營養(yǎng)與食品衛(wèi)生學

(2)Classification

proteinlipids

macronutrientscarbohydrate(dietaryfiber)nutrientswatervitamin

micronutrientsmacroelementsminerals

核酸nucleicacid?microelements

當前1頁，總共98頁。3.合理營養(yǎng)（RationalDiet）通過合理的膳食和科學地烹調(diào)加工，能向機體提供足夠數(shù)量的熱能和各種營養(yǎng)素，并保證各種營養(yǎng)素之間的數(shù)量平衡，以滿足人體的正常生理需要，并保持人體健康。Nutrientsintakesmeettherequirementsofthebody5.膳食營養(yǎng)供給量(RecommendedDietaryAllowance，RDA)

是對各種人群提出的保證人體營養(yǎng)需要的膳食中應含有的熱能和營養(yǎng)素的適宜量。Theaveragedailyamountofanutrientconsideredadequatetomeettheknownnutrientneedsofpracticallyallhealthypeople;agoalfordietaryintakebyindividuals.4.營養(yǎng)生理需要量（NutritionalRequirement）

是指能保持人體健康，達到應有發(fā)育水平和能充分有效地完成各項體力和腦力活動所需要的熱能和各種營養(yǎng)素的必需量。Thelowestcontinuingintakeofenergyandnutrientsthatmaintainthespecifiedcriterionofadequacy(thatwillmaintainthespecificbiochemicalandphysiologicalfunctionsofthebody).當前2頁，總共98頁。Chapter1BasicNutrition

第一章營養(yǎng)學基礎

含量----16%——19%.更新：動態(tài)平衡，不斷更新，每天約3%，腸和骨髓最快。Section1Protein(蛋白質(zhì))一、蛋白質(zhì)（一）人體中蛋白質(zhì)：（二）功能：

1.機體構(gòu)成成分

2.構(gòu)成各種生理活性物質(zhì)和重要的生理功能

3.提供熱能

當前3頁，總共98頁。（三）Thefirststructure

蛋白質(zhì)(protein)

氨基酸（Aminoacid,AA）

非必需AA(nonessential-)：9種

半必需AA（條件必需AA）：2種

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

多肽（poly-）10AA以上寡肽（oligo-）4—10AA以下

3肽（tri-）3AA2肽（di-）2AA

肽(peptide)

當前4頁，總共98頁。

二、氨基酸和必需AA(essentialaminoacid,EAA)

1.種類：20種

(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：人體不能合成或合成速度不能滿足機體需要，必需從食物中直接獲得的AA。Aminoacidsthatthebodycannotsynthesizeinamountsufficienttomeetphysiologicalneedsandhastoobtainthemfromfoods.

當前5頁，總共98頁。氨基酸英文氨基酸英文必需氨基酸非必需氨基酸異亮氨酸Isoleucine(Ile)丙氨酸Alanine(Ala)亮氨酸Leucine(Leu)精氨酸Arginine(Arg)賴氨酸Lysine(Lys)天門冬氨酸Asparticacid(ASP)蛋氨酸Methionine(Met)谷氨酸Asparagine(Asn)苯丙氨酸Phenylalanine(Phe)谷氨酰胺Glutamicacid(Glu)蘇氨酸Threonine(Thr)甘氨酸Glycine(Gly)色氨酸Tryptophan(Trp)脯氨酸Proline(Pro)纈氨酸Valine(Val)絲氨酸Serine(Ser)組氨酸*Histidine(His)天冬酰胺Asparagine(ASN)條件必需氨基酸半胱氨酸Cysteine(Cys)酪氨酸Tyrosine(Tyr)表1-1人體內(nèi)的氨基酸*組氨酸為嬰兒必需氨基酸，成人需要量可能較少。

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

蛋白質(zhì)中各種必需氨基酸的構(gòu)成比例。當前7頁，總共98頁。氨基酸人體全雞蛋牛奶牛肉大豆面粉大米異亮氨酸4.0亮氨酸7.0賴氨酸2.3蛋氨酸+半胱氨酸2.3苯丙氨酸+酪氨酸6.0蘇氨酸4.0纈氨酸5.0色氨酸1.01.01.01.01.01.01.0表1-2幾種食物和人體蛋白質(zhì)氨基酸模式數(shù)據(jù)摘自營養(yǎng)與食品衛(wèi)生學，第3版，第9頁。當前8頁，總共98頁。2.限制氨基酸

