Post on 23-Feb-2018
871. Water-Soluble Vitamins 872. Fat-Soluble Vitamins & Nutrients
2. Fat-Soluble Vitamins and Nutrients
Vitamins A and E and Carotenoids VitaminA Retinylpalmitate Retinylstearate VitaminE gamma-Tocopherol alpha-Carotene trans-beta-Carotene cis-beta-Carotene beta-Cryptoxanthin Luteinandzeaxanthin trans-Lycopene Totallycopene(cis-andtrans-)
Vitamin D 25-HydroxyvitaminD
Fatty AcidsSaturated
Myristicacid(14:0) Palmiticacid(16:0) Stearicacid(18:0) Arachidicacid(20:0) Docosanoicacid(22:0) Lignocericacid(24:0)
Monounsaturated Myristoleicacid(14:1n-5) Palmitoleicacid(16:1n-7) cis-Vaccenicacid(18:1n-7) Oleicacid(18:1n-9) Eicosenoicacid(20:1n-9) Docosenoicacid(22:1n-9) Nervonicacid(24:1n-9)
Polyunsaturated Linoleicacid(18:2n-6) alpha-Linolenicacid(18:3n-3) gamma-Linolenicacid(18:3n-6) Eicosadienoicacid(20:2n-6) homo-gamma-Linolenicacid
(20:3n-6) Arachidonicacid(20:4n-6) Eicosapentaenoicacid(20:5n-3) Docosatetraenoicacid(22:4n-6) Docosapentaenoicacid(22:5n-3) Docosapentaenoicacid(22:5n-6) Docosahexaenoicacid(22:6n-3)
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Vitamins A, E and CarotenoidsBackground InformationSources and Physiological Functions. VitaminsA(retinol)andE(alpha-tocopherol)andthecarotenoidsarefat-solublemicronutrientsfoundinmanyfoods,includingsomevegetables,fruits,meats,andanimalproducts.Fish-liveroils,liver,eggyolks,butter,andcreamareknownfortheirhighercontentofvitaminA.NutsandseedsareparticularlyrichsourcesofvitaminE(Thomas2006).Atleast700carotenoidsfat-solubleredandyellowpigmentsarefoundinnature(Britton2004).Americansconsume4050ofthesecarotenoids,primarilyinfruitsandvegetables(Khachik1992),andsmalleramountsinpoultryproducts,includingeggyolks,aswellasinseafoods(Boylston2007).Eightdifferentcarotenoidsareeasilymeasuredinhumanserum:alpha-carotene,cis-andtrans-beta-carotene,beta-cryptoxanthin,lutein,cis-andtrans-lycopene,andzeaxanthin.Mainsourcesofcarotenesareorange-coloredfruitsandvegetablessuchascarrots,pumpkins,andmangos.Luteinandzeaxanthinarealsofoundindarkgreenleafyvegetables,whereanyorangecoloringisovershadowedbychlorophyll.Trans-lycopeneisobtainedprimarilyfromtomatoesandtomatoproductsandsomefruits.ForinformationonthecarotenoidcontentofU.S.foods,seethe1998carotenoiddatabasecreatedbytheU.S.DepartmentofAgricultureandtheNutritionCoordinatingCenterattheUniversityofMinnesota(http://www.nal.usda.gov/fnic/foodcomp/Data/car98/car98.html).
VitaminA,foundinfoodsthatcomefromanimalsources,iscalledpreformedvitaminA.SomecarotenoidsfoundincolorfulfruitsandvegetablesarecalledprovitaminAbecausetheyaremetabolizedinthebodytovitaminA.Amongthecarotenoids,beta-carotene,aretinoldimerconsistingoftwolinkedretinolmolecules,hasthemostsignificantprovitaminAactivity.Approximately12micrograms(g)ofdietarybeta-carotenecanprovidetheequivalentof1gofretinol.OtherprovitaminAcarotenoids,suchasalpha-caroteneandbeta-cryptoxanthin,arehalfasactiveasbeta-carotene(InstituteofMedicine2000).ThebioconversionofcarotenoidstovitaminAishighlyvariablefrompersontoperson(Krinsky2005).RetinylestersserveasthestorageformofvitaminAandaremostlyconcentratedintheliver.
