SpEAKING OF NUtRItION . . . SOME BASICS · 2011-10-24 · Chapter 1 Speaking of Nutrition . . ....

SpEAKING OF NUtRItION . . . SOME BASICSWelcometotheworldofnutrition,thestudyoffoodandhealth.Takingthisclassmeansyouhaveaninterestinyourhealthandfitness.Iapplaudyouforwantingtotakechargeofyourbody—learningaboutwhatyourbodyneedsforoptimalhealthfortodayandalifetime.Yourfoodchoicesimpactyourperformancetodayaswellassetthestageforhealthanddiseasepreventionlaterinlife.

Inthiscourse,youwill learnthatwhilemanypeopletendtocategorizefoodsas“good”or“bad,”suchascarrotsandorangesversusburgersandfries,thatallfoodsfitinyourdiet.Somedoprovideyouwithanarrayofsubstancesbetterforyourhealththanothers,buteatingandlivingwellisaboutmakingbalancedchoices.Duringthiscourse,youwillhavetheopportunitytoassessyourfoodchoicesbycompletingtheDietProject.Asyoulearnabouttherolesofprotein,fiber,fat,vitamins,andmoreinyourbody,youcancomparehowyourdietrateswithrecommendationsforoptimalhealth,andthenlearnhowtobestmeetyourneedsthroughfoodsandunderstandwheresupplementsmaybeanoption.

Beforewecanexplorespecificsaboutwhat’sbestforyoutoeat,afewbasicsmustbeintroduced.Solet’sgetstarted!

wHAT Are NuTrIeNTs, THeIr BAsIC FuNCTIoNs, AND How MuCH Do You NeeD (THe rDA)?Howmuchfooddoyoueatinayear’stime?Or,whatabouttheamountoffoodyoumayeatoverthenextfourdecades?Likemanycollegestudents,youmostlikelyaverageabout1millioncaloriesayearorin45yearsalmost70,000poundsoffood.Sowhereisallthisfoodgoing?Whatcouldyourbodypossiblybedoingwithsuchatremendousamountoffoodenergyandmaterial?Thisfoodandenergygoesintomakingthe“parts”thatmakeyouupandhelptomaintainyour“appearance.”Everydayyourbodyrenewsitself—makingnewcells,tissue,hair,andmore.Infact,takealookinthemirror.Eventhoughyoulookthesameasyoudidayearago(perhapsyoumayhaveanewhaircolororstyle,oranearpiercing),youarenotthe

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sameperson.You actually have an entirely new skin surface, newly remodeledbones,andfreshliningtoyourintestinaltract.Infact:

• About1%ofyourbloodcellsareneweveryday.• Thecellsinyourintestinerenewthemselveseverythreetofivedays.• Yourskinisslougheddaily(whichissomeofthedustinyourdormroomor

apartment!).• You’rebusygrowingnewbodyhairdaily.

Thefoodthatyoueatsuppliesyouwiththepartsandfuel—nutrients—neededtokeepupthistypeofrebuildingandrenewingschedule.Foodsuppliesnutrientsthat:

• provideenergy• serveasbuildingmaterials• helptomaintainorrepairbodyparts

Therearesixcategoriesofnutrients(alltotaledthereare50nutrients):

1. Proteins(madeof20differentsubunits)2. Carbohydrates(simpleandcomplex)3. Fats(twocategorieswithseveraltypes)4. Minerals(15plusminterals)5. Vitamins(13differentones)6. Water(asinglenutrientinaclassbyitself)

Foods,suchasfruits,vegetablesandwholegrains,containothersubstancesthatmayhavebiologicalactivityindiseasepreventionandhealthpromotion.Thesesubstances,calledphytochemicals,ofwhichtherearethousandsinwholefoods,helpprotecttheplantsweeatfromUVlight,insects,andotherpests.Onceweeatthesecolorfulphytochemicalsincarrots,peppers,orangesandthelike,thesesub-stancespromotebetterhealthandhelpprotectusfromchronicdiseases,suchascancer.Scientificstudiesshowthatphytochemicalsinsoybeanscalledisoflavoneshelplowerrisksforcertaincancers.

