www.jped.com.br
REVIEW
ARTICLE
Probiotics:
an
update
夽
Yvan
Vandenplas
a,∗,
Geert
Huys
b,
Georges
Daube
caUZBrussel,DepartmentofPediatrics,VrijeUniversiteitBrussel,Brussels,Belgium
bLaboratoryofMicrobiology&BCCM/LMGBacteriaCollection,FacultyofSciences,GhentUniversity,Ghent,Belgium cFacultédeMédecineVétérinaire,DépartementdesSciencesdesDenréesAlimentaires,UniversityofLiège,Liège,Belgium
Received14July2014;accepted6August2014 Availableonline23October2014
KEYWORDS Bifidobacteria; Gastro-intestinal microbiota; Lactobacillus; Microbiome; Probiotic
Abstract
Objective: Triggeredbythegrowingknowledgeonthelinkbetweentheintestinalmicrobiome andhumanhealth,theinterestinprobioticsiseverincreasing.Theauthorsaimedtoreviewthe recentliteratureonprobiotics,fromdefinitionstoclinicalbenefits,withemphasisonchildren. Sources: RelevantliteraturefromsearchesofPubMed,CINAHL,andrecentconsensus state-mentswerereviewed.
Summaryofthefindings: While abalancedmicrobiome isrelated tohealth,animbalanced microbiomeordysbiosisisrelatedtomanyhealthproblemsbothwithinthegastro-intestinal tract,suchasdiarrheaandinflammatoryboweldisease,andoutsidethegastro-intestinaltract suchasobesityandallergy.Inthiscontext,astrictregulationofprobioticswithhealthclaimsis urgent,becausethevastmajorityoftheseproductsarecommercializedasfood(supplements), claiminghealth benefits thatareoften not substantiatedwith clinicallyrelevant evidence. Themajorindicationsofprobioticsareintheareaofthepreventionandtreatmentof gastro-intestinalrelateddisorders,butmoredatahasbecomeavailableonextra-intestinalindications. Atleasttwopublishedrandomizedcontrolledtrialswiththecommercializedprobioticproduct inthe claimed indicationarea minimalcondition before aclaim can besustained. Today, LactobacillusrhamnosusGGandSaccharomycesboulardiiarethebest-studiedstrains.Although adverseeffectshavesporadicallybeenreported,theseprobioticscanbeconsideredassafe. Conclusions: Although regulationis improving,more stringent definitions arestill required. Evidenceofclinicalbenefitisaccumulating,althoughstillmissinginmanyareas.Misuseand useofproductsthathavenotbeenvalidatedconstitutepotentialdrawbacks.
©2014SociedadeBrasileiradePediatria.PublishedbyElsevierEditoraLtda.Allrightsreserved.
夽
Pleasecitethisarticleas:VandenplasY,HuysG,DaubeG.Probiotics:anupdate.JPediatr(RioJ).2015;91:6---21.
∗Correspondingauthor.
E-mail:yvan.vandenplas@uzbrussel.be(Y.Vandenplas).
http://dx.doi.org/10.1016/j.jped.2014.08.005
PALAVRAS-CHAVE Bifidobactérias; Microbiota gastrointestinal; Lactobacillus; Microbioma; Probiótico
Probióticos:informac¸õesatualizadas
Resumo
Objetivo: Motivado pelo conhecimento cada vez maior da associac¸ão entre o microbioma intestinal easaúdehumana, ointeresse nosprobióticos vemcrescendo cadavez mais.Os autoresvisaramanalisaraúltimaliteraturaarespeitodosprobióticos,dedefinic¸õesabenefícios clínicoscomênfasenascrianc¸as.
Fontesdosdados: FoianalisadaaliteraturarelevantedepesquisasdoPubMed,doCINAHLe dosúltimosconsensos.
Síntesedosdados: Apesar de um equilíbrio no microbioma estar relacionado à saúde, um desequilíbrionomicrobiomaoudisbioseestárelacionadoaváriosproblemasdesaúdenotrato gastrointestinal,comodiarreiaedoenc¸ainflamatóriaintestinal,eforadotrato gastrointesti-nal,como obesidadeealergia.Nessecontexto,aregulamentac¸ãorigorosadosprobióticosa alegac¸õesdesaúdeéurgente,poisagrandemaioriadessesprodutosécomercializadacomo alimentac¸ão (suplementos),alegando benefíciosàsaúdequefrequentementenão são com-provadoscomevidênciasclinicamenterelevantes.Asprincipaisindicac¸õesdeprobióticossão feitasnaáreadaprevenc¸ãoetratamentodedoenc¸asgastrointestinais,porémmaisdadostêm sidodisponibilizadosarespeitodeindicac¸õesextraintestinais.Pelomenosdoisensaiosclínicos controladoserandomizadospublicadoscomoprobióticocomercializadonaindicac¸ãodeclarada sãoacondic¸ãomínimaantesdeumaafirmac¸ãopodersermantida.Atualmente,oLactobacillus rhamnosusGGeSaccharomycesboulardiisãoasmelhorescepasestudadas.Apesardeefeitos adversosteremsidoesporadicamenterelatados,osprobióticospodemserconsideradosseguros. Conclusões: Apesardearegulamentac¸ãoestaraumentando,aindasãonecessáriasdefinic¸ões maisrigorosas.Asevidênciasdebenefíciosclínicosestãoaumentando,apesardeaindaausentes emváriasáreas.Ousoinadequadoeautilizac¸ãodeprodutosnãovalidadosconstituempossíveis desvantagens.
©2014SociedadeBrasileiradePediatria.PublicadoporElsevierEditoraLtda.Todososdireitos reservados.
Introduction
ThejointFoodandAgricultureOrganization(FAO)andWorld HealthOrganization(WHO)ExpertConsultation on evalua-tionofhealthandnutritionalpropertiesofprobioticsinfood includingpowdermilkwithlivelacticacidbacteriadefined probiotics as: ‘‘live microorganisms that, when adminis-teredinadequateamounts,conferahealthbenefitonthe host’’.1In2002,ajointFAO/WHOWorkingGroup2released
guidelinesfortheevaluationofprobioticsinfood.The min-imumrequirementsneededforprobioticstatusinclude:
- assessmentofstrainidentity(genus,species,strainlevel); - in vitro teststo screen potential probiotics:e.g. resis-tancetogastricacidity,bileacid,anddigestiveenzymes, antimicrobial activity against potentially pathogenic bacteria;
- safetyassessment:requirementsforproofthataprobiotic strain is safe and without contaminationin itsdelivery form;
- invivostudiesforsubstantiationofthehealtheffectsin thetargethost.
FollowingtheFAO/WHOdefinition,theInternationalLife Science Institute (ILSI)3 andthe European Food andFeed
CulturesAssociation(EFFCA)4 havereleasedsimilar
defini-tionsforaprobiotic:‘‘alivemicrobialfoodingredientthat,
whenconsumedinadequateamounts,confershealth bene-fitsontheconsumers’’and‘‘livemicroorganismsthat,when ingestedorlocallyappliedinsufficientnumbers,providethe consumerwithoneormoreprovenhealthbenefits’’.These definitionsdefactoimplythatprobioticingestionprovides benefitsforhosthealth.
The sciencerelatedtoprobioticsis recent,andis thus inconstantevolution.Probiotics usedinfood,supplied as dietarysupplement,orasactivecomponentsofaregistered medication,shouldnotonlybecapableofsurvivingpassage throughthedigestivetractbyexhibitingacidandbile sur-vival,butshouldalsohavethe capabilitytoproliferatein thegut. Probioticsmustbeabletoexerttheirbenefitson thehostthroughgrowthand/oractivityinthehumanbody. Topicalorlocalapplicationofprobioticsisalsoproposedin viewof therecentevolutionofscientific data.Therefore, theabilitytoremainviableandeffectiveatthetargetsite shouldbe studied and confirmed for each strain, or even better, for each commercialized product. Clinical studies shouldbeperformedwiththecommercializedproductand notwiththeisolatedstrain.However,lackofprotection con-tributestothefactthatsomecompaniesrefusetodeliver informationonthespecificstrainsintheirproduct.5Recent
According to the European Union (EU), health claims shouldonlybeauthorizedfor usein theEUaftera scien-tificassessment of thehighestpossible standard hasbeen carriedoutbythePanelonDieteticProducts,Nutrition,and Allergies(NDA)oftheEuropeanFoodSafetyAuthority(EFSA) [Regulation(EC)N1924/2006].6Thekeyquestionsthatwere
addressedbytheEFSANDApanelare:
- Isthefood/constituentsufficientlydefinedand characte-rized?
- Istheclaimedeffectsufficientlydefined,andisita ben-eficialphysiologicaleffect?
- Havepertinenthumanstudiesbeenpresentedto substan-tiatetheclaim?
