Efficacy of probiotic supplementary therapy for asthma, allergic rhinitis, and wheeze: a meta-analysis of randomized controlled trials

Background: Probiotic supplementary therapy to prevent allergic diseases, including asthma in children, has been widely explored in many randomized controlled trials. However, there is conflicting evidence on the effect of probiotic supplementation during pregnancy and infancy to the incidence of asthma and allergic rhinitis. Method: This study was designed to systematically explore the potential effects of probiotic supplementation on the occurrence and development of asthma, wheeze, and allergic rhinitis. Randomized controlled trials were searched in several medical literature data bases. A meta-analysis was undertaken by using the fixed-effects model or the random effects model to calculate the pooled risk of significant heterogeneity. Two writers were designated to perform the study selection and data extraction. The primary outcome was clinically diagnosed asthma; the secondary outcomes included wheeze, allergic rhinitis, and a positive aeroallergen skin-prick test result. Results: Seventeen randomized controlled trials, which composed a total of 5264 children, were analyzed. The pooled data for risk of developing asthma after probiotic supplementation showed no significant reduction compared with controls (risk ratio [RR] 0.86 [95% confidence interval {CI}, 0.73-1.01]; I² = 0%; p = 0.06). A subgroup of strains indicated that Lactobacillus rhamnosus GG supplementation only had a reduction to the occurrence of asthma (RR 0.75 [95% CI, 0.57-0.99]; I² = 11%; p = 0.04). The supplement in the postnatal group had a similar result, but the incorporated data were limited. Meanwhile, it is failed to identify that probiotic supplementary therapy have a clear benefit to the secondary outcomes: wheeze, allergic rhinitis, positive aeroallergen skin-prick test result. Conclusion: This study showed a significant benefit that supplementation with probiotics in pre- and postnatal periods was likely to play an essential strategic role in the prevention of asthma. However, these effects were based on the type of probiotics used, which also need more large-sample and high-quality RCTs to confirm the reliability of this study.