（limitingaminoacid）：與人體蛋白質(zhì)模式比較，食物蛋白質(zhì)中含量相對較低的必需AA。Theessentialaminoacidfoundintheshortestsupplyrelativetotheamountneededforproteinsynthesisinthebody.FourAAaremostlikelytobelimiting:Lysine，Methionine，Threonine，Tryptophan.當前9頁，總共98頁。3.參考蛋白、完全蛋白和蛋白質(zhì)的互補作用參考蛋白用于測定食物蛋白質(zhì)質(zhì)量的標準蛋白。

ReferenceProtein:Astandardagainstwhichtomeasurethequalityofotherproteins.完全蛋白必需氨基酸模式與人體蛋白質(zhì)相對一致，能滿足機體蛋白質(zhì)合成需要的食物蛋白質(zhì)。

CompleteProtein:Adietaryproteincontainingalltheessentialaminoacidsinrelativelythesameamountsthathumanbeingrequired.(includinganimalproteinandsoyprotein)

Incompleteprotein蛋白質(zhì)互補將兩種或兩種以上的食物蛋白質(zhì)混合事用，使不同食物中必需氨基酸以多補少，從而提高膳食蛋白質(zhì)的營養(yǎng)價值。

ComplementaryProtein:Twoormoreproteinswhoseaminoacidsassortmentscomplementeachotherinsuchawaythattheessentialaminoacidsmissingfromonearesuppliedbytheother.當前10頁，總共98頁。幾種食物混合后蛋白質(zhì)的生物價食物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混合后生物價---747389當前11頁，總共98頁。三、蛋白質(zhì)的消化、吸收和代謝

（一）消化和吸收

（digestionandabsorption）

當前12頁，總共98頁。GastricJuice

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

dietary

Protein

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

trypsin(胰蛋白酶)--NH2-

juice

chymotrypsine(糜蛋白酶)--lysine,arginine

dipeptide,tripeptideandfreeAAabsorbedthroughthemucosalcellsofsmallintestinepeptidase

throughthreeactivefreeAAtransportsystemsneutral-,basic-andacidic-.Liverandotherorgans當前13頁，總共98頁。（二）

代謝與氮平衡(metabolismandnitrogenbalance)1.代謝攝入蛋白質(zhì)90克

消

化

道(30%)肌肉(50%)器官體液其它機體蛋白質(zhì)氨基酸池糞便10g(1.6gN)尿75g(12gN)其它5g(0.8gN)(20%)腸道內(nèi)源性蛋白質(zhì)70g消化、吸收蛋白質(zhì)150g圖1-1蛋白質(zhì)代謝及氮平衡當前14頁，總共98頁。2.氮平衡（Nitrogenbalance）必要的氮損失（obligatorynitrogenlosses）(2)氮平衡：B＝I－（U＋F＋S）Positive

nitrogen

balanceNin>NoutNin=NoutNitrogen

equillibriumNegativenitrogen

balanceNin<Nout當前15頁，總共98頁。四、食物蛋白質(zhì)營養(yǎng)學評價

(1)真消化率（true-）(一)蛋白質(zhì)含量(content）(2)表觀消化率（apparent-）:(二)蛋白質(zhì)消化率(digestibility)當前16頁，總共98頁。(三)蛋白質(zhì)利用率（utilization）1.Biologicalvalue,BV:生物價

Theamountofproteinnitrogenthatisretainedforgrowthandmaintenance,

expressedasapercentageoftheproteinnitrogenthathasbeendigestedandabsorbed.

Todeterminetheactualvalueofanabsorbedproteinasitisusedbythebody.當前17頁，總共98頁。2.NetProteinUtilization,NPU蛋白質(zhì)凈利用率

Theamountofproteinnitrogenthatisretainedfromagivenamountofproteinnitrogeneaten.Todeterminetheaminoacidcompositionanddigestibilityofatestprotein.當前18頁，總共98頁。

3.ProteinEfficiencyRatio,PER:蛋白質(zhì)功效比值Ameasureofproteinqualityassessedbydetermininghowwellagivenproteinsupportsweightgainingrowingrats.

