卡拉胶可能引起胃损伤，癌
Wednesday,October17,2001
ByEnvironmentalNewsNetwork
布丁、冰淇淋奶酪或乡间干酪等可能含有添加剂卡拉胶――一种来自于红藻的增稠剂。几十年来，人们一直假定吃卡拉胶是安全的，但是，来自于爱荷华大学的一名医生最新研究显示这种是假设是错误的。卡拉胶是一水溶性多聚体，用于肉制品中代替脂肪，以及浓缩奶和一些豆奶制品，最引人注目的是口香糖。爱荷华大学临床内科医学助理教授JoanneTobacman医学博士认为：“动物模型显示卡拉胶的降解将引起胃肠道溃疡和病变”经对卡拉胶进行流行病学和实验研究，Tobacman博士发表了一篇综述，叙述了45项有关动物实验中卡拉胶对胃肠道有害影响的研究。发表于EnvironmentalHealthPerspectives（环境健康观察）的十月刊，该刊由环境健康科学国家协会主办。欧美过去几年的研究发现建议：卡拉胶是安全应该重新考虑，卡拉胶应受FDA（FoodandDrugAdministration）较好的控制。有足够的证据表明，严重的肠胃道损伤，包括恶性肿瘤，与卡拉胶有关。她说：“我认为，首先应考虑告诉人们与卡拉胶相关的危险性。早在1970年应有证据显示卡拉胶有害，我们对此消息有所动作已经等了很长时间。”1972年，FDA认定有足够动物实验证据提议限制卡拉胶在食品中的应用。Tobacman说：“许多权威者认为“提议”实际上已成为规则。然而，它并没有实施。”1979年FDA废除了该提议，同时声称未来将有一个较综合的规则。但是从未提出过限制，因此对卡拉胶在食品的使用也未有一个真实的规则。她说：“现已不可能重现1970年的构想来限制卡拉胶。很明显FDA期待建立一个更为综合的规范，但是却什么都没有。我发现了这种矛盾及卡拉胶作为安全食品的状态继续存在，这令人担忧。”1982年，国际癌症研究所发现足够的动物模型证据，即卡拉胶降解与胃肠道癌症相关，这证明它对人是一种致癌物质。其它的一些研究组织基于动物实验也将其列为致癌物。降解的卡拉胶分子量为30000或更低，而未降解的卡的分子量为100000或更高。有证据显示降解的卡拉胶引起肠胃溃疡和癌症。另外，Tobacman解释到，未降解的卡拉胶，其因为有较高的分子量，被认为不被肠道吸收，可能也与促进肠胃道炎症和病变相关。微生物、胃酸以及食物制造过程可能导致将较高分子量的卡拉胶转变为较低分子量的卡拉胶。Tobacman说：“如果有一个象FDA1972年提议般的规则也许能消除一些低分子组份进入食品，但实际上其本身就不足以阻止所有降解的卡拉胶，因为较高分子量形式可以转变成较低分子量形式。”卡拉胶于1930年申请专利，并在20世纪后半叶在美国广泛使用。它原用于受尔兰布丁作为增稠剂，并掺合于各种类型的食品，并要西方食物中更为普通。它也用于化妆品、牙膏和室内清洁剂。Tobacman认为其它具有相似增稠性质的胶体可代替卡拉胶。这些胶体包括刺槐豆胶、guar和黄原胶。仔细阅读标签上的添加剂，卡拉胶是否是食品的一部分。但是因为卡拉胶是次要添加剂，如可包括在浓缩奶中，可能不显示出名字。Tobacman已经开始研究调查与卡拉胶相关的致癌机理，并确定与乳腺癌之间可能的关系。
Carrageenanmaycausestomachlesions,cancer Wednesday,October17,2001ByEnvironmentalNewsNetwork
Containersofpudding,icecream,yogurt,orcottagecheesemayincludetheingredientcarrageenan,athickenerderivedfromredseaweed.Fordecades,ithasbeenpresumedtobesafetoeat,butnewresearchfromamedicaldoctoronthefacultyoftheUniversityofIowashowsthatpresumptionmaybewrong.Carrageenanisawater-solublepolymer,alsoknownasagum,thatisusedasafatsubstituteinprocessedmeatsandcanbefoundincondensedmilkandsomesoymilkproducts."Evidencefromanimalmodelshasdemonstratedthatdegradedcarrageenancausesulcerationsandmalignanciesinthegastrointestinaltract,"saidJoanneTobacman,M.D.,UniversityofIowaassistantprofessorofclinicalinternalmedicine.Afterconductingepidemiologicandlaboratoryresearchoncarrageenan,Dr.Tobacmanpublishedanextensivereviewof45investigationsonharmfulgastrointestinaleffectsofcarrageenaninanimalexperiments.ThearticlewaspublishedintheOctoberissueofEnvironmentalHealthPerspectives,thejournaloftheNationalInstituteforEnvironmentalHealthSciences.FindingsovertheyearsinEuropeandtheUnitedStatessuggestthatassumptionsaboutthesafetyofcarrageenanneedtobereconsideredandthatcarrageenanmayneedtobebetterregulatedbytheFoodandDrugAdministra-tion（FDA）,saidDr.Tobacman."Thereseemstobeenoughevidenceassociatingcarrageenanwithsignificantgastrointestinallesions,includingmalignanci-es,toavoidingestingit,"shesaid."Ithinkthefirstconsiderationistoinformpeopleabouttherisksthathavebeenassociatedwithcarrageenan,"sheadded."Therewasevidencebackinthe1970sthatcarrageenanhasharmfuleffects,andIthinkwe'vewaitedtoolongtoactonthatinformation."In1972theFDAdeterminedtherewassufficientevidencefromanimalexperimentstoproposelimitingthetypeofcarrageenanthatcouldbeusedinfoodproducts."Manyauthoritativesourcesthoughtthattheproposalactuallybecamearegulation.However,itdidn't,"Tobacmansaid.In1979theFDArescindedtheproposalyetatthesametimeindicatedtherewouldbeamorecomprehensiveregulationinthefuture.Butnorestrictionhassincebeenproposed,sothereisnosubstantiveregulationofcarrageenaninfood."It'simpossibletoreconstructthethinkingthatwentoninthe1970saboutregulatingcarrageenan,"shesaid."ApparentlytheFDAanticipatedestablishingamorecomprehensiveregulation,butnonehasbeenforthcoming.IfindthisdiscrepancyandthecontinuedstatusofcarrageenanasGRAS[generallyregardedassafe]verydisturbing."In1982,theInternationalAgencyforResearchonCancerfoundenoughevidenceinanimalmodelslinkingdegradedcarrageenanwithgastrointestinalcancerstostatethatitposedacarcinogenicrisktohumans.Otherresearchgroupsalsohavelisteditasaknowncarcinogenbasedonanimalstudies.Degradedcarrageenanhasamolecularweightof30,000orlower,whereasundegradedcarrageenanhasamolecularweightof100,000orhigher.Thereisevidencethatdegradedcarrageenancausesintestinalulcerationsandcancers.Inaddition,Tobacmanexplained,undegradedcarrageenan,whichhasthehighermolecularweightandisthoughtnottobeabsorbedintheintestine,mayalsobeassociatedwiththepromotionofmalignancyandinflammationinthegastrointestinaltract.Bacterialaction,stomachacid,andfoodpreparationmayleadtodegradedcarrageenanbytransformingthehighermolecularweightformofthegumintothelowermolecularweightform."AregulationliketheoneproposedbytheFDAin1972mighthelpeliminatesomeofthelowmolecularweightcomponentsbutprobablyinitselfwouldnotbesufficienttopreventallexposuretodegradedcarrageenanbecausethehigherweightformcanbetransformedintolowerweightproducts,"Tobacmansaid.Carrageenanusewaspatentedinthe1930sandcameintoincreasinglywidespreaduseintheUnitedStatesduringthesecondhalfofthe20thcentury.ItoriginallywasusedasathickenerinIrishpuddingandwasincorporatedintodifferenttypesofprocessedfoodsastheybecamemorecommonintheWesterndiet.Italsohasbeenusedincosmetics,toothpaste,androomfresheners.Tobacmansaidothergumswithsimilarthickeningpropertiescanbeusedinsteadofcarrageenan.Thesegumsincludelocustbean,guar,andxanthan.Readingtheingredientsonalabelcanrevealwhethercarrageenanispartofthefood.Butsincecarrageenancanbeasecondaryingredient,forexample,includedincondensedmilk,itmaynotalwaysbelistedbyname.Tobacmanhasstudiesunderwaytoreviewthecarcinogenicmechanismsassociatedwithcarrageenanandtoidentifypossiblelinkstobreastcancer.
