Vitamin D Supplementation in Adults with Vitamin D Deficiency and Its Effect on Metabolic Syndrome - A Randomized Controlled Study.

Background: Inverse relationship between metabolic syndrome (MetS) and 25-hydroxyvitamin D (25(OH) D) levels is controversial. Hypovitaminosis-D has long been suspected as a risk factor for glucose intolerance.

Aim: A randomized double blind placebo controlled study to evaluate effects of vitamin D supplementation on insulin resistance in subjects with hypovitaminosis-D and MetS.

Materials And Methods: Subjects were randomized to receive either oral 25(OH) D3 supplement (60000 (IU) per week for 8 weeks followed by 60,000 IU monthly for 4 months) or a placebo for six months. The parameters measured were blood pressure, vitamin D, fasting blood sugar (FBS), insulin, homeostasis model assessment (HOMA), quantitative insulin sensitivity check index (QUICKI), body mass index (BMI), and waist circumference (WC).

Results: There were no significant changes in parameters of vitamin-D group compared to placebo group except serum vitamin-D was significantly increased in vitamin-D group (p < 0.0001). In vitamin-D group, mean WC at baseline was 95.9 ± 6.66, which significantly changed to 94.6 ± 7.47 (p = 0.001). Mean BMI at baseline was 29.1 ± 4.06 which significantly changed to 28.5 ± 4.16 (p = 0.001). The mean vitamin-D concentration at baseline was 15.4 ± 9.03 which significantly (p < .0001) increased to 26.1 ± 11.8. In placebo group mean insulin levels was 10.7 ± 4.81IU / L which increased significantly (p = 0.03) to 15.4 ± 14.0. Mean QUICKI at baseline was 0.34 ± 0.03 which decreased significantly (p = 0.02) to 0.32 ± 0.03.

Conclusion: In this study the relationship between vitamin D supplementation and MetS or IR was not established. Whether achieving vitamin D sufficiency in large population-based trials with a longer duration would produce more favorable results needs to be assessed.