营养与食品卫生学

(2)Classification

proteinlipids

macronutrientscarbohydrate(dietaryfiber)nutrientswatervitamin

micronutrientsmacroelementsminerals

核酸nucleicacid?microelements

当前1页，总共98页。3.合理营养（RationalDiet）通过合理的膳食和科学地烹调加工，能向机体提供足够数量的热能和各种营养素，并保证各种营养素之间的数量平衡，以满足人体的正常生理需要，并保持人体健康。Nutrientsintakesmeettherequirementsofthebody5.膳食营养供给量(RecommendedDietaryAllowance，RDA)

是对各种人群提出的保证人体营养需要的膳食中应含有的热能和营养素的适宜量。Theaveragedailyamountofanutrientconsideredadequatetomeettheknownnutrientneedsofpracticallyallhealthypeople;agoalfordietaryintakebyindividuals.4.营养生理需要量（NutritionalRequirement）

是指能保持人体健康，达到应有发育水平和能充分有效地完成各项体力和脑力活动所需要的热能和各种营养素的必需量。Thelowestcontinuingintakeofenergyandnutrientsthatmaintainthespecifiedcriterionofadequacy(thatwillmaintainthespecificbiochemicalandphysiologicalfunctionsofthebody).当前2页，总共98页。Chapter1BasicNutrition

第一章营养学基础

含量----16%——19%.更新：动态平衡，不断更新，每天约3%，肠和骨髓最快。Section1Protein(蛋白质)一、蛋白质（一）人体中蛋白质：（二）功能：

1.机体构成成分

2.构成各种生理活性物质和重要的生理功能

3.提供热能

当前3页，总共98页。（三）Thefirststructure

蛋白质(protein)

氨基酸（Aminoacid,AA）

非必需AA(nonessential-)：9种

半必需AA（条件必需AA）：2种

（semi-,orconditionally-）必需AA（essentional-）：9种

多肽（poly-）10AA以上寡肽（oligo-）4—10AA以下

3肽（tri-）3AA2肽（di-）2AA

肽(peptide)

当前4页，总共98页。

二、氨基酸和必需AA(essentialaminoacid,EAA)

1.种类：20种

(1)必需AA（EAA）(2)非必需氨基酸（NEAA）

(3)半必需氨基酸(semi-EAAorconditionalEAA)半胱酸（Cysteine）——蛋氨酸（Methionine）酪氨酸（Tyrosine）——苯丙氨酸（Phenylalanine）2.必需氨基酸：人体不能合成或合成速度不能满足机体需要，必需从食物中直接获得的AA。Aminoacidsthatthebodycannotsynthesizeinamountsufficienttomeetphysiologicalneedsandhastoobtainthemfromfoods.

当前5页，总共98页。氨基酸英文氨基酸英文必需氨基酸非必需氨基酸异亮氨酸Isoleucine(Ile)丙氨酸Alanine(Ala)亮氨酸Leucine(Leu)精氨酸Arginine(Arg)赖氨酸Lysine(Lys)天门冬氨酸Asparticacid(ASP)蛋氨酸Methionine(Met)谷氨酸Asparagine(Asn)苯丙氨酸Phenylalanine(Phe)谷氨酰胺Glutamicacid(Glu)苏氨酸Threonine(Thr)甘氨酸Glycine(Gly)色氨酸Tryptophan(Trp)脯氨酸Proline(Pro)缬氨酸Valine(Val)丝氨酸Serine(Ser)组氨酸*Histidine(His)天冬酰胺Asparagine(ASN)条件必需氨基酸半胱氨酸Cysteine(Cys)酪氨酸Tyrosine(Tyr)表1-1人体内的氨基酸*组氨酸为婴儿必需氨基酸，成人需要量可能较少。

摘自ModernNutritioninHealthandDisease,第9版,第14页,1999。当前6页，总共98页。(三)氨基酸模式(AAPattern)和限制氨基酸(limitingAA)1.氨基酸模式(AAPattern)：

