哈医大精品课程营养与食品卫生学第一章营养学基础3

脂类（Lipids）单毓娟(Dr.&AssociatedProf.)第一章营养学基础yujuan72@163.com(B703)Inthefallof1995when28-year-oldskaterSergeiGrinkov,atwo-timeOlympicgoldmedalist,collapsedanddiedofafatalheartattackwhiletraininginLakePlacid,NewYork.戈尔蒂耶娃／格林科夫一、脂类概述IntroductionofLipidsMaincontentsIntroductionofLipidLipidsinNutritionScienceClassificationoftriglyceridesω-3andω-6fattyacidsFatdigestionandabsorptionFunctionsoffatDisadvantagesoffatsNutritionalassessmentofdietaryfatDietaryreferenceintakes(DRIs)offatAnautopsyrevealedthathiscoronaryarterieswereasseverelycloggedasthoseofa70-year-oldwithestablishedheartdisease.Normalarterycontaininglittlecholesterol-richplaque.Arterythatispartiallyblockedwithplaque,whichcanleadtoaheartattack.Cholesterol-richHighfatdietHeartdisease?Lipid----Friendorfoe?Whatcausesaheartattack?Althoughsomepeoplethinkofdietaryfatassomethingtobeavoided,acertainamountoffatisabsolutelyessentialforgoodhealth.Sowhatsuggestionsdoyougivewhenpeopleeatfoodsabundantinfat?Canyoutalkaboutsomethingrelatedwithlipidorfat?Foodsrichinfats?Lipidsarefoundinallsortsoflivingthings.二、营养学上的脂类LipidsinNutritionScience什么是脂类？Lipid:Adiversegroupoforganicsubstancesthatareinsolubleinwater;lipidincludetriglycerides,phospholipids,andsterols.脂类：是由多种有机物质构成的一类物质的总称，它们一般不溶于水，脂类包括甘油三酯、磷脂和固醇。DefinitionoflipidOrganic:todescribefoodsthataregrownwithouttheuseofnon-naturalfertilizersorchemicals.Organic:Thesenutrientscontaintheelementcarbon.两种不同的含义---Organic95%triglyceridesPhospholipids(磷脂)sterols(固醇)(甘油三酯)CompositionofLipids甘油三酯的分子结构MolecularstructureoftriglyceridesCH2OCOCOCOCH2OCH2OR1R3R21Glycerol3Fattyacids(甘油)(脂肪酸)Triglyceridesisamoleculeconsistingofthreefattyacidsattachedtoathree-carbonglycerolbackbone.Mostofthefatweeat(95%)isintheformoftriglycerides,thesamewaybywhichmostofthefatinourbodyisstored.甘油三酯既是食物中脂肪的主要存在形式，也是机体内脂肪的主要贮存形式磷脂（Phospholipids）:Atypeoflipidinwhichafattyacidiscombinedwithanothercompoundthatcontainsphosphate;unlikeotherlipids,phospholipidsaresolubleinwater.GlycerolFattyacidFattyacidPhosphatePhospholipidCellmembrane甘油脂肪酸磷脂主要贮存在脑、神经和肝脏中；磷脂是构成细胞膜的主要成分；磷脂的主要功能有：提供能量；具有极性和非极性双重特性，有助于物质转运；作为乳化剂，有利于脂溶性物质的吸收、转运及代谢；转运血液中的脂类物质，防治胆固醇在血中的沉积；促进和改善神经系统功能。Atypeoflipidfoundinfoodsandthebodythathasaringstructure;thesemultiple-ringstructureisquitedifferentfromthatoftriglycerides.Sterolringstructure固醇Sterols环状结构SterolsSterolsarefoundinbothplantandanimalfoodsandareproducedinthebody.Plantscontainsomesterols,buttheyarenotverywellabsorbedandappeartoblocktheabsorptionofdietarycholesterol.CholesterolCholesterolisonlyfoundinthefattypartofanimalproductssuchasbutter,eggs,wholemilk,meatsandpoultry（胆固醇只存在于动物性食品中）.Wedon’tneedtoconsumecholesterolinourdietbecauseourbodycontinuallysynthesizesit,mostlyintheliverandintestines（机体能够合成胆固醇）.Toomuchconsumptionisharmful。