in the East Los Angeles area,” said Anne Peters, professor of clinical medicine at the Keck School of Medicine of USC and director of the USC Clinical Diabetes program. “Because the risk of prediabetes and diabetes is so high among Latinos, it’s particularly important to study methods of preventing diabetes in this population.”

Half of the participants will receive vitamin D. The other half will receive a placebo. Participants will have checkups for the study twice a year and will receive regular health care through their own health care providers.

The study will be double-blinded, so neither participants nor the study’s clinical staff will know who is receiving vitamin D and who is receiving a placebo. The study will continue until enough people have developed Type 2 diabetes to be able to make a scientifically valid comparison between diabetes development in the two groups, likely about four years.

D2d builds on previous NIH-funded studies of methods to delay or prevent Type 2 diabetes, including the Diabetes Prevention Program, which showed that, separately, lifestyle changes to lose a modest amount of weight and the drug metformin are both effective in slowing development of Type 2 diabetes in people with prediabetes. However, additional safe and effective preventative strategies are needed to stem the increasing numbers of people developing Type 2 diabetes.

D2d (ClinicalTrials.gov grant number NCT01942694) is supported by the NIH (grant number U01DK098245). The NIDDK is the primary sponsor of the trial, with additional support from the NIH Office of Dietary Supplements and the American Diabetes Association. Support in the form of educational materials is provided by the National Diabetes Education Program.

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