脂類

（Lipids）單毓娟

(Dr.&AssociatedProf.)第一章營(yíng)養(yǎng)學(xué)基礎(chǔ)yujuan72@163.com(B703)Inthefallof1995when28-year-oldskaterSergeiGrinkov,atwo-timeOlympicgoldmedalist,collapsedanddiedofafatalheartattackwhiletraininginLakePlacid,NewYork.戈?duì)柕僖蓿窳挚品蛞弧⒅惛攀鯥ntroductionofLipidsMaincontentsIntroductionofLipidLipidsinNutritionScienceClassificationoftriglyceridesω-3andω-6fattyacidsFatdigestionandabsorptionFunctionsoffatDisadvantagesoffatsNutritionalassessmentofdietaryfatDietaryreferenceintakes(DRIs)offatAnautopsyrevealedthathis

coronaryarteries

wereasseverely

clogged

asthoseofa

70-year-old

withestablishedheartdisease.Normalarterycontaininglittlecholesterol-richplaque.Arterythatispartiallyblockedwithplaque,whichcanleadtoaheartattack.Cholesterol-rich4HighfatdietHeartdisease?Lipid----Friendorfoe?Whatcausesaheartattack?Althoughsomepeoplethinkofdietaryfatassomethingtobeavoided,acertainamountoffatisabsolutelyessentialforgoodhealth.Sowhatsuggestionsdoyougivewhenpeopleeatfoodsabundantinfat?

Canyoutalkaboutsomethingrelatedwithlipidorfat?Foodsrichinfats?Lipidsarefoundinallsortsoflivingthings.二、營(yíng)養(yǎng)學(xué)上的脂類

LipidsinNutritionScience什么是脂類？Lipid:Adiversegroupoforganicsubstancesthatareinsolubleinwater;lipidincludetriglycerides,phospholipids,andsterols.脂類：是由多種有機(jī)物質(zhì)構(gòu)成的一類物質(zhì)的總稱，它們一般不溶于水，脂類包括甘油三酯、磷脂和固醇。Definitionoflipid

Organic:todescribefoodsthataregrownwithouttheuseofnon-naturalfertilizersorchemicals.

Organic:Thesenutrientscontaintheelementcarbon.

兩種不同的含義---Organic95%triglycerides

Phospholipids

(磷脂)

sterols(固醇)

(甘油三酯)CompositionofLipids甘油三酯的分子結(jié)構(gòu)

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，也是機(jī)體內(nèi)脂肪的主要貯存形式磷脂（Phospholipids）:Atypeoflipidinwhichafattyacidiscombinedwithanothercompoundthatcontainsphosphate;unlikeotherlipids,phospholipidsaresolubleinwater.GlycerolFattyacidFattyacidPhosphatePhospholipidCellmembrane甘油脂肪酸磷脂主要貯存在腦、神經(jīng)和肝臟中；磷脂是構(gòu)成細(xì)胞膜的主要成分；磷脂的主要功能有：提供能量；具有極性和非極性雙重特性，有助于物質(zhì)轉(zhuǎn)運(yùn)；作為乳化劑，有利于脂溶性物質(zhì)的吸收、轉(zhuǎn)運(yùn)及代謝；轉(zhuǎn)運(yùn)血液中的脂類物質(zhì)，防治膽固醇在血中的沉積；促進(jìn)和改善神經(jīng)系統(tǒng)功能。Atypeoflipidfoundinfoodsandthebodythathasaringstructure;thesemultiple-ringstructureisquitedifferentfromthatoftriglycerides.Sterolringstructure固醇Sterols環(huán)狀結(jié)構(gòu)SterolsSterolsarefoundinbothplantandanimal

foodsandareproducedinthebody.Plantscontainsomesterols,buttheyarenotverywellabsorbedandappeartoblocktheabsorption

of

dietarycholesterol.CholesterolCholesterolisonlyfoundinthefattypartofanimalproductssuchasbutter,eggs,wholemilk,meatsandpoultry（膽固醇只存在于動(dòng)物性食品中）.Wedon’tneedtoconsumecholesterolinourdietbecauseourbodycontinuallysynthesizesit,mostlyintheliverandintestines（機(jī)體能夠合成膽固醇）.Toomuchconsumptionisharmful。（膽固醇攝入過多對(duì)人體有害）Cholesterol（膽固醇）

Cholesterolispartofeverycellmembrane,whereitworksinconjunctionwithfattyacidstohelpmaintaincellmembraneintegrity

（保持細(xì)胞膜的完整性）.Cholesterolisparticularlyplentifulintheneuralcellsthatmakeupourbrain,spinalcord,andnerves（神經(jīng)細(xì)胞中含量豐富，參與腦、脊髓和神經(jīng)等的形成）.CholesterolistheessentialforlifeThebodyalsousescholesteroltosynthesizeseveralimportantsterolcompoundsincludingsexhormones(estrogen,androgen,andprogesterone),adrenalhormones,andvitaminD（是合成多種物質(zhì)的原料：性激素(雌激素、雄激素和黃體激素），腎上腺激素和維生素D.Phytosterols

