Vitamin D 20 000 IU per Week for Five Years Does Not Prevent Progression From Prediabetes to Diabetes

Context: Vitamin D deficiency is associated with insulin resistance and risk of future diabetes. Objective: The objective of the study was to test whether supplementation with vitamin D to subjects with prediabetes will prevent progression to type 2 diabetes mellitus (T2DM). Design: This was a randomized controlled trial performed in 2008 through 2015. Setting: The study was conducted at the clinical research unit at a teaching hospital. Patients: Five hundred eleven subjects (mean age 62 y, 314 males) with prediabetes diagnosed with an oral glucose tolerance test as part of the Tromso Study 2007–2008 were included. A total of 256 were randomized to vitamin D and 255 to placebo. Twenty-nine subjects in the vitamin D and 24 in the placebo group withdrew because of adverse events. Interventions: Interventions included vitamin D (cholecalciferol) 20 000 IU/wk vs placebo for 5 years. Annual oral glucose tolerance tests were performed. Main Outcome Measure: Progression to T2DM was the main outcome measure. Sec...