Intratrial Exposure to Vitamin D and New-Onset Diabetes Among Adults With Prediabetes: A Secondary Analysis From the Vitamin D and Type 2 Diabetes (D2d) Study. Diabetes Care 2020;43:2916-2922.

This letter concerns the secondary analysis (1) of the Vitamin D and Type 2 Diabetes (D2d) study (2). The D2d study was a randomized controlled trial to determine whether vitamin D supplementation (4,000 IU per day) reduced the risk of diabetes among adults with prediabetes (2). In an intention-to-treat analysis, vitamin D nonsignificantly reduced new-onset diabetes by 12% compared with the placebo (2). A secondary analysis was subsequently …