Effect of infant formula supplemented with prebiotics and probiotics on incidence of respiratory tract infections: a systematic review and meta-analysis of randomized clinical trials.

BACKGROUND Previous investigations have proposed that the consumption of infant formula supplemented with prebiotics, probiotics and synbiotics (PRO- formula) may have protective impacts on respiratory tract infections (RTIs). Nevertheless, the findings of studies are contradictory. This meta-analysis aimed to explore the influence of PRO-formula on RTIs in infants by pooling randomized controlled trials (RCTs). METHODS To obtain eligible RCTs, Scopus and PubMed databases were systematically searched from their inception to November 2020. A random-effects model was applied to pool the relative risks (RR) and corresponding 95% confidence intervals (CI) for RTIs following consumption of PRO-formula. RESULTS A total of 15 RCTs, with a total sample size of 3805 participants (1957 for intervention and 1848 for placebo), were included in the present meta-analysis. In the overall analysis, in comparison to placebo, consumption of PRO-formula had a significant protective impact against RTIs (RR= 0.89, 95%CI: 0.82 to 0.97) in infants, with a remarkable evidence of heterogeneity across studies (I2=61.4%, P<0.001). In the meta-regression analysis, the effect of PRO-formula on RTIs was not modified by the follow-up duration. No evidence for publication bias was detected. CONCLUSIONS Administration of PRO-formula may be a potential approach for the prevention of respiratory tract infections in infants.