Effects of calcium-vitamin D co-supplementation on glycaemic control, inflammation and oxidative stress in gestational diabetes: a randomised placebo-controlled trial

Aims/hypothesis This study was designed to assess the effects of calcium and vitamin D supplementation on the metabolic status of pregnant women with gestational diabetes mellitus (GDM). Methods This randomised placebo-controlled trial was performed at maternity clinics affiliated to Kashan University of Medical Sciences, Kashan, Iran. Participants were 56 women with GDM at 24-28 weeks' gestation (18 to 40 years of age). Subjects were randomly assigned to receive calcium plus vitamin D supplements or placebo. All study participants were blinded to group assignment. Individuals in the calcium-vitamin D group (n=28) received 1,000 mg calcium per day and a 50,000 U vitamin D-3 pearl twice during the study (at study baseline and on day 21 of the intervention), and those in the placebo group (n=28) received two placebos at the mentioned times. Fasting blood samples were taken at study baseline and after 6 weeks of intervention. Results The study was completed by 51 participants (calcium-vitamin D n=25, placebo n=26). However, as the analysis was based on an intention-to-treat approach, all 56 women with GDM (28 in each group) were included in the final analysis. After the administration of calcium plus vitamin D supplements, we observed a significant reduction in fasting plasma glucose (-0.89 +/- 0.69 vs +0.26 +/- 0.92 mmol/l, p < 0.001), serum insulin levels (-13.55 +/- 35.25 vs +9.17 +/- 38.50 pmol/l, p=0.02) and HOMA-IR (-0.91 +/- 1.18 vs + 0.63 +/- 2.01, p=0.001) and a significant increase in QUICKI (+0.02 +/- 0.03 vs -0.002 +/- 0.02, p=0.003) compared with placebo. In addition, a significant reduction in serum LDL-cholesterol (-0.23 +/- 0.79 vs +0.26 +/- 0.74 mmol/l, p=0.02) and total cholesterol: HDL-cholesterol ratio (-0.49 +/- 1.09 vs +0.18 +/- 0.37, p = 0.003) and a significant elevation in HDL-cholesterol levels (+0.15 +/- 0.25 vs -0.02 +/- 0.24 mmol/l, p=0.01) was seen after intervention in the calcium-vitamin D group compared with placebo. In addition, calcium plus vitamin D supplementation resulted in a significant increase in GSH (+51.14 +/- 131.64 vs -47.27 +/- 203.63 mu mol/l, p=0.03) and prevented a rise in MDA levels (+0.06 +/- 0.66 vs +0.93 +/- 2.00 mu mol/l, p=0.03) compared with placebo. Conclusions/interpretation Calcium plus vitamin D supplementation in women with GDM had beneficial effects on their metabolic profile.