The Effect of Vitamin D Supplementation on Glycaemic Control in Women with Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

International Journal of Environmental Research and Public Health

May 2019

DOI: 10.3390/ijerph16101716

Citations:45

Influential Citations:3

Systematic Reviews / Meta-Analyses

Enhanced Details

Methods

Five randomized controlled trials conducted in Iran and China enrolled pregnant women with gestational diabetes mellitus (GDM). Participants had mean ages around 28–32 years; supplementation started in mid-pregnancy (24–28 weeks) and lasted 4–16 weeks; some trials used double-blind designs.

Intervention

Vitamin D3 supplementation during pregnancy with regimens varying across trials: high-dose pulses (e.g., 50,000 IU at baseline and day 21; 50,000 IU every two weeks for 8 weeks), a single intramuscular dose of 300,000 IU, and daily oral dosing ranging from 200 to 4000+ IU (one trial used 1000 IU/day via vitamin D3–fortified yogurt). One study used vitamin D3–fortified yogurt delivering 500 IU per serving (two servings daily). Treatment duration ranged from 4 to 16 weeks, typically starting around 24–28 weeks of gestation; administration forms included tablets, fortified yogurt drinks, and injections.

Results

Vitamin D3 supplementation during pregnancy improves glycemic parameters in women with GDM. Fasting plasma glucose decreased by 0.46 mmol/L (95% CI −0.68 to −0.25; p<0.001), HbA1c decreased by 0.37 percentage points (−0.65 to −0.08; p<0.01), and serum insulin decreased by 4.10 μIU/mL (−5.50 to −2.71; p<0.001). Heterogeneity for FPG was modest (I2 ≈ 41%). Sensitivity analyses supported the findings. Conclusion: Vitamin D supplementation has the potential to promote glycemic control in GDM, but interpretation should be cautious due to the small number of trials; more research is needed to understand mechanisms and long-term outcomes.

Limitations

Limitations include a small number of trials (n=5) with limited total sample sizes, varying dosing regimens and durations, studies conducted in only Iran and China, potential bias in some trials (blinding and attrition), and English-language restrictions potentially excluding eligible studies.

Abstract

Vitamin D deficiency is highly prevalent amongst pregnant women and is linked to a range of adverse complications, including gestational diabetes. However, there is no consensus among researchers regarding the impact of vitamin D supplementation in alleviating adverse effects in gestational diabetes. The objective of this systematic review and meta-analysis was to determine whether supplementation of vitamin D given to women with gestational diabetes can promote glycaemic control. EMBASE and PubMed were searched up to November, 2018. The selection criteria included randomised controlled trials of the effect of vitamin D supplementation (1000–4762 IU/day) on pregnant women with gestational diabetes mellitus. Study data and outcome measures (fasting blood glucose, glycated haemoglobin and serum insulin) were extracted from included studies. Random-effects models were used for meta-analyses. Heterogeneity tests, and analysis of the risk of bias were conducted. Most of the studies were graded as having either low risk or moderate risk of bias although two studies had a high risk of bias in the areas of blinding of participants and personnel, and incomplete outcome data. On the other hand, the heterogeneity statistic (I2) ranged from 0–41% in the studies included. Five randomised controlled trials were selected for this review and meta-analysis (involving a total of 173 participants supplemented with vitamin D and 153 participants as control drawn from the studies). Vitamin D supplementation was associated with a decrease in fasting blood glucose by a mean of 0.46 mmol/L (−0.68, −0.25) (p < 0.001), glycated haemoglobin by a mean of 0.37% (−0.65, −0.08) (p < 0.01) and serum insulin concentration by mean of 4.10 µIU/mL (−5.50, −2.71) (p < 0.001) compared to controls. This review shows evidence that vitamin D supplementation has the potential to promote glycaemic control in women with Gestational Diabetes Mellitus (GDM). However, due to the limited number of studies in the meta-analysis, the conclusion should be interpreted with caution. Further studies are needed to fully understand the exact mechanism by which vitamin D influences glucose metabolism. show less