Foods and Nutrition 1021 Lecture Notes - Lecture 7: Retinol, Spinach, Biotin

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Chapter7:TheVitamins
FoodsandNutrition1021Section531
DefinitionandClassificationofVItamins
Vitamins
● Organiccompoundsvitaltolife
● Indispensabletobodyfunctions
● Neededinminuteamounts
● Noncaloricessentialnutrients
Precursors/Provitamins
● Compoundsinfoodsconvertedtoactivevitamins
Theonlydiseaseavitamincancureistheonecausedbyadeficiencyofthatvitamin!
FatSolubleVitamins
● VitaminsA,D,E,K
WaterSoluble
● BVitamins,niacin,folate,B12,B6,Biotin
● VitaminC
FactorsthatDestroysVitamins
● Acids,bases,oxygen,UVLight,heat
CharacteristicsofFatSolubleVitamins
VitaminsA,D,E,K
● Absorbedintothelymph,travelinthebloodinassociationwithproteincarriers
● Dissolveinlipid
● Requirebileforabsorption
● Storedintheliver&bodytissues
● Maybetoxicinexcessfromsupplements(A,D,K)
● Deficienciesoccurwithlowintakeorfatmalabsorption
VitaminA
Threeactiveformsinthebody
● Retinol(sotredintheliver)
● RetinalandRetinoicacid(convertedbycellsfromretinol)
● Plantderivedprecursor(BetaCarotene)
GoodFoodSources
● Liver,fortifiedmilk
● Deeporangefruits&darkgreenleafyvegetables[sweetpotatoes,carrots,spinach,‘bok
choy’,broccoli,apricots,mango,cantaloupe]
BetaCarotene
MostabundantcarotenoidprecursorforvitaminA
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Dietaryantioxidant
Measuredinretinolactivityequivilents(RAE)
● ConvertBcarotene[&othercarotenoids]toretino
● Takes12ugBcarotenetoequal1ugretinolforthebody
● Bcaroteneinexcess–nottoxiccomparedtoretinol;turnspeoplebrightyellow/orange
ifeateninexcess[duetobuildupinfattissuesbeneaththeskin]
● RichsourceofBcarotene:carrots,sweetpotatoes/yams,pumpkins,mango,canteloupe,
spinach,brocooli
● Othercolorfulveggies:redcabbage,beets,yellowcorn,whiteyam–poorsourcesof
Bcarotene
FunctionofVitaminA
Eyesight:Lightperceptionattheretina
● PigmentrhodopsincontainsvitaminA
Process:
● whenlighthitstheeye,itbleachestherhodopsin,
● apieceofvitaminAbreaksoff,whichconveysthesensationofsighttotheopticcenter
ofthebrain.
● newvitaminAisneededtoreplacethepartthatbreaksoff.
● Ifdeficientinvitamin:lackinrecoveryofvitaminA=flashoflightoccurs=
Nightblindness
Eyesight:Maintainshealthycrystalclearcornea
● Coveringtheoutsideoftheeye
● ProgressivewithDeficiency
Keratinizationofthecornea:protein“keratin”accumulatesinthecornea
Xerosis:dryingofthecornea
● Xerophthalmia:thickeningofthecorneaandpermanentblindness
Maculardegeneration[intheelderly]–lossofthecentralfocusofvisionintheretina;
macula’sprotectiveyellowpigmentprovidedbyBcarotene&othercarotenoids
Prevention–capsulesproviding60,000ug2xayear;regularintakeofF&V
Geneexpression:
Retinoicacidregulatesactivitiesofgenesthatdirectthesynthesisofproteins&enzymes(thus,
affectingmetabolicactivitiesoftissues)
Analogy:Caralonecant’takeyouacrosstown–needkeyandtoturnthekeyintheignitionto
startthemotor
Havingthemachinerytomakegenesisnotenough,needretonoicacidtoactivateand
deactivategenes
Skin&bodylinings:
● Epithelialcells(externalskin&protectiveliningsofthelungs,intestines,vagina,urinary
tract,&bladder)needvitaminA
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● Serveasprotectivebarrierstoinfectionbybacteriaandtodamagefromothersources
Majorantioxidant:
Bcarotene[togetherwithvitaminsC&E,selenium]
Celldifferentiation:
● Allowseachtypeofcelltomatureandperformaparticularfunction,e.g.,gobletcells
producemucus[inlungs]toprotectitfromrespiratoryinfections
Keratinizationcanoccurinthewrongplace(seenextslide)
● Makesthesurfacehard/dry/cracked–riskofinfection
Linkstocancer,esp.roleofretinoicacidinregulatinggenesthatmaysuppressoreven
reversemalignantcellchanges
VitaminARecommendations
● AmountsofvitaminAneededproportionaltoB.Wt.
RDA–700ugRAE/d/F;900ugRAE/d/M
RAE=retinolactivityequivalents(consideramountsfromBcarotene&precursorsor
forms)
Storedinthebody,soaverageintakedoesnotneedtobefromdailyintake,butoverall
intake
UL–3000ugRAE/d,fromretinol(preformedvitamin)only–avoidsupplements
exceedingthis(adults18yrs+)
IU(internationalunit)=0.3ugretinol–ensureyouconvertappropriatelybetween
foodandsupplements
● Recommendationseasilyreachedthroughfoodaloneinhealthybalanceddietfrom
retinolandbetacarotene
VitaminAToxicity
● Viasupplementorfortifiedfoods(andliver)
● Earlysymptomsofoverdose:lossofappetite,blurredvision,growthfailureinchildren,
headache,itchingoftheskin,irritability,bonefractures
● Othersigns:abdominalpain,hairloss,jointpain,stuntedgrowth,bone&muscle
soreness,cessationofmenstruation,nausea,diarrhea,rashes,damagetotheliver,
enlargementofthespleen
34xRDAinpregnancy–toxictofetus[malformations];singledoseof100xwill
causetoxicreactions;bewareofheavilyfortifiedfoods!
Acne–vit.Awillnotcureacne;Accutane–derivedfromvit.Abutchemicallyaltered&
dosescontrolled
● Increasedactivityofbonedismantlingcells–reducedbonedensity&pain
VitaminADeficiencyintheWorld
● 310Mchildrensufferfromxerophthalmis,diarrhea,reducedfoodintake
● 275Mchildrensufferfromthemilderdeficiency
● VitaminASupplements:recommendedforprotectionagainstmeasles,malaria,lung
diseases,HIV
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