Theabsorptionoffat-solublemicronutrientsfromthegastrointestinaltractdependsonprocessesresponsibleforfatabsorptionormetabolism.Thus,peoplewithconditionsresultinginfatmalabsorption(e.g.,celiacdisease,Crohnsdisease,pancreaticdisorders)candevelopvitaminAdeficiencyovertime.VitaminAalsohasinteractionswithothernutrients.IronandzincdeficiencycanaffectvitaminAmetabolismandtransportofvitaminAstoresfromthelivertobodytissues(InstituteofMedicine2001).Theabsorptionofcarotenoidsfromfoodsishighlydependentoncookingtechniquesthatbreakdownplantcellwallsandreleasecarotenoids;itisalsodependentontheavailabilityofdietaryfattoenhancecarotenoiduptake(Krinsky2005).TheliverregulatestheconcentrationofvitaminAinthecirculationbyreleasingstoredretinylestersasneeded;onlywhenliverreservesarenearlyexhausteddoesserumvitaminAfallintothedeficientrange(Napoli2006).ThevariationinserumcarotenoidconcentrationsamongpeopleintheUnitedStatesisrelativelylarge,primarilyreflectingwide-rangingdifferencesindietaryintake(Lacher2005).
VitaminEactivityisderivedfromatleasteightnaturallyoccurringtocopherols,themostpotentofwhichisalpha-tocopherol.OtherlessactiveformsofvitaminEareplentifulintheU.S.diet,withgamma-tocopherolbeingthepredominantform.Themostcommonlyconsumedsourcesofalpha-tocopherolinthedietofAmericanadultsaremixedfoods(spaghettisauce,pizzaandchili),friedpotatoes,saladdressings,andbakerygoods(Ahuja2004).Otherimportantsourcesare
http://www.nal.usda.gov/fnic/foodcomp/Data/car98/car98.htmlhttp://www.nal.usda.gov/fnic/foodcomp/Data/car98/car98.html
891. Water-Soluble Vitamins 892. Fat-Soluble Vitamins & Nutrients
tomatoes,eggs,nutsandseeds,andsnackfoods.Plasmaconcentrationsoftocopherolsvarywidelyamonghealthyindividualsandarehighlycorrelatedwithplasmalipidconcentrations(Ford1999;Ford2006).
Health Effects.InadequateorexcessiveintakeofvitaminsAorEcanleadtovariousdisorders.Forexample,vitaminAdeficiency,consideredtobethemaincauseofchildhoodblindnessinlow-incomecountries(Roodhooft2002),isarareconditionintheUnitedStates.ProminentsignsofvitaminAdeficiencyincludenightblindness,cornealthinning,andconjunctivalmetaplasia.VitaminAisalsoessentialforproperimmunefunction,epithelialgrowthandrepair,bonegrowth,reproduction,andnormalembryonicandfetaldevelopment(West2006).Acutetoxicityresultingfromsingleorshort-termlargedosesofpreformedvitaminAischaracterizedbynausea,vomiting,headache,vertigo,blurredvision,increasedcerebrospinalfluidpressure,andlackofmuscularcoordination.Centralnervoussystemeffects,liverabnormalities,boneandskinchanges,andothernonspecificadverseeffectscanbeindicativeofchronichypervitaminosisA.ConsumingexcessamountsofvitaminAduringearlypregnancymayleadtoseriousbirthdefects(InstituteofMedicine2001).
Serumorplasmaconcentrationsofcarotenoidsareconsideredamongthebestbiologicalmarkersforfruitandvegetableintake.Thestrongestdietarypredictorsofserumcarotenoidconcentrationsarefruits(forsourcesofbeta-cryptoxanthin),carrotsandrootvegetables(forsourcesofcarotenes),andtomatoproducts(forsourcesoftrans-lycopene)(Al-Delaimy2005).Researchstudieshaveshowninconsistenciesintherelationbetweencarotenoidintakeandprotectionfromcancer.Carotenoidsinfoods,evenwhenconsumedoverlongperiodsandinlargeamountsarenotknowntoproduceadversehealtheffects.However,resultsofinterventionstudiesofsmokerswhoused2030milligrams(mg)ofbeta-caroteneperdayshowedthatthisgrouphadmorelungcancersthanplacebo-treatedgroups(Albanes1996;Redlich1998).
