UNit6儿童营养 Nutritional requirements ofchildernWord文件下载.docx
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Dietaryreferencevalues
Ithaslongbeenrecognizedthatgoodnutritionisofcrucialimportanceforthewell-being,growthanddevelopmentofchildren.Eventhoughtheenergycostofgrowthisaminorcomponentoftotalenergyrequirements,growthrateisasensitiveindicatorofoveralldietaryadequacy.Inthelongerterm,foodpatternsinchildhood,particularlyadolescence,cansetthesceneforfuturedietarypreferencesandeatingbehaviorinadultlife.Thereisalsosubstantialevidencethatpoordietandpoorphysicalactivitypatternsinchildhoodcanstoreupproblemsthatmanifestlaterinlife,particularlyinrelationtoheartdisease,obesity,type2diabetesandsomeformsofcancer.
Thenutritionalrequirementsofchildrenarehighinrelationtotheirsizebecauseofthedemandsforgrowth,inadditiontorequirementsformaintenanceandphysicalactivity.Earlypubertywillalsoaffectnutritionalrequirements.
Tables1and2showtheUKDietaryReferenceValues(DRV)forenergyandselectednutrientsforchildrenfrom4to18years.Theseareusedasaguidetotheadequacyofchildren’sdiets.Theestimatesofrequirementsforprotein,vitaminsandmineralsforgroupsofchildrenareexpressedasReferenceNutrientIntakes(RNI),theRNIbeingtheamountthatissufficientforalmostall(97.5%)individuals.TheEstimatedAverageRequirement(EAR)isusedasanindicationofenergyrequirements,andbydefinition50%ofpeopleinadefinedgroupwillneedlessthanthistomaintainenergybalanceand50%willneedmore.TheenergyEARassumesasedentarylifestyle(asthisisthesituationforthemajorityofpeopleinBritain,thoughincreasedactivityisadvised);
useoftheRNI(equivalenttothemeanplus2standarddeviations)wouldmeanthatpredictedintakeswouldbegreaterthanmostpeople’sneedsandhencewouldresultinweightgainoveraperiodoftime.Becauseofinsufficientdata,atthetimetheDRVswereset,fromUKstudiesmeasuringactualenergyexpenditureinchildrenaged4–10years,theestimatedaveragerequirementsforenergybydifferentageandgendergroupshavebeenbasedonintakedatafromanumberofstudiesconductedinhealthywell-nourishedchildrenintheUKandelsewhereTheenergyrequirementsforolderchildren11–18years,however,arebasedonenergyexpendituredata,expressedasmultiplesofbasalmetabolicrate.
Table1DietaryReferenceValuesforboysaged4–18years
Age(years)Units4–67–1011–1415–18
EnergyMJ7.168.249.2711.51
Kcal1715197022002755
Proteing19.728.342.155.2
Ironmg6.18.711.311.3
Calciummg45055010001000
Zincmg6.57.09.09.5
Magnesiummg120200280300
Phosphorusmg350450775775
Sodiummg700120016001600
VitaminAmg500500600700
VitaminB1,thiaminmg0.70.70.91.1
VitaminB2,riboflavinmg0.81.01.21.3
Niacinmg11121518
VitaminB6mg0.91.01.21.5
VitaminB12mg0.81.01.21.5
Folatemg100150200200
VitaminCmg30303540
Recommendationsforthepopulationingeneral,i.e.allages
Fat%foodenergy35
ofwhichsaturates%foodenergy11
Carbohydrate%foodenergy50
ofwhichstarch,intrinsicsugarsandmilksugars
%foodenergy39
ofwhichNMEsugars*%foodenergy11
Source:
DepartmentofHealth1991.*Non-milkextrinsicsugars.
Table2DietaryReferenceValuesforgirlsaged4–18years
EnergyMJ6.467.287.928.83
Kcal1545194018452110
Proteing19.728.341.245.0
Ironmg6.18.714.814.8
Calciummg450550800800
Zincmg6.57.09.07.0
Magnesiummg120200280300
Phosphorousmg350450625625
Sodiummg700120016001600
VitaminAmg500500600600
VitaminB1,thiaminmg0.70.70.70.8
VitaminB2,riboflavinmg0.81.01.11.1
Niacinmg11121214
VitaminB6mg0.91.01.01.2
VitaminB12mg0.81.01.21.5
Folatemg100150200200
VitaminCmg30303540
ofwhichstarch,intrinsicsugarsandmilksugars
Sincethe1985FAO/WHO/UNU(FoodandAgricultureOrganization/WorldHealthOrganization/UnitedNationalUniversity)report,morehasbeenlearntabouttheenergyexpenditureofchildrenandadolescents,andthedistributionoftimespentinactivitiesofdifferinglevelsofenergyexpenditure,largelyasaresultoftheapplicationofthedoublylabeledwatermethodandothertechniquessuchasheartratemonitoring(Torunetal.1996).Torunetal.havereviewedtheavailabledataandpublishedrecommendationsforresearchpriorities,designedtohelpprovideamorecompletepictureofchildren’senergyneeds.Theyhighlighttheimportanceofcouplingdietaryenergyguidelineswithstrongrecommendationsonphysicalactivity,notingthattheminimumamountofactivitycompatiblewithgoodhealthinchildhoodhasnotbeenpreciselydetermined.AreviewofenergyrequirementsiscurrentlybeingundertakenbyFAOandothers.
