Effect of Vitamin D supplementation on glycemic control in Type 2 diabetes subjects in Lagos, Nigeria

INTRODUCTION: Improvement of glycemic control reduces the risk of diabetic complications. Reports suggest that Vitamin D supplementation improves glycemia. However, there are no data on the influence of Vitamin D on diabetes mellitus (DM) in Nigeria. OBJECTIVE: To determine the effect of Vitamin D supplementation on glycemic control in Type 2 DM (T2DM) participants with Vitamin D deficiency. DESIGN: This was a single-blind, prospective randomized placebo-controlled trial, involving T2DM participants attending the Diabetes Clinic of the Lagos University Teaching Hospital. Forty-two T2DM participants with poor glycemic control and Vitamin D deficiency were selected following a prior cross-sectional study on 114 T2DM participants for the determination of Vitamin D status and glycemia. These participants were randomized into two equal groups of treatment and placebo arms. INTERVENTION: Three thousand IU of Vitamin D(3) were given to the participants in the treatment arm. Glycemic status was determined at baseline and after 12 weeks. Statistical analysis was performed using Statistical Package for Social Sciences version 20. P < 0.05 was considered statistically significant. RESULTS: Vitamin D(3) supplementation resulted in a significant improvement in serum Vitamin D level and fasting plasma glucose in the treatment arm compared to placebo. There was a nonsignificant reduction in the mean HbA1c level in the treatment group after 12 weeks of Vitamin D(3) supplementation (Z = −1.139; P = 0.127) compared to the placebo group, which had a further increase in the mean HbA1c level (Z = −1.424; P = 0.08). The proportion of participants with poor glycemic control (HbA1c > 6.5%) who converted to good control after Vitamin D supplementation was significantly higher in the treatment arm compared to placebo (P < 0.05). CONCLUSION: Vitamin D(3) supplementation in persons with T2DM and Vitamin D deficiency results in a significant improvement in glycemic control.