(植物固醇，也稱植物甾醇）

arefoundinplantfoodssuchascererols,soybeans….Andrecentstudiesindicatedthattheyhavemultipleandbeneficialfunctionsforhumanhealth.Phytosterols-goodfutureAnti-inflammation,regulatingbloodlipid,bloodsugar,anti-cancer（抗炎癥、調(diào)節(jié)血脂、血糖、抗癌等作用）Tounderstandwhysomeonewantmore/lessofsomefatsthanothers……weneedtoknowmoreabouttheirpropertiesandhow

they

workinourbody.分類基礎(chǔ)Basisofclassification碳鏈長(zhǎng)度Chainlength

碳鏈飽和度Saturationlevel空間結(jié)構(gòu)Spatialshape三、甘油三酯的分類ClassificationofTriglyceridesClassificationbychainlengthShort-chaintriglycerides(SCT)

Long-chaintriglycerides(LCT)

<6Carbons≥12CarbonsMedium-chaintriglycerides(MCT)

8-12Carbons中鏈脂肪長(zhǎng)鏈脂肪important短鏈脂肪W(wǎng)hatinformationcanwegetbasedonthisclassification？Fattyacidchainlengthisimportantbecauseitdeterminesthemethodsoffatdigestionandabsorptionandaffectshowfatsfunctionwithinthebody.Forexample,short-andmedium-chainfattyacidsaredigestedandtransportedmorequicklythanlong-chainfattyacids.食物中主要是以中鏈和長(zhǎng)鏈脂肪為主。Foods:椰子油(coconutoil)和棕櫚油(palmoil)Advantages:NewadvanceddevelopmentsofMCT123消化快

(Fastdigestion)吸收快

(Fastabsorption)易氧化分解

(Easyoxygenolysis)Application:

減肥和提高耐力(Controlweight,Improveendurance)按飽和度分類Classificationbysaturationlevel飽和脂肪酸Saturatedfattyacid

多不飽和脂肪酸PolyunsaturatedfattyacidNodoublebondMorethanonedoublebond單不飽和脂肪酸Monounsaturatedfattyacid

Onedoublebondcoconutoil(椰子油)butterCream(奶酪)wholemilkbeefoliveoil(橄欖油)Peanutoil(花生油)oliveoilcottonseedoilcornoil(玉米油)saffloweroils(紅花油)Saturatedfattyacidsaresaturatedwithhydrogen,meaningtheyhavenocarbonsbondedtogetherwithadoublebond.（無(wú)雙鍵）Monounsaturatedfattyacidscontaintwocarbonsboundbyonedoublebond.（1個(gè)雙鍵）Polyunsaturatedfattyacidhavemorethanonedoublebondlinkingcarbonatoms.（≥2個(gè)雙鍵）DefinitionHowtofeelthisdifferencebetweensaturatedandunsaturated？Long-chainsaturatedfattyacidsstackwelltogethertomakesolidformsatroomtemperature.Mono-andpoly-unsaturatedfattyacidsdonotstackwelltogetherbecausetheyarebent.Thesefattyacidareliquidatroomtemperature.Differences

betweensaturatedandunsaturatedfattyacidsTypesoffattyacidinourfoodsFoodscanbeidentifiedbyanimal-andplant-foods.Animalfatsprovideapproximately40to60%oftheirenergyfromsaturatedfatsWhileplant

fatsprovide80to90%oftheirenergyfrommono-andpoly-unsaturatedfats.Food%oftotalkcalfromfatButter100Milk,Whole(3.3%)49Milk,skim(non-fat)5Beef,ground54Turkey,boneless26Salmon33Egg,large62Oliveoil100Coconutoil100Saffloweroil100MajorsourcesofDietaryFatPurefoodsprovidingenergy按空間構(gòu)型分類Classificationbyspatialshape順式脂肪酸Cis-fattyacid反式脂肪酸Trans-fattyacid氫原子在雙鍵的一側(cè)氫原子在雙鍵的兩側(cè)Classifiedbyshape—saturatedfatMoleculesofsaturatedfatarelikestraighttoothpicks:theyhavenodoublecarbonbondsandalwaysformstraight,rigidchains.Astheyhavenokinks,thesechainscanpacktogethertightly.Thatiswhysaturatedfats,suchasthefatinmeats,aresolidatroomtemperature.Incontrast,eachdoublecarbonbondofunsaturatedfatsgivesthemakinkalongtheirlength.Thismeansthattheyareunabletopacktogether.Basedonthis,unsaturatedfatscanoccurineitheracis

oratransshape.