Desirableintakesofcarbohydratesandfatsareexpressedasaproportionoftotaldietaryenergy.ThesetakeintoaccounteatinghabitsintheUKandthepracticalimplicationsofachievingchangeinlinewithwhatisconsidereddesirableforhealth.Theyhavebeencalculatedwiththeneedsoftheadultpopulationinmind.Whilstthesevaluesprovideausefulguideforolder(schoolage)children,theyshouldnotbeappliedrigorouslytothedietsofpre-schoolchildren.
Therearenospecificestimatesforthedesirableamountoffibre(non-starchpolysaccharide,[NSP])forchildren.TheDepartmentofHealth(1991)recommendsthatchildrenshouldhaveproportionallylowerfibreintakesthanadults;
theDRVforadultsis18gofNSPperday.ItshouldbenotedthatrecentlytheFoodStandardsAgencyhasannouncedthatdifferentmethodology(theAmericanAssociationofAnalyticalChemists(AOAC)methodratherthantheEnglystmethod)istobeusedtoassessthedietaryfibrecontentoffoods;
thischangewillnecessitatereassessmentoftheDRVfigureasthetwomethodsarenotcomparable.
Formostessentialnutrients,requirementshavebeenestimatedbyextrapolatingfrompublisheddataforinfantsandadults,aslittlespecificinformationforschoolagedchildrenexists.Duringadolescence,nutrientrequirementsaresethigherforboysthanforgirlsbecauseoftheirincreasedratesofgrowth,bonesynthesisandbonemineralisation.Oncemenarcheisreachedandperiodsstart,girlsloseonaveragetheequivalentof12.5mmol(1mmol=55.9mg)ofironperday,althoughthereiswidevariationintheamountofbloodlost,withgirlsonthe95thcantlelosingaround34mmolperday.Thesedatahavebeenusedtosettheironrequirementsforgirlsatalevelhigherthanforboysandmuchhigherthanduringtheprepubertalperiod.
Similarly,therearenoestimatedrequirementsforvitaminDbecauseitisexpectedthat,withtheexceptionofveryyoungandveryelderlypeople,mostpeopleobtainanadequateamountofthevitaminviatheactionofsunlightontheskin.However,ithasbecomeapparentthatasubstantialproportionofchildrenhavelowvitaminDstatusandthismaycarrypublichealthimplications.Thereislittleevidencetosuggestdifferentrequirementsamongethnicgroups,althoughtheDepartmentofHealth(1980)continuestorecommendthatallAsianchildrentakevitaminDsupplementsasaprecaution,particularlywherereligionandcustomsdictatethattheirskiniskeptcoveredoutside,resultinginareducedexposureoftheirdarkerskintotherelativelyweaksunlightavailableintheUK.
Fluidrequirements
Fluidrequirementsareanoftenoverlookedaspectofdiet.Toreplacefluidlosses,whichoccurviaurine,sweatandbreath,1.5mLperkcalexpendedhasbeenrecommendedasatotalfluidrequirement.Thisamountstoatotalfluidintakeofapproximately2600mLperdayfora7-year-oldgirland4000mLperdayfora15-year-oldboy.However,allowancesneedtobemadeforthefluidcontentoffoodsincludedinthediet.Itisnowgenerallyacceptedthat6–8glassesoffluidperday(appropriateforthesizeandageofthechild)shouldbesufficient,althoughmorewillbeneededinhotweatherandaftervigorousphysicalactivity.Inadults,thirstisagoodindicatoroffluidneeds,ifrespondedtopromptly.However,childrenmayneedtobeencouragedtodrinksufficienttorehydrate,e.g.afterexercise,andprovisionofflavoredwaterisoftenmoreacceptable.Iflostfluidisnotreplaced,dehydrationwillresult.Intheshortterm,poorhydrationcausesheadaches,continenceproblemsandconstipation,butinthelongertermcanleadtourinarytractinfections,kidneystonesandkidneydisease.Thereisalsoanecdotalevidencethatalertnessandcognitiveperformancecanbecompromisedby