Vitamin D supplementation in pregnant women or infants for preventing allergic diseases: a systematic review and meta-analysis of randomized controlled trials

Background: It is still unclear if and to what extent antenatal or infant or childhood vitamin D supplementation would affect the development of allergy diseases later in life. This study aimed to review the efficacy of vitamin D supplementation in pregnant women, infants, or children for the prevention of allergies.Methods: MEDLINE (PubMed), EMBASE (OVID), and the Cochrane Central Register of Controlled Trials were searched up to March 1, 2020. We included only randomized controlled trials (RCTs). We performed a systematic review and meta-analysis for vitamin D supplementation in primary allergy prevention. These trials were assessed for risk of bias using the Cochrane Collaboration domains and the consensus was reached via discussion with the full study group. We descriptively summarized and quantitatively synthesized original data to evaluate vitamin D supplementation in primary allergy prevention by using Review Manager software for meta-analysis.Results: The search yielded 1251 studies. Seven RCTs were included in this analysis. A meta-analysis revealed that vitamin D supplementation for pregnant women or infants may not decrease the risk of developing allergic diseases, such as asthma or wheezing (supplementation for pregnant women, risk ratio [RR]: 1.01, 95% confidence interval [CI]: 0.81-1.26,P = 0.90,I2 = 47%; supplementation for infants, RR: 1.00, 95% CI: 0.70-1.43,P = 0.99,I2 = 0%; supplementation for pregnant women and infants, RR: 0.35, 95% CI: 0.10-1.25,P= 0.11), eczema (supplementation for pregnant women, RR: 0.95, 95% CI: 0.80-1.13,P= 0.77,I2= 0%; supplementation for infants, RR: 0.84, 95% CI: 0.64-1.11,P= 0.19,I2= 42%), allergic rhinitis (supplementation for pregnant women, RR: 0.93, 95% CI: 0.78-1.11,P = 0.15,I2 = 47%), lower respiratory tract infection (LRTI) (supplementation for pregnant women, RR: 0.97, 95% CI: 0.85-1.11,P = 0.59,I2 = 0%), or food allergy.Conclusions: Supplementation of vitamin D in pregnant women or infants does not have an effect on the primary prevention of allergic diseases.Systematic Review Registration: PROSPERO (CRD42020167747)