Usedtoestablishtheproteinqualityforinfantformulasandbabyfoods.當前19頁，總共98頁。4.AminoAcidScore,AAS氨基酸評分

ThelowestscoreisthescoreoflimitingAAwhichistheAASoftheprotein.

Amethodofevaluatingproteinqualitybycomparingatestprotein’saminoacidpatternwiththatofareferenceprotein;sometimescalledchemicalscoring.當前20頁，總共98頁。表1-4幾種食物和不同人群需要的氨基酸評分模式氨基酸人群（mg/g蛋白質(zhì)）1歲以下2~5歲10~12歲成人食物(mg/g蛋白質(zhì))雞蛋牛奶牛肉組氨酸26191916222734異亮氨酸46282813544748亮氨酸93664419869581賴氨酸66584416707889蛋氨酸+半胱氨酸42252217573340苯丙氨酸+酪氨酸726322199310280蘇氨酸4334289474446纈氨酸55352513666450色氨酸171195171412總計460339241127512504479摘自WTOTechnicalReportSeries724,第12頁,1985年。當前21頁，總共98頁。表1-5常見幾種食物蛋白質(zhì)質(zhì)量食物BVUPN(%)PERAAS全雞蛋94843.921.06全牛奶87823.090.98魚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“營養(yǎng)與食品衛(wèi)生學”，第3版，第11頁。當前22頁，總共98頁。5.ProteinDigestibilitycorrectedAAS,PDCAAS:

（經(jīng)消化率校正的氨基酸評分）

AmeasureofproteinqualityassessedbycomparingtheaminoacidscoreofafoodproteinWiththeaminoacidrequirementsofpreschool-ageChildrenandthencorrectingforthetruedigestibilityoftheprotein;RecommendedbytheFAO/WHOandusedtoestablishproteinqualityoffoodsfordailyvaluepercentageonfoodlabels.當前23頁，總共98頁。表1-6幾種食物蛋白質(zhì)的PDCAAS食物蛋白PDCAAS食物蛋白PDCAAS酪蛋白1.00斑豆0.63雞蛋1.00燕麥粉0.57大豆分離蛋白0.99花生粉0.52牛肉0.92小扁豆0.52豌豆粉0.69全麥0.40菜豆0.68摘自UnderstandingNutrition,第7版，第215頁，1996年。當前24頁，總共98頁。

五、蛋白質(zhì)營養(yǎng)不良

（protein-energymalnutrition,PEM）

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

Marasmus:Aseveredeprivationoffoodoveralongtime(chronicPEM)andthereforeiscausedbyaninadequateenergyandproteinintake(andbyinadequateessentialfattyacids,vitamins,andmineralsaswell).當前25頁，總共98頁。蛋白質(zhì)營養(yǎng)不良KwashiorkorMarasmus當前26頁，總共98頁。Marasmus

Kwashiorkor

Infancy(lessthan2yr)

olderinfantsandyoungchildren(1-3yr)

Developsslowly;chronicPEMrapidonset;acutePEM

Severeweightloss

someweightloss

Severemusclewasting,withfatSomemusclewasting,withretentionofsomebodyfatGrowth:<60%weight-for-agegrowth:60%-80%weight-for-age當前27頁，總共98頁。NodetectableedemaedemaNofattyliverenlargedfattyliverAnxiety焦急,apathy淡漠

apathy,misery痛苦,irritability易怒,sadnessGoodappetitepossiblelossofappetiteHairissparse,thinanddry;Easilypulledouthairisdryandbrittle;easilypullout;changescolor;becomesstraightSkinisdry,thin,andeasilywrinklesskindevelopslesion當前28頁，總共98頁。3.高蛋白質(zhì)膳食過多的危害

（problemsofexcessprotein）

AdultBoneLoss(Osteoporosis骨質(zhì)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.當前29頁，總共98頁。六、蛋白質(zhì)供給量和食物來源

