Does vitamin D3 supplementation improve glucose homeostasis in overweight or obese women? A double-blind, randomized, placebo-controlled clinical trial

AimsVitaminD deficiency is considered as a risk factor in cardiometabolic disorders, including cardiovascular diseases, hypertension and Type2 diabetes mellitus. We have investigated the effect of vitamin D3 supplementation on glucose homeostasis in healthy overweight and obese women. MethodsIn a double-blind randomized placebo-controlled clinical trial, 77 healthy overweight or obese women (mean age 388years; BMI 29.94.2kg/m(2)) were randomly assigned to the vitaminD3 group (25g/day as cholecalciferol tablets) or the placebo group. Selected anthropometric indices, glucose, insulin, HbA(1c) and homeostasis model assessment of insulin resistance at baseline and after 12weeks were measured. Dietary intakes using 24-h food recall and food frequency questionnaires were assessed. Physical activity was assessed by the International Physical Activity Questionnaire. Adjusted mean differences were calculated using analysis of covariance. Correlation coefficients were calculated by Pearson's analysis. ResultsMean fasting blood glucose concentrations declined in the vitaminD3 and placebo groups (-0.280.4 vs. -0.650.4 mmol/l, P<0.001) and the mean percentage of HbA(1c) was decreased (-13 +/- 18 vs. -19 +/- 17mmol/l, P=0.06) in both groups, respectively. Mean 25-hydroxyvitaminD concentrations increased in the vitaminD3 and placebo groups (38.2 +/- 32 vs. 4.6 +/- 14nmol/l, P<0.001), respectively. There was a significant correlation between HbA(1c) and 25-hydroxyvitaminD concentrations (r=-0.271; P=0.018). ConclusionsThe results indicate that the vitaminD3 supplement of 25g/day had no beneficial effect on glycaemic indices in healthy overweight or obese women.