Allsixcategoriesofnutrientsarepresentinthebodybutindifferingamountsorpercentofyourbodyweightasfollows:

1. 50–60%�water—malesgenerallyhaveabout60%,andfemaleshave50%duetodifferencesinbodyfatandmusclecontent.

2. 15–25%�fat• Desirablelevels:15%formalesand22–25%forfemales• Bodyfatlevelsinfluencebodywatercontentbecausefattissueisverylow

inwatercontent(about23%)comparedtomuscleorbraintissue(70%).• Asbodyfatincreases,bodywaterdecreases;asbodyfatdecreases,body

waterincreases.Thisexplainswhymostmaleshaveahigherpercentageofbodywaterthanfemales.

3. 18–20%�protein—maleshavemorethanfemalesduetohigherleanormusclemass.

4. 4–5%�minerals—thebody’smineralcontentisprimarilyinbonesandteeth.Thisvariesbygender(maleshavehigherlevelsthanfemales)andrace(blackshavemorethanwhites,whohavemorethanAsians).

Nutrition BiteFunfactaboutyourhair—yougrowover350milesofhairinalifetime!

Nutrition BiteIsthereabestbodyfatlevelforathletes?

Herearesomenum-bersforbodyfatincollegiateathletes(seeFigure1.1).Andasyou’llseeinChapter7,thereisnotaperfectoridealbodyfatlevelthatdepictsoptimalhealthbutratherthereareranges.

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Chapter 1 SpeakingofNutrition...SomeBasics 3

5. Less�than�1%�carbohydrates—storageofcarbohydrates in themusclesandliverisvitalforfuelduringexerciseandrest(especiallyforthebrain).

6. Less�than�1%�vitamins—verytraceamountsexistineachcell.

Foods,aswellasthebody,containallsixcategoriesofnutrientsinvaryingamounts.Mustyoueatall50nutrientsoronlysome?

Essential�nutrientsarethosenutrientsthatthebodycannotmakeorcannotmakeataratesufficienttomeetyourneeds.Therefore,thedietrequiresthem.Forexample,calciumisamineralthatoriginatesinsoil(rocks),getsintoplantsthatcowseat,andthengetsintomilk,andeventuallygetsintoourbodies.Weareinca-pableofmakingcalcium,sowemustgetitfromthefoodweeat.

Ontheotherhand,waterismadeeverydayinourbodiesaswemetabolizefoodforenergy.However,weonlymakeaboutacupeachday,whichfallsshortoftheseveralcupsweneed.Therefore,waterisessentialinthediet.

How Do Nutrients Function in the Body?1.� �Energy—Onlyproteins,carbohydrates,andfats(themacronutrients)contain

potentialenergy.Elements,primarilycarbon,areconnectedtoeachotherviachemicalbondsthataremuchliketinystretchedrubberbands.Whenletgo,theenergyisreleased.Theenergyreleasedfromchemicalbondsismeasuredascalories.(We’lllearnmoreaboutthisinChapter3.)

2.� �Structure—Nutrients,suchasproteinandcalcium,arethebuildingmaterialandstructureforboneandteeth.

3.� �Regulation—As regulators, nutrients help manage and oversee many pro-cessesinthebodysuchasbuildingnewhormones,regulatingfluidbalance,orcatalyzingareactionsuchasenzymes,whicharemadeofprotein.Regulatorynutrientsaremuchliketrafficlightsthathelpregulatetheflowofvehiclesonbusystreets.

