The effects of vitamin D and omega-3 fatty acids co-supplementation on biomarkers of inflammation, oxidative stress and pregnancy outcomes in patients with gestational diabetes

Randomized, placebo-controlled trial in pregnant women with gestational diabetes mellitus aged 18 to 40 years at 24 to 28 weeks' gestation, conducted in Ardabil, Iran from September 2016 to March 2017. Thirty participants completed each active arm, and biomarkers were measured at baseline and after 6 weeks with pregnancy and newborn outcomes followed through delivery.

Women with gestational diabetes were assigned to vitamin D 50,000 IU by capsule every 2 weeks for 6 weeks, omega-3 fatty acids 1000 mg by capsule twice daily for 6 weeks, or both regimens together for 6 weeks. The omega-3 capsules contained 180 mg eicosapentaenoic acid and 120 mg docosahexaenoic acid per 1000 mg dose. The placebo capsule contained 500 mg liquid paraffin.

Vitamin D plus omega-3 fatty acids co-supplementation improved several inflammatory and oxidative stress biomarkers and was associated with fewer newborn complications in women with gestational diabetes. Compared with the other groups, co-supplementation reduced hs-CRP by -2.0 ± 3.3 mg/L, MDA by -0.5 ± 0.5 μmol/L, and increased TAC by +92.1 ± 70.1 mmol/L and GSH by +95.7 ± 86.7 μmol/L; all were statistically significant. It also lowered newborn hyperbilirubinemia and hospitalization to 10.0% and 10.0%, respectively, versus 33.3% and 33.3% in the omega-3 arm, with between-group P = 0.037 for both. Plasma nitric oxide did not show a clear beneficial between-group effect. No side effects were reported.

Small per-arm sample size and short 6-week intervention limit certainty about durability and clinical impact. Confidence intervals were not reported, and findings are specific to women with gestational diabetes in one Iranian center. Participants were asked not to change diet or physical activity, but residual confounding and limited generalizability remain possible.