（DRIsandFoodsource）

RNI:1)數(shù)量2）質(zhì)量(優(yōu)質(zhì)蛋白質(zhì))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當前30頁，總共98頁。中國居民膳食蛋白質(zhì)的推薦攝入量:RNI與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當前31頁，總共98頁。RNI與RDA：續(xù)表Age(year)RNI（2000）RDA（1988）manwomanmanwoman11~757570~8070~8014~858080~9080輕7565807018~中80709080重908010090孕期早+5中+15+15晚+20+25乳母+20+2560~75657565當前32頁，總共98頁。Section2Lipids(脂類

)固醇類,sterols：脂類甘油三脂,triglycerides：磷脂,phospholipids99%inbody,95%infood99%inbody,95%infood一、脂類的分類Classification當前33頁，總共98頁。一、脂類的功能(function)

Structure：1glycerol＋3fattyacidsFunction（一）triglycerides,甘油三脂(TG)當前34頁，總共98頁。(1)triglyceridesinthebody:

A:Storingandprovidingthebodywithenergy:1g9.46kcal(兩個特點）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(血管緊張素),IGFbindingprotein3,plasminogenactivatorinhibitor(PAI,纖維蛋白溶酶原激活因子抑制物)當前35頁，總共98頁。(2).Triglyceridesinthefoods:

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

satietyandsatisfaction.D:Tosupplybodywithfat-solublevitamins

andaidintestinalabsorptionofthem.當前36頁，總共98頁。(3).riskofhigh-fatdiet

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

dramatically,whichcausesheartattackorstroke.Obesity肥胖:High-fatdiettendtostorebodyfatefficiently.

(3)Cancer:Prostatecancerisastrongassociationwithfat;Breastcancerisalittleornoassociationwithdietfat.

(4)Riskfromtrans-fattyacids:TheyraiseLDLandlowerHDL.

當前37頁，總共98頁。(二)fattyacids,脂肪酸(FA)

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

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

異構(gòu)體:cis順式；trans反式(1)Classification當前38頁，總共98頁。(2).Essentialfattyacid,必需脂肪酸(EFA)

Definition:Classification:

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

–亞麻酸）.C18:3,n-3

Fattyacidsneededbythebody,butnotmadebyittomeetphysiologicalneeds.當前39頁，總共98頁。SynthesizeofMUFAinbody

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

6去飽和酶

γ-linolenicacid(C18:3,n-6)十八碳四烯酸(C18:4,n-3)碳鏈延長酶bi-homotypeγ-linolenic二十碳四烯酸(C20:4,n-3)acid(C18:3,n-6)

5去飽和酶arachidicacid(AA)timnodonicacid(EPA)(C20:4,n-6)(C20:5,n-3)碳鏈延長酶二十二碳四烯酸(C22:4,n-6)clupanodonicacid(C22:5,n-3)

4去飽和酶二十二碳五烯酸(C22:5,n-6)docosahexenoicacid(DHA)(C22:5,n-3)當前40頁，總共98頁。FunctionofEFATomaintainthestructuralpartsofcellmembranes.(itisapartofphospholipids)

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

素)，Thromboxane(TXA,凝血惡烷)，leukotrienes(LT,白三烯),hydroxyfattyacids,andlipoxins(脂素).

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

Theymodulatecardiovascular,pulmonary,immune,reproductive,andsecretoryfunctionsinmanycells.當前41頁，總共98頁。DeficiencyofEFAAffectdevelopment,production,liver,kidney,nerve,vision,andskin.

當前42頁，總共98頁。(三)磷脂(phospholipid)1.Structure：

Itconsistofaglycerolbackbonewithoneortwoattachedfattyacids,plusadifferentstructurethatincludesaphosphategroupattachedtotheotherhydroxylgroup(s).Themostimportantmemberislecithins（卵磷脂）.當前43頁，總共98頁。2.Function

(1)Importantconstituentsofcellmembranes.