PERCENT BODY FAT VALUES IN ATHLETES

MALES FEMALES

Basketball 7–12 18–27

Distance Running 3–8 8–18

Gymnastics 7–12 16–22

Soccer 4–10 14–25

Swimming 5–12 10–20

Tennis 12–16 15–22

Nonathlete, avg. 15–16.9 20–26.9

FLUID BALANCE

INTAKE: OUTPUT:

Fluid 1.2 liters Urine 1.5 liters

Food 1.0 liters Stool 0.1 liters

Metabolic 0.3 liters Sweat and breath vapor 0.9 liters

2.5 liters 2.5 liters

Figure 1.1

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How Do We Express Our Nutrient Needs or Requirements?Theamountofprotein,VitaminCorothernutrientsapersonneedsdependsonahostoffactorsincluding:

• Gender• Age• Physiologicalstate(e.g.,pregnantorbreastfeeding)• Illness• Geneticstraits

Whileweallneedthesamenutrients,theamountsvarydependingontheseandotherfactors.Settingnutrientstandardsisthetaskofanarmofthegovernment—theFoodandNutritionBoard.HealthprofessionalsandotherscallthesestandardsDietary�Reference� Intakes� (DRI) (seeFigure1.2)anduse them inestablishingnutrientintakesforplanningandassessingthedietsofhealthyindividuals.

Thesenutrientrequirementsaredesignedtopreventdeficiencydiseases,suchasscurvyfromtoolittleVitaminCorrickets(abonedeformity)duetotoolittlecalciumandVitaminD.TheDRIsarealsodesignedtopromoteoptimalhealthandthereductionofchronicdiseaserisks,suchascancer,potentiallyfromamarginalintakeofVitaminsC,D,andcalcium.

UndertheumbrellatermofDRI,therearefourseparatenutrientstandardval-uesofwhichtheRecommendedDietaryAllowance(RDA)isone.

Inaddition,theDRIsaredesignedtosetanupperlimitofintaketoavoidtheriskofadversereactionduetooverdose.

Youareprobably familiarwithorat leastheardof this termbefore. In thiscourse,wewillmakereferencetotheRDA,whatitmeans,howtheRDAforagivennutrientisdetermined,andhowbesttomeetyourneeds.Whiletheothernutrientstandardvaluesareimportantintheworldofnutrition,inthiscoursewewillnotutilizetheseexceptformakingreferencetotheTolerableUpperIntakeLevelorUL.Thisstandardrepresentsthehighestlevelofdailynutrientintakethatislikelytobesafeandnotposeanyadversehealtheffectstomostpeopleinthepopulation.But

Figure 1.2

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Chapter 1 SpeakingofNutrition...SomeBasics 5

dietaryorsupplementintakeexceedingtheULforacertainnutrient,suchasiron,maypresentsomehealthproblems.AswewillcoverinthetopicofsupplementsinChapter9,notonlycanwegettoolittleofanutrient,butexcessiveintakethroughfoods thatare fortifiedwithnutrients,suchasvitaminsaswellassupplements,posehealthrisks.

A Closer Look at the RDATheRDAisthedailyamountofnutrientconsidered adequatetomeettheneedsofnearlyallhealthypeopleinthepopulation(about98%ofus),whiledecreas-ing riskofchronicdiseases.TheRDA isNOTaminimumamountnor is itanaverageneedbutinsteadagenerousvalue.AndtheRDAissetbasedonscientificinformation.

• TheRDAhasbeendeterminedforproteinandothernutrients(vitamins,min-erals,etc.).

• TheRDAisestablishedforseveralagegroups,gender,andphysiologicalstates(pregnancyandlactation).

• TheRDAisdesignedtobeanaverageoverseveraldays.(Inotherwords,youdon’thavetomeettheRDAeachday,butinsteadaverageditoverseveral.)

• AdjustmentsaremadewhensettingtheRDAbaseduponseveralfactorsthatwewillhighlightaseachnutrientiscovered,suchasthequalityofthediet(asinproteincoveredinChapter2),bioavailability(aswithmineralscoveredinChapter8),andlossesduetofoodpreparation(aswithvitaminscoveredinChapter9).

YouwillnotneedtomemorizeeachRDA(except forprotein)but insteadknowwhatgoesintosettingtheRDAandwhatitmeanstoyou.

