Effect of moderate-dose vitamin D supplementation on insulin sensitivity in vitamin D–deficient non-Western immigrants in the Netherlands: a randomized placebo-controlled trial

Background: Low serum 25-hydroxyvitamin D [25(OH)D] concentrations have been associated with insulin resistance, the metabolic syndrome, and type 2 diabetes. Because many non-Western immigrants in the Netherlands are vitamin D deficient, obese, and at high risk of diabetes, vitamin D supplementation may contribute to prevent diabetes and insulin resistance.Objective: We examined the effect of vitamin D supplementation on insulin sensitivity and β cell function in overweight, vitamin D–deficient, non-Western immigrants at high risk of diabetes.Design: The study was a 16-wk, randomized, placebo-controlled trial. A total of 130 non-Western immigrants with prediabetes (fasting glucose concentration >5.5 mmol/L or random glucose concentration from 7.8 to 11.1 mmol/L) and vitamin D deficiency (serum 25[OH]D concentration