Theythusallowfat-solublesubstances,includingvitaminsandhormones,topasseasilyinoroutofcells.(3)Asemulsifiers（乳化劑）inthebodyorfoodmanufacturers.(4)Tosupplybodywith9kcaloriespergram.(5)Healthfunction:differentpoints.當前44頁，總共98頁。(四)固醇(Sterols)

1.Structure:

Asamemultiple–ringwithdifferentsidegroupsattached.Cholesterolisthemostimportant.當前45頁，總共98頁。

2.Function:

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

Itformsdeposits(沉積物)inthearterywallswhichleadtoatherosclerosis(動脈粥樣硬化)---adiseasethatcausesheartattacksandstrokes.當前46頁，總共98頁。二、脂類代謝（metabolism）

mouth

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

Stomach’schurning

攪拌actionmixesfatwithwaterandacid.Agastriclipasehydrolyzesaverysmallamountoffat.當前47頁，總共98頁。Smallintestine

emulsificationoffatbybile

PancreaticlipaseIntestinallipase

bile

trappedbydietaryfibersandcarriedoutofthebodywiththefecesReabsorbedintothebloodliverGallbladder(膽囊)Monoglyceride,fattyacidsandglycerol

Long-chainfattyacidsMonoglyceridesGlycerol,short-andmedium-chainFattyacidsabsorbeddirectlyintobloodMerge（結(jié)合）intomicelles(微膠粒)

當前48頁，總共98頁。Merge（結(jié)合）intomicelles

(微膠粒)

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

Livercellscollectthechylomicronremnants（殘體）,andpackthemwithlipids,cholesterolandproteinsasVLDLwhichwilltravelthroughthebodyintheblood.當前49頁，總共98頁。HDLmadeinthelivercarrycholesterolsandphospholipidsfromthecellsbacktotheliver.

TheylosetriglyceridesandgathercholesterolfromOtherlipoproteinscirculatingthroughthebloodstreamAndbecomeLDL當前50頁，總共98頁。Metabolismofcholesterol當前51頁，總共98頁。三、FoodsourceandRDA

脂類的食物來源及供給量1.Foodsource:1).Animalfat:plentyofSFA

2).Vegetableoil:plentyofMUFA當前52頁，總共98頁。LinoleicAcid(n-6)

leafyvegetables,seeds,nuts,grains,vegetableoil(corn,safflower紅花,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鮐魚,tuna金槍魚,salmon大麻哈魚,sturgeon鱘魚,herring鯡魚,trout鱒魚,sardines沙丁魚),canbemadefromlinolenicacid.

當前53頁，總共98頁。當前54頁，總共98頁。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燕麥素Ostrim

當前55頁，總共98頁。AIsofdietaryfat(percentageoftotaldietaryenergy)注1：SFA為飽和脂肪酸；MUFA為單不飽和脂肪酸；PUFA為多不飽和脂肪酸注2：n-6/n-3表示n-6系列不飽和脂肪酸與n-3系列不飽和脂肪酸的比例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當前56頁，總共98頁。Section3.carbohydrate

碳水化合物一、分類與食物來源Classificationandfoodsource

單糖(monosaccharide)雙糖(disaccharide)寡糖(oligosaccharide)多糖（polysaccharide）當前57頁，總共98頁。（一）單糖(monosaccharide)1.Glucose:D-andL-.Alittleinthenaturalfoods.

2.Fructose（果糖）:

主要存在于水果和蜂蜜中，人工制造的玉米糖漿中含40%-90%。

Itisfoundinfruits,honey(abouthalffructoseandhalfglucose),andhigh-fructosecornsyrupwhichisusedintheproductionofsoftdrinks,frozendesserts,andconfections(糖果和蜜餞等).InmostAmericandiets,fructoseaccountsforabout8%-10%oftotalenergyintake.當前58頁，總共98頁。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(脫氧核糖)、arabinose(阿拉伯糖)、xylose(木糖)、

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

當前59頁，總共98頁。(二)雙糖（disaccharide）

1.Sucrose(蔗糖)：葡萄糖＋果糖，foundinsugarcane（甘蔗）andsugarbeets（甜菜）2.Maltose（麥芽糖）：葡萄糖＋葡萄糖，淀粉水解產(chǎn)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）及細菌中當前60頁，總共98頁。(三)寡糖（oligosaccharide）：

3-10單糖組成。有些具有重要的生理功能

(四)多糖（polysaccharide）

1.糖原(glycogen)：

動物淀粉2.淀粉（starch）：直鏈淀粉(amylose)---老化,支鏈淀粉(amylopectin)---胡化。3.纖維（fibre）

Nonstarchpolysaccharidesinplantfoodsthatarenotdigestedbyhumandigestiveenzymes,butsomearedigestedbyGItractbacteria.Fiberinfoodsisalsocalleddietaryfiber.