The EFSA recommendationsare an important step for-wardintryingtobringclaimsforprobioticfoodsupplements andmedicationclosertogether.However,companies discov-eredside-waystoavoidEFSArestrictions.Someofthefood supplementsareintheprocessofregistrationas‘‘medical device’’,for whichclaims canbemade withoutproviding hard scientific evidence. Moreover, production require-mentsonqualitycontrolandsafetystilldiffersubstantially betweenfoodsupplementsandmedication, putting medi-cationinadisadvantageoussituation.
Official controls by national authorities are performed toensurecompliancewithfoodlaw.Apartfromtheriskof usingunauthorizedstrains,productmislabelingis aknown problem,partlyduetotheuseofphenotypingor genotyp-ingmethodsthatlackdiscriminativepower.7Inadditionto
officialcontrols,privatecontrolsbyfoodproducing compa-niesareimportantinthecontextofprotectionofpatented strainsandindustrialpropertyrights.
In their ‘Guidelines for the Evaluation of Probiotics in Food’,theFAO/WHOWorkingGroup2recommendsthatthe
followinginformation shouldbedescribed onthe labelof probioticproducts:
• Genus,species,andstraindesignation.Straindesignation
shouldnotmisleadconsumersregardingthefunctionality ofthestrain;
• Minimumviable numbersof eachprobioticstrain atthe
endoftheshelf-life;
• Suggestedservingsize,whichmustdelivertheeffective
doseofprobioticsrelatedtothehealthclaim;
• Healthclaim(s);
• Properstorageconditions;
• Corporatecontactdetailsforconsumerinformation.
In most countries, only general health claims are cur-rentlyallowedonfoodscontainingprobiotics.TheFAO/WHO WorkingGroup2recommendedthatspecifichealthclaimson
foodsshould beallowed relatingtotheuse of probiotics, whenever sufficient scientific evidence is available. Such specifichealthclaimsshouldbepermittedonthelabeland inpromotionalmaterial.Forexample,aspecificclaim stat-ingthataprobiotic‘reducestheincidenceandseverityof rotavirusdiarrheaininfants’wouldbemoreinformativeto theconsumerthanageneralclaimthatstates‘improvesgut health’.Therecommendationisthattheproduct manufac-turershouldberesponsibleforconductingan independent
thirdpartyreviewbyscientificexpertsinordertoestablish thetruthfulnessofthehealthclaims.
In line with the suggestions of the FAO/WHO Working Group,2 on December 20, 2006, the European Parliament
andtheCouncilpublishedanewregulation(No.1924/2006) regarding‘‘NutritionandHealthClaimsMadeonFoods’’.6
This regulationappliestoallnutritionalandhealth claims relatingtoalltypes offood intendedfor final consumers; thusincludingprobioticproductsbroughttothemarketwith ahealthclaim.Theregulationaimstoconsolidatethe nutri-tionandhealthclaimsatEuropeanlevelinordertobetter protect consumers, includingcommercial communications (labeling, presentation, and promotional campaigns), as well as trademarks andother brandnames that could be construedasnutritionorhealthclaims.
Functional
effects
of
probiotics
The definition ‘‘probiotics are live microorganisms which when administered in adequate amounts confer a health benefit onthe host’’ only generalizes the probiotic func-tionalityasconferringahealthbenefittothehost.Hence, thisdefinitionentailsthattheremustbeameasurable phys-iologicalbenefittothehostwhousestheprobioticproduct. In addition, it is not specified that the probiotic strain mustbeprovidedthroughoraldelivery,norarethere spe-cificrequirementsregardingthemodeofaction.Thelatter also implies thatsurvival of the probiotic microorganisms throughoutthegastrointestinal(GI)tractisnota prerequi-sitefor recognitionof probioticeffects. Forexample,the delivery oflactasethroughadministrationof live Strepto-coccusthermophilustothesmallintestinecanbeconsidered asa probiotic activity,although the bacterialstrain itself doesnotsurvivethedigestivetract.8
Whenconsideringprobioticfunctionality,the abovemen-tioneddefinitionofprobioticsistobeinterpretedinavery broad way.This broad functionalitydefinitioncomplicates theprocessoffunctionalcharacterizationofprobiotics.The useofprobioticsmaytargetseveralbodysites (mouth,GI tract, respiratory tract, urinary tract, skin, vagina, etc), anditsapplicationcanalsotargetspecifichuman subpop-ulations:healthyindividuals,children,elderly,illsubjects, andimmunecompromisedandgeneticallypredisposed indi-viduals,amongothers.Thereisanextremelydiverserange of potential biological effects,and new functional activi-tiesareconstantlybeingexplored.Whilesomemodelsare perfectly suited for studying the colonization potency of probiotics, other modelsneed to beapplied for assessing theirimmune-modulatingpotential,theirresilienceagainst pathogeninvasionoftheGItract,ortheiranti-inflammatory properties.
Functional
characterization
of
probiotics
Targetsites
is themostimportant targetfor themajority ofprobiotic applications,otherbodysites,suchasthemouth,the uro-genitaltract,andtheskin,arealsoconsidered.Probiotics mayplayanimportantinoralmedicineanddentistry.9,10
Probiotics arealso considered for controlling and pre-ventinginfectionsofthereproductiveandurinarytract.11---14
Regarding skin applications, probiotics may be consumed orally to induce an immune response that has systemic effects, e.g.,for controllingskin inflammation15 and
der-matological diseases in general.16 Probiotics have also
been used as protection against respiratory tract infec-tions.Lactobacillus(L.)rhamnosusGGpreventsrespiratory tractinfectionsin additiontotheconventional protection against GI infections.17 There is a plethora of probiotic
strainsandapplicationsavailablewiththeGItractas tar-get site.Suchapplicationsaim at severalhealth benefits, suchasdecreasingpathogencolonization,improvingvitamin synthesis, optimizing intestinaltransit, alleviating lactose intolerance, reducing bloating, and promoting immune-modulatoryeffects,amongothers.
Deliverymode
Inordertoprovidehealth benefits,probiotic strainsoften requireaspecificmatrixtoguaranteeoptimalstrainsurvival along the GItract. Forinstance, probiotics have recently beenformulatedinachocolatematrix,whichresultedina moreoptimalsurvivaloftheprobioticstrainsincomparison withconventional probiotic formulationmethods.18 Other
methodsincludetheintroductionofprobioticsinmore con-ventionalproductssuchasmilk,19 kefir,20 andyoghurts,or
inmorespecificmatricessuchascereals,cheese,sausages, andcookies.Obviously,manyprobioticsareintroducedfor commercialreasons,toobtainabetterproductplacement ortointegratetheprobioticmarket(commonexamplesare fruitjuices,icecreams,candies,granolabars,etc).
Besides the incorporation of probiotics in food prod-ucts,probioticstrainsarealsoprovidedasfoodsupplement, often targeting specific health problems. Probiotic food supplements(e.g.L.rhamnosus GG,L.reuteri)and med-ication(e.g.Saccharomycesboulardii)havealmostbecome standardinthetreatmentofpediatricgastroenteritis.There aremanyinfantformulaswithprobiotics,bothtoprevent andalleviatediarrhea.
L. lactis strains that secrete IL-10 or immunomodula-tory Yersinia LcrVprotein weredeveloped totreat colitis inmousemodels.21,22Suchapproachiscurrentlybeing
con-sideredforthetreatmentoforalmucositis(highincidence inhead/neckcancerpatientsreceivingradiotherapy)witha humantrefoilfactor1-secretingL.lactis.Amolecularbasis of the therapeutic applications and the chemopreventive activitiesofcertainprobioticmetabolites,withemphasison theinteractionbetweenthesemetabolitesandthe molec-ular signaling cascades, are considered to be epigenetic targetsinpreventingcoloncancer.23
Finally, probioticdelivery notonlypertainsthefoodor pharmaceuticalenvironmentinwhich theprobiotic is for-mulated. Specific ointments and nasal sprays have been developed;24 currently,eventheintroductionofprobiotics
inmattressesandcleaningagentsisgainingmomentumfor
an optimized hygienic control. The latter illustrates the need to broaden the control on claims larger than food supplementsandfood. Ifthe EUinstalls authorities, such astheEFSA, tocontrolclaims for foods and food supple-ments,health-claimsfor non-foodrelatedproductsshould beequallycontrolled.
