The large-scale clinical trial is the first definitive study to investigate whether vitamin D supplementation can help delay or prevent type 2 diabetesin adults who have pre-diabetes and are at high risk for developing the condition.
The goal of the multiyear 'Vitamin D and Type 2 Diabetes' (D2d) study is to learn if vitamin D — specifically D3 (cholecalciferol) — will prevent or delay type 2 diabetes in adults aged 30 or older with pre-diabetes.
"This study aims to definitively answer the question: Can vitamin D reduce the risk of developing type 2 diabetes?" said Dr Myrlene Staten, D2d project officer at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of NIH.
"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."
Funded by the NIH, the study is taking place at about 20 study sites across the United States and will include around2,500 people.
D2d is the first study to directly examine if a daily dose of 4,000 International Units (IUs) of vitamin D — greater than a typical adult intake of 600-800 IUs a day, but within limits deemed appropriate for clinical research by the Institute of Medicine — helps keep people with pre-diabetes from getting type 2 diabetes.
The team are now recruiting volunteers to take part in D2d. Half of the participants will receive vitamin D, while the other half will receive a placebo. 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 placebo.
Participants will have check-ups for the study twice a year, and will receive regular health care through their own health care providers.
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, said the research team.
Vitamin D hope
Based on observations from earlier studies, researchers speculate that vitamin D could reduce the diabetes risk by 25%. The study will also examine if sex, age or race affect the potential of vitamin D to reduce diabetes risk.
"Past observational studies have suggested that higher levels of vitamin D may be beneficial in preventing type 2 diabetes, but until this large, randomised and controlled clinical trial is complete, we won't know if taking vitamin D supplements lowers the risk of diabetes," explained Dr Anastassios Pittas - the study's principal investigator at Tufts Medical Center, USA.
"With D2d, we seek evidence for an affordable and accessible way to help prevent or delay type 2 diabetes," added NIDDK director Dr Griffin P. Rodgers.