（胆固醇摄入过多对人体有害）Cholesterol（胆固醇）Cholesterolispartofeverycellmembrane,whereitworksinconjunctionwithfattyacidstohelpmaintaincellmembraneintegrity（保持细胞膜的完整性）.Cholesterolisparticularlyplentifulintheneuralcellsthatmakeupourbrain,spinalcord,andnerves（神经细胞中含量丰富，参与脑、脊髓和神经等的形成）.CholesterolistheessentialforlifeThebodyalsousescholesteroltosynthesizeseveralimportantsterolcompoundsincludingsexhormones(estrogen,androgen,andprogesterone),adrenalhormones,andvitaminD（是合成多种物质的原料：性激素(雌激素、雄激素和黄体激素），肾上腺激素和维生素D.Phytosterols(植物固醇，也称植物甾醇）arefoundinplantfoodssuchascererols,soybeans….Andrecentstudiesindicatedthattheyhavemultipleandbeneficialfunctionsforhumanhealth.Phytosterols-goodfutureAnti-inflammation,regulatingbloodlipid,bloodsugar,anti-cancer（抗炎症、调节血脂、血糖、抗癌等作用）Tounderstandwhysomeonewantmore/lessofsomefatsthanothers……weneedtoknowmoreabouttheirpropertiesandhowtheyworkinourbody.分类基础Basisofclassification碳链长度Chainlength碳链饱和度Saturationlevel空间结构Spatialshape三、甘油三酯的分类ClassificationofTriglyceridesClassificationbychainlengthShort-chaintriglycerides(SCT)Long-chaintriglycerides(LCT)<6Carbons≥12CarbonsMedium-chaintriglycerides(MCT)8-12Carbons中链脂肪长链脂肪important短链脂肪Whatinformationcanwegetbasedonthisclassification？Fattyacidchainlengthisimportantbecauseitdeterminesthemethodsoffatdigestionandabsorptionandaffectshowfatsfunctionwithinthebody.Forexample,short-andmedium-chainfattyacidsaredigestedandtransportedmorequicklythanlong-chainfattyacids.食物中主要是以中链和长链脂肪为主。Foods:椰子油(coconutoil)和棕榈油(palmoil)Advantages:NewadvanceddevelopmentsofMCT123消化快(Fastdigestion)吸收快(Fastabsorption)易氧化分解(Easyoxygenolysis)Application:减肥和提高耐力(Controlweight,Improveendurance)按饱和度分类Classificationbysaturationlevel饱和脂肪酸Saturatedfattyacid多不饱和脂肪酸PolyunsaturatedfattyacidNodoublebondMorethanonedoublebond单不饱和脂肪酸MonounsaturatedfattyacidOnedoublebondcoconutoil(椰子油)butterCream(奶酪)wholemilkbeefoliveoil(橄榄油)Peanutoil(花生油)oliveoilcottonseedoilcornoil(玉米油)saffloweroils(红花油)Saturatedfattyacidsaresaturatedwithhydrogen,meaningtheyhavenocarbonsbondedtogetherwithadoublebond.（无双键）Monounsaturatedfattyacidscontaintwocarbonsboundbyonedoublebond.（1个双键）Polyunsaturatedfattyacidhavemorethanonedoublebondlinkingcarbonatoms.（≥2个双键）DefinitionHowtofeelthisdifferencebetweensaturatedandunsaturated？Long-chainsaturatedfattyacidsstackwelltogethertomakesolidformsatroomtemperature.Mono-andpoly-unsaturatedfattyacidsdonotstackwelltogetherbecausetheyarebent.Thesefattyacidareliquidatroomtemperature.DifferencesbetweensaturatedandunsaturatedfattyacidsTypesoffattyacidinourfoodsFoodscanbeidentifiedbyanimal-andplant-foods.Animalfatsprovideapproximately40to60%oftheirenergyfromsaturatedfatsWhileplantfatsprovide80to90