We continue to analyze study data to examine the effect of vitamin D supplementation on additional outcomes, including new onset cancer and cardiovascular disease. For a list of D2d publications, visit our publications page.
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Draw your own conclusions D2d is a large-scale NIH-supported trial to test whether vitamin D supplementation reduces diabetes risk in adults with prediabetes. The main results were published in the New England Journal of Medicine. Vitamin D supplementation did not significantly lower diabetes risk (hazard ratio 0.88; 95% CI 0.75 to 1.04). D2d and two other diabetes prevention trials (in Norway and Japan) among people at risk for diabetes have reported nearly identical results. We recently published a systematic review in this topic and we plan to combine results in an individual participant data meta-analysis.
Currently, we do not know how large the risk of developing diabetes is among people with pre-diabetes, as defined the American Diabetes Association criteria. Some researchers think that we need to screen for pre-diabetes and intervene to keep glucose levels as normal as possible. Others advocate that the current definitions of pre-diabetes risk unnecessary medicalization and create unsustainable burdens for health care systems. D2d will define the natural history of diabetes and, as such, will reconcile these two opposing views.
Learn More About D2dLearn More About Pre-Diabetes
We continue to analyze study data to examine the effect of vitamin D supplementation on additional outcomes, including new onset cancer and cardiovascular disease. For a list of D2d publications, visit our publications page.
Visit Our D2d Publications Page
D2d is a large-scale NIH-supported trial to test whether vitamin D supplementation reduces diabetes risk in adults with prediabetes. The main results were published in the New England Journal of Medicine. Vitamin D supplementation did not significantly lower diabetes risk (hazard ratio 0.88; 95% CI 0.75 to 1.04). D2d and two other diabetes prevention trials (in Norway and Japan) among people at risk for diabetes have reported nearly identical results. We recently published a systematic review in this topic and we plan to combine results in an individual participant data meta-analysis. Draw your own conclusions 
Currently, we do not know how large the risk of developing diabetes is among people with pre-diabetes, as defined the American Diabetes Association criteria. Some researchers think that we need to screen for pre-diabetes and intervene to keep glucose levels as normal as possible. Others advocate that the current definitions of pre-diabetes risk unnecessary medicalization and create unsustainable burdens for health care systems. D2d will define the natural history of diabetes and, as such, will reconcile these two opposing views.
Learn More About Pre-Diabetes Learn More About D2d
86 million Americans have pre-diabetes (1/3 of the adult population) and their chance of developing diabetes is about 10% per year. Physical activity and weight loss can lower diabetes risk. However, many people still develop diabetes despite efforts at changing their lifestyle.
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Post-randomization biases may influence the estimate of efficacy of supplemental vitamin D in diabetes prevention trials. In the Vitamin D and Type 2 Diabetes (D2d) study, to overcome this challenge, we calculated intra-trial vitamin D exposure as the cumulative rolling mean of annual serum 25(OH)D measurements. Among participants at risk for diabetes treated with vitamin D, those who maintained intra-trial blood 25(OH)D levels of 40-49 ng/mL (100–124 nmol/L) had a 52% lower risk of developing diabetes compared to those who maintained a level of 20-29 ng/mL (50–74 nmol/L). Those who maintained blood 25(OH)D levels equal to or greater than 50 ng/mL (125 nmol/L) had a 71%, lower risk of developing diabetes. We concluded that daily vitamin D supplementation to maintain a blood 25(OH)D level greater than 40 ng/mL (100 nmol/L) is a promising approach to reducing the risk of diabetes in adults with prediabetes.
Post-randomization biases may influence the estimate of efficacy of supplemental vitamin D in diabetes prevention trials. In the Vitamin D and Type 2 Diabetes (D2d) study, to overcome this challenge, we calculated intra-trial vitamin D exposure as the cumulative rolling mean of annual serum 25(OH)D measurements. Among participants at risk for diabetes treated with vitamin D, those who maintained intra-trial blood 25(OH)D levels of 40-49 ng/mL (100–124 nmol/L) had a 52% lower risk of developing diabetes compared to those who maintained a level of 20-29 ng/mL (50–74 nmol/L). Those who maintained blood 25(OH)D levels equal to or greater than 50 ng/mL (125 nmol/L) had a 71%, lower risk of developing diabetes. We concluded that daily vitamin D supplementation to maintain a blood 25(OH)D level greater than 40 ng/mL (100 nmol/L) is a promising approach to reducing the risk of diabetes in adults with prediabetes.
Draw your own conclusionsWe love our participants and we are fully committed to them
D2d takes place in 22 medical centers across the United States. Approximately 35% of the US population lives within the larger metropolitan areas covered by the D2d sites.