definition:

當前61頁，總共98頁。

Insolublefiber

Cellulose（纖維素）:

Itistheprimaryconstituentofplantcellwallsandthereforeoccursinallvegetables,fruitsandlegumes（豆類）.Hemicellulose（半纖維素）:

Itisthemainconstituentofcerealfiber.Themanybackbonesandsidechainsmakethehemicelluloseadiversegroup;somearesoluble,manyofthemareinsoluble.Lignin（木質(zhì)素）：Itisanonpolysaccharidefiber.Itoccursinthewoodypartsofvegetablesuchascarrotsorthesmallseedsoffruitssuchasstrawberries.ligninhemicellulose當前62頁，總共98頁。

solublefiber

(1)Pectins（果膠）：Itisβ-1,4-D-galacturonicacidpolymersmethylate(被甲酯化至一定程度的半乳糖醛酸多聚體).Commonlyfoundinvegetablesandfruits(especiallycitrus柑橘andapples).Pectinsmaybeisolatedandusedbythefoodindustrytothickenjelly,becausetheyreadilyformgelsinwater.(2)Gumsandmucilages（樹膠和粘膠）：Gumsarecomposedofvariousmonosaccharidesandtheirderivatives.Gumssuchasgumarabic(阿拉伯膠)areusedasadditivesbythefoodindustry.Mucilagesaresimilartogumsinstructure.Theyincludeguar（瓜拉膠）,whichareaddedtofoodasstabilizers.當前63頁，總共98頁。Foodsourceofdietaryfiber當前64頁，總共98頁。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，釋放)theglycogenintosinglemoleculesofglucoseandreleasethemintothebloodstreamtobeusedbycentralnervoussystemandotherorgans.Musclecellscanalsostoreglucoseasglycogen(theothertwo-thirds),buttheyuseitjustforthemselvesduringexercise.當前65頁，總共98頁。3).

Sparringproteinfromuseasenergysource（節(jié)約蛋白質(zhì)作用）

If

bodycannotconsumeenoughcarbohydratetoyieldglucose,itisforcedtomakeglucosefromprotein(thisprocessistermedglyconeogenesis糖異生),becausefatsgenerallycannotbeconvertedintoglucose.Soenoughcarbohydratescansparebodyproteinwhichcanbeusedtomakebodytissuesandtoperformothervitalprocesses.(即足夠的碳水化物可以使體內(nèi)蛋白質(zhì)不被分解作為熱能而消耗的作用)sparingproteinaction?當前66頁，總共98頁。4).Preventingketosis（抗生酮作用）

A

lowcarbohydrateintake,withtheresultingdeclineinreleaseoftheinsulin,leadstoincompletebreakdownoffattyacidsintheliver’smetabolicpathwayandtoformationofketones.

Soenoughcarbohydrateisnecessaryforthecompletemetabolismoffatsinthebody.當前67頁，總共98頁。2.Functionofcarbohydrateinfoods

1).Supplyingenergy

Carbohydrateisthecheapestandbroadestfoodenergysourceintheworld(4kcal/g).

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

Thesugaristhemostimportantsweetener.Modifiedstarchisrichinamylopectin(支鏈淀粉)andmaymakefoodstablewhichisusedinbabyfoods,saladdressings,andinstant(速溶)puddings.當前68頁，總共98頁。幾種糖及糖醇的相對甜度名稱相對甜度名稱相對甜度乳糖0.2果糖1.2-1.8麥芽糖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頁，1996。當前69頁，總共98頁。3).Supplyingdietaryfiber

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

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

Enoughfibercanmakestoollargeandsoftbecauseitattractswater.Thelargesizestimulatestheintestinalmuscles,whichaidselimination.當前71頁，總共98頁。(4)playingakeyroleinpreventingcoloncancerofthelargeintestine

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

Fibermayhelppreventcoloncancerbydiluting,binding,andrapidlyremovingpotentiallycancer-causingagentsfromthecolon.當前72頁，總共98頁。三、碳水化合物的消化吸收

DigestionandAbsorption1.Theprocessesofdigestion

2).Inthestomach

Toasmallextent,thestomach’sacidcanbreakstarchdown,butitsjuicescontainnoenzymestodigestca