Strainsurvival
Inmanycases,healthbenefitsareonlyobtainedwhena pro-bioticstrainreachesthetargetsiteinametabolicallyactive stateandinsufficientnumbers.Fororaldelivery,probiotic microorganismsmustsurvivethedifferentphysicochemical, enzymatic,andmicrobialstressesthroughouttheGItransit. Firstly, microorganisms have to cross the acidic envi-ronment from the stomach. In addition, the absence or presenceof afoodmatrix significantlydetermines thepH profiletowhichtheprobioticstrainissubjected.Whilethe initialpHbufferingeffectfromfoodmaysubjectthe pro-biotic strain toinitially less stringentacidic conditions,a longerdigestiontimeinthestomach underfedconditions mayexposepartofthedosedprobiotictoacidicconditions foralongertime.Manyprobioticmicroorganismshavebeen selectedfortheirhigherresilienceinsuchconditions,and newmethodologiesareavailabletoallowencapsulationof probioticstrainsinthatpurpose.25
A second stress component is the presence of bile saltsthatelicitmembrane-compromisingpropertiestowards microorganisms,duetotheiramphiphiliccharacter.A par-ticularfunctionalcharacteristic ofmicroorganismsistheir abilitytodealwithbilesaltstress via bilesalt hydrolase. Bilesalthydrolasebacteriatypicallycleavetheglycinor tau-rinmoietyfromconjugatedbilesalts,renderingthelatter lessbacteriostatic.Thisfeatureisofparticularimportance tooptimizestrainsurvivalduringintestinaltransitandhas been proposed asa mechanism toexplain howprobiotics couldlowerserumcholesterollevels.26
Anotherfeatureof probiotic strain survivalis the abil-itytocolonize theGI tract.This property can bedivided intoan ecological component and a mucosal component. Firstly,onceaprobiotic organismhassurvivedgastricacid and duodenal bile salts and thus reaches the ileum and colon, it hasthe possibilitytodevelop ina less stringent environment.Yet,itreachesanenvironmentwithahighly significant microbial background --- the ileum and colon reachingbacterialconcentrationsof107and1011 cells/mL
chyme, respectively. Obviously, a probiotic strain can be considered as foreign to the residing endogenous micro-biota, and unless specific nutrients are provided for the probiotic in the product formulation (e.g. synbiotic), the strainmustcompetewiththeresidingmicrobialcommunity foravailablesubstrates.Inecologicalterms,thedosed pro-bioticmustoccupyafunctionalnicheinthegut microbial ecosystem.Secondly,animportantpropertyforprobiotics, e.g.withrespecttopathogencontrol,isitsabilitytoadhere toandthriveinthemucussurfacethatcoversthegut epithe-lium.Mucosaladhesioncanrelyoncellwallproperties.The hydrophobicnatureofmicrobialstrainscanbeassessedwith astraightforwardBATHassay,27whileaspecificmucus
gut-derivedmucins (mostly fromanimal origin).27,28
How-ever, the aspecific adhesion of gut microorganismsto gut mucinsisonlysufficientformicrocolonyformation,anddoes notguaranteeaprolongedcolonizationofthemucuslayer.It hasbeenwelldescribedthatspecificmicroorganisms modu-latetheirgeneexpressionfollowingtheirincorporationinto themucosalsurface.Thishasnotonly beendescribed for pathogens,28,29butalsoforprobioticmicroorganisms,such
asL.rhamnosusGG,whichmayupregulatetheformationof specificpiliinthemucosalenvironment.30
Humantargetgroups
Probioticproductshavebeendevelopedforawidevariety ofhealthclaims.Probioticscantargetbothhealthyandill individuals.Theexpectedeffectscanbeofapreventiveor curativenature.Thegoalcanbetofightthecauseofthe diseaseormetabolicalterations,ortolessenthesymptoms associatedwiththeoccurrenceorprogressionofadisease ormetabolicalteration.
With the aim of improving health in the human body, the intake of a probiotic strain by healthy subjects has primarily preventive objectives. Yet, it must be empha-sizedthat theintroductionof aforeignstrain ---evenifit is a probiotic --- must be approached with care and must beperformed aftera well-considered evaluationprocess. Particularly,thegutenvironmentfromsensitivehuman sub-populations,suchasinfantsandtoddlers,undergoesahigh degreeofdevelopmentor transition.Manystudieson pro-bioticapplicationsreportedapositiveoutcomeinmarkers thatcanbeofrelevanceforhumanhealth.Probioticstudies haveshownbeneficialeffectsinallage-relatedsubgroups, such as mother-infant pairs, preterm infants, newborns, infants,olderchildren,andelderlypeople.
Forexample,fermentedmilkdrinkswithL.caseistrain Shirotapositivelystimulatetheimmunesystem inhealthy human subjects.31 With respect to different age groups,
theeffects fromlong term consumption of probiotic milk oninfectionswasevaluatedinchildrenattendingdaycare centers,32whileL.delbrueckiisubsp.bulgaricus
OLL1073R-1wasgiventoelderlypersonswiththeaimofreducingthe riskofinfection.33
In case the microbial community from a specific body regionisdisturbed,leadingtotheso-calleddysbiosis, func-tionalnichesbecomeavailableintheecosystem.Examples ofdysbiosisarethechangesinmicrobial ecosysteminthe mouth associated with dental caries, or dysbiosis associ-atedwithbacterial vaginosis. Twetman recentlyreviewed the effects from probiotics on oral health in children.34
Forexample,long-termapplicationofprobioticstrainssuch as L. rhamnosus GG lowered the risk of dental caries in children;35 the importance of probiotic supplementation
duringorthodontic therapy wasalsoreported.36 Similarly,
microbialdysbiosisintheurogenitaltract,particularly bac-terial vaginosis, can alsobe treated withprobiotics.37 L.
rhamnosusGGandspecificL.acidophilusstrainshavebeen usedtotreatbacterialvaginosis.38,39Probioticsmayalsobe
applied orally to reduce health risks that originate from the gut environment. Helicobacter pylori-colonized sub-jects have been treated with L. casei milk drinks40 and
L.gasseriOLL2716(LG21),41whilespecificBifidobacterium
strains display anti-Helicobacter effects through the pro-ductionofantimicrobialpeptides.42However,thereisproof
that dysbiosis occurs in Crohn’s disease (either as cause orconsequence),butprobioticsupplementationhasalways failedtopreventrelapse,exceptinpouchitis.Inaddition, thereisspecificattentionfordevelopingprobioticconcepts for children undermodified risks.Preterm infants display an increased risk for developing necrotizing enterocolitis, whichisdecreasedbytheapplicationoforalprobiotics.43
Basis
of
the
biological
effect
of
probiotics
Thehealthbenefitsfromprobioticproductsandapplications areextremelydiverseandarecontinuouslyexpandedwith newinsightsandscientificdevelopments.
Microbiologicalfunctionality
Theultimategoalsofmicrobiologicalinterventionsthrough probioticsmaybetostabilizeorimprovemicrobial homeo-stasisinabodyenvironmentandtolowerpathogeninvasion andcolonization.The resilienceof amicrobialcommunity against invasion by exogenous strains largely depends on theavailabilityofnon-occupiedfunctionalniches.Ifnotall functionalnichesareoccupiedbytheendogenousmicrobial community,thereisanincreasedriskforpathogeninvasion intheecosystem,colonization,andsubsequentinfection.
Probiotic microorganisms can be used to improve or restoremicrobialhomeostasisintwoscenarios.Firstly,they may occupy functional niches that are left open by the endogenous community, thereby preventing (opportunis-tic)pathogens fromoccupying thatniche. Suchprocess is often referred to as competitive exclusion, and primar-ily targets the competition for nutrients, physical sites (e.g.mucusadhesion)orreceptors.Thesecondscenariois more ofan antagonistic natureasprobioticsmayactively lower (opportunistic) pathogen invasion or development intotheecosystem.Suchapproachprimarilytargets:i)the production of short chain fatty acids and other organic acids (e.g. lactic acid) by probiotics, thereby lowering the pHandincreasing thebacteriostaticeffectof organic acids towards pathogens; ii) the production of bacteri-ocins,whicharesmallmicrobialpeptideswithbacteriostatic or bactericidal activity; and iii) the production of reac-tive oxygen species, such ashydrogen peroxide, that are highlyreactiveandincreaseoxidativestressforpathogens inmicro-environments.
