Effects of Vitamin D on Dose of Hypoglycaemic Medication in Diabetes Patients

Abstract

Background: Studies have suggested that vitamin D may have a role in assisting the management of diabetes by increasing insulin secretion and decreasing insulin resistance. If so, it could decrease the dose of hypoglycaemic medication required by diabetes patients. Aims: This study aimed to investigate whether vitamin D supplementation has any effect on the dose of hypoglycaemic medication prescribed to diabetes patients. Methods: The Vitamin D Assessment (ViDA) study is a large randomized controlled trial with the primary aim of determining whether a monthly 100,000 IU (2.5mg) dose of cholecalciferol prevents cardiovascular disease compared to placebo. Participants were recruited in 2011-2012 and were followed for a median period of about 3 years until July 2015. At the baseline interview, 624 participants reported they had diabetes. They were all linked by National Health Index (NHI) numbers to Ministry of Health data on dispensed prescriptions collected in the 6 months before randomization and during follow-up. The prescription data included name, dose and amount of each dispensed hypoglycaemic medication. From this information, medication effect scores, which estimate the decrease in glycosylated haemoglobin produced by a hypoglycaemic medication, were calculated for each medication group and summarized. Results: The mean (SD) measured serum 25(OH)D concentration for all diabetes participants was 57±27nmol/L at baseline. In participants who had repeat blood tests, after 6 months following the intervention, the serum 25(OH)D concentration increased significantly in the vitamin D group (122 nmol/), whereas in the placebo group it was similar to baseline (58nmol/L).The same pattern was maintained for the vitamin D and placebo groups throughout the study. Despite the significant increase in serum 25(OH)D in the vitamin D group, no reduction in the dose of diabetes medication was observed, as indicated by the change from baseline in the total medication effect scores of all prescribed hypoglycaemic medications by -0.03, 0.03 and 0.09 at 1, 2 and 3 years respectively, in the vitamin D group, compared to the change in the placebo group of 0.07, 0.09 and 0.27 at the same respective periods ( p-values comparing the changes in MES: 0.02, 0.28 and 0.30 at 1, 2 and 3 years, respectively). Conclusion: Our study did not show that vitamin D supplementation of 100,000 IU cholecalciferol monthly for a period of about 3 years improves glycaemic control in diabetes patients.