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

Randomised placebo-controlled trial in pregnant women with gestational diabetes mellitus (GDM), aged 18-40 years, at 24-28 weeks' gestation. 56 participants randomized (28 per group); single-blind (participants blinded); 51 completed; intention-to-treat analysis included all 56.

Calcium carbonate 1,000 mg daily plus vitamin D3 50,000 IU per dose, given twice (baseline and day 21) during 6 weeks.

Calcium plus vitamin D supplementation for 6 weeks improved glycemic control, lipid profile, and oxidative stress markers in pregnant women with GDM versus placebo. Glycemic outcomes: fasting plasma glucose −0.89 ± 0.69 mmol/L vs +0.26 ± 0.92 (p<0.001); serum insulin −13.55 ± 35.25 vs +9.17 ± 38.50 (p=0.02); HOMA-IR −0.91 ± 1.18 vs +0.63 ± 2.01 (p=0.001); QUICKI +0.02 ± 0.03 vs −0.002 ± 0.02 (p=0.003). Lipids: LDL −0.23 ± 0.79 vs +0.26 ± 0.74 (p=0.02); TC:HDL ratio −0.49 ± 1.09 vs +0.18 ± 0.37 (p=0.003); HDL +0.15 ± 0.25 vs −0.02 ± 0.24 (p=0.01). Oxidative stress: GSH +51.14 ± 131.64 vs −47.27 ± 203.63 μmol/L (p=0.03); MDA rise prevented (+0.06 ± 0.66 vs +0.93 ± 2.00 μmol/L, p=0.03). 25(OH)D increased markedly (+48.19 ± 46.64 vs +1.75 ± 15.36 nmol/L, p<0.001). No significant effects on HOMA-B, total cholesterol, triglycerides, hs-CRP, NO or TAC. Conclusion: Calcium plus vitamin D supplementation may confer metabolic benefits in GDM by improving glucose metabolism, lipid balance, and oxidative status.

Small sample size and short duration; baseline imbalances in several biomarkers; some loss to follow-up with LOCF imputation; single-center design; pregnancy outcomes not assessed.