OBJECTIVES: To determine the efficacy and safety of prebiotics, probiotics and synbiotics for asthma treatment or prevention.

METHODS: A systematic review and network meta-analysis (NMA) was performed. A systematic search was conducted in PubMed, Cochrane Library, Scopus and CINAHL databases up to October 8, 2019. Inclusion criteria were 1.) randomized controlled trial (RCT) 2.) studies determining the efficacy of prebiotics, probiotics and synbiotics 3.) studies reporting outcomes as asthma treatment or occurrence and its related symptoms. Risk of bias version 2.0 was used to assess the quality of included studies. Random-effects model was used to combine findings across included studies with similar outcome measures. Inconsistency was assessed by design-by-treatment global inconsistency test. Two reviewers independently identified studies, extracted data, assessed the quality of studies and cross-checked.

RESULTS : Of 2,517 studies retrieved, only 34 met inclusion criteria. Approximately, 11.76% of included were assessed as low risk-of-bias, while 82.35% and 5.88% were assessed as some concerns and high risk-of-bias, respectively. Asthma and wheezing occurrences in children were the outcomes of interest. Our NMA indicated no significant difference among all interventions for asthma occurrence outcome. However, Lactobacillus acidophilus is likely to be the most effective intervention based on surface under cumulative ranking curve. To be noted, there was no study determining the effect of synbiotics for the outcome. For wheezing occurrence outcome, synbiotics (Bifidobacterium breve + galacto-oligosaccharide + fructo-oligosaccharide) was likely to reduce wheezing prevalence compared to Lactobacillus acidophilus [relative risk (RR) = 2.93 (95% CI 1.01-8.53)] and Lactobacillus reuteri [RR = 2.86 (95% CI 1.03-7.97)] but it did not differ from placebo. For safety standpoint, there was no serious adverse effects from any interventions reported in all included studies.

CONCLUSIONS : No difference among prebiotics, probiotics and synbiotics for asthma prevention was found. In addition, no serious adverse effects reported for all included interventions.