蛋白质中各种必需氨基酸的构成比例。当前7页，总共98页。氨基酸人体全鸡蛋牛奶牛肉大豆面粉大米异亮氨酸4.0亮氨酸7.0赖氨酸2.3蛋氨酸+半胱氨酸2.3苯丙氨酸+酪氨酸6.0苏氨酸4.0缬氨酸5.0色氨酸1.01.01.01.01.01.01.0表1-2几种食物和人体蛋白质氨基酸模式数据摘自营养与食品卫生学，第3版，第9页。当前8页，总共98页。2.限制氨基酸

（limitingaminoacid）：与人体蛋白质模式比较，食物蛋白质中含量相对较低的必需AA。Theessentialaminoacidfoundintheshortestsupplyrelativetotheamountneededforproteinsynthesisinthebody.FourAAaremostlikelytobelimiting:Lysine，Methionine，Threonine，Tryptophan.当前9页，总共98页。3.参考蛋白、完全蛋白和蛋白质的互补作用参考蛋白用于测定食物蛋白质质量的标准蛋白。

ReferenceProtein:Astandardagainstwhichtomeasurethequalityofotherproteins.完全蛋白必需氨基酸模式与人体蛋白质相对一致，能满足机体蛋白质合成需要的食物蛋白质。

CompleteProtein:Adietaryproteincontainingalltheessentialaminoacidsinrelativelythesameamountsthathumanbeingrequired.(includinganimalproteinandsoyprotein)

Incompleteprotein蛋白质互补将两种或两种以上的食物蛋白质混合事用，使不同食物中必需氨基酸以多补少，从而提高膳食蛋白质的营养价值。

ComplementaryProtein:Twoormoreproteinswhoseaminoacidsassortmentscomplementeachotherinsuchawaythattheessentialaminoacidsmissingfromonearesuppliedbytheother.当前10页，总共98页。几种食物混合后蛋白质的生物价食物BV混合比例小米-6737---31大米57324046大豆6416208豌豆4815------玉米60---40---牛肉（干）76------15混合后生物价---747389当前11页，总共98页。三、蛋白质的消化、吸收和代谢

（一）消化和吸收

（digestionandabsorption）

当前12页，总共98页。GastricJuice

:1.Acid–denaturation2.Pepsin--nothighlyspecificbutpreferentialattackonbondsadjacenttoaromaticAAandleucine.3.Carboxypeptidase--terminalaromaticorbranch-chained;arginineorlysine;neutral-

dietary

Protein

Panc-elastase(弹性蛋白酶)--arometicAAreatic

trypsin(胰蛋白酶)--NH2-

juice

chymotrypsine(糜蛋白酶)--lysine,arginine

dipeptide,tripeptideandfreeAAabsorbedthroughthemucosalcellsofsmallintestinepeptidase

throughthreeactivefreeAAtransportsystemsneutral-,basic-andacidic-.Liverandotherorgans当前13页，总共98页。（二）

代谢与氮平衡(metabolismandnitrogenbalance)1.代谢摄入蛋白质90克

消

化

道(30%)肌肉(50%)器官体液其它机体蛋白质氨基酸池粪便10g(1.6gN)尿75g(12gN)其它5g(0.8gN)(20%)肠道内源性蛋白质70g消化、吸收蛋白质150g图1-1蛋白质代谢及氮平衡当前14页，总共98页。2.氮平衡（Nitrogenbalance）必要的氮损失（obligatorynitrogenlosses）(2)氮平衡：B＝I－（U＋F＋S）Positive

nitrogen

balanceNin>NoutNin=NoutNitrogen

equillibriumNegativenitrogen

balanceNin<Nout当前15页，总共98页。四、食物蛋白质营养学评价

(1)真消化率（true-）(一)蛋白质含量(content）(2)表观消化率（apparent-）:(二)蛋白质消化率(digestibility)当前16页，总共98页。(三)蛋白质利用率（utilization）1.Biologicalvalue,BV:生物价

Theamountofproteinnitrogenthatisretainedforgrowthandmaintenance,

expressedasapercentageoftheproteinnitrogenthathasbeendigestedandabsorbed.

