The effect of different doses of vitamin D3 on markers of vascular health in patients with type 2 diabetes: A randomised controlled trial

Abstract

Aims/hypothesis Low 25-hydroxyvitamin D levels predict future cardiovascular events and are common in patients with type 2 diabetes. We compared the effect of 100,000 and 200,000 IU doses of vitamin D3 on endothelial function, blood pressure and markers of glycaemic control in patients with type 2 diabetes. Methods This was a randomised, parallel group, placebocontrolled trial. Patients with type 2 diabetes and baseline 25-hydroxyvitamin D levels <100 nmol/l were enrolled from community and hospital-based diabetes clinics. Participants were assessed in a university department of clinical pharmacology and received a single oral dose of placebo or vitamin D3 (100,000 IU or 200,000 IU) at baseline, randomly allocated via numbered bottles prepared offsite; participants and investigators were both blinded to treatment allocation. Endothelial function, office blood pressure, B-type natriuretic peptide, insulin resistance and glycosylated haemoglobin were measured at baseline, and at 8 and 16 weeks. Results We randomised 61 participants to the three groups (placebo 22, 100,000 IU vitamin D3 19, 200,000 IU vitamin D3 20). There was no significant difference in the primary outcome of endothelial function at 8 weeks (placebo 5.2%, n=22; 100,000 IU 4.3%, n =19; 200,000 IU 4.9%, n =17) or at 16 weeks. Insulin resistance and glycosylated haemoglobin did not improve with either dose of vitamin D3.On covariate analysis, systolic blood pressure was significantly lower in both treatment arms than in the placebo group at 8 weeks (placebo 146.4 mmHg, 100,000 IU 141.4 mmHg [p=0.04 vs placebo], 200,000 IU 136.8 mmHg [p=0.03 vs placebo]). B-type natriuretic peptide levels were significantly lower in the 200,000 IU group by 16 weeks (placebo 34 pg/ml, 200,000 IU21pg/ml, p=0.02). No significant excess of adverse effects was noted in the treatment arms. Conclusions/interpretation High-dose vitamin D3 improved systolic blood pressure and B-type natriuretic peptide levels, but not endothelial function, insulin resistance or glycosylated haemoglobin in patients with type 2 diabetes. © Springer-Verlag 2010.