RETRACTED: Effects of vitamin D supplementation on glucose metabolism, lipid concentrations, inflammation, and oxidative stress in gestational diabetes: a double-blind randomized controlled clinical trial (Publication with Expression of Concern. See vol. 112, pg. 1406, 2020) (Retracted article. See vol. 113, pg. 1382, 2021)

Background: To our knowledge, there is no study that has examined the effects of vitamin D supplementation on metabolic status in gestational diabetes mellitus (GDM). Objective: This study was designed to assess the effects of vitamin D supplementation on metabolic profiles, high-sensitivity C-reactive protein, and biomarkers of oxidative stress in pregnant women with GDM. Design: This randomized, double-blind, placebo-controlled clinical trial was conducted in 54 women with GDM. Subjects were randomly assigned to receive either vitamin D supplements or placebo. Individuals in the vitamin D group (n = 27) received capsules containing 50,000 IU vitamin D-3 2 times during the study (at baseline and at day 21 of the intervention) and those in the placebo group (n = 27) received 2 placebos at the same times. Fasting blood samples were collected at baseline and after 6 wk of the intervention to quantify relevant variables. Results: Cholecalciferol supplementation resulted in increased serum 25-hydroxyvitamin D concentrations compared with placebo (+18.5 +/- 20.4 compared with +0.5 +/- 6.1 ng/mL; P < 0.001). Furthermore, intake of vitamin D supplements led to a significant decrease in concentrations of fasting plasma glucose (-17.1 +/- 14.8 compared with -0.9 +/- 16.6 mg/dL; P < 0.001) and serum insulin (-3.08 +/- 6.62 compared with +1.34 +/- 6.51 mu IU/mL; P = 0.01) and homeostasis model of assessment-insulin resistance (-1.28 +/- 1.41 compared with +0.34 +/- 1.79; P < 0.001) and a significant increase in the Quantitative Insulin Sensitivity Check Index (+0.03 +/- 0.03 compared with -0.001 +/- 0.02; P = 0.003) compared with placebo. A significant reduction in concentrations of total (-11.0 +/- 23.5 compared with +9.5 +/- 36.5 mg/dL; P = 0.01) and low-density. lipoprotein (LDL) (-10.8 +/- 22.4 compared with +10.4 +/- 28.0 mg/dL; P = 0.003) cholesterol was also seen after vitamin D supplementation. Conclusions: Vitamin D supplementation in pregnant women with GDM had beneficial effects on glycemia and total and LDL-cholesterol concentrations but did not affect inflammation and oxidative stress.