營(yíng)養(yǎng)與食品衛(wèi)生學(xué)第九節(jié) 維生素

1第九節(jié)維生素(Vitamins)PhysicalandChemicalpropertiesFunctionsofvitaminesAbsorptionandMetabolismDeficiencyandexcessofvitaminsEvaluationonthenutritionalvalueofvitaminsAllowanceandFoodSource

Objectives121.Definition

ofvitaminVitaminsareorganiccomponentsinfoodthatareneededinverysmallamountsforgrowthandformaintaininggoodhealth.23

VitaminsB族&CWater-solubleFat-solubleA、D、E、K2.Classification34Fat-solubleversuswater-solublevitaminsFat-solublewater-solublesolubilityinfatinwaterChemicalcompositionC,H,OC,H,O;N,S,Coabsorption、excretionlymphbilebloodstreamurinestorageLiver,fattytissues(VKexcepted)__deficiency__+toxicity+__5(1)Inadequateintakeofanyparticularvitamin

inthedietFoodisinshortsupply(2)Thelowabsorptionandutilizationability(3)Increasedphysiologicalrequirements3.Influencingfactorsforvitamindeficiency664.CategoryofvitamindeficiencyCauses：Primary、Secondary

Degree：Clinic、Sub-clinicStoragelowerpathologyclinicalsignbiochemicalindicatorsphysiologicalfunctions75.Interactionwithothernutrientsvitamin-othernutrients：associationbetweenB1、B2、niacin

andenergymetabolism，theirrequirementincreasewithenergyincrease.Vitamin-vitamin：VE

promoteabsorptionandstorageofVAinliver，VE

anti-oxidantincoordinationwithGPx.78維生素A視黃醇(retinol)視黃醛(retinal)視黃酸(retinoicacid)視黃基酯復(fù)合物

類胡蘿卜素α-胡蘿卜素（alpha-carotene）β-胡蘿卜素（beta-carotene）β-隱黃素(beta-cryptoxanthin)

-胡蘿卜素(gamma-carotene)玉米黃素(zeaxanthin)辣椒紅素(capsanthin)葉黃素(xanthophyll)番茄紅素(lycopene)8維生素A原二、VitaminA92.Absorption&metabolismRetinylesterIntestinallipasesretinyllipidsLymphaticcirculationretinolFattytissueMucousmembraneofsmallintestinecarotenoidGlucosealdehydebilefeces9Targetorgan103.FunctionsofvitaminA

(1)VisionThebest

characterizedfunctionofvitaminAisitsrole

intheretinaoftheage.

Darkadaptation：theprocessofadjustingtheeyestolowlevelsofilluminationRhodopsin：abiologicalpigmentinthephotoreceptorsoftheretinaimmediatelyphotobleachesinresponsetolight1011(2)Cellgrowthanddifferentiation

Theretinoicacidreceptors（RAR/RXR）:Modulatinggeneexpressionbyactivationofnuclearreceptor12(3)Immunefunction

Ithelpsmaintainthehealthofepithelialtissuesagainstbacterial,parasitic,andviralattack;itsupportsthegenerationofTlymphocytes.(4)Antioxidation(5)Anticanceractivity1213ResultsAtotalof388newcasesoflungcancerwerediagnosedduringthe73,135person-yearsoffollow-up(meanlengthoffollow-up,4.0years).Theactive-treatmentgrouphadarelativeriskoflungcancerof1.28,ascomparedwiththeplacebogroup，therelativeriskofdeathfromanycausewas1.17.Onthebasisofthesefindings,therandomizedtrialwasstopped21monthsearlierthanplanned.14Methods

