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PartILivingintheMicrobialWorldInthispart...Iexplorethebasicsofhowbacteria—goodandbad—impactyourbodyanditsfunctions.Fromyourimmunesystemtoyourintestines,bacteriaaffectyourhealthinnumerousways.Understandingthebasicsofthatimpactwillhelpyouunderstandhowprobioticscanhelpyounotonlyachievebetterhealthbutalsofightsomediseases.Lastly,Ihelpyouunderstandwhatprobioticsareandwhatyou’lllookforasyouincorporatethisimportantsup-plementintoyourdiet.Chapter1GettingaHandleontheTrueNatureofBacteriaInThisChapter▶Exploringthediscoveryofbacteriaandtheirroleinhealth▶Lookingattheconnectionbetweenbacteriaandbraindevelopment▶Investigatingbacteria’sroleinmoodandanxietyTheUnitedStates,theworldleaderinsomanyotherareasofhealthandmedicalscience,isconsideredan“emerg-ingmarket”inthedevelopmentanduseofprobiotics;suchsupplementsarefarmorepopularinEuropeandAsia,andprobiotic-richfoods(seeChapter11)arestaplesinmanyculturesaroundtheglobe.Interestingly,accordingtotheNationalHealthInterviewSurveyconductedbytheNationalInstitutesofHealth’sNationalCenterforComplementaryandAlternativeMedicine(),Americansuseprobioticsfortheirchildren,butnotforthemselves.Certainly,childrencanbenefitfromprobiotics(seeChapter8),butresearchindi-catesthatprobioticsareappropriateforgrown-upstoo.Evenhealthyadultscanhelpmaintaintheirgoodhealthbytakingprobiotics.Asinothercountries,yogurtmanufacturersintheUnitedStateshavelongtoutedthebenefitsofliveculturesofbacte-riaintheirproducts.Morerecently,companieslikeDannonhavebegunaggressivelymarketingyogurtanditsfriendlybacteriaasawaytoregulateyourdigestivesystem—andtheybackuptheirclaimsbyfinancingorconductingclinicalstudies.PartI:LivingintheMicrobialWorld10TheNationalCenterforComplementaryandAlternativeMedicinealsohasmadeprobioticresearchahighpriorityforfundingprojects.Thecentersupportsresearchonusingprobioticstoalleviateorpreventvariousgastrointestinaldisordersininfantsandchildren;treatingandpreventingantibiotic-relateddiarrhea(seeChapter4);andimprovingtheefficacyoffluvaccines.Governmentandprivatelyfundedresearchisturninguplotsofevidencethatprobioticscandomorethanregulateyourdigestivesystem.Iprovideinformationonvarioushealthapplicationsforspecificprobioticstrainsthroughoutthisbook.Butresearchersalsoareuncoveringfascinatinglinksbetweenthebacteriainyourdigestivesystemandyourbrain’sdevelopment,aswellasmentalhealthissueslikeanxietyanddepression,whichIdiscusslaterinthischapter.First,though,thenextsectionprovidesabriefoverviewofthetheoriesanddiscoveriesaboutbacteria’sroleinsicknessandhealth.ExploringtheHistoryofBacteriaTheoriesandPracticesCenturiesbeforetheinventionofthemicroscopeenabledresearcherstoobservelivingorganismsthatareinvisibletothenakedeye,somescientiststheorizedthattinycreaturesspreaddiseaseamonganimalsandhumans.AncientHindutexts,forexample,refertolivingagentsascausingdisease.In36BCMarcusTerentiusVarrowarnedagainstbuildinghomesandfarmsnearswampsbecausesuchareasbreed“certainminutecreatures,whichcannotbeseenbytheeyes,whichenterthebodythroughthemouthandnoseandtherecauseseriousdiseases.”Evenso,conventionalwisdomdiscountedtheideathatorgan-ismslikebacteria,orgerms,causedillness.Theprevalenttheorywasthatdiseasegeneratedspontaneously.EvenAntonvanLeeuwenhoek,consideredthefatherofmicrobiology,didn’tconnecttheorganismshesawunderhismicroscopewithdisease.Andtheideathathumancontactcouldtransmitharmfulmicroorganismsmetwithmassiveresistanceamongthemedicalandscientificcommunities.Chapter1:GettingaHandleontheTrueNatureofBacteria11Inthefollowingsections,Iprovideabriefoverviewofhowthegermtheoryofdiseasedevelopedandthehistoryofusingprobiotics,orgoodbacteria,topromotegoodhealth.UnderstandinggermtheoryAlthoughitformsthebasisofmedicaltreatmentandhygienepracticestoday,germtheory—theideathatmicroorgan-ismsareresponsibleforcausingandspreadingillness—wasquitecontroversialforcenturies.Beforetheinventionofthemicroscope,mostpeople(includingmostdoctorsandscien-tists)believedthatdiseaseeitherarosespontaneouslyorwasspreadthrough“badair,”ormiasma.IgnazSemmelweis,aHungarianobstetricianworkingataViennahospitalin1847,noticedthatwhendoctorsandmedi-calstudentsattendedbirths,newmotherswerefarmorelikelytodieofpuerperalfever,commonlyknownaschildbedfever,thanwomenwhodeliveredtheirbabiesathomewiththeaidofamidwife.Semmelweisobservedthatdoctorsandmedicalstudentsatthehospitaloftendeliveredbabiesrightafterperformingautopsies,andheinsistedthatdoctorswashtheirhandsinachlorinatedsolutionbeforeexaminingpreg-nantwomen.Thiselementarytechniqueloweredthechildbedfeverdeathrateatthehospitalfromnearly1in5toabout1in50.EnglishphysicianJohnSnowaddedevidencesupportingthegermtheorywhenhetracedtheoriginsofacholeraout-breakinLondoninthe1850s.Snownoticedthatthehomesofpeopleaffectedbytheoutbreakallgottheirwaterfromthesamepump,andheidentifiedthatwaterasthemechanismforspreadingthedisease.Inthe1860s,LouisPasteurconductedexperimentsthatprovedthatlivingorganismsinfreshlyboiledbrothcamefromoutsidethebrothratherthanspontaneouslygenerat-ingwithinit.Adecadelater,JosephLister(forwhomtheLi