How Does Your BoDY Cope?Everwonderwhyyoustillfunctioneventhoughyouhaven’teatenallday,orwhyyourbody’sinternaltemperaturehoversaround37degreesCelsiusor98.6degreesFahrenheitdespitefreezingorscorchingtemperaturesoutside?

Thereasonisactuallymoreofaconceptorprocesscalledhomeostasis.Thisisthemaintenanceofrelativelyconstantinternalconditions(suchasbodytemperatureandbloodsugarlevels)throughtheeffortsandcontrolofmanysystemsinthebody.

Theconceptofhomeostasiswillbeemphasizedthroughoutthiscoursetohelpuspredict aswell asunderstandwhyourbodies respondandperform the waytheydo.Forexample,onceyougrasptheconceptofhomeostasis,youwillsoonunderstandwhytakinglargeamountsofaparticularsupplementsuchasvitaminsoraminoacids(componentsofprotein)willnotdrasticallychangeoralterthewayyourbodyorcellsworksoasnottoupsetothersystemsinyourbody.

Let’susetheexampleofbodywatercontenttohelpunderstandhomeostasisaswellaslearnmoreaboutthenutrientwater.Recallthatabout50%to60%ofyourbodyweightiswater.Figure1.3depictsthefluidinsideandoutsidethebodycells;thedistributionofbodywaterisdeterminedandcontrolledbyseveralfactorssuchashormones,theactionofthekidneys,andthemineralandproteinlevelsinbodyfluids.

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PERCENT BODY FAT VALUES IN ATHLETES

MALES FEMALES

Basketball 7–12 18–27

Distance Running 3–8 8–18

Gymnastics 7–12 16–22

Soccer 4–10 14–25

Swimming 5–12 10–20

Tennis 12–16 15–22

Nonathlete, avg. 15–16.9 20–26.9

FLUID BALANCE

INTAKE: OUTPUT:

Fluid 1.2 liters Urine 1.5 liters

Food 1.0 liters Stool 0.1 liters

Metabolic 0.3 liters Sweat and breath vapor 0.9 liters

2.5 liters 2.5 liters

Yourbodywatercontentasfluidhomeostasis is regulatedwell.Onaveragea typicalperson takes inabout2½ litersoffluiddailyand loses thesame(seeFigure1.4).

Onyourfinal,youwillbeaskedtodefinehomeostasisandgiveanexampleofanutrientunderhomeostaticcontrol.Bytheendofthecourse,you’llsurelyhavemanyideasforyouranswer.

INsIDe worK—THe proCess oF DIGesTIoN AND ABsorpTIoNHowdoweprocessfoodandprepareittoenterourbodies?Ourbodiesaccomplishthistaskthroughtheprocessofdigestionandabsorption.Digestionistheprocessbywhichfoodisbrokendownintoaformthatcanbeabsorbedbytheintestines.Absorptionistheprocessofmovingnutrientsintothebodyorbloodstream.Diges-tionoccursinthedigestivetract,whichbeginsatthemouthandis26feetlong.Visualizethedigestivetractas“outside”yourbody;thatis,thedigestivetractisa

Figure 1.3

Figure 1.4

Nutrition BiteThesurfaceareaofyourintestinaltractwouldcoveraboutathirdofafootballfield.

BODY

CELLS

Fluid

Cell

Cell

Cell

Cell

CellCell

Cell

2/3 of body water located inside cells

Intracellular Fluid

1/3 of body water located outside cells

Extracellular Fluid

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Chapter 1 SpeakingofNutrition...SomeBasics 7

tubethatrunsthroughyourbody,butthecontents(ifyouswallowagolfball,forexample)arenotreallyinsideofyou.Absorptiononlyoccurswhenthefood(itscomponents)istransportedfromthesmallintestineintothecirculation.

Figure1.5illustratesthedigestivetract(witheachpartidentified)alongwithsomeoftheaccessoryorgans,collectivelycalledthedigestivesystem.

Therearetwophasesofdigestion.