Nutritionalfunctionality
Specificmicrobialgroupsproducevitaminsandmaythereby contributetovitaminavailabilitytothehumanhost.Apart from vitamin K,44 vitamin B12,45 and pyridoxine,46 other
Lactase deficiency causes lactose intolerance, which resultsinabdominalcramping,nausea,andbloating. Probio-ticstrainsthatarelactase-positivehavebeensuccessfully appliedtorelievediscomfortfromlactoseintolerance.47
Other nutritional functionalities may include the pro-duction of health-promoting compounds. The metabolic potency of gut microorganisms is enormous and may rival or even exceed that of the liver.48 The gut
envi-ronment harbors several small chemical factories that produce numerous chemical components with putative health-modulating effects.49 Isolatedstrains that produce
health-promotingproductsmayalsobeconsideredas hav-ing probiotic potential. For instance, the production of health-promotingconjugatedlinoleicacids (CLA)hasbeen reported for Bifidobacterium strains,50 L. plantarum JCM
1551,51 and specific L. acidophilus strains. Also,
conver-sion of phytoestrogenprecursors tobioactive metabolites bysupplementedmicroorganismsisapotentialpathwayfor futureprobiotic applications.Forexample, Decroos etal. previously isolated a microbial consortium that converts soy-deriveddaidzeinintothebioactive equol,52 while
Pos-semiers et al. performed an in vitro investigation of the probioticpotentialofEubacteriumlimosumstrainsto con-verthopisoxanthohumolinto8-prenylnaringenin.53
Physiologicalfunctionality
Probiotic microorganisms have been reported to enhance GItransit.Hamilton-Miller previouslyreviewed such func-tionalityfortheapplicationofprobioticproductsinelderly persons.54Otherpotentialphysiologicaleffectsmayinclude
thereduction byprobiotics ofbloating or gas production, theenhancementofion absorptionbyintestinalepithelial cells55andthedecreaseofbilesalttoxicityorthedecrease
of serumcholesterol levelsby bilesalthydrolase positive probiotics.56,57
Loweringhealthdetrimentalcomponentsinthegut
Probiotic microorganisms are also applied to reduce the healthrisksfromhazardouscomponents.Forexample,oral exposure to contaminants, either from a food matrix or fromanenvironmentalmatrix(soil,dust,water)isthemost dominantscenariobywhichthehumanbodygetsinternally exposedtocontaminants.Thesecanbe:i)mycotoxins, pro-duced from fungi on a wide variety of crops, cereals in particular;ii)xenobioticswithtoxicpropertiesasunwanted residues from environmental contamination of the food chain;or iii) hazardouscompounds fromthefood produc-tion process as such (e.g. PAH production during grilling of meat). The mode of action by which these probiotics lowertheriskderivedfromingestedhazardouscomponents often relates to the sorption of the compound to micro-bialbiomass.ThisisthecaseforaflatoxinB1,forexample, which has been shown in vitro tobe bound by probiotic strains.58 Anothermode of action maybe direct
detoxifi-cationofthehazardouscompound,suchasthebreakdown offumonisinbyPediococcuspentosaecusL006isolatedfrom corn leaves. A final mode of action is more indirect and
resemblestheabovementionedprobioticmodulationofgut microenvironment,where(food)pathogensproducetoxins. For example, the production of organic acids by probio-ticmicroorganisms was reported tonegatively affect the productionofShiga-toxin2fromenterohemorrhagicE.coli
O157:H7.
Immunologicalfunctionality
The immunological benefits of probiotics can be due to activation of local macrophages and modulation of IgA productionlocallyandsystemically,tochangesin pro/anti-inflammatory cytokine profiles, or to the modulation of responsetowardsfoodantigens.59,60
Probioticproductsinpreventionandtreatment
Thefollowingparagraphsdoesnotaimtoprovideacomplete overview of all indications in which probioticshave been studiedaspossiblepreventiveand/ortherapeutic interven-tion,sincenewmanuscripts arepublishedweekly. Rather, the authors focused on the most relevant indications for children.
Acuteinfectiousdiarrhea
Probiotics have been largely studied for the prevention ofacuteinfectiousdiarrhea.Large,randomizedcontrolled trials(RCT)provideevidenceofaverymodesteffect (statis-ticallysignificant,butofquestionableclinicalimportance) ofsomeprobioticstrains(L.rhamnosusGG,andstrainsofL. reuteriandBifidobacterium(B.)animalissubsp.lactis)on thepreventionof community-acquireddiarrhea.61---69 Many
randomizedandplacebo-controlledtrialsconductedin dif-ferentpartsoftheworldhaveassessedtheuseofprobiotics forpreventionofdiarrheaacquiredinday-carecenters.The mainprobioticstested wereL.rhamnosusGG,B.animalis
subsp.lactisaloneorincombinationwithS.thermophilus, andL.reuteri,L.rhamnosus (notGG),andL.acidophilus
eitheraloneorinacomparativestudy.Theevidenceoftheir efficacyinthesesettingsisonlymodestfortheprevention ofdiarrheaandsometimesalsoforpreventingupper respira-toryinfections.66However,theprotectiveeffectondiarrhea
preventionbecomesfarlesssignificant iftheincidenceof diarrhea(episodesperpatient-month)ratherthanthe per-centageofpatients withdiarrheaistakenintoaccount.68
In hospitalized children, the administration of L. reuteri
DSM 17938 compared with placebo had no effect on the overallincidenceofnosocomialdiarrhea,includingrotavirus infection.70Althoughthesamestrainpreventeddiarrheain
preschoolchildren,71theclinicalimpactofsuchfindingscan
bequestioned.72
L.reuteriDSM 17938(very lowqualityof evidence;weak recommendation) and heat-inactivated L. acidophilus LB (verylowqualityofevidence;weakrecommendation).73The
latter, although traditionally discussed withother probio-tics,does notfitin thedefinitionofprobiotics.Anumber of RCTs have evaluated the effect of Enterococcus fae-cium SF6873.73 A sub-group analysis performed within a
Cochrane review (search date: July of 2010) found that
E. faecium SF68 reduced the risk of diarrhea lasting ≥
four days (four RCTs, n=333; RR: 0.21; 95% CI: 0.08 to 0.52).73 However, in vitro studies have documented that
theE. faeciumSF68 strain is a possible recipient of van-comycin resistance genes.74 Considering that the risk for
in vivo conjugation cannot be discarded, probiotics with safety issues should not be used.73 Recent publications
have strengthened the evidence for L. reuteri in the treatment of diarrhea in hospitalized children.75,76 Other
strains or combinations of strains have been tested, but evidence of their efficacy is weak or preliminary. Mix-turesofdifferentstrainsdonotnecessarilyscorebetter.77
Since in tropical countries with zinc-deficient regions, zinc is now added to oral rehydration salts (ORS), the impactofprobioticsaboveitsefficacyshouldbestudied.77
Considering that an acute gastroenteritis will heal spon-taneously in almost every child, the cost/benefit impact willingreatpart determine whetherprobioticsshouldbe used.78,79
Antibiotic-associateddiarrhea(AAD)
Thepooledrelativeriskinameta-analysisof63RCTs,which included11,811participants,indicatedastatistically signif-icantassociationofprobioticadministrationwithreduction inAAD(relativerisk,0.58;95%CI,0.50to0.68;p<0.001; I(2),54%; [risk difference, -0.07;95% CI, -0.10 to-0.05], [NNT 13; 95% CI, 10.3 to 19.1])80 Another meta-analysis
concludedthe NNT was8.81 According toa recent
meta-analysis,probioticssignificantly reduce the risk ofAAD in children.82Preplannedsubgroupanalysisshowedthat
reduc-tionof the risk of AAD wasassociated withthe use of L. rhamnosusGG (95% CI:0.15to0.6), S. boulardii(95% CI: 0.07-0.6),orB.lactisandS. thermophilus(95% CI:0.3to 0.95).82 Foreverysevenpatientsthatwoulddevelop
diar-rhea while being treated withantibiotics, one fewerwill developAADifalsoreceivingprobiotics82 OnlyS.boulardii
was reported to be effective in C. difficile disease.83---85
Recently,alargesingle-centerstudyshowedinelderlythat
S. boulardii wasnot effective in preventing the develop-mentofAADorin preventionofC.difficileinfection.86 In
many studies, thereis no evidenceto supportthe use of any(other) probiotic topreventtherecurrenceof C. dif-ficile infectionor totreat existing C.difficile diarrhea.64
Anewmeta-analysisconcludedthatprobioticssignificantly reducetheincidenceofpediatricAAD(22trials;RR=0.42; 95%CI:0.33-0.53) andtheincidenceof pediatricC. diffi-cileinfection(fivetrials;RR=0.35;95%CI:0.13-0.92).85 S.
boulardii(RR=0.43; 95% CI:0.32-0.60) and L. rhamnosus
GG(RR=0.36;95%CI:0.19-0.69)arethetwobeststudied strains.87 Inmoststudies,theprobioticisstartedtogether
withantibiotictreatment.88
Traveler’sdiarrhea
Traveler’s diarrheais a frequent condition of great socio-economic impact. In this topic, there are more reviews thanoriginalresearchstudiespublished.DifferentRCTshave beenperformedevaluatingtheefficacyofprobioticsinthe prevention of traveler’s diarrhea. One trial with L. aci-dophilusandtwowithL.rhamnosusGGobservednegative results.89---91OnetrialwithS.boulardiireportedasmallbut
significantpreventiveeffectinasubgroup,suggesting geo-graphical differences in efficacy.92 In a review,McFarland
concludedthatthereiscomparableevidenceforefficacyfor
L.rhamnosusGG,L.caseiDN-114001,andS.boulardii,and noefficacyforL.acidophilus.93Sincethenumberofstudies
intraveler’sdiarrheaisverylimited,arecentmeta-analysis concluded that probiotics are not efficient for traveler’s diarrhea.94Therearenodataonprebioticsandprevention
ortreatmentoftraveler’sdiarrhea.Overall,thenumberof studiesistoosmalltoallowforrecommendations.95
IrritableBowelSyndrome(IBS)
Thereissubstantialliteratureontheeffectofprobioticson IBSinadults,butdatainchildrenarelimited.ACochrane review from2009failedtodemonstratean effectoffiber supplements and recordeda limited effect of lactobacilli onsymptomscomparedtoplacebo(OR:1.17;95%CI:0.62, 2.21).96
ARCTofsixweekswithL.rhamnosusGGversusplacebo showed overall negativeresults in 50 children and young adults,althoughtherewasalowerincidenceof perceived abdominal distension in the L. rhamnosus GG group.97 L.
