预防医学英文版课件：Character 3 Nutrition,Diet and Health

Character3Nutrition,Dietand

Health

Section1Nutrition:

thesumoftheprocessesinvolvedintakinginfoodnutrients,assimilatingandusingthemtomaintainbodytissueandprovideenergy;afoundationforlifeandhealth.Nutrients:

componentsoffoodthatareindispensabletothebody’sfunctioning.Theyprovideenergy,serveasbuildingmaterial,helpmaintainorrepairbodyparts,andsupportgrowth.Thenutrientsincludeprotein,lipids,carbohydrate,mineral,andvitamin.

Functionofnutrients:◆provideenergy◆constitutestructuralmaterialofbody

◆regulatephysiologicalfunctionMacronutrients:thethreelargeenergy-yieldingnutrients:carbohydrates,lipids,andproteins.Micronutrients:thetwoclassesofsmallnon-energy-yieldingelementsandcompounds:mineralsandvitamins,essentialinverysmallamountsforregulationandcontrolfunctionsincellmetabolismandbuildingcertainbodystructure.Calorigenicnutrients(Energy-yieldingnutrients):

thenutrientsthebodycanuseforenergy.Theymayalsosupplybuildingblocksforbodystructures.Foodandthehumanbodyaremadeofthesamematerials.Malnutrition:Anyconditioncausedbyexcessordeficientfoodenergyornutrientintakeorbyanimbalanceofnutrients.Nutrientorenergydeficienciesareclassedasformsofundernutrition.Nutrientorenergyexcessesareclassedasformsofovernutrition.1.Carbohydrates:compoundscomposedofsingleormultiplesugars.Thenamemeans“carbonandwater,”andachemicalshorthandforcarbohydrateisCHO,signifyingcarbon(C),hydrogen(H),andoxygen(O).Function:provideandstoreenergy:16.7kJ/g(4kcal/g)constitutecellstructuresparingproteinaction（节约蛋白质作用）

antiketogenesis(抗生酮作用)

preventchronicdiseases

sparingproteinactionTheactionofcarbohydrateandfatinprovidingenergythatallowsproteintobeusedforpurposesitalonecanserve.Ketonesareintermediateproductsoffatmetabolism,whichnormallyareproducedatalowlevelduringfatoxidation.However,insuchextremeconditionsasstarvationanduncontrolleddiabetes,aswellastheunwiseuseofverylow-carbohydratediets,carbohydrateisinadequateorunavailableforenergyneeds,sotoomuchfatisoxidized.Ketonesaccumulate,andtheresultisketoacidosis.Sufficientcarbohydratepreventthisdamagingexcessofketones.antiketogenesisClassification

monosaccharides:glucose,fructose,galactose

disaccharides:sucrose,maltose,lactose

Carbohydrateoligosaccharides:raffinose(棉子糖)

stachyose(水苏糖)glycogenstarch(amylose,amylopectin)polysaccharidessoluble:pectin,balata

dietaryfiber

dissoluble:cellulose,hemicellulose

(1)monosaccharides:Thesimplestformofcarbohydrateisthemonosaccharide,oftencalledasinglesugar.Thethreemainmonosaccharidesimportantinhumannutritionareglucose,fructose,galactose

糖醇山梨醇(sorbitol)

甘露醇(mannitol)

木糖醇(xylitol)

麦芽糖醇(maltitol)

肌醇(inositol)