�1.� �Physical�digestion:�themovingandgrindingoffood.Thisstartsinthemouthwithchewing,thoughyoudonothavetochewyourfood(despitethatmomtoldyoutochewyourfoodwellbeforeswallowing)tocompletelydigestyourfood.Onceyouhavechewed(orjustswallowed)yourfood,thebolus(swal-lowedfood)movesdownyouresophagusintothestomachwhereitis“blender-ized.”Thestomach,whichhasa4-cupcapacity,ismuchlikeablender(strongmuscles)thatmakesasmoothieoutofyourswallowedfood.

2.� �Chemical�digestion:thechemicalbreakdownoffoodthroughtheuseofdiges-tiveenzymes(actualbreakingofchemicalbondsinfoodsandstomachacid).Thisprocessstartsinthestomachwithamajorityoccurringinthesmallintes-tine.Thedigestiveenzymesneededtobreakthesebondsaresecretedbythepancreas into thesmall intestine.Once theprocessofchemicaldigestion iscomplete,thefoodhasbeendigestedandtheprocessofabsorptionoccurs.

Absorptionistheprocessoftakingthesesmallfoodfragmentsfromthesmallintestineandtransportingthemintotheblood.Thesurfaceofthesmallintestineiswhereabsorptionoccurs.Thesurfaceof thesmall intestine,asshowninFig-ure1.6,isdesignedformaximumsurfacearea.Thefolds,thefoldsonthesefoldscalledvilli, and thenhair-like structuresonvilli calledmicrovilli all contribute toa tremendously large surface area that allows the nutrients an opportunity to betakenupintothebodyandeventuallyintothecirculation.Figure1.7illustratesvilliandmicrovillistructuresandtheplacementofcapillariesthatallowfortransportofabsorbedsmallfoodunitsintothebodyviathecirculation.

Mouth

Stomach

Esophagus

Small Intestine

Gallbladder

Large Intestine

Pancreas

Digestive SystemFigure 1.5

Myth: “We should eat food, such as fruit, separately because our digestive tracts can’t handle diff er-ent foods at once.”

The design of our digestive enzymes and intestinal tract allows for the processing of dif-ferent food types, such as fruits, meats and vegetables, all at once. In fact, nutrient absorp-tion improves when a variety of foods are present. There is no need to separate foods when eating.

Urban Myth

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However,somefoodisnotdigestedandabsorbed.Theseitems,suchasfiber(or if you happened to swallow a food wrapper), move into the large intestinewherethebodyextractswaterandminerals,andpreparestheremnantsasstool.Thestoolthenrepresentsmaterialthatnevergotintothebodyinthefirstplace,butonlypassedthroughthedigestivetract.Youmighthavewonderedwhaturinerepresents.Thismetabolicwasterepresentssubstances,suchasexcesssodiumthatthebody(kidneys)havefilteredfromthecells,blood,andelsewhere,andsendsoutintheurine.

Figure 1.6

Figure 1.7

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Name________________________________________________________ StudentID#_______________

C H A p t E R

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1Quiz Yourself

1. Mostoftheenzymesresponsibleforthedigestionoftheenergynutrientscomefromthe:

a. mouth

b. stomach

c. liver

d. pancreas

2. Whatistheapproximateaveragebodywatercontentofayoungadulthumanexpressedasapercentofbodyweight?

a. 10–20%

b. 30–40%

c. 50–60%

d. 70–80%

e. 90%

3. Listthesixclassesofnutrients,giveafoodsourceexampleandnotewhichonesprovideenergy.

1.

2.

3.

4.

5.

6.

4. Whatarethethreebasicfunctionsofnutrients?

1.

2.

3.

5. Mostofthebody’swateroccursinextracellularfluidcompartments(outsideofthebodycells.

a. true

b. false

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10 Chapter 1SpeakingofNutrition...SomeBasics

6. Defineanessentialnutrient.

7. DefinetheRecommendedDietaryAllowance(RDA)andlistthreefactorsthataretakenintoconsiderationwhenestablishingtheRDA.

1.

2.

3.

8. Definedigestionanddescribethetwotypesofdigestion.

9. Whatisabsorptionandwheredoesitoccur?

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