Weconductedamulticenter,RCT—theBeta-CaroteneandRetinolEfficacyTrial—involvingatotalof18,314smokers,formersmokers,andworkersexposedtoasbestos.Theeffectsofacombinationof30mgofbetacaroteneperdayand25,000IUofretinol(vitaminA)intheformofretinylpalmitateperdayontheprimaryendpoint,theincidenceoflungcancer,werecomparedwiththoseofplacebo.1IU維生素A=0.3μg視黃醇當(dāng)量（RE）25,000IU=25,000X0.3ug=7500ugRE我國(guó)成人維生素A推薦攝入量（RNI），男性為800μgRE/d，女性為700μgRE/d。UL在成人為3000μgRE/d，孕婦為2400μgRE/d。154.DeficiencyofVitaminAVitaminAdeficiencyoccursmostoftenandremainsamajorprobleminlargeareasofdevelopingworld,beingthesinglemostcommonpreventablecauseofblindness.1516TheprevalenceofVAdeficiencyininfantsandchildrenarehigherthanthatinadultsInadults,excessivealcoholconsumptionreducesliverreservesofVA.DigestivetractdiseasesincreaseriskofVAdeficiency1617185.ExcessofvitaminAVAisbothacutelyandchronicallytoxic.LargedosesofVAcausenausea,vomitingandheadache.Extremelyhighdosescanprovefatal.ThechronictoxicityofVAaffecttheskin,centralnervoussystem,liverandbones.CarotenoidsdonotcausehypervitaminosisA.18196.NutritionalevaluationNutritionalstatusofVitaminA：deficiencyinsufficiency（marginalstatus）sufficiencyexcesstoxicityIdentify:biochemicalindicatorsclinicalsymptomphysiologicalresponsesdietaryintake1920BiochemicalIndicators（1）theplasmalevelofretinol(2)therelativedoseresponsetest

RDR（％）=（A5－A0）20deficiencymarginalacceptablegoodPlasmalevel(ug/L）<100100-200>200>300RDR(％)>5050-20<20Nutritionalevaluation

ofVA

A5X10021(3)plasmaretinolbindingprotein

thefastingplasmaconcentrationofretinolremainsconstantoverawiderangeofintakes

normalvalue：>23.0mg/L(4)signandsymptom(5)AssessmentoftheDarkadaptation

time227.Dietaryrequirements&foodsources23Createastandardizedmeasurementbasedonretinol,calledretinolactivityequivalents(RE)

1μg視黃醇=1μg視黃醇當(dāng)量(RE)

1μgβ-胡蘿卜素=0.167μg視黃醇當(dāng)量(RE)

1μg其他維生素A原=0.084μg視黃醇當(dāng)量(RE)238.Dietaryrequirements&foodsources總視黃醇當(dāng)量(μgRE)=視黃醇(μg)+β-胡蘿卜素(μg)×0.167+其他維生素A原(μg)×0.084RecommendedbyCNSin2000:RNI800μgRE/dformaleand700μgRE/dforfemaleadults;UL3000μg/dforadults.Foodsouces:

VAfromanimalfoodprovitaminAcarotenoidfromdark-greenandyelloworangevegatables.2424

2525VitaminD維生素D2維生素D3酵母菌或麥角固醇皮下7-脫氫膽固醇26VitaminDisnotstrictlyavitamin,ratheritistheprecursorofthehormonesinvolvedincalciumhomeostasisandtheregulationofcellproliferationanddifferentiation26麥角醇7-脫氫膽固醇1,25（OH）VD3維生素D2維生素D325（OH）VD327272.

Absorption&metabolismVitaminDinFoodLymph28283.

Deficiencyandexcess

Whenexposuretosunlightisinadequateanddietaryintakeisrestricted,deficiencyinvitaminDoccurs.ThemajorsymptomsofvitaminDdeficiencyarericketsinyoungchildrenandosteomalaciainadults.ExcessivelyhighintakesofVDareassociatedwithhypercalcaemiacalcinosis.2929Serumlevelsof25（OH）-D3<20ng/mLdeficiency20ng/mL~30ng/mLinsufficiency>30ng/mLsufficiency4.Nutritionalevaluation3030五、FoodsourcesofvitaminDTherearefewdietarysourcesofcholecalciferollivermusclemilkeggsFisheggs

vegetable31Cod-liveroil31東印度群島19世紀(jì)80年代，當(dāng)時(shí)荷蘭統(tǒng)治下

beriberi32

荷蘭醫(yī)學(xué)家艾伊克曼，1929年諾貝爾生理學(xué)或醫(yī)學(xué)獎(jiǎng)得主VitaminB1（硫胺素Thiamin）321.

