Effect of Vitamin D Supplementation on Glycemic Control in Newly Diagnosed Patients With Type 2 Diabetes Mellitus: A Randomized Controlled Trial

Vitamin D deficiency is commonly associated with type 2 diabetes and it has been linked to impaired glycemic control in these patients. This study was done to determine if vitamin D supplementation improves glycemic parameters in type 2 diabetes. This randomized controlled trial was done in 140 newly diagnosed adult patients with type 2 diabetes. The participants were randomly divided into two groups where one group received vitamin D (60,000 International Units (IU) of oral vitamin D3 weekly for a duration of three months, followed by 1000 IU twice daily for another three months in vitamin D deficient patients; 1000 IU (25 mcg) twice daily for six months for subjects with sufficient vitamin D level) along with standard anti-diabetic drugs while the other group received standard anti-diabetic drugs only. The effect of vitamin D supplementation was assessed by measuring glycated haemoglobin (HbA1c), fasting blood sugar (FBS), postprandial blood sugar (PPBS), fasting insulin, and insulin resistance as Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) at the baseline and after six months. Vitamin D deficiency was observed in 60% (n=84) of the subjects with the rest 40% (n=56) having sufficient serum vitamin D levels. The baseline mean HbA1c was 8.48 ± 1.46% and 8.21 ± 1.24% in the control and vitamin D group, respectively. After supplementing vitamin D for six months, no significant difference was observed between the two groups in terms of HbA1c (p= 0.263). Similarly, there was no significant change in other parameters like FBS, PPBS, fasting insulin, and insulin resistance (HOMA-IR). A subgroup analysis within the vitamin D group between the vitamin D sufficient and deficient patients also revealed no significant changes in the above parameters. Vitamin D supplementation, within the parameters of this study, did not yield a distinctive advantage in improving glycemic outcomes in individuals with type 2 diabetes.