营养与食品卫生学第九节 维生素

1第九节维生素(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维生素A视黄醇(retinol)视黄醛(retinal)视黄酸(retinoicacid)视黄基酯复合物

类胡萝卜素α-胡萝卜素（alpha-carotene）β-胡萝卜素（beta-carotene）β-隐黄素(beta-cryptoxanthin)

-胡萝卜素(gamma-carotene)玉米黄素(zeaxanthin)辣椒红素(capsanthin)叶黄素(xanthophyll)番茄红素(lycopene)8维生素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维生素A=0.3μg视黄醇当量（RE）25,000IU=25,000X0.3ug=7500ugRE我国成人维生素A推荐摄入量（RNI），男性为800μgRE/d，女性为700μgRE/d。UL在成人为3000μgRE/d，孕妇为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视黄醇=1μg视黄醇当量(RE)

1μgβ-胡萝卜素=0.167μg视黄醇当量(RE)

1μg其他维生素A原=0.084μg视黄醇当量(RE)238.Dietaryrequirements&foodsources总视黄醇当量(μgRE)=视黄醇(μg)+β-胡萝卜素(μg)×0.167+其他维生素A原(μg)×0.084RecommendedbyCNSin2000:RNI800µgRE/dformaleand700µgRE/dforfemaleadults;UL3000µg/dforadults.Foodsouces:

VAfromanimalfoodprovitaminAcarotenoidfromdark-greenandyelloworangevegatables.2424

2525VitaminD维生素D2维生素D3酵母菌或麦角固醇皮下7-脱氢胆固醇26VitaminDisnotstrictlyavitamin,ratheritistheprecursorofthehormonesinvolvedincalciumhomeostasisandtheregulationofcellproliferationanddifferentiation26麦角醇7-脱氢胆固醇1,25（OH）VD3维生素D2维生素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东印度群岛19世纪80年代，当时荷兰统治下

beriberi32

荷兰医学家艾伊克曼，1929年诺贝尔生理学或医学奖得主VitaminB1（硫胺素Thiamin）321.

Functions

of

Thiamin

CHOs

TPPDecaboxylation

Citricacidcycle1.Produceenergytofuelnervetissue33

Thiaministhevitaminportionofthecoenzymethiaminpyrophosphate(焦磷酸硫胺素,TPP)ATP2.HelpsynthesizeandregulateneurotransmittersperipheralnervoussystemsCentralnervoussystemamongalcoholics33OthersfunctionAcetylcholine乙酰胆碱

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（红细胞转酮醇酶活力系数)37375.Dietaryrequirements&foodsources

ThiaminrequirementsdependlargelyonenergyintakeRecommendedbyCNSin2000:0.5mg／1000kcal

richsource：yeast、corn、bean、dryfruit

goodsource：milkeggfishmeat、fish、internalorgans

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

(angularstomatitis)唇炎

(cheilosis)舌炎

(glossitis)41413.Assessmentofriboflavinnutritionalstatus细胞谷胱甘肽还原酶活性系数(erythrocyteglutathionereductaseactivationcoefficient，EGRAC)activitycoefficient,AC＜1.2isnorml;＞1.4isdeficiencyUrinaryloadingVB2trial：

清晨口服维生素B25mg，4h尿中排出量

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

＞1300μgsufficiency

或测任意一次尿中核黄素与尿肌酐比值42424.Dietaryrequirements&foodsourcesRecommendedbyCNSin2000:RNI1.4mg/dformale1.2mg/dforfemaleadults，UL50mg/d.Riboflavinispresentinmostfoodsalthoughthebestsourcesaremilkandmilkproducts,eggs,liver,kidney,yeastextractsandfortifiedbreakfastcereals.4343维生素C.

5644八.VitaminCVitaminCisprobablythemosttalkedaboutvitaminandiscertainlytheonemostwidelyusedasasupplement.ThechemicalnameforvitaminCisascorbicacid.59456046Functions抗氧化作用：很强的抗氧化剂，在体内可以氧化型和还原型存在作为羟化过程底物和酶的辅助因子促进类固醇的代谢清除自由基参与合成神