Effect of oral vitamin D supplementation on glycemic control in patients with type 2 diabetes mellitus with coexisting hypovitaminosis D: A parellel group placebo controlled randomized controlled pilot study

Abstract

Context: Vitamin D supplementation in type 2 diabetes mellitus patients may lead to improved glycemic control by improving insulin secretion and decreasing insulin resistance.

Aims: To investigate effect of oral vitamin D supplementation on glycemic control, in patients with type 2 diabetes mellitus and coexisting hypovitaminosis D.

Settings and design: Randomized, Parallel Group, Placebo Controlled Trial carried out in a tertiary care hospital of Indian Armed Forces.

Methods and material: Sixty patients with coexisting type 2 diabetes mellitus and hypovitaminosis D were randomized into cases and controls and were supplemented with oral Vitamin D and microcrystalline cellulose respectively for six months. Subjects' HbA1c and vitamin D levels were monitored at the beginning and end of the study, fasting plasma glucose (FPG) & post prandial plasma glucose (PPPG) during monthly OPD visits.

Statistical analysis used: Intra-group comparison was made by paired t test & unpaired t test was used for inter-group (A v/s B) comparisons. Repeated measures ANOVA was undertaken to compare values over time.

Results: The two groups were comparable for all parameters at baseline. Case group showed significant decrease in mean HbA1c levels (7.29% to 7.02%; P = 0.01), mean FPG levels (131.4 to 102.6 mg/dl; P = 0.04) and mean PPPG levels (196.2 to 135.0 mg/dl; P < 0.001). Incidentally, significant improvement in systolic as well as diastolic blood pressure and total cholesterol was also noted in the cases, while for LDL cholesterol improvement tended towards significance (p = 0.05).

Conclusions: We found that oral vitamin D supplementation was associated with improved glycemic control and other metabolic parameters in patients with type 2 diabetes mellitus. Supplementation to achieve normal levels of vitamin D can be a promising adjuvant therapy for T2DM patients & coexisting hypovitaminosis D.

Keywords: Glycated hemoglobin; Glycemic control; Hypovitaminosis D; Type 2 diabetes mellitus; Vitamin D.