Todeterminetheactualvalueofanabsorbedproteinasitisusedbythebody.当前17页，总共98页。2.NetProteinUtilization,NPU蛋白质净利用率

Theamountofproteinnitrogenthatisretainedfromagivenamountofproteinnitrogeneaten.Todeterminetheaminoacidcompositionanddigestibilityofatestprotein.当前18页，总共98页。

3.ProteinEfficiencyRatio,PER:蛋白质功效比值Ameasureofproteinqualityassessedbydetermininghowwellagivenproteinsupportsweightgainingrowingrats.

Usedtoestablishtheproteinqualityforinfantformulasandbabyfoods.当前19页，总共98页。4.AminoAcidScore,AAS氨基酸评分

ThelowestscoreisthescoreoflimitingAAwhichistheAASoftheprotein.

Amethodofevaluatingproteinqualitybycomparingatestprotein’saminoacidpatternwiththatofareferenceprotein;sometimescalledchemicalscoring.当前20页，总共98页。表1-4几种食物和不同人群需要的氨基酸评分模式氨基酸人群（mg/g蛋白质）1岁以下2~5岁10~12岁成人食物(mg/g蛋白质)鸡蛋牛奶牛肉组氨酸26191916222734异亮氨酸46282813544748亮氨酸93664419869581赖氨酸66584416707889蛋氨酸+半胱氨酸42252217573340苯丙氨酸+酪氨酸726322199310280苏氨酸4334289474446缬氨酸55352513666450色氨酸171195171412总计460339241127512504479摘自WTOTechnicalReportSeries724,第12页,1985年。当前21页，总共98页。表1-5常见几种食物蛋白质质量食物BVUPN(%)PERAAS全鸡蛋94843.921.06全牛奶87823.090.98鱼83814.551.00牛肉74732.301.00大豆73662.320.63精制面粉52510.600.34大米63632.160.59土豆6760－－0.48摘自“营养与食品卫生学”，第3版，第11页。当前22页，总共98页。5.ProteinDigestibilitycorrectedAAS,PDCAAS:

（经消化率校正的氨基酸评分）

AmeasureofproteinqualityassessedbycomparingtheaminoacidscoreofafoodproteinWiththeaminoacidrequirementsofpreschool-ageChildrenandthencorrectingforthetruedigestibilityoftheprotein;RecommendedbytheFAO/WHOandusedtoestablishproteinqualityoffoodsfordailyvaluepercentageonfoodlabels.当前23页，总共98页。表1-6几种食物蛋白质的PDCAAS食物蛋白PDCAAS食物蛋白PDCAAS酪蛋白1.00斑豆0.63鸡蛋1.00燕麦粉0.57大豆分离蛋白0.99花生粉0.52牛肉0.92小扁豆0.52豌豆粉0.69全麦0.40菜豆0.68摘自UnderstandingNutrition,第7版，第215页，1996年。当前24页，总共98页。

五、蛋白质营养不良

（protein-energymalnutrition,PEM）

Kwishiorkor:AGhanaianwordmeaning“theevilspiritthatinfectsthefirstchildwhenthesecondchildisborn”.Thesecondchildsuddenlyswitchedfromnutrientdense,protein-richbreastmilktoastarchy,protein-poorcereal,soonbeginstosickenanddie.

Marasmus:Aseveredeprivationoffoodoveralongtime(chronicPEM)andthereforeiscausedbyaninadequateenergyandproteinintake(andbyinadequateessentialfattyacids,vitamins,andmineralsaswell).当前25页，总共98页。蛋白质营养不良KwashiorkorMarasmus当前26页，总共98页。Marasmus

Kwashiorkor

Infancy(lessthan2yr)

olderinfantsandyoungchildren(1-3yr)