rhamnosusGG,butnotplacebo,causedasignificant reduc-tion of both frequency and severity of abdominal pain comparedtobaseline,andinfluencedintestinal permeabil-itytesting.98Ameta-analysisdemonstratedthat,compared
withplacebo,L.rhamnosusGGsupplementationwas associ-atedwithasignificantlyhigherrateoftreatmentresponders intheoverallpopulationwithabdominalpain-related func-tionalGIdisordersandintheIBSsubgroup.99 However,no
differencewasobservedinchildrenwithfunctional abdom-inal painor functionaldyspepsia whoreceivedplaceboor
L.rhamnosusGG.Arandomizedcross-overtrialwithVSL#3 andplacebo, comprising59patients for sixweeks,witha two-week washout period in-between, showed a superior effect of VSL#3 compared to placebo in symptom relief, aswell asinabdominalpain/discomfort,abdominal bloat-ing/gassiness,andfamilyassessmentoflifedisruption.99No
significantdifferencewasfoundinthestoolpattern.100
There are no data on prevention or treatment of IBS withprebiotics.Datafromonetrialsuggestthat,ininfants, a prebiotic-containing whey-basedformula provides supe-riorGIcomfortthanacontrolformula.101 Apeptide-based
formula containing fiberwas aswell-tolerated asa fiber-free formula in a small population of children with GI impairments.102Extremesofstoolconsistencywere
normal-izedwiththefiberformula.Nosignificantdifferenceswere observed invomiting, abdominalpain,feedingintakes,or weightgainbetweenthetwoformulas.103Synbioticsshould
more effective thanplacebo in the treatment ofpatients withabdominalpain-relatedfunctionalgastro-intestinal dis-orders,especiallywithrespecttopatientswithIBS.104
Helicobacterpylori
The use of probioticsin H.pylori-colonized subjectswith gastric inflammation is supported by many observations. Specific strains of Lactobacillus and Bifidobacerium exert in vitro bactericidal effectsagainst H.pylori through the release of bacteriocins or production of organic acids, and/orinhibititsadhesiontoepithelialcells.Such protec-tiveeffectshavebeenconfirmedinanimalmodels.Clinical trialsareveryimportant,sinceinvitroresultscannotalways bereproducedin patients. Probioticsdecreasethe bacte-rial load andimprove the immune response.105 Results of
clinicaltrialsindicatethatprobioticsgenerallydonot erad-icate H.pylori, but decreasethe density of colonization, thereby maintaining lower levels of this pathogen in the stomach; in association with antibiotic treatments, some probiotics increased eradication rates and/or decreased adverse effects duetothe antibiotics. Manystudies show a moderate higher eradication rate (∼10%) of H. pylori
when probiotics are added to the antibiotics and proton pumpinhibitor.106AlthoughL.rhamnosusGGappearsnotto
improveeradication,107 mostprobioticbacteriaandyeasts
reducetheadverseeffectsofstandardH.pylorieradication regimens.108,109 Probiotics supplementation in triple
ther-apy forH.pylori infectionmay havebeneficial effectson eradication and therapy-related side effects, particularly diarrhea,inchildren.110
Constipation
Constipation is a frequent problem in childhoodin which pre-andprobioticscouldhave apositiveinfluence onthe intestinal microbiota with an effect on stool consistency andfrequency.Unfortunately, studyresults are contradic-tory.Inanopen trial,B.brevewaseffective inincreasing stoolfrequencyinchildrenwithfunctionalconstipation.111
Furthermore,it had apositive effectregarding improving stool consistency,decreasing the numberof fecal inconti-nenceepisodes,andreducingabdominalpain.111Inanother
opentrial, aprobioticmixture(EcologicRelief®,Winclove ProBiotics,Netherlands)containingB.bifidum,B.infantis,
B.longum,L.casei,L.plantarum,andL.rhamnosusshowed positive effects on constipation symptoms.112 L.
rhamno-sus Lcr35 was effective in treating children with chronic constipation.113B.lactiswasreportedtobenoneffectivefor
constipation.94,114L.reuteriDSM17938hadapositiveeffect
in infants with chronic constipation on bowel frequency, evenwhentherewasnoimprovementinstoolconsistency andepisodesofinconsolablecryingepisodes.115ABrazilian
study showedapositiveinfluence of yoghurtonstool fre-quencywithanadditionaleffectofyoghurtsupplemented with B. longum.116 In constipated children, a fermented
dairy product containing B.animalis subsp. lactis DN-173 010increasestoolfrequency,butthisincreasewas compa-rable withthatobserved inthe controlgroup.117 Thereis
currentlynotsufficientevidencetorecommendfermented dairy products containing strain DN-173 010 in this cate-goryof patients.117 No evidencefor any effectwasfound
forfluidsupplements,prebiotics,probiotics,orbehavioral intervention.118 Probiotics have not proven effective for
childrenwithfunctionalconstipation.104Untilmoredataare
available,theuseofprobioticsforthetreatmentof consti-pationconditionshouldbeconsideredinvestigational.119
Necrotizingenterocolitis
Necrotizingenterocolitis(NEC)isaseverecondition occur-ringespeciallyinpreterminfants.AbnormalGImicrobiota developmenthas been hypothesized as one of the possi-bleetiologicfactors.ThefirstpublicationreportingthatL. acidophilus and B.infantis reducedNEC dates back from 1999.120Thiswasfollowedbyanegativestudyshowingthat
seven days of L. rhamnosus GG supplementation starting withthe firstfeed wasnoteffective in reducingthe inci-denceofurinarytractinfection,NECandsepsisinpreterm infants.121 Then, several randomized trials with different
lactobacilliand bifidobacteriashowed asignificant reduc-tionindevelopmentofNEC.122,123AlthoughS.boulardiiwas
shown toamelioratehypoxia/reoxygenation-induced NECs inyoung mice,124 it didnot protectfor NECin infants.125
ACochranereviewconcludedin2008 thatenteral probio-ticsupplementationreducedtheincidenceofNECstageII ormoreandmortality.126 Nosystemicinfectionsorserious
adverseeventsweredirectlyattributedtotheadministered probioticmicroorganism.126Accordingtothepublished
tri-als, the NNTto preventone case of NEC is 21 and27.126
However,thecentersinwhichthesetrailshave been per-formed have a much higher incidence of NEC than most European or North American centers. The recommenda-tionmaybe differentin centers witha highincidence of NEC,inwhichothermeasurementstodecreaseNECare dif-ficult to apply. The updated Cochrane review from 2011 comes to different conclusions: enteral supplementation of probiotics prevents severe NEC and all cause mortal-ityinpreterm infants.127 The updatedreviewof available
evidencesupports a change in practice.More studies are needed to assess efficacy in extremely low birth weight infants and to assess the most effective formulation and dosetobeused.127Thedebateregardingwhetherprobiotics
shouldbesystematicallygiventopretermsisstillongoing. The2012systematicreviewoftheAmericanPediatric Sur-gical Association Outcomes and Clinical Trials Committee acknowledgesthatrecentCochranereviewssupporttheuse ofprophylacticprobioticsinpreterminfantsweighingless than2,500gtoreducetheincidenceofNEC,aswellasthe useofhumanbreastmilkratherthanformulawhen possi-ble.Thereisnoclearevidencetosupportdelayedinitiation orslowadvancementoffeeds.128However,anexpertgroup
ofnutritionistsandneonatologistsconcludedthatthereis insufficientevidencetorecommendtheroutineuseof pro-bioticstodecreaseNEC.129Accordingtothisgroup,thereis
encouragingdatatojustify furtherinvestigationregarding the efficacy and safety of specific probiotics in circum-stancesofhighlocalincidenceofsevereNEC.129According
recommendprobioticstoreduceNEC.130 Athirdgroup
sug-geststhatitmaybecomeunethicalnottogiveprobioticsto pretermbabiestodecreaseNEC.131Enteralsupplementation
ofprobioticspreventssevereNECandallcausemortalityin preterminfants.132
Colic
Colic is a frequent problem in infants and often parents aredesperate fora solution.Inthisindication,the effect of L. reuteri has been exhaustively studied in breastfed infants.133---135However,recentdatasuggested thatinfants
giventhesameprobioticcryfor50minutesmorethanthose givenplacebo.136Dupontetal.reportedefficacyofanother
probioticstraininformulafedinfants.137Asynbioticsachet
containing1billionCFUofL.casei,L.rhamnosus,S. ther-mophilus,B.breve,L.acidophilus,B.infantis,L.delbrueckii
subsp.bulgaricus,andfructooligosacharidewasshowntobe effectiveinreducingcolic inbreastfedinfantswhen com-paredtoplacebo.138
Allergyandatopicdermatitis
Simultaneous pro- and prebiotic treatment (a mixture of fourstrainsandGOS)giventopregnantwomenfortwoto fourweeksbeforedeliveryandtotheinfantsforsixmonths showedno effectonthe cumulative incidenceof allergic diseasesattheageof2yearswhencomparedwithplacebo, buttendedtoreduceIgE-associated(atopic)diseasessince asignificant reduction of (atopic) eczemawasnoticed.139
However,Taylor etal challenged therole of probioticsin allergy prevention, observing that early probiotic supple-mentation with L. acidophilus did not reduce the risk of atopic dermatitis (AD) in high-risk infants, and was even associatedwithincreased allergen sensitizationin infants receivingsupplements.140ACochranereviewfrom2007
con-cludedthattherewasinsufficientevidencetorecommend theadditionofprobioticstoinfantfeedsforpreventionof allergicdiseaseor foodhypersensitivity.141 Although there
wasa reduction in clinical eczema in infants, this effect wasnotconsistentbetweenstudies,andcautionwasadvised inviewofmethodologicalconcernsregardingtheincluded studies.142However,theefficacyofprobioticinterventionto
reduceatopicdermatitisand/orallergicdiseasemaydepend onthemomentofintervention. Preventiveadministration of probiotics may be only effective if given during preg-nancy.Probioticsgiventounselectedmothersreducedthe cumulativeincidence of AD, but had no effect on atopic sensitization.142 A recent meta-analysis showed that the
administrationof lactobacilli during pregnancy prevented atopiceczema in children aged2 to 7years.143 However,
amixture of various bacterial strainsdoes not affect the development of atopic eczema, independent of whether theycontainlactobacilliornot.143L.rhamnosusHN001was
reportedeffectiveagainsteczemainthefirsttwoyearsof life,persistingtoage4years,whileB.animalissubsp.lactis HN019hadnoeffect.144Therefore,notonlytimingof
admin-istrationappears toimportant, but also strain specificity. However,timingofadministrationandstrainspecificitywere
then again contradicted in the meta-analysis by Pelucchi et al., supporting a moderate role of probiotics in the prevention of atopicdermatitis and IgE-associatedatopic dermatitisininfants,regardlessofthetimeofprobioticuse (pregnancyorearlylife)orthesubject(s)receiving probio-tics(mother,child,orboth).145 Thedataonprobioticsand
allergyneed furtherclarification, becausedataare some-howcontradictory.Geographicalorgeneticdifferencesmay haveadetrimentalrole,especiallyforatopicdermatitis.