%oftheirenergyfrommono-andpoly-unsaturatedfats.Food%oftotalkcalfromfatButter100Milk,Whole(3.3%)49Milk,skim(non-fat)5Beef,ground54Turkey,boneless26Salmon33Egg,large62Oliveoil100Coconutoil100Saffloweroil100MajorsourcesofDietaryFatPurefoodsprovidingenergy按空间构型分类Classificationbyspatialshape顺式脂肪酸Cis-fattyacid反式脂肪酸Trans-fattyacid氢原子在双键的一侧氢原子在双键的两侧Classifiedbyshape—saturatedfatMoleculesofsaturatedfatarelikestraighttoothpicks:theyhavenodoublecarbonbondsandalwaysformstraight,rigidchains.Astheyhavenokinks,thesechainscanpacktogethertightly.Thatiswhysaturatedfats,suchasthefatinmeats,aresolidatroomtemperature.Incontrast,eachdoublecarbonbondofunsaturatedfatsgivesthemakinkalongtheirlength.Thismeansthattheyareunabletopacktogether.Basedonthis,unsaturatedfatscanoccurineitheracisoratransshape.Cis—thingsarelocatedonthesamesideorneareachother;Trans—meansacrossoranopposite.Classifiedbyshape—unsaturatedfatAcis-fattyacidhasbothhydrogenatomslocatedonthesamesideofthedoublebond.（氢原子在双键的一侧）Transfattyacidhasthehydrogenatomsattachedonoppositesidesofthedoublecarbonbond.（氢原子在双键的两侧）自然界中存在的脂肪酸主要为Cis-脂肪酸；食物中也是如此。Dotheybothexistedinnatureandfoods？反式脂肪酸与人体健康不饱和脂肪酸的不饱和键能与氢结合变成饱和键，随着饱和程度的增加，油类可由液态变为固态，这一过程称为氢化。在氢化过程中，可能会产生反式脂肪酸。氢化的作用：提高脂肪的抗氧化作用；改变食物的结构。反式脂肪酸与人体健康反式脂肪酸不具有必需脂肪酸的生物活性和对脂蛋白的作用；流行病资料也显示膳食反式脂肪酸与心脏病之间存在某些联系；反式脂肪酸的主要食物来源：人造奶油、蛋糕、饼干、油炸食品、乳酪产品、花生酱等食品。近日，全球最大的快餐集团麦当劳公开承认，在每份麦当劳薯条中，反式脂肪酸含量从过去的6克增加到了8克。在每份麦当劳炸薯条中，不利于身体健康的反式脂肪酸含量比过去增加了1/3。反式脂肪酸与人体健康In2003theU.S.FDAruledthattransfattyacids,ortransfats,mustbelistedasaseparatelineitemonNutritionFactslabelsforconventionalfoodsandsomedietarysupplements.尽量避免购买食物标签中标有：植物氢化油、人造黄（奶）油、人造植物黄（奶）油、人造脂肪、氢化油、起酥油等字样的食物。每周应食用两次鱼，以利于ω-3脂肪酸的摄入，从而减少其危害。如何减少反式脂肪酸的危害？ω-3脂肪酸四、ω-3和ω-6脂肪酸CCCCCCCHHHHHHHHHHHHHHCHHHCOOHω-3脂肪酸DHA（22：6）EPA（20：5）α-亚麻酸ω-6脂肪酸花生四烯酸亚油酸必需脂肪酸(essentialfattyacid，EFA)：是指人体不可缺少而自身又不能合成，必须通过食物供给的脂肪酸。Definition:EFAareindispensableandmustbeconsumedinthedietbecausetheycannotbemadebyourbodies.亚油酸(Linoleicacid,LA)和α-亚麻酸(α-linolenicacid，ALA)是人体必需的两种脂肪酸。必需脂肪酸EssentialFattyAcid必需脂肪酸的功能FunctionofEFA是磷脂的重要组成成分与精子形成有关是合成前列腺素的前体有利于组织修复与胆固醇的代谢有关缺乏生长迟缓生殖障碍皮肤损伤(皮疹等)其他（心血管疾病等）ω-3脂肪酸EPAandDHAarederivedfromALA.Alpha-linolenicacid(ALA)降低甘油三酯的作用阻碍甘油三酯掺入到肝的VLDL颗粒中，分泌到血液循环中的甘油三酯减少；降血压作用。抗炎症作用抗癌作用脑和视网膜发育上的重要物质ω-3脂肪酸的生物学功能ω-6脂肪酸亚油酸(LA)花生四烯酸（AA)降低胆固醇的作用具有促进生长、发育及妊娠的作用是一些特殊脂类（如磷脂）的组成成分，维持组织膜结构的完整性和最佳的不饱和水平。ω-6脂肪酸的生物学功能ω-3和ω-6脂肪酸的食物来源ω-3脂肪酸:主要存在于鱼油(Fishoil)和鱼类产品(fishproducts)。ω-6脂肪酸:主要存在于植物油中,如葵花油(sunfloweroil)、红花油(safflower)、玉米油(cornoil)、豆油(soyoil)和花生油(peanutoil)。ω-3和ω-6脂肪酸的比例人类最早食用的基本都是野生植物和散养动物，食物中的ω-3和ω-6有着严格比例,基本保持平衡。工业化时代，人类大量食用加工和养殖产品，使得体内所含ω-6越来越多，比例严重失调。据估计，目前美国等发达国家里，人体内的ω-6和ω-3比例可能达到30：1，甚至达50：1。