Developsslowly;chronicPEMrapidonset;acutePEM

Severeweightloss

someweightloss

Severemusclewasting,withfatSomemusclewasting,withretentionofsomebodyfatGrowth:<60%weight-for-agegrowth:60%-80%weight-for-age当前27页，总共98页。NodetectableedemaedemaNofattyliverenlargedfattyliverAnxiety焦急,apathy淡漠

apathy,misery痛苦,irritability易怒,sadnessGoodappetitepossiblelossofappetiteHairissparse,thinanddry;Easilypulledouthairisdryandbrittle;easilypullout;changescolor;becomesstraightSkinisdry,thin,andeasilywrinklesskindevelopslesion当前28页，总共98页。3.高蛋白质膳食过多的危害

（problemsofexcessprotein）

AdultBoneLoss(Osteoporosis骨质疏松):Calciumexcretionrisesasproteinintakeincreases.Recommen-dationofcalcium-to-proteinismorethan20(mg)to1(g).Cancer:populationstudiessuggestacorrelationbetweenhighintakesofanimalproteinandsometypecancer(cancerofcolon,breast,kidneys,pancreas,andprostate)GainWeight:Protein-richfoodsareoftenfat-richfoods.

Others.HeartDisease:Foodsrichinanimalproteintendtoberichinsaturatedfatsandcholesterol;homocystei（高半胱氨酸）maybeanindependentriskfactorforheartdisease.当前29页，总共98页。六、蛋白质供给量和食物来源

（DRIsandFoodsource）

RNI:1)数量2）质量(优质蛋白质)Assessmentofproteinnutritioninhumanbody(1)Serumalbumin:35-50g/L(2)Serumtransferritin:2.2-4g/L(3)Retinol-bindingprotein:26-76mg/L(4)Thyroxine-binding-albumin:280-350mg/L3.FoodSource:animalandplantfoods.

MilkandSoybeen当前30页，总共98页。中国居民膳食蛋白质的推荐摄入量:RNI与RDAAge(year)RNI（2000）RDA（1988）manwomanmanwoman0~1.5~3.0g/kg.bw.2.0~4.0g/kg.bw.0.5~1~353535352~404040403~454545454~505050455~555555506~555555557~606060608~656565609~6565656510~70657065当前31页，总共98页。RNI与RDA：续表Age(year)RNI（2000）RDA（1988）manwomanmanwoman11~757570~8070~8014~858080~9080轻7565807018~中80709080重908010090孕期早+5中+15+15晚+20+25乳母+20+2560~75657565当前32页，总共98页。Section2Lipids(脂类

)固醇类,sterols：脂类甘油三脂,triglycerides：磷脂,phospholipids99%inbody,95%infood99%inbody,95%infood一、脂类的分类Classification当前33页，总共98页。一、脂类的功能(function)

Structure：1glycerol＋3fattyacidsFunction（一）triglycerides,甘油三脂(TG)当前34页，总共98页。(1)triglyceridesinthebody:

A:Storingandprovidingthebodywithenergy:1g9.46kcal(两个特点）B:Thelayeroffatbeneaththeskinhelpskeepthebodywarm(insulatingthebody)C:ProtectingandproppinguptheorgansinthebodyD:Helpingthebodyuseitstwootherenergynutrients—carbohydrateandprotein(sparingprotein)E:TheveryimportantcompositionofthebodyF:Incretion:leptin,TNF-α,IL-6,IL-8,adiponectin,resistin,estrogen,Insulin-likegrowthfactor(IGF),angiotensinogen(血管紧张素),IGFbindingprotein3,plasminogenactivatorinhibitor(PAI,纤维蛋白溶酶原激活因子抑制物)当前35页，总共98页。(2).Triglyceridesinthefoods:

A:Providingbodywithenergyandessentialfattyacid.B:Improvingthecolor,flavor,tasteandshapeoffoods.C:Becausedietaryfatcausesthestomachtoemptymoreslowlythaneithercarbohydrateorprotein,itimparts

satietyandsatisfaction.D:Tosupplybodywithfat-solublevitamins

andaidintestinalabsorptionofthem.当前36页，总共98页。(3).riskofhigh-fatdiet

Heartdisease:Foodsaturatedfat(especially12,14,16carbons)raisesbloodcholesterol

dramatically,whichcausesheartattackorstroke.Obesity肥胖:High-fatdiettendtostorebodyfatefficiently.