Ninety infants with atopic dermatitis, age<7 months, wererandomizedtoreceiveaninfantformulawithB.breve
M-16VandamixtureofshortchainGOSandlongchainFOS, orthesameformulawithoutsynbioticsduring12weeks.146
Therewerenosignificantdifferencesbetweenthesynbiotic andtheplacebogroup.146Thesamegroupshowedthat
syn-bioticspreventasthma-likesymptomsininfantswithAD.147
Atthesametime,anothergroupreportedthatasynbiotic combinationofL.salivariusplusFOSissuperiortothe prebi-oticalonefortreatingmoderatetoseverechildhoodAD.148
While somestudies withprobiotics asa treatment for AD showabenefit,149moststudiesarenegative.Nobenefitwas
reportedfromsupplementationwithB.animalissubsp. lac-tisorL.paracaseiinthetreatmentofeczema,whengiven asanadjuncttobasictopicaltreatment,andnoeffecton theprogressionofallergicdiseasefromage1to3yearswas observed.150 Mostreviewsconcludethatprobioticsarenot
effectiveinreducingatopicdermatitis.Thesecontradictory resultssuggeststrainspecificityorageneticinfluenceonthe efficacyof probioticsinchildren withatopicdermatitis.A review of 13studies of probioticsfor treating established eczema did not show convincing evidence of a clinically worthwhilebenefit.151However,accordingtoarecent
meta-analysis,theoverallresultsuggeststhatprobioticscouldbe anoptionforthetreatmentofatopicdermatitis,especially for moderatetoseverecases, andnoevidencewasfound supportingthebeneficialroleofprobioticsininfants.152
Extra-intestinalinfectionsandothereffects
Nopediatricstudieshavedemonstrateddefinitebeneficial effectsofadministeringprobioticstotreatextra-intestinal infections such as respiratory tract infections or otitis media.88,153 Thereis noevidencethat probioticsdecrease
extra-intestinal infections. There is some evidence that some lactobacilli might prevent recurrent urinary tract infectioninwomen.However,datainchildrenarelacking. Thesameistrueforrecurrentvulvovaginitis.Sazawaletal. showedthatprebioticandprobioticfortifiedmilkprevented morbiditiesamongchildreninacommunity-basedRCT.154
Candidiasis accounts for 10% to 20% of bloodstream infections in pediatric intensive care units (PICUs) and a significant increase in morbidity, mortality, and length of hospital stay.155 A few studies have demonstrated that
probioticsareabletopreventCandidaoutgrowthand col-onization in neonates, whereas their role in preventing invasivecandidiasisinsuchpatientsisstillunclear.155
triphosphate.156 This is the first example of the
applica-tionofpurifiedbifidobacterialphytasesinfoodprocessing, demonstratingthe potential of theseenzymesto beused inproductsforhumanconsumption.156Lacticacidbacteria
improvethesynthesisofvitaminsB2,B11andB12andhave thepotentialstrategiestoincreaseB-groupvitamincontent incereals-basedproducts.157Vitamin-producingL.hasbeen
leading to the elaboration of novel fermented functional foods.157
Pandemicobesityisnowamatterofinterestinall devel-opedanddeveloping countries.Treatment withprobiotics selectively changesthecompositionof thegut microbiota infavorofspecificgenusandevenstrains.Fewintervention studies withprobiotics in overweight or obeseindividuals havebeenpublisheduntilnow,andmostlyfocusonL.orB.
TheadministrationofastrainofL.gasseriinobeseandtype 2diabeticpatientshasbeenshowntodecreasefatmass (vis-ceralandsubcutaneous)andbodymassindex.158Inaddition,
Andreasen et al. have demonstrated that the adminis-tration of Lactobacillus spp. positively impact on insulin sensitivity.159 Compellingevidence suggests thatearly gut
microbiota modulation with probiotics reduces the body massindexinyoungchildrenbyrestrainingexcessiveweight gainduringthefirstyearsoflife(from0to10yearsof follow-up).160 Sofar, onlyfew dataareavailable onthepossible
application of lactobacilli or bifidobacteria to counteract adiposity.
Fecalmicrobiotatransplantation
A new approach in microbial therapeutic applications is transplantation of intestinal microbiota, especiallyin dif-ficult to treat conditions in which it is known that the fecal microbiota is abnormal.161,162 Observed side effects
warrant caution in the ongoing pursuit of this treatment option.162Thereisevidencethatmanydiseasesarerelated
tointestinaldysbiosis.As aconsequence, manipulationof the intestinal microbiota is a very attractive therapeutic approach.However,resultsareoftennegative,162although
positive results have been reported.163 The transplanted
microbiota shouldbe carefully screenedfor pathogens.164
Bacteremia has been reported as an adverse event.165
However, the first cure of early onset colitis after fecal microbiota transplantation has been reported.166 Further
studies should now focus on the reasons for success and failure.
Safetyandsideeffects
Probiotics have a long record of safety, which relates primarily to the use of lactobacilli and bifidobacteria.167
Experience withother microorganismsusedasprobioticis morelimited.Thereisnosuchthingaszerorisk, particu-larlyinthecontextofcertainformsofhostsusceptibility.167
Probioticsaregenerallyregardedassafe,andside effects in ambulatory carehave almost notbeen reported.Large scale epidemiologicalstudies in countrieswhereprobiotic use is endemic demonstrate (in adults) low rates of sys-temicinfection,between0.05and0.40%.168Administration
during pregnancy and early infancy is considered safe.169
Probioticcompoundsmaycontainhiddenallergensoffood and may not be safe for subjects with allergy to cow’s milkorhen’seggs.170Documentedinvasiveinfectionshave
been primarily noted to occur in immunocompromised adults,but invasive infections in infants and children are extremelyrare.171---173Twocasesofbacteremiaattributable
toLactobacillussupplementationwithgenotypically identi-calclinicalandsupplementisolateswererecentlyreported in an infant and a child without underlying GI disease or immunocompromised status.174 Sepsis with probiotic
lac-tobacilli has been reported in children with short gut. Recently,plasmidtransferofantibioticresistancehasbeen showntobeclinicallypossible.Long-termuseofprobiotics underantibiotic selection pressure couldcause antibiotic resistance,andtheresistancegenecouldbetransferredto other bacteria.175 Translocation from thegastro-intestinal
tractintothe systemiccirculation hasnotbeen reported. Thereispoorpublicunderstandingoftheconceptofrisk,in general,and risk/benefit analysis, in particular.168
Uncer-tainty regarding the potential for transfer of antibiotic resistancewithprobioticspersists,buttheriskappearstobe lowwithcurrentlyavailable probioticproducts.168 As with
otherformsoftherapeutics,thesafetyofprobioticsshould beconsidered onastrain-by-strain basis.168 The potential
benefitsofsupplementationshouldbeweighedagainstthe riskofdevelopmentofaninvasiveinfectionresultingfrom probiotictherapy.