VitaminEdeficiencyoccursonlyrarelyinpeople,andovertdeficiencysymptomsinpeopleconsuminglow-vitaminEdietshaveneverbeendescribed(InstituteofMedicine2000).ThemainmanifestationofvitaminEdeficiencyisperipheralneuropathycharacterizedbythedegenerationofthelarge-caliberaxonsofsensoryneurons(InstituteofMedicine2000).Theupperlimit(UL)forvitaminEintake(1000mg/day)isbasedonhemorrhagiceffects;however,acausalassociationbetweenexcessalpha-tocopherolintakeinapparentlyhealthyindividualsandadversehealthoutcomeshasnotconsistentlybeenshown(InstituteofMedicine2000).Studiesevaluatingtocopherolstoreducetheriskforcardiovasculardiseasedemonstratedinconsistentfindings(AgencyforHealthcareResearchandQuality2003).TheAmericanHeartAssociationcurrentlyadvisesthatantioxidantsupplements(suchasvitaminsEandCandbeta-carotene)shouldnotbeusedforprimaryorsecondarypreventionofcardiovasculardisease(Lichtenstein2006).Nevertheless,theAmericanHeartAssociationrecommendsconsumingfoodsourcesofantioxidantnutrients,principallyfromavarietyofplant-derivedfoodssuchasfruits,vegetables,wholegrains,andvegetableoils.
Intake Recommendations. TheNationalAcademyofScienceshasestablisheddietary-requirementintakevaluesforvitaminsAandEbydeterminingtheAdequateIntake(AI)forinfantsandtherecommendeddietaryallowance(RDA)forolderagegroups(InstituteofMedicine2000and2001).TheRDAforvitaminAinretinolequivalentsis900g/dayformenand700g/dayforwomen;forchildrenandadolescents(118years),theRDArangesfrom300900g/day.Forinfants(012months),theAIissetat400500g/dayofretinolequivalents.TheTolerableUpperIntakeLevel(UL)foradultsissetat3,000g/dayofpreformedvitaminA,whereastheULforinfants(600g/day),youngerchildren18years(600-900g/day),olderchildren913years(1700g/day),and
90 2nd National Report on Biochemical Indicators of Diet and Nutrition in the U.S. Population90 2nd National Report on Biochemical Indicators of Diet and Nutrition in the U.S. Population
adolescents1418years(2800g/day)areage-dependent.Foradults,theRDAforvitaminEis15mg/dayofalpha-tocopherol;forchildrenandadolescents(118years),theRDArangesfrom615mg/day.ThereisnoRDAforotherformsofvitaminE,suchasgamma-tocopherol.TheULforvitaminEwhichappliestoalleightstereoisomersofalpha-tocopherolis1000mg/dayforadults;aULforinfantscouldnotbeestablishedandthusonlyfoodandformulasourcesofdietaryintakearerecommended.TheULforchildrenandadolescentsrangesfrom200-800mg/dayofvitaminE.Althoughnoquantitativerecommendationsareavailablefortheintakeofcarotenoids,existingrecommendationssupportincreasedconsumptionofcarotenoid-richfruitsandvegetables.Currentpublichealthguidelinesadvisethatpeopleconsumeatleast2.5cupsoffruitsandvegetablesaday,dependingoncaloricneed,toensureadequatenutrientintake(U.S.DepartmentofAgricultureandU.S.DepartmentofHealthandHumanServices2010).
Biochemical Indicators and Methods.ThebestwaytodetermineinadequatevitaminAstatusisthroughhepaticbiopsy,butthisinvasiveprocedureisunsuitableforpopulationstudies.Serumorplasmaretinolismeasuredbyuseofhighperformanceliquidchromatography(HPLC)withultraviolet(UV)detectionafterseparationfromitscarrierretinolbindingprotein(RBP).BecauseretinoliscloselycorrelatedwithRBP,themeasurementofthistransportproteinthroughenzyme-linkedimmunosorbentassay(ELISA