(3)Cancer:Prostatecancerisastrongassociationwithfat;Breastcancerisalittleornoassociationwithdietfat.

(4)Riskfromtrans-fattyacids:TheyraiseLDLandlowerHDL.

当前37页，总共98页。(二)fattyacids,脂肪酸(FA)

chainlength:long-chain(10~14carbonsormore)medium-chain(6or8--)short-chain(2—4or2—6)Saturation（饱和度）:saturatedFA(SFA)monounsaturatedFA(MUFA)polyunsaturatedFA(PUFA)position

ofdoublebond:“n”or“ω”“n-3”:theinitialdoublebondsituatedbetweenthethirdand4thcarbonatomsfromthemethylend.“n-6”:theinitialdoublebondisbetweenthe6and7isomericforms

异构体:cis顺式；trans反式(1)Classification当前38页，总共98页。(2).Essentialfattyacid,必需脂肪酸(EFA)

Definition:Classification:

(1)linoleicacid(亚油酸).C18:2,n-6(2)α-linolenicacid（α

–亚麻酸）.C18:3,n-3

Fattyacidsneededbythebody,butnotmadebyittomeetphysiologicalneeds.当前39页，总共98页。SynthesizeofMUFAinbody

linoleicacid(C18:2,n-6)α-linolenicacid(C18:3,n-3)

6去饱和酶

γ-linolenicacid(C18:3,n-6)十八碳四烯酸(C18:4,n-3)碳链延长酶bi-homotypeγ-linolenic二十碳四烯酸(C20:4,n-3)acid(C18:3,n-6)

5去饱和酶arachidicacid(AA)timnodonicacid(EPA)(C20:4,n-6)(C20:5,n-3)碳链延长酶二十二碳四烯酸(C22:4,n-6)clupanodonicacid(C22:5,n-3)

4去饱和酶二十二碳五烯酸(C22:5,n-6)docosahexenoicacid(DHA)(C22:5,n-3)当前40页，总共98页。FunctionofEFATomaintainthestructuralpartsofcellmembranes.(itisapartofphospholipids)

Usedtosynthesizemanyhormonelikesubstances-eicosanoids（二十烷）:prostaglandins(PG,前列腺

素)，Thromboxane(TXA,凝血恶烷)，leukotrienes(LT,白三烯),hydroxyfattyacids,andlipoxins(脂素).

(3)Lowerbloodcholesterolandriskofheartattackorstroke,especiallyEPA(eicosapentaenoicacid)andDHA(docosahaxaenoicacid).

Theymodulatecardiovascular,pulmonary,immune,reproductive,andsecretoryfunctionsinmanycells.当前41页，总共98页。DeficiencyofEFAAffectdevelopment,production,liver,kidney,nerve,vision,andskin.

当前42页，总共98页。(三)磷脂(phospholipid)1.Structure：

Itconsistofaglycerolbackbonewithoneortwoattachedfattyacids,plusadifferentstructurethatincludesaphosphategroupattachedtotheotherhydroxylgroup(s).Themostimportantmemberislecithins（卵磷脂）.当前43页，总共98页。2.Function

(1)Importantconstituentsofcellmembranes.

Theythusallowfat-solublesubstances,includingvitaminsandhormones,topasseasilyinoroutofcells.(3)Asemulsifiers（乳化剂）inthebodyorfoodmanufacturers.(4)Tosupplybodywith9kcaloriespergram.(5)Healthfunction:differentpoints.当前44页，总共98页。(四)固醇(Sterols)

1.Structure:

Asamemultiple–ringwithdifferentsidegroupsattached.Cholesterolisthemostimportant.当前45页，总共98页。

2.Function:

Essentialtothestructureandfunctionofcells,especiallythecellmembrane(about90%oftotalbodycholesterol).Cholesterolistheoriginalmaterialforsynthesisofmanyvitallyimportantbodycompoundssuchasbile,sexhormones,adrenalhormone,andvitaminD.3.Harmfuleffects:

