Vitamin D Supplementation Does Not Delay Type 2 Diabetes in High-Risk Patients

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Supplementation with vitamin D does not delay onset of type 2 diabetes in high-risk patients.

SAN FRANCISCO — Supplementation with vitamin D does not delay the onset of type 2 diabetes (T2D) in high-risk patients, according to results from the Vitamin D and Type 2 Diabetes Study (D2d; Identifier: NCT01942694) presented at the American Diabetes Association 79th Scientific Sessions, held June 7 to 11, 2019.

The results were simultaneously published in the New England Journal of Medicine.

Given some previous observational data that serum 25-hydroxyvitamin D may be associated with risk for type 2 diabetes, researchers aimed to assess whether vitamin D supplementation can affect risk of developing T2D in high-risk patients. To meet the criteria for high risk, patients had to have ≥2 of the following glycemic measures: fasting plasma glucose between 100 and 125 mg/dL, plasma glucose level after 75-g oral glucose of 140 to 199 mg/dL, and hemoglobin A1c (HbA1c) between 5.7% and 6.4%. Participants were randomly assigned to receive 4000 IU/d of vitamin D3 or placebo.

Of 2423 participants, 1211 were assigned to the vitamin D group and 1212 received placebo. After 2 years, serum 25-hydroxyvitamin D was 54.3 ng/mL for the vitamin D group and 28.8 ng/mL for the placebo group compared with 27.7 and 28.2 ng/mL at baseline, respectively.

New-onset diabetes occurred in 293 participants receiving vitamin D and 323 participants receiving placebo (hazard ratio for vitamin D vs placebo, 0.88; 95% CI, 0.75-1.04; P =.12). Incidence of adverse events also did not differ between the groups.

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The researchers concluded that at a dose of 4000 IU/d, vitamin D supplementation did not lower risk for diabetes in high-risk patients not selected for vitamin D deficiency.


Pittas AG, Dawson-Hughes B, Sheehan P, et al. Vitamin D supplementation and prevention of type 2 diabetes [published online June 7, 2019]. N Engl J Med. doi:10.1056/NEJMoa1900906