Conclusion
Probioticshaveenteredthemainstreamofhealthcare.The gastro-intestinalmicrobiotaisfundamentalforthe develop-mentoftheimmunesystem.Althoughthemainindications of the medical use of probiotics is still in the area of theprevention and treatment of gastro-intestinalrelated disorders,gradually more evidence is collected on extra-intestinalindications, suchasvaginitis,atopicdermatitis, andrespiratorytractinfections.Randomizedcontrolled tri-als with commercially available products in the claimed indicationsaremandatorybeforetheirusecan be recom-mended.Currently,L.rhamnosusGGandS.boulardiiarethe best-studiedstrains,whilerecent literatureprovides posi-tivedataonL.reuteri.Althoughadverseeffectshavebeen sporadically reported, probiotics can be considered safe. Misuseand use of products that have notbeen validated mayconstitutepotentialdrawbacks.
Conflicts
of
interest
Yvan Vandenplas is consultant for Biocodex and United Pharmaceuticals.Theco-authorsdidnotreportany poten-tialconflictsofinterest.
References
of probiotics infoodincluding powder milkwith live lac-tic acid bacteria.1-4 October2001, Córdoba, Argentina. [cited18Aug2014].Availablefrom:http://www.who.int/ foodsafety/publications/fsmanagement/en/probiotics.pdf 2.FoodandAgricultureOrganization(FAO).WorldHealth Orga-nization(WHO).ReportofaJointFAO/WHOworkinggroup on drafting guidelines for the evaluation of probiotics in food.April30,May1;LondonOntario,Canada;2002.[cited 18 Aug 2014]. Available from: ftp://ftp.fao.org/es/esn/ food/wgreport2.pdf.
3.AshwellM.Conceptsoffunctionalfoods.Brussels. Interna-tionalLifeSciencesInstitute(ILSI)Europe.2002.
4.EuropeanFoodandFeedCulturesAssociation(EFFCA). Def-inition of microbial food culture (MFC). Brussels: EFFCA; 2003.
5.Vandenplas Y. Author’s reply: Identification of probiotics byspecificstrainname.AlimentPharmacolTher.2012;35: 860.
6.European Parliament and Council. Regulation (EC) No 1924/2006 of the European Parliament and of the Coun-cil of 20 December 2006 on nutrition and health claims madeonfoods.OfficialJournaloftheEuropeanUnion.OJ L404,30.12.2006.CorrigendumOJL12,18.1.2007,p. 3-18.[cited18Aug2014].Availablefrom:ttps://www.fsai.ie/ uploadedFiles/CorReg19242006.pdf.
7.Huys G, Vancanneyt M, D’Haene K, Vankerckhoven V, Goossens H, Swings J. Accuracy of species identity of commercial bacterial cultures intended for probiotic or nutritionaluse.ResMicrobiol.2006;157:803---10.
8.Sanders ME. Probiotics: considerations for human health. NutrRev.2003;61:91---9.
9.StamatovaI,MeurmanJH.Probiotics:healthbenefitsinthe mouth.AmJDent.2009;22:329---38.
10.MeurmanJH.Probiotics:dotheyhavearoleinoralmedicine anddentistry?EurJOralSci.2005;113:188---96.
11.HoeslCE,AltweinJE.Theprobioticapproach:analternative treatmentoptioninurology.EurUrol.2005;47:288---96. 12.BarronsR,TassoneD.UseofLactobacillusprobioticsfor
bac-terialgenitourinaryinfectionsinwomen:areview.ClinTher. 2008;30:453---68.
13.ReidG,BockingA.Thepotentialforprobioticstoprevent bacterialvaginosisandpretermlabor.AmJObstetGynecol. 2003;189:1202---8.
14.FalagasME,BetsiGI, TokasT,AthanasiouS.Probioticsfor preventionofrecurrenturinarytractinfectionsinwomen: areviewoftheevidencefrommicrobiologicalandclinical studies.Drugs.2006;66:1253---61.
15.Hacini-RachinelF1,Gheit H,Le LuduecJB, DifF,Nancey S,KaiserlianD.Oralprobioticcontrolskininflammationby acting onbotheffector andregulatory Tcells.PLoSOne. 2009;4:e4903.
16.CaramiaG1,AtzeiA,FanosV.Probioticsandtheskin.Clin Dermatol.2008;26:4---11.
17.HojsakI,Abdovi´cS,SzajewskaH,Milosevi´cM,Krznari´cZ, Kolacek S. Lactobacillus G.G. in the prevention of noso-comial gastrointestinal and respiratory tract infections. Pediatrics.2010;125:e1171---7.
18.Possemiers S,Marzorati M,Verstraete W,VandeWiele T. Bacteria andchocolate:asuccessfulcombinationfor pro-bioticdelivery.IntJFoodMicrobiol.2010;141:97---103. 19.Pereg D, Kimhi O, TiroshA, Orr N, KayoufR, Lishner M.
Theeffectoffermentedyogurtonthepreventionof diar-rhea in a healthyadult population. AmJ Infect Control. 2005;33:122---5.
20.MagalhãesKT,PereiraMA,NicolauA,DragoneG,Domingues L, Teixeira JA, et al. Production of fermented cheese
whey-basedbeverageusingkefirgrainsasstarterculture: evaluationofmorphologicalandmicrobialvariations. Biore-sourTechnol.2010;101:8843---50.
21.SteidlerL,HansW,SchotteL,NeirynckS,ObermeierF,Falk W,etal.TreatmentofmurinecolitisbyLactococcuslactis
secretinginterleukin-10.Science.2000;289:1352---5. 22.FoligneB,DesseinR,MarceauM,PoiretS,ChamaillardM,
PotB,etal.Preventionandtreatmentofcolitiswith Lacto-coccuslactissecretingtheimmunomodulatoryYersiniaLcrV protein.Gastroenterology.2007;133:862---74.
23.KumarM,NagpalR,VermaV,KumarA,KaurN,Hemalatha R,etal.Probioticmetabolitesasepigenetictargetsinthe preventionofcoloncancer.NutrRev.2013;71:23---34. 24.HuseiniHF,RahimzadehG,FazeliMR,MehrazmaM,Salehi
M.Evaluationofwoundhealingactivitiesofkefirproducts. Burns.2012;38:719---23.
25.CookMT,TzortzisG,CharalampopoulosD,KhutoryanskiyVV. Microencapsulationofprobioticsforgastrointestinal deliv-ery.JControlRelease.2012;162:56---67.
26.Kumar M, Nagpal R, Kumar R, Hemalatha R, Verma V, KumarA,etal.Cholesterol-loweringprobioticsaspotential biotherapeuticsformetabolic diseases.ExpDiabetes Res. 2012;2012:902917.
27.VandenAbbeeleP,GrootaertC,PossemiersS,VerstraeteW, VerbekenK,etal.Invitromodeltostudythemodulation ofthemucin-adheredbacterialcommunity.ApplMicrobiol Biotechnol.2009;83:349---59.
28.MacfarlaneS,FurrieE, KennedyA,CummingsJH, Macfar-laneGT. Mucosalbacteria inulcerative colitis. BrJNutr. 2005;93:S67---72.
29.ChassaingB,Darfeuille-MichaudA.Thecommensal micro-biotaandenteropathogensinthepathogenesisof inflamma-toryboweldiseases.Gastroenterology.2011;140:1720---8. 30.LebeerS,ClaesI,TytgatHL,VerhoevenTL,MarienE,von
OssowskiI,etal.FunctionalanalysisofLactobacillus rham-nosusGGpiliinrelationtoadhesionandimmunomodulatory interactions with intestinal epithelial cells. Appl Environ Microbiol.2012;78:185---93.
31.Nagao F, Nakayama M, Muto T, Okumura K. Effects of a fermentedmilkdrinkcontainingLactobacillus caseistrain Shirotaontheimmunesysteminhealthyhumansubjects. BiosciBiotechnolBiochem.2000;64:2706---8.
32.HatakkaK,SavilahtiE,PönkäA,MeurmanJH,PoussaT,Näse L,etal.Effectoflongtermconsumptionofprobioticmilk oninfectionsinchildrenattendingdaycarecentres:double blind,randomisedtrial.BMJ.2001;322:1327.
33.Makino S, Ikegami S, Kume A, Horiuchi H, Sasaki H, Orii N. Reducing the risk of infection in the elderly by dietaryintakeofyoghurtfermentedwithLactobacillus del-brueckiissp.bulgaricus OLL1073R-1.BrJNutr. 2010;104: 998---1006.