Itformsdeposits(沉积物)inthearterywallswhichleadtoatherosclerosis(动脉粥样硬化)---adiseasethatcausesheartattacksandstrokes.当前46页，总共98页。二、脂类代谢（metabolism）

mouth

salivarygland（唾液腺）---lipase（脂肪酶）:Itplaysasmallroleindigestioninadults,butefficientlydigeststheshort-andmedium-chainfattyacidsofmilkininfants.Stomach

Stomach’schurning

搅拌actionmixesfatwithwaterandacid.Agastriclipasehydrolyzesaverysmallamountoffat.当前47页，总共98页。Smallintestine

emulsificationoffatbybile

PancreaticlipaseIntestinallipase

bile

trappedbydietaryfibersandcarriedoutofthebodywiththefecesReabsorbedintothebloodliverGallbladder(胆囊)Monoglyceride,fattyacidsandglycerol

Long-chainfattyacidsMonoglyceridesGlycerol,short-andmedium-chainFattyacidsabsorbeddirectlyintobloodMerge（结合）intomicelles(微胶粒)

当前48页，总共98页。Merge（结合）intomicelles

(微胶粒)

Easilydiffuse(扩散)intotheintestinalcellsandreassembled(重新合成)intonewtriglycerides.Withcholesterolandphospholipids,ChylomicronswithintheintestinalcellsAbsorbedintolymph,thenintobloodCellsalloverthebodyremovelipidsfromthechylomicrons（乳糜微粒）astheypassby,tein

Livercellscollectthechylomicronremnants（残体）,andpackthemwithlipids,cholesterolandproteinsasVLDLwhichwilltravelthroughthebodyintheblood.当前49页，总共98页。HDLmadeinthelivercarrycholesterolsandphospholipidsfromthecellsbacktotheliver.

TheylosetriglyceridesandgathercholesterolfromOtherlipoproteinscirculatingthroughthebloodstreamAndbecomeLDL当前50页，总共98页。Metabolismofcholesterol当前51页，总共98页。三、FoodsourceandRDA

脂类的食物来源及供给量1.Foodsource:1).Animalfat:plentyofSFA

2).Vegetableoil:plentyofMUFA当前52页，总共98页。LinoleicAcid(n-6)

leafyvegetables,seeds,nuts,grains,vegetableoil(corn,safflower红花,soybean,cottonseed,sesame芝麻,sunflower)ArachidonicAcid(n-6)

meats,canbesynthesizedfromlinoleicacid

linolenicacid（n-3）

fatsandoil(soybean,walnut胡桃,wheatgerm)EPAandDHA(n-3)

Humanmilk,shellfishandfish(mackerel鲐鱼,tuna金枪鱼,salmon大麻哈鱼,sturgeon鲟鱼,herring鲱鱼,trout鳟鱼,sardines沙丁鱼),canbemadefromlinolenicacid.

当前53页，总共98页。当前54页，总共98页。2.DRIs:basicprinciple

percentageoftotaldietaryenergy：20%---30%SFA/totaldietaryenergy<10%n-6/totaldietaryenergy≥3%,n-6∶n-3＝4∶1Cholesterol<300mg/d3.Substituteoffat

蔗糖聚酯sucrosepolyester,Olestra燕麦素Ostrim

当前55页，总共98页。AIsofdietaryfat(percentageoftotaldietaryenergy)注1：SFA为饱和脂肪酸；MUFA为单不饱和脂肪酸；PUFA为多不饱和脂肪酸注2：n-6/n-3表示n-6系列不饱和脂肪酸与n-3系列不饱和脂肪酸的比例AgeyearFat%SFA%MUFA%PUFA%n-6/n-3Cholesterolmg0~45~504∶10.5~35~404∶12~30~354~6∶17~25~304~6∶114~25~30<108104~6∶118~20~30<1010104~6∶1<30060~20~306~8108~104∶1<300当前56页，总共98页。Section3.carbohydrate

碳水化合物一、分类与食物来源Classificationandfoodsource

单糖(monosaccharide)双糖(disaccharide)寡糖(oligosaccharide)多糖（polysaccharide）当前57页，总共98页。（一）单糖(monosaccharide)1.Glucose:D-andL-.Alittleinthenaturalfoods.