Functions

of

Thiamin

CHOs

TPPDecaboxylation

Citricacidcycle1.Produceenergytofuelnervetissue33

Thiaministhevitaminportionofthecoenzymethiaminpyrophosphate(焦磷酸硫胺素,TPP)ATP2.HelpsynthesizeandregulateneurotransmittersperipheralnervoussystemsCentralnervoussystemamongalcoholics33OthersfunctionAcetylcholine乙酰膽堿

TPPgastrointestinalmotility

glandularsecretion401.

Functions

ofThiamin

342.ThiamindeficiencyThiaminrequirementsdependlargelyoncarbohydrateintake.Theclassicalthiamindeficiencydisease,beriberi,affectingtheperipheralnervoussystem,isnowrare.Thiamindeficiency,leadingtocentralnervoussystemdamage,isasignificant,andunderdiagnosed,problemamongalcoholicsandpeoplewithHIV-AIDS.35353.ThiamintoxicityTherearenoreportsofthiamintoxicityfromeitherfoodorsupplementsThereisnotsetatolerableupperintakelevel(UL)forthisnutrient.Largedosesofthiaminappeartoberelativelyinnocuous,inaddition,thekidneysrapidlyexcreteexcessthiaminviaurine.364.Assessmentofthiaminnutritionalstatusurinaryloadtest（5mgisgivenorally，urinaryexcretionlevelsof

thiaminafter4h）<100μgdeficiency100~199μginsufficiency>200μgnormal>400μgsufficiencyTheratioofurinarythiaminandcreatinine尿中硫胺素和肌酐含量比值theactivationofapo-transketolaseinerythrocytelysate（紅細(xì)胞轉(zhuǎn)酮醇酶活力系數(shù))37375.Dietaryrequirements&foodsources

ThiaminrequirementsdependlargelyonenergyintakeRecommendedbyCNSin2000:0.5mg／1000kcal

richsource：yeast、corn、bean、dryfruit

goodsource：milkeggfishmeat、fish、internalorgans

poorsource：vegetablefruit.38381.RiboflavinFunctionsRiboflavinispartoftwoimportantcoenzymes,FMNandFADwhichareoxidizingagents.39VitaminB2（核黃素Riboflavin）392.RiboflavinDeficiencyRiboflavindeficiencyisrelativelycommon,butrarely(ifever)fatal,becausethereisefficientconservationofthevitaminindeficiency.RiboflavindeficiencycancausesecondarydeficiencyofironandfunctionaldeficiencyofVB6.Clincially,deficiencyischaracterisedbylesionsofthemarginofthelipsandcornersofmouth,andasebhorroeicdermatitis.4040口角炎

(angularstomatitis)唇炎

(cheilosis)舌炎

(glossitis)41413.Assessmentofriboflavinnutritionalstatus細(xì)胞谷胱甘肽還原酶活性系數(shù)(erythrocyteglutathionereductaseactivationcoefficient，EGRAC)activitycoefficient,AC＜1.2isnorml;＞1.4isdeficiencyUrinaryloadingVB2trial：

清晨口服維生素B25mg，4h尿中排出量

＜400μgdeficiency，400～799μginsufficiency，800～1300μgnormal

＞1300μgsufficiency

或測(cè)任意一次尿中核黃素與尿肌酐比值42424.Dietaryrequirements&foodsourcesRecommendedbyCNSin2000:RNI1.4mg/dformale1.2mg/dforfemaleadults，UL50mg/d.Riboflavinispresentinmostfoodsalthoughthebestsourcesaremilkandmilkproducts,eggs,liver,kidney,yeastextractsandfortifiedbreakfastcereals.4343維生素C.

5644八.VitaminCVitaminCisprobablythemosttalkedaboutvitaminandiscertainlytheonemostwidelyusedasasupplement.ThechemicalnameforvitaminCisascorbicacid.59456046Functions抗氧化作用：很強(qiáng)的抗氧化劑，在體內(nèi)可以氧化型和還原型存在作為羥化過(guò)程底物和酶的輔助因子促進(jìn)類固醇的代謝清除自由基參與合成神