TheEffectsofPrebiotics,Synbiotics,and Short-ChainFattyAcidsonRespiratoryTract InfectionsandImmuneFunction:ASystematic ReviewandMeta-Analysis

Abstract

Prebiotics, synbiotics, and SCFAs have been shown to decrease systemic inflammation and play a protective role in chronic respiratory conditions. However,theireffectsoninfectionandimmunefunctionareunclear.Theobjectiveofthissystematicreviewwastosummarizethecurrentevidence for prebiotic, synbiotic, and SCFA supplementation on respiratory tract infections (RTIs) and immune function. The protocol for this systematic reviewwasregisteredwithPROSPERO(NationalInstituteforHealthResearch,UniversityofYork,UK),accessedonlineathttps://www.crd.york.ac.uk/ prospero (CRD42019118786).RelevantEnglish-languagearticlesuptoMay2021wereidentifiedviaonlinedatabases:MEDLINE,EMBASE,CINAHL, and Cochrane Library. Included studies (n=58) examined the effect of prebiotics, synbiotics, or SCFA, delivered orally, on the incidence, severity, or duration of RTIs and/or markers of immune function (e.g., peripheral blood immunophenotyping, NK cell activity). The majority of studies were randomized controlled trials reporting on RTIs in infants and children. The meta-analysis indicated that the numbers of subjects with≥1 RTI were reducedwithprebiotic(OR,0.73;95%CI:0.62–0.86;P=0.0002;n=17)andsynbiotic(OR,0.75;95%CI:0.65–0.87;P=0.0001;n=9)supplementation comparedtoplacebo.Further,NKcellactivitywasincreasedwithsynbiotic(standardizedmeandifference,0.74;95%CI:0.42–1.06;P<0.0001,n=3) supplementation. This review provides evidence that prebiotic, specifically oligosaccharide, supplementation may play a protective role in RTIs in infants and children. There is less evidence for this effect in adults. Supplementation with prebiotic and synbiotic treatment may alter immune functionbyincreasingNKcellactivity,thougheffectsonimmunophenotypewerelessclea