營養(yǎng)與食品衛(wèi)生學第九節(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視黃醇當量（RE）25,000IU=25,000X0.3ug=7500ugRE我國成人維生素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視黃醇當量(RE)

1μgβ-胡蘿卜素=0.167μg視黃醇當量(RE)

1μg其他維生素A原=0.084μg視黃醇當量(RE)238.Dietaryrequirements&foodsources總視黃醇當量(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80年代，當時荷蘭統(tǒng)治下

beriberi32

荷蘭醫(yī)學家艾伊克曼，1929年諾貝爾生理學或醫(yī)學獎得主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（紅細胞轉酮醇酶活力系數(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：很強的抗氧化劑，在體內可以氧化型和還原型存在作為羥化過程底物和酶的輔助因子促進類固醇的代謝清除自由基參與合成神