2.Fructose（果糖）:

主要存在于水果和蜂蜜中，人工制造的玉米糖浆中含40%-90%。

Itisfoundinfruits,honey(abouthalffructoseandhalfglucose),andhigh-fructosecornsyrupwhichisusedintheproductionofsoftdrinks,frozendesserts,andconfections(糖果和蜜饯等).InmostAmericandiets,fructoseaccountsforabout8%-10%oftotalenergyintake.当前58页，总共98页。3.Galactose（半乳糖）：以乳糖形式存在于天然食物中。

Itisnotusuallyfoundfreeinnatureinlargequantities,butrathercombineswithglucosetoformlactose.4.Others:

ribose(核糖)，deoxyribose(脱氧核糖)、arabinose(阿拉伯糖)、xylose(木糖)、

sugaralcohols(糖醇)：sorbitol（山梨醇）、mannitol（甘露醇）、dulcitol（卫矛醇）、inocitol（肌醇）

当前59页，总共98页。(二)双糖（disaccharide）

1.Sucrose(蔗糖)：葡萄糖＋果糖，foundinsugarcane（甘蔗）andsugarbeets（甜菜）2.Maltose（麦芽糖）：葡萄糖＋葡萄糖，淀粉水解产物3.Lactose（乳糖）：葡萄糖＋半乳糖，乳及乳制品中

4.Trehalose(海藻糖)：葡萄糖＋葡萄糖，真菌（fungus）及细菌中当前60页，总共98页。(三)寡糖（oligosaccharide）：

3-10单糖组成。有些具有重要的生理功能

(四)多糖（polysaccharide）

1.糖原(glycogen)：

动物淀粉2.淀粉（starch）：直链淀粉(amylose)---老化,支链淀粉(amylopectin)---胡化。3.纤维（fibre）

Nonstarchpolysaccharidesinplantfoodsthatarenotdigestedbyhumandigestiveenzymes,butsomearedigestedbyGItractbacteria.Fiberinfoodsisalsocalleddietaryfiber.

definition:

当前61页，总共98页。

Insolublefiber

Cellulose（纤维素）:

Itistheprimaryconstituentofplantcellwallsandthereforeoccursinallvegetables,fruitsandlegumes（豆类）.Hemicellulose（半纤维素）:

Itisthemainconstituentofcerealfiber.Themanybackbonesandsidechainsmakethehemicelluloseadiversegroup;somearesoluble,manyofthemareinsoluble.Lignin（木质素）：Itisanonpolysaccharidefiber.Itoccursinthewoodypartsofvegetablesuchascarrotsorthesmallseedsoffruitssuchasstrawberries.ligninhemicellulose当前62页，总共98页。

solublefiber

(1)Pectins（果胶）：Itisβ-1,4-D-galacturonicacidpolymersmethylate(被甲酯化至一定程度的半乳糖醛酸多聚体).Commonlyfoundinvegetablesandfruits(especiallycitrus柑橘andapples).Pectinsmaybeisolatedandusedbythefoodindustrytothickenjelly,becausetheyreadilyformgelsinwater.(2)Gumsandmucilages（树胶和粘胶）：Gumsarecomposedofvariousmonosaccharidesandtheirderivatives.Gumssuchasgumarabic(阿拉伯胶)areusedasadditivesbythefoodindustry.Mucilagesaresimilartogumsinstructure.Theyincludeguar（瓜拉胶）,whichareaddedtofoodasstabilizers.当前63页，总共98页。Foodsourceofdietaryfiber当前64页，总共98页。二、碳水化合物的功能Function

1.Functionofcarbohydrateinbody1).Componentofcellsandtissues:glycoprotein（糖蛋白）andglycolipid（糖脂）,mucin（粘蛋白）,andDNA,RNA.2).Storingglucoseasglycogenandusingitforenergy

Theliverstoresone-thirdofthebody’stotalglycogen.Whenbloodglucosefalls,thelivercellsdismantle(拆除，释放)theglycogenintosinglemoleculesofglucoseandreleasethemintothebloodstreamtobeusedbycentralnervoussystemandotherorgans.Musclecellscanalsostoreglucoseasglycogen(theothertwo-thirds),buttheyuseitjustforthemselvesduringexercise.当前65页，总共98页。3).

