The effect of vitamin D on insulin resistance in patients with type 2 diabetes

Introduction: Over the past decade, numerous non-skeletal diseases have been reported to be associated with vitamin D deficiency including type2 diabetes mellitus (T2DM). Different studies provide evidence that vitamin D may play a functional role in glucose tolerance through its effects on insulin secretion and insulin sensitivity. This study evaluates the effects of vitamin D supplementation on insulin resistance in T2DM. Method: Through a before-after study, 100 patients with T2DM, 30-70 years old, were recruited from an Arak diabetes clinic as consecutive attenders. Participants were assessed for clinical and biochemistry. Serum insulin and, 25(OH) D concentration, and HOMA-IR was calculated. All measurements were performed at the beginning and the end of the study. Patients received 50,000 unit of vitamin D-3 orally per week for eight weeks, Statistical analysis was made using SPSS17. The results were analyzed by descriptive tests, and a comparison between variables were made using paired T-tests or Wilcoxon tests, as appropriate. Results: 100 participants including 70 women (70%) and 30 men (30%) took part in the study. All results were presented as Mean +/- SD, or medians of non-normally distributed. 24% of the participants were Vitamin D deficient {serum 25(OH) D <= 20 ng/ml(50 nmol/l)}. Mean serum 25 (OH) D concentration was 43.03 +/- 19.28 ng/ml (107.5 +/- 48.2 nmol/l). The results at baseline and at the end, for FPG were 138.48 +/- 36.74 and 131.02 +/- 39 mg/dl (P=0.05), for insulin, 10.76 +/- 9.46 and 8.6 +/- 8.25 mu Iu/ml (P=0.028) and for HOMA-IR, 3.57 +/- 3.18 and 2.89 +/- 3.28 (P=0.008) respectively. Conclusion: Our data showed significant improvements in serum FPG, insulin and in HOMA-IR after treatment with vitamin D, suggested that vitamin D supplementation could reduce insulin resistance in T2DM.