Amoderatelysweetsugar,glucoseisfoundnaturallypreformedinonlyafewfoods,suchascornsyrup.Itismainlycreatedinthebodyfromstarchdigestion.Inhumanmetabolism,allothertypesofsugarareconvertedintoglucose.Thesweetestofthesimplesugars,fructoseisfoundinfruitsandothersubstances,suchashoney.Inhumanmetabolism,fructoseisconvertedtoglucosetobeburnedforenergy.Thesimplesugargalactoseisnotfoundfreeinfoodsbutisproducedinhumandigestionfromlactose(milksugar)andisthenchangedtoglucoseforenergy.Thisreactionisreversible,andduringlactationglucosemaybereconvertedtogalactoseforuseinmilkproduction.GlucoseGalactoseFructose(2)disaccharides:

composedoftwomonosaccharideslinkedtogether.Thethreemaindisaccharidesofphysiologicimportancearesucrose,lactose,andmaltose.Theirrespectivemonosaccharidecomponentsfollow:＋GlucoseGalactoseLactose＋GlucoseFructosesucrose＋GlucoseGlucoseMaltoseLactoseintolerance:

Inabilitytodigestlactoseduetoalackoftheenzymelactase.Lactase:theintestinalenzymethatsplitsthedisaccharidelactosetomonosaccharidesduringdigestion.

(3)oligosaccharides:Thesecarbohydratesareranginginsizefromabout3to10monosaccharides.stachyose

andraffinose

arefoundinlegumes,suchasbeans,peas,andsoybeans.Thesesmallsugarsprovideafeastforbacterialfloraintheintestines,producingalargeamountofgasthatcanbringdiscomfortandembarrassment.(4)polysaccharides:Themostimportantpolysaccharideinhumannutritionisstarch.Otherformsareglycogenanddextrins.Thenondigestibleformsofdietaryfiber.Starchglycogenfibertheindigestiblepolysaccharidesinplants.Alsocallednonstarchpolysaccharides.Fibersinfoodsarecalleddietaryfiber.Nomeatsordairyproductscontainfiber.Fibers:DefinitionOnewaytoclassifyfibersisaccordingtohowreadilytheydissolveinwater.Somefibersareinsolublefibers;othersaresolublefibers.ClassificationInsolublefibers:1)cellulose:itisthechiefconstituentoftheframeworkofplants.2)somehemicellulose:itisthechiefconstituentofgrainfibers.3)Lignin（木质素）Solublefibers:Solublefibersareindigestiblebyhumanenzymesbutmaybebrokendowntoabsorbableproductsbybacteriainthedigestivetractincludepectin（果胶）,gum（树胶）,mucilage（胶浆，粘胶）etal.Alsosomehemicelluloseissoluble.Table1Watersolubilities,sources,andhealtheffectsoffiberFibertypeMajorfoodsourcesPossiblehealtheffectsSolubleGums,mucilages,pectins,psyllium,somehemicelluloseBarley,fruits,legumes,oats,oatbran,rye,seeds,vegetablesThesefiberslowerbloodcholesterol;slowglucoseabsorption;slowtransitoffoodthroughupperdigestivetract;holdmoistureinstools,softeningthem;arepartlyfermentableintofragmentsthebodycanuseInsolubleCellulose,lignin,somehemicelluloseBrownrice,fruits,legumes,seeds,vegetables,wheatbran,wholegrainsThesefiberssoftenstools;regulatebowelmovements;speedtransitofmaterialthroughsmallintestine;increasefecalweightandspeedfecalpassagethroughcolon;reducecoloncancerrisk;reducerisksofdiverticulosis,hemorrhoids,andappendicitisIngeneral,fibershavefunctionsfollowed.Improveintestinalfunctionandeasytoeliminatecontentsofintestine.WeightcontrolDecreasebloodglucoseandbloodcholesterolPossiblereducetheriskofcoloncancer.FunctionSourcesandRNI

Mainsources:

plantsfoodsincludingcereals,potatoes,rhizome,legumes,nutsDietaryfiber:vegetableandfruitproviding55%~65%oftotalenergyDietaryfiber:25~35g/day2.ProteinAminoacids

(figure6-1).

