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)

88 2nd National Report on Biochemical Indicators of Diet and Nutrition in the U.S. Population88 2nd National Report on Biochemical Indicators of Diet and Nutrition in the U.S. Population

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