34.Twetman S,Stecksén-Blicks C. Probiotics and oralhealth effectsinchildren.IntJPaediatrDent.2008;18:3---10. 35.NäseL,HatakkaK,SavilahtiE,SaxelinM,PönkäA,Poussa
T,etal.Effectoflong-termconsumptionofaprobiotic bac-teriumLactobacillusrhamnosusGG,inmilkondentalcaries andcariesriskinchildren.CariesRes.2001;35:412---20. 36.SarantosSR.Theimportanceofprobioticsupplementation
inconjunctionwithorthodontictherapy.JNJDentAssoc. 2006;77:10---3.
37.Reid G, Beuerman D, Heinemann C, Bruce AW. Probiotic
Lactobacillusdoserequiredtorestoreandmaintaina nor-mal vaginal flora. FEMSImmunol Med Microbiol. 2001;32: 37---41.
ofclinicalefficacyinapopulationof40womentreatedfor 24months.ArchGynecolObstet.2010;281:1065---9. 39.Andreeva P, Dimitrov A. The probiotic Lactobacillus
aci-dophilus---analternativetreatmentofbacterialvaginosis. AkushGinekol(Sofiia).2002;41:29---31.
40.CatsA,KuipersEJ,BosschaertMA,PotRG, Vandenbroucke-GraulsCM,KustersJG.Effectoffrequent consumptionof a Lactobacillus casei-containing milk drink in Helicobac-ter pylori-colonized subjects. Aliment Pharmacol Ther. 2003;17:429---35.
41.Ushiyama A, Tanaka K, Aiba Y, Shiba T, Takagi A, Mine T, et al. Lactobacillus gasseri OLL2716 as a probiotic in clarithromycin-resistant Helicobacter pylori infection. J GastroenterolHepatol.2003;18:986---91.
42.Collado MC, González A, González R, Hernández M, Ferrús MA, Sanz Y. Antimicrobial peptides are among theantagonisticmetabolitesproducedbyBifidobacterium
against Helicobacter pylori. Int J Antimicrob Agents. 2005;25:385---91.
43.Alfaleh K, Anabrees J, Bassler D. Probiotics reduce the riskofnecrotizingenterocolitisinpreterminfants:a meta-analysis.Neonatology.2010;97:93---9.
44.Weber TK, Polanco I. Gastrointestinal microbiota and somechildrendiseases:areview.GastroenterolResPract. 2012;2012:676585.
45.SantosF,VeraJL,vanderHeijdenR,ValdezG,deVosWM, SesmaF, etal.The complete coenzyme B12 biosynthesis geneclusterofLactobacillusreuteriCRL1098.Microbiology. 2008;154:81---93.
46.FabianE, MajchrzakD, Dieminger B,MeyerE, Elmadfa I. Influenceofprobioticandconventionalyoghurtonthestatus ofvitaminsB1B2andB6inyounghealthywomen.AnnNutr Metab.2008;52:29---36.
47.deVreseM,StegelmannA,RichterB,FenselauS,Laue C, SchrezenmeirJ.Probiotics---compensationforlactase insuf-ficiency.AmJClinNutr.2001;73:421S---9S.
48.Sousa T, Paterson R, Moore V, Carlsson A, Abrahamsson B,BasitAW. The gastrointestinalmicrobiotaas asite for the biotransformation of drugs. Int J Pharm. 2008;363: 1---25.
49.FischbachMA.Antibioticsfrommicrobes:convergingtokill. CurrOpinMicrobiol.2009;12:520---7.
50.Gorissen L, Raes K, Weckx S, Dannenberger D, Leroy F, De Vuyst L, et al. Production of conjugated linoleic acid and conjugated linolenic acid isomers by Bifi-dobacteriumspecies.Appl MicrobiolBiotechnol. 2010;87: 2257---66.
51.AndoA,OgawaJ,KishinoS,ShimizuS.CLAproductionfrom ricinoleicacidbylacticacidbacteria.JAmOilChemSoc. 2003;80:889---94.
52.DecroosK, Vanhemmens S,CattoirS, Boon N, Verstraete W. Isolation and characterisation of an equol-producing mixedmicrobialculturefrom ahuman faecalsampleand itsactivityundergastrointestinalconditions.ArchMicrobiol. 2005;183:45---55.
53.Possemiers S, Rabot S,Espín JC, Bruneau A, Philippe C, González-SarríasA, etal.Eubacteriumlimosumactivates isoxanthohumol from hops (Humuluslupulus L.) into the potentphytoestrogen8-prenylnaringenininvitroandinrat intestine.JNutr.2008;138:1310---6.
54.Hamilton-MillerJM.Probioticsandprebioticsintheelderly. PostgradMedJ.2004;80:447---51.
55.Borthakur A, Gill RK, Tyagi S, Koutsouris A, Alrefai WA, Hecht GA, et al. The probiotic Lactobacillus acidophilus
stimulates chloride/hydroxyl exchange activity in human intestinalepithelialcells.JNutr.2008;138:1355---9.
56.De Boever P, Wouters R, Verschaeve L, Berckmans P, SchoetersG,VerstraeteW.Protectiveeffectofthebilesalt hydrolase-activeLactobacillusreuteriagainstbilesalt cyto-toxicity.ApplMicrobiolBiotechnol.2000;53:709---14. 57.DeSmetI,DeBoeverP,VerstraeteW.Cholesterolloweringin
pigsthroughenhancedbacterialbilesalthydrolaseactivity. BrJNutr.1998;79:185---94.
58.GratzS,MykkänenH,OuwehandAC,JuvonenR,SalminenS, El-NezamiH.Intestinalmucusalterstheabilityofprobiotic bacteriatobindaflatoxinB1invitro.ApplEnvironMicrobiol. 2004;70:6306---8.
59.Kabeerdoss J, Devi RS, Mary RR, Prabhavathi D, Vidya R, Mechenro J, et al. Effect of yoghurt containing Bifi-dobacteriumlactisBb12®onfaecalexcretionofsecretory immunoglobulin A and human beta-defensin 2 in healthy adultvolunteers.NutrJ.2011;10:138.
60.GhadimiD, Fölster-Holst R,deVreseM, WinklerP,Heller KJ,SchrezenmeirJ.Effectsofprobioticbacteriaandtheir genomicDNAonTH1/TH2-cytokineproductionbyperipheral bloodmononuclearcells(PBMCs)ofhealthyandallergic sub-jects.Immunobiology.2008;213:677---92.
61.Saavedra JM, Bauman NA, Oung I, Perman JA, Yolken RH. Feeding of Bifidobacterium bifidum and Streptococ-cus thermophilus to infants in hospital for prevention of diarrhoea and shedding of rotavirus. Lancet. 1994;344: 1046---9.
62.Szajewska H, Kotowska M, Mrukowicz JZ, Arma´nska M, Mikołajczyk W.Efficacy of LactobacillusGGin prevention of nosocomial diarrhea in infants. J Pediatr. 2001;138: 361---5.
63.MastrettaE,LongoP,LaccisagliaA,BalboL,RussoR, Mazza-ccaraA,etal.EffectofLactobacillusGGandbreast-feeding inthepreventionofrotavirusnosocomialinfection.JPediatr GastroenterolNutr.2002;35:527---31.
64.SzajewskaH,SettyM,MrukowiczJ,GuandaliniS.Probiotics in gastrointestinal diseasesin children: hard and not-so-hard evidence of efficacy. J Pediatr Gastroenterol Nutr. 2006;42:454---75.
65.AgustinaR,KokFJ,vandeRestO,FahmidaU,FirmansyahA, LukitoW,etal.Randomizedtrialofprobioticsandcalcium on diarrheaand respiratorytract infectionsin Indonesian children.Pediatrics.2012;129:e1155---64.
66.Guandalini S.Probiotics for prevention and treatment of diarrhea.JClinGastroenterol.2011;45:S149---53.
67.SzajewskaH, MrukowiczJZ. Use ofprobiotics in children withacutediarrhea.PaediatrDrugs.2005;7:111---22. 68.ChouraquiJP,VanEgrooLD,FichotMC.Acidifiedmilk
for-mulasupplementedwithBifidobacteriumlactis:impacton infantdiarrheainresidentialcaresettings.JPediatr Gas-troenterolNutr.2004;38:288---92.
69.ThibaultH,Aubert-JacquinC,GouletO.Effectsoflong-term consumptionofafermentedinfantformula(with Bifidobac-teriumbrevec50andStreptococcusthermophilus065)on acute diarrheain healthyinfants.J PediatrGastroenterol Nutr.2004;39:147---52.
70.WankeM, SzajewskaH.LackofaneffectofLactobacillus reuteriDSM17938inpreventingnosocomialdiarrheain chil-dren:arandomized,double-blind,placebo-controlledtrial. JPediatr.2012;161:40---3.
71.Gutierrez-Castrellon P, Lopez-VelazquezG, Diaz-GarciaL, Jimenez-GutierrezC,Mancilla-RamirezJ,Estevez-Jimenez J, et al. Diarrhea in preschool children and Lactobacil-lus reuteri: a randomized controlled trial. Pediatrics. 2014;133:e904---9.