Itisthesidechainthatgivesidentityandchemicalnaturetoeachaminoacid.About20aminoacidswith20differentsidechainsmakeupmostoftheproteinsoflivingtissue.EAA

aretheaminoacidsthatthebodycannotsynthesizeatallorinsufficientamountstomeetbodyneeds,soitmustbesuppliedbydiet.

valine缬氨酸,isoleucine异亮氨酸,leucine亮氨酸,phenylalanine苯丙氨酸,methionine蛋氨酸,tryptophan色氨酸,threonine苏氨酸,lysine赖氨酸,histidine组氨酸(婴儿必需氨基酸)AminoacidpatternThecontentandratioofEAAinprotein.AminoacidbodyeggEggwhitemilkmeatbeefsoybeanflourriceIso4.02.53.33.03.43.23.02.32.5Leu7.04.05.66.46.35.65.14.45.1Lys5.53.14.35.45.75.84.41.52.3Met+cys3.52.33.92.42.52.81.72.72.4Phe+tyr6.03.66.36.16.04.96.45.15.8Thr4.02.12.72.73.53.02.71.82.3Val5.02.54.03.53.93.23.52.73.4Try1.01.01.01.01.01.01.01.01.0Aminoacidpatternofdifferentfoods

anaminoacidthatisnormallynonessential,butmustbesuppliedbythedietinspecialcircumstanceswhentheneedforitexceedsthebody’sabilitytoproduceit,includingtyrosineandcysteine.Semi-EAA(conditionallyessentialaminoacid):

cysteine(半胱AA);tyrosine(酪AA)NonessentialaminoacidLimitingaminoacid:

insufficiencyofoneorseveralEAAinfoodwilllimitthesynthesisofproteininthebody.Complementaryaction:

severalfoodsarecombinedandingestedtogether,thenthedisadvantageofsinglefoodproteincanbecompensated,theAA-patternisclosertotherequirementofhumanbody,andeventuallythenutritionalvalueoffoodproteinisgreatlyenhanced.Forexample,cornislackoflysine;beanisrichinlysine.IleLysMetTrpLegumesGrainsTogetherIngeneral,legumesprovideplentyoftheaminoacidsisoleucine(Ile)andlysine(Lys),butfallshortinmethionine(Met)andtryptophan(Trp).Grainshavetheoppositestrengthsandweaknesses,makingthemaperfectmatchforlegumes.Physiologicalfunctions:tissue-buildingmaintenanceandbioactivesubstanceconstructionprovidenitrogen:nitrogenbalance(NB)providingenergy16.7kJ/g(4.0kcal/g)

Nitrogenbalance(NB)

NB=IN-(UN+FN+SN)NB＞0PositiveNBinfants,childrenandadolescents,pregnantwoman,lactatingwomanNB＜0NegativeNBoldpersons,somewastingdiseases.NB＝0zeroNBadultsTheamountofproteininfood,Thedigestibilityandabsorptivityofproteininfood,Thelevelofutilizationofproteininfood.Evaluationofnutritionalvalue（quantityandquality）Theamountofproteininfood:theamountofprotein=amountofN×6.25

soybean:30~40%meat:10~20%grain:<10%.Proteindigestibility(PD):netdigestibility(ND);apparentdigestibility(AD)

I—（F-Fm）

ND=————————×100%II—FAD=————————×100%IF:nitrogencontentoffeces.Fm:nitrogencontentoffecesmetabolism.Digestibilityofseveralfoodproteins(%)FoodDigestibilityFoodDigestibilityFoodDigestibilityEgg97±3Rice88±4Soybeanpowder87±7Milk95±3Flour96±4Bean78Meat,fish94±3Oat86±7Peanutbutter88Corn85±6Millet79Biologicalvalueofprotein(BV):bodycanstoreproteinafterproteinabsorption.

I-(F-Fm)-(U-Um)BV=×100I-(F-Fm)

Influencefactors:thecontentandratioofEAANetproteinutilization(NPU):

basedonBVandPD,thelevelofbodyutilizingprotein

NPU=BV×PD×100%I-(F-Fm)-(U-Um)=———————————×100%IProteinefficiencyratio(PER)：

basedonweightgainofagrowingtestanimaldividedbyitsproteinintake