北京儿童医院与瑞典皇家医院在河北石家庄地区的调查，该地区妇女ω-6和ω-3的比例在26：1ω-3脂肪酸有益的生物学功能过多ω-6脂肪酸有害的生物学功能Becausefatsarenotsolubleinwater,theycannotenterourbloodstreameasilyfromthedigestivetract.Thus,fatsmustbedigested,absorbed,andtransportedwithinthebodydifferentlyfromotherwater-solublenutrients.五、脂肪的消化、吸收FatdigestionandabsorptionMouth:Salivaryglandsinthemouthproduceanenzyme,linguallipase,thatdigestssometriglycerides.Salivaryenzymeshavealimitedroleinthebreakdownoffats.Fatdigestion--inmouthPartiallydigestMoistureandchewFatdigestion-inStomachFatarrivesintactatthestomachwhereitismixedandbrokenintodroplets.Gastriclipasedigestssometriglycerides.Becausetheyarenotsolubleinwater,thesefatdropletstypicallyfloatontopofthewaterydigestivejuicesinthestomachuntiltheyarepassedintothesmallintestine.Asfatentersthesmallintestinefromthestomach,thegallbladdercontractsandreleasesbile,whichactingmuchlikesoap,breakingdownthefatintosmallerandsmallerdroplets.Atthesametime,lipid-digestingenzymesproducedinthepancreastravelintothesmallintestine.TwoorgansassistingfatdigestionDoyourememberthestructureoftriglycerides？Oncebilehasbrokenthefatintosmalldroplets,thesepancreaticenzymestakeover,breakingthefattyacidsawayfromtheirglycerolbackbones(Realbreakdown).Eachtriglyceridemoleculeisbrokendownintotwofreefattyacidsandonemonoglyceride(onefattyacidwasleft).Inthiscase,aglycerolmoleculewithonefattyacidstillattached.Fatdigestion—inthesmallintestineTheprocessoffatdigestionSalivaryglandsproduceenzymetodigestafewfats.Fatismixedandbrokenintodroplets.Gastriclipasedigestsomefats.GallbladderreleasesbileintothesmallintestineBilebreaksfatsintosmallerdroplets;Lipid-digestingenzymebreakfatsintomonoglyceridesand2fattyacids.Lipid-digestingenzymesenteredintosmallintestineThemajorityoffatabsorptionoccursinthemucosalliningofthesmallintestinewiththehelpofamicelle.Amicelleisaspherical(round)compoundthatcantrapthefreefattyacidsandthemonoglyceridesandtransportthemtothemucosalcellsforabsorption.Fatabsorption-primarilyinthesmallintestineBecausefatsdonotmixwithwater,mostfatscannotbetransportedfreelyinthebloodstream.Howdoestheabsorbedfatgetintothebloodstream?Tosolvethisproblem,thefattyacidsarereformulatedbackintotriglyceridesandthenpackagedintolipoproteinbeforebeingreleasedintothebloodstream.Whylipoproteincanbeabsorbedintothebloodstream?StructureofalipoproteinLipoproteinisasphericalcompoundinwhichthefatclustersinthecenterandphospholipidsandproteinsformtheoutsideofthesphere.Chylomicron（乳糜微粒）isaspecificlipoproteinproducedinthemucosalcelloftheintestinetotransportdietaryfatoutoftheintestinetractintotheblood.Chylomicronisafatcarrierinthesmallintestine.Haveyouremembered?Imentionedthattheshort-andmedium-chainfattyacidsaredigestedmorequicklythanlong-chainfattyacids?Why?Whenshortandmedium-chainfattyacidsaredigestedandtransportedtothemucosalcellofthesmallintestine,theydonothavetobereformedintotriglyceridesandincorporatedintochylomicrons.Instead,theycantravelinthebloodstreamboundtoeitheratransportproteinoraphospholipid.ItshouldbementionedthattwofollowinglipoproteinservedastransporterindifferentwayLowdensitylipoprotein（LDL）：lesstriglycerides，morecholesterolsHighdensitylipoprotein（HDL):carrycholesterolbacktoliverforbreakingdownTransportoffatinthebodyObviously…….Howdoesourbodydealwithfatabsorbed？Therearethreeprimaryfatesofthefatabsorbed.Itcanimmediatelybetakenupandusedasasourceofenergyforthecells.Itcanbeusedtomakelipid-containingcompounds(someexamples?)inthebody.Itcanbestoredinthemuscleoradiposetissueasatriglycerideforlateruse.六、脂肪的功能FunctionsofFat1提供能量和贮存能量（Provideandstoreenergy）Fatprovide9kilocalories(kcals)pergram.Fatisaprimarysourceofenergy.特点：不能给脑、神经细胞和红细胞提供能量2保持体温正常（Maintainbodytemperature）Howmuchenergyforprotein?34维持细胞功能及保护机体（Helpmaintaincellfunctionandprovideprotectiontothebody）5提供必需脂肪酸（Provideessentialfattyacid）内分泌作用（Endocrinesecretion）瘦素FunctionsofFat更有效地利用碳水化合物和节约蛋白质作用（Utilizemoreeffectivelycarbohydratesandproteinsparingaction）转运脂溶性维生素(transportoffat-solublevitamins)改善食物的感官性状(色香味型)(Contributetotheflavorandtextureoffoods)增加饱腹感(Helpustofeelsatisfied)67FunctionsofFat89Summary--FunctionsofFatWouldyousummarysomekeywordsaboutfunctionsoffat?EnergyBodytemperatureFattyacidFat-solublevitaminsCellfunction/ProtectionSecretionFlavorandtextureSatietyLikemanythings,alittlecanbegood,butalotcanbeharmful.Toomuchfat,regardlessofthetype,canbedamagingtoourbodies.七、脂肪的不利影响Disadvantagesoffats1摄入过多脂肪将导致疾病(Eatingtoomuchofcertainfatscanleadtodisease)2脂肪限制了食物的保质期(Fatslimittheshelflifeoffoods)DietshighinSFAcardiovasculardiseaseDietstoohighinUFAStrokeDietstoohighinfatWeightgain/Obesity八、脂肪的营养学评价脂肪的消化率（Digestiverate)必需脂肪酸的含量(QuantityofEFA)所含各种脂肪酸的比例(Ratioamongthevariousfattyacids)脂溶性维生素的含量(Quantitiesoffat-solublevitamins)EPA和DHA的含量(QuantitiesofDHAandEPA)适宜的数量和类型Rightamount&Righttypes九、脂肪的膳食参考摄入量DietaryreferenceintakesoffatadvantageDis-Fats中国营养学会(ChineseNutritionSociety):成人脂肪摄入量应占总能量摄入20%～30%；一般认为EFA的摄入量应不少于总能量的3%。建议ω-3与ω-6脂肪酸摄入比为1:4～6较适宜。中国居民膳食脂肪适宜摄入量（AIs）（脂肪供能占总能量的百分比）年龄/岁脂肪%SFAMUFAPUFAω-6/ω-3胆固醇（mg）0～45～504:10.5～35～404:12～30～354～6:17～25～304～6:114～25～30<108104～6:1成人20～30<1010104～6:1<300老年20～306～8108～104:1<300人类膳食脂肪主要来源于动物的脂肪组织和肉类以及植物的种子。动物脂肪相对含饱和脂肪酸和单不饱和脂肪酸多，而多不饱和脂肪酸含量较少。植物油主要含不饱和脂肪酸。亚油酸（ω-6）普遍存在于植物油中，亚麻酸（ω-3）在豆油和紫苏籽油中较多，深海鱼贝类食物相对含EPA和DHA较多。脂肪的食物来源FoodItemOmega-3Fattyacid(g/serving)Salmonoil(fishoil)4.39Herringoil（青鱼油）1.52Shrimp（河虾）1.11Trout（鳟鱼）1.05Walnuts（核桃）0.51Salmon0.5Crab（螃蟹）0.34Omega-3FattyacidcontentofselectedfoodsSummary脂肪的分类必需脂肪酸/ω-3脂肪酸脂肪的功能脂肪推荐的膳食供给量Thanksverymuch&Hopeyouenjoyit!