Effects of vitamin D supplementation on serum 25-hydroxyvitamin D levels and markers of metabolic and hs-CRP levels in women with gestational diabetes

Abstract

Background and Objectives: Gestational diabetes mellitus (GDM) is defined as any degree of glucose intolerance occurring in or first recognizable during pregnancy. GDM is considered to be a pregnancy complication. Worldwide, GDM prevalence varies from 1% to 28% of all pregnancies. Studies have shown that beta-cell dysfunction and insulin resistance resulted excess weight gain during pregnancy intensify pregnancy-induced insulin resistance. Some studies have shown that poor vitamin D status increases risks for impaired insulin secretion, and insulin resistance. Vitamin D deficiency has been reported in 80% of pregnant Iranian women. Therefore, this study was designed to assess the effects of vitamin D supplementation on the metabolic profiles and hs-CRP statuses of pregnant women with GDM. Materials and Methods: The study was a randomized, placebo-controlled, doubleblinded clinical trial. Seventy-six pregnant women with GDM and gestational ages between 24-28 weeks were randomly assigned to receive four oral treatments once every 2 weeks for a total of 2 months that consisted of 50,000 IU of vitamin D3 (n = 38) or placebo (n = 38). The fasting blood glucose (FG), insulin, HbA1c, 25- hydroxyvitamin D, lipid profile, hs-CRP, and HOMA-IR were measured before and after the treatment. For normally distributed data, we performed an independent samples Student’s t-test, to detect basic differences between 2 groups, and a paired t-test to detect differences in each group before and after the intervention. For nonparametric distributions, we used the Mann-Whitney U test and the Wilcoxon paired rank test. To assess the effects of vitamin D supplementation on biochemical parameters between the 2 groups after the intervention, ANCOVA was used by adjusting for the baseline measurements and covariates. Differences were considered to be significant at a P value ≤ 0.05. Results: As compared with the placebo group, in the vitamin D group, the serum level of 25hydroxyvitamin D increased (19.15 vs. -0.40 ng/ml; p < 0.01) and that of FG (- 4.72 vs. 5.27 mg/dl; p = 0.01) as well as HbA1c (-0.18% vs. 0.17%; p = 0.02) decreased. There were improvements in the lipid profiles of the vitamin D group, but they were not statistically significant. Significant increases in the concentrations of total and LDL cholesterol as well as in fasting glucose, HbA1c, and hs-CRP were seen in the placebo group. The fasting insulin and HOMA-IR did not change significantly in either group. Conclusion: Based on the results in GDM patients, vitamin D supplementation improves FG, HbA1c, and vitamin D status but has no significant effects on lipid profile or hs-CRP. Further studies are needed to determine more clearly the effect of vitamin D on various biochemical markers in GDM patients.