Sparringproteinfromuseasenergysource（节约蛋白质作用）

If

bodycannotconsumeenoughcarbohydratetoyieldglucose,itisforcedtomakeglucosefromprotein(thisprocessistermedglyconeogenesis糖异生),becausefatsgenerallycannotbeconvertedintoglucose.Soenoughcarbohydratescansparebodyproteinwhichcanbeusedtomakebodytissuesandtoperformothervitalprocesses.(即足够的碳水化物可以使体内蛋白质不被分解作为热能而消耗的作用)sparingproteinaction?当前66页，总共98页。4).Preventingketosis（抗生酮作用）

A

lowcarbohydrateintake,withtheresultingdeclineinreleaseoftheinsulin,leadstoincompletebreakdownoffattyacidsintheliver’smetabolicpathwayandtoformationofketones.

Soenoughcarbohydrateisnecessaryforthecompletemetabolismoffatsinthebody.当前67页，总共98页。2.Functionofcarbohydrateinfoods

1).Supplyingenergy

Carbohydrateisthecheapestandbroadestfoodenergysourceintheworld(4kcal/g).

2).Imparting(把---给予)color,flavortofoodsandchangingtheirshape.

Thesugaristhemostimportantsweetener.Modifiedstarchisrichinamylopectin(支链淀粉)andmaymakefoodstablewhichisusedinbabyfoods,saladdressings,andinstant(速溶)puddings.当前68页，总共98页。几种糖及糖醇的相对甜度名称相对甜度名称相对甜度乳糖0.2果糖1.2-1.8麦芽糖0.4山梨醇0.6葡萄糖0.7甘露醇0.7蔗糖1.0木糖醇0.9摘自：PerspectiveinNutrition，第三版，第77页，1996。当前69页，总共98页。3).Supplyingdietaryfiber

(1).Weightcontrol:Fiberslowstherateoffoodleavingthestomachanddrawwaterintotheintestine,whichcandelaythestomach’semptyingandglucoseabsorption.(2).Lowingserumcholesterol:Solublefibercanbindwithbileandfoodcholesterolwhichwoulddecreasefatandcholesterolabsorption;ThenliversynthesizesmorebilefromcholesterolandexcretedintheGItract,whichreducesbloodcholesterolfurther;Theshort-chainfattyacidsresultingfrombacterialdegradationsolublefiberalsoreducecholesterolsynthesisintheliveroncethesefattyacidsareabsorbedandentertheliver.FunctionofdietaryfiberThesixthnutrient当前70页，总共98页。(3)Makingeliminationoffecesmucheasier

Toolittlefibereatingmakesstoolsmallandhard,andconstipation(便秘)mayresultwhichcanforceonetoexertexcessivepressureinthelargeintestineduringdefecation（排便）.Thishighpressurecanformmanysmallpouches(囊)onthelargeintestinewallcalleddiverticula(憩室)andhemorrhoid(痔疮).

Enoughfibercanmakestoollargeandsoftbecauseitattractswater.Thelargesizestimulatestheintestinalmuscles,whichaidselimination.当前71页，总共98页。(4)playingakeyroleinpreventingcoloncancerofthelargeintestine

Itmaybeduetothefermentationofresistantstarch(抗性)fiber,inthecolon,whichlowersthepH.AdecreasedpHinthecolonisassociatedwithdecreasedcoloncancerrisk.Itisunclearwhethertheprotectionderivesfromthefiberorthevitamins.

Fibermayhelppreventcoloncancerbydiluting,binding,andrapidlyremovingpotentiallycancer-causingagentsfromthecolon.当前72页，总共98页。三、碳水化合物的消化吸收

DigestionandAbsorption1.Theprocessesofdigestion

2).Inthestomach

Toasmallextent,thestomach’sacidcanbreakstarchdown,butitsjuicescontainnoenzymestodigestca