现代营养学之水和矿物质

Chapter6

WaterandMinerals第六章水和矿物质1Water:TheMostEssentialNutrientNutrientmostneededbythebodyMakesuppartofeverycell,tissue,organAccountsforabout60%ofbodywt:Bone>20%waterMuscle~75%waterTeeth~10%waterlb=pound=0.454kg2WaterFunctionsCarriesnutrientsthroughoutthebodyServesasthesolventforchemicalsinthebodyCleansesthetissuesandbloodofwastesParticipatesinchemicalreactionsActsasalubricantaroundjointsServesasashockabsorberinsideeyes,spinalcord,joints,andamnioticsac(羊膜囊)Aidsinmaintainingthebody’stemperature3Humanlifebeginsinwater4TheBody’sWaterBalanceTomaintainwaterbalance,apersonmustconsumeatleastthesameamountlosteachdaytoavoidlife-threateninglosses.Achangeinbody’swatercontentcanbringaboutatemporarychangeinbodyweight.Anextradrinkofwaterbenefitsbothyoungandold5QuenchingThirstandBalancingLosses6QuenchingThirstandBalancingLosses7

ThirstlagsbehindalackofwaterToignorethirstistoinvitedehydration Whenapersonisthirsty,theymayalreadyhavelostupto2cupsoftotalfluidWaterintoxicationoccurswhentoomuchplainwaterfloodsthebody’sfluidsanddisturbstheirnormalcompositionCanoccurifseveralgallons(≈3.8liter)ofwaterareconsumedinafewhours’timeCanbefatal QuenchingThirstandBalancingLosses8HowMuchWaterDoINeedtoDrinkinaDay?9AreSomeKindsofWaterBetterforMyHealthThanOthers?Hardwater–highconcentrationsofcalciumandmagnesiumSoftwater–highsodium,anditdissolvescadmium(Cd)andlead(Pb)frompipes10SafetyandSourcesofDrinkingWaterWaterispracticallyauniversalsolvent:itdissolvesalmostanythingitencounterstosomedegree.Hundredsofcontaminantshavebeendetectedinpublicdrinkingwater.11SafetyofPublicWaterTheEnvironmentalProtectionAgency(EPA)isresponsibleforensuringthatpublicwatersystemsmeetminimumstandardsforprotectionofhealth.Publicwatersystemsremovesomehazards;treatmentincludestheadditionofadisinfectant(usuallychlorine)tokillmostmicroorganisms.12WaterSourcesAlldrinkingwateroriginatesfromsurfacewaterorgroundwaterthatisvulnerabletocontaminationfromhumanactivities.含水层地下水地表水13BottledWaterNotnecessarilyanypurerormorehealthfulthantapwaterAbout25-40%ofbottledwatercomesfromthesamemunicipal(市政)

watersuppliesBottledwatermaynotcontainadequateamountsoffluoride(氟)Costmaybe250-10,000timeshigherthantapwaterAconsumergrouptestedbottledwater,however,anddisprovedthenotionofsuperiorsafetyAbout1/3werecontaminatedwithbacteria,arsenic(砷),orsyntheticorganicchemicals14Introduction–Minerals“Ashestoashes,dusttodust”–whenwedie,whatisleftbehindbecomesnothingbutapileofashes.Carbonatomsincarbohydrates,fats,proteins,andvitaminscombinewithoxygentoproducecarbondioxide,whichgoesintotheair.Hydrogensandoxygensformwater,andalongwithbodywater,thisevaporates.Ashesareabout5pounds(5*0.454kg)ofminerals.About¾iscalciumandphosphorusLessthanateaspoonofiron1516MineralFunctionsBoneHealthBloodHealthFluidBalanceEnergyMetabolismAntioxidant171Mineralsfor:BoneHealthMajorminerals

CalciumMagnesiumPhosphorousSodiumPotassiumChlorideSulfurTraceMinerals

IronZincCopperFluorideSeleniumIodineChromiumVitaminDVitaminK1819Make-up

ofbonesCalciumMostabundantmineralinbody–2%ofbodyweightProvidesstructuretobonesandteeth99%ofcalciuminbonesPhosphorousSecondmostabundantmineralinthebodyCriticalroleinboneformationGivesbonesandteethstrengthandrigidityMagnesiumMostisinthebone.Helpsregulateboneandmineralstatus–cofactorProteinBonematrixandbonegrowth20FluorideFluoridestabilizesbonesandmakesteethresistanttodecay.Excessfluoridediscolorsteeth;largedosesaretoxic.Topreventfluorosis,youngchildrenshouldnotswallowtoothpaste21BoneHealthandOsteoporosis(骨质疏松)Osteoporosisisthemostcommonbonedisease10millionAmericans>50haveosteoporosis34millionatriskfordevelopingosteoporosisdirectcarecostsforosteoporoticfractures(骨折)alonearealreadyupto$18billioneachyearby2020,50%ofAmerican>50willbeatriskforfractures(骨折)fromosteoporosisandlowbonemassAReportoftheSurgeonGeneral22OsteoporosisAdultboneloss(成年骨质流失)AconditionwherethebonesbecomefragileandporousNormalBoneOsteoporoticBone23BoneMassandAgeBonemass(骨密度):DecreaseswithagePeaksaround3024CalciumSourcesDairy:milk,cheese,yogurtBroccoli,kale(羽衣甘蓝),darkgreenvegetablesOrangejuicewithcalciumSalmon,sardineswiththebones25MaintainingBoneHealthOsteoporosisPreventionAbalanceddietrichincalcium(1000mgwhen<50y,1200mgwhen>50y)vitaminD(5–15mg)Weight-bearingexerciseAhealthylifestylewithnosmokingorexcessivealcoholintakeBonedensitytestingandmedicationwhenappropriate26Milk,CalciumandBoneHealthMilkandmilkproductstypicallycontainmorecalciumthanotherfoodsourcesMilkalsocontainsvitaminDandlactosewhichcanenhancecalciumabsorption27Animalvs.VegetableProteinSources28Betterbonehealthwithwalnuts1/17/2007-AnewstudypublishedinNutritionJournalsuggeststhatwalnuts,richinα-linolenicacid(ALA,亚麻酸),anessentialω-3fattyacid,helpthehumanskeletalsystembydecreasingthebreakdownofbone.ConductedbyPennStateresearchers,thestudyisthefirsthumanstudyevaluatingtheeffectofplant-basedsourcesofω-3fattyacids(ALA)onbonehealth.TheresultssuggesthigherconsumptionofALAleadsto