大学一年级下学期-Unit2-passage-english-a

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<P1>Sportsmedicineexpertshaveobservedforyearsthat<1>endurance</1>athletes,particularlyfemales,frequentlyhaveirondeficiencies.

NowanewstudybyateamofPurdueUniversityresearcherssuggeststhateven<2>moderate</2>exercisemayleadtoreducedironinthebloodofwomen.

"Wefoundthatwomenwhowerenormallyinactiveandthenstartedaprogramofmoderateexerciseshowed<3>evidence</3>ofironloss,"saysRoseanneM.Lyle,associateprofessoratPurdue.

Herstudyof62<4>formerly</4>inactivewomenwhobeganexercisingthreetimesaweekforsixmonthswaspublishedinthe<5>journal</5><em>Medicine&ScienceinSports&Exercise.</em>

"<P2>Womenwho<6>consumed</6>additionalmeatortookiron<7>supplements</7>wereableto<8>bounce</8>back,"shenotes.

"Butthenewexerciserswhofollowedtheirnormaldietshowedadecreaseinironlevels."

Irondeficiencyisverymonamongwomeningeneral,affectingoneinfourfemaleteenagersandoneinfivewomenaged18to45,<9>respectively</9>.

Butthe<10>ratio</10>isevengreateramongactivewomen,affectingupto80percentoffemaleenduranceathletes.

Thismeans,Lylesays,that"toomanywomenignoretheamountofirontheytakein".

<P3>Womenof<11>childbearing</11>ageareatgreatestrisk,sincetheirmonthlybleedingisamajorsourceofironloss.

<12>Plus</12>,manyhealth-consciouswomenincreasetheirriskbyrejectingredmeat,whichcontainsthemosteasily<13>absorbed</13>formofiron.

Andbecausewomenoften<14>restrict</14>theirdietinanefforttocontrolweight,theymaynotconsumeenoughiron-richfood,andare<15>liable</15>toexperienceadeficiency.

"Theaveragewomantakesinonlytwothirdsoftheremendeddaily<16>allowance</16>ofiron,"notesanotherexpert.

"<P4>Forawomanwhoalreadyhasapoorironstatus,anyadditionalironlossfromexercisemaybeenoughtotipherovertheedgeintoamoreseriousdeficiency,"notestheexpert.

Exercisecanresultinironlossthroughavarietyofmechanisms.

Someironislostinsweat,and,forunknownreasons,intenseenduranceexerciseissometimesassociatedwithbleedingofthe<18>digestive</18>system.

Athletesinhigh-<19>impact</19>sportssuchasrunningmayalsoloseironthroughaphenomenonwheresmallblood<20>vessels</20>inthefeet<21>leak</21>blood.

Therearethreestagesofirondeficiency.

Thefirstandmostmonishavinglowironreserves,aconditionthat<23>typically</23>hasnosymptoms.

Fatigueandpoorperformancemaybegintoappearinthesecondstageofdeficiency,whennotenoughironispresenttoformthe<24>molecules</24>ofblood<25>protein</25>thattransportoxygentotheworkingmuscles.

Inthethirdandfinalstage,peopleoftenfeelweak,tired,andoutofbreath¡ª<P5>andexerciseperformanceisseverelypromised.

"Peoplethinkthatifthey'renotatthethirdstage,nothingiswrong,butthat'snottrue,"saysJohnL.Beard,whohelpeddesignthePurduestudy.

"You'renotinstage3untilyourironreservesgotozero,andifyouwaituntilthatpoint,you'reintrouble."

However,mostpeoplewithlowironreservesdon'tknowtheyhaveadeficiency,becausetraditionalmethodsof<26>calculating</26>theamountofironinblood(bycheckinglevelsofthebloodproteinthattransportsoxygen)arenot<27>sufficient</27>,Beardstates.

Instead,it'simportanttochecklevelsofadifferent<28>pound</28>,whichindicatetheamountof<29>storage</29>ofironintheblood.

Whileactive,childbearingagewomenaremostlikelytohavelowironstores,henotes,"Menarenotsafe,especiallyiftheydon'teatmeatandhaveahighlevelofphysicalactivity."

(Anestimated15percentofmalelongdistancerunnershavelowironstores.)Beardandotherexpertssay<P6>it's<30>advisable</30>forpeopleinthesegroupstohavea<31>yearly</31>bloodtesttocheckbloodironreserves.

Ifironlevelsarelow,talkwitha<32>physician</32>toseeifthedeficiencyshouldbecorrectedby<33>modifying</33>yourdietorbytakingsupplements.

Ingeneral,it'sbetterto<34>undo</34>theproblembyaddingmoreiron-richfoodstothediet,becauseironsupplementscanhaveserious<35>shortings</35>.Supplementsmayproduceafeelingofwantingtothrowup,andmaybepoisonousinsomecases.

Thebestsourcesofiron,andtheonlysourcesoftheformofironmostreadilyabsorbedbythebody,aremeat,chicken,andfish.

Goodsourcesofotherformsofironincludedates,beans,andsome<36>leafy</36>greenvegetables.

"<37>Select</37>breadsand<38>cereals</38>withthewords'iron-added'onthelabel,"writessportsdietexpertNancyClark.

"<P7>Thisaddedironsupplementsthesmallamountthatnaturallyoccursingrains.Eatthesefoodswith<39>plentiful</39>VitaminC(forexample,drinkorangejuicewithcerealorputatomatoonasandwich)toenhancetheamountofironabsorbed."

Clarkalsoremendscookinginironpans,asfoodcan<40>derive</40>ironfromthepanduringthecookingprocess.

"<P8>Theironcontentoftomatosaucecookedinanironpotforthreehoursshoweda<41>striking</41>increase,thelevelgoingupnearly30times,"shewrites.Andpeoplewhoarelikelytohavelowironshouldavoiddrinkingcoffeeorteawithmeals,shesays,<P9>since<42>substances</42>inthesedrinkscan<43>interfere