Cis—thingsarelocatedonthesamesideorneareachother;

Trans—meansacrossoranopposite.Classifiedbyshape—unsaturatedfatAcis-fattyacidhasbothhydrogenatomslocatedonthesamesideofthedoublebond.（氫原子在雙鍵的一側(cè)）Transfattyacidhasthehydrogenatomsattachedonoppositesidesofthedoublecarbonbond.（氫原子在雙鍵的兩側(cè)）自然界中存在的脂肪酸主要為Cis-脂肪酸；食物中也是如此。Dotheybothexistedinnatureandfoods？反式脂肪酸與人體健康不飽和脂肪酸的不飽和鍵能與氫結(jié)合變成飽和鍵，隨著飽和程度的增加，油類可由液態(tài)變?yōu)楣虘B(tài)，這一過程稱為氫化。在氫化過程中，可能會(huì)產(chǎn)生反式脂肪酸。

氫化的作用：提高脂肪的抗氧化作用；改變食物的結(jié)構(gòu)。反式脂肪酸與人體健康

反式脂肪酸不具有必需脂肪酸的生物活性和對(duì)脂蛋白的作用；

流行病資料也顯示膳食反式脂肪酸與心臟病之間存在某些聯(lián)系；

反式脂肪酸的主要食物來(lái)源：人造奶油、蛋糕、餅干、油炸食品、乳酪產(chǎn)品、花生醬等食品。

近日，全球最大的快餐集團(tuán)麥當(dāng)勞公開承認(rèn)，在每份麥當(dāng)勞薯?xiàng)l中，反式脂肪酸含量從過去的6克增加到了8克。在每份麥當(dāng)勞炸薯?xiàng)l中，不利于身體健康的反式脂肪酸含量比過去增加了1/3。

反式脂肪酸與人體健康In2003theU.S.FDAruledthat

trans

fattyacids,

or

trans

fats,mustbelistedasa

separateline

itemonNutritionFactslabelsforconventionalfoodsandsomedietarysupplements.

盡量避免購(gòu)買食物標(biāo)簽中標(biāo)有：植物氫化油、人造黃（奶）油、人造植物黃（奶）油、人造脂肪、氫化油、起酥油等字樣的食物。每周應(yīng)食用兩次魚，以利于ω-3脂肪酸的攝入，從而減少其危害。如何減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-亞麻酸ω-6脂肪酸花生四烯酸亞油酸必需脂肪酸(essentialfattyacid，EFA)：是指人體不可缺少而自身又不能合成，必須通過食物供給的脂肪酸。Definition:EFAareindispensableandmustbeconsumedinthedietbecausetheycannotbemadebyourbodies.亞油酸(Linoleicacid,LA)和α-亞麻酸(α-linolenicacid，ALA)是人體必需的兩種脂肪酸。必需脂肪酸EssentialFattyAcid必需脂肪酸的功能

FunctionofEFA是磷脂的重要組成成分與精子形成有關(guān)是合成前列腺素的前體有利于組織修復(fù)與膽固醇的代謝有關(guān)缺乏生長(zhǎng)遲緩生殖障礙皮膚損傷(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

阻礙甘油三酯摻入到肝的VLDL顆粒中，分泌到血液循環(huán)中的甘油三酯減少；降血壓作用?？寡装Y作用抗癌作用腦和視網(wǎng)膜發(fā)育上的重要物質(zhì)ω-3脂肪酸的生物學(xué)功能ω-6脂肪酸亞油酸(LA)花生四烯酸（AA)降低膽固醇的作用具有促進(jìn)生長(zhǎng)、發(fā)育及妊娠的作用是一些特殊脂類（如磷脂）的組成成分，維持組織膜結(jié)構(gòu)的完整性和最佳的不飽和水平。ω-6脂肪酸的生物學(xué)功能ω-3和ω-6脂肪酸的食物來(lái)源

ω-3脂肪酸:主要存在于魚油(Fishoil)

和魚類產(chǎn)品(fishproducts)。ω-6脂肪酸:主要存在于植物油中,如葵花油(sunfloweroil)

、紅花油(safflower)、玉米油(cornoil)、豆油(soyoil)和花生油(peanutoil)。ω-3和ω-6脂肪酸的比例人類最早食用的基本都是野生植物和散養(yǎng)動(dòng)物，食物中的ω-3和ω-6有著嚴(yán)格比例,基本保持平衡。工業(yè)化時(shí)代，人類大量食用加工和養(yǎng)殖產(chǎn)品，使得體內(nèi)所含ω-6越來(lái)越多，比例嚴(yán)重失調(diào)。據(jù)估計(jì)，目前美國(guó)等發(fā)達(dá)國(guó)家里，人體內(nèi)的ω-6和ω-3比例可能達(dá)到30：1，甚至達(dá)50：1。北京兒童醫(yī)院與瑞典皇家醫(yī)院在河北石家莊地區(qū)的調(diào)查，該地區(qū)婦女ω-6和ω-3的比例在26：1ω-3脂肪酸有益的生物學(xué)功能過多ω-6脂肪酸有害的生物學(xué)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,breakingthefatty

acidsawayfromtheirglycerolbackbones

(Realbreakdown).Eachtriglyceridemoleculeisbrokendownintotwofreefattyacidsandonemonoglyceride

(onefattyacidwasleft).Inthiscase,aglycerolmoleculewithonefattyacidstillattached.Fatdigestion—