Omega-3 Fatty Acids: An Essential Contribution

Alpha-linolenic acid (ALA), the most common omega-3 fatty acid in most Western diets, is found in vegetable oils and nuts (especially walnuts), flax seeds and ... Menu CloseMenu Skiptocontent TheNutritionSource HarvardT.H.ChanSchoolofPublicHealth>TheNutritionSource>WhatShouldIEat?>FatsandCholesterol>TypesofFat>Omega-3FattyAcids:AnEssentialContribution TheNutritionSource Menu Searchfor: Home NutritionNews WhatShouldIEat? HealthyEatingPlate&Pyramid HealthyEatingPlateTranslations Kid’sHealthyEatingPlate WholeGrains Protein VegetablesandFruits FatsandCholesterol TypesofFat Cholesterol DietaryFatandDisease VitaminsandMinerals HealthyDrinks Water OtherHealthyBeverageOptions DrinkstoConsumeinModeration SugaryDrinks SportsDrinks EnergyDrinks PublicHealthConcerns:SugaryDrinks Low-CalorieSweeteners SaltandSodium TakeAction:HowtoReduceYourIntake PublicHealthConcerns Carbohydrates CarbohydratesandBloodSugar Fiber AddedSugarintheDiet Sustainability PlateandthePlanet FoodWaste HealthyWeight MeasuringBodyFat TheBestDiet:QualityCounts HealthyDietaryStyles DietReviews StayingActive ActiveCommunities Stress Sleep DiseasePrevention HeartDisease Prevention Diabetes Prevention Cancer Prevention PrecisionNutrition NutritionandImmunity Recipes HomeCooking FoodServiceResources FoodFeatures AdditionalResources About FAQ Contact Thehumanbodycanmakemostofthetypesoffatsitneedsfromotherfatsorrawmaterials.Thatisn’tthecaseforomega-3fattyacids(alsocalledomega-3fatsandn-3fats).Theseareessentialfats—thebodycan’tmakethemfromscratchbutmustgetthemfromfood.FoodshighinOmega-3includefish,vegetableoils,nuts(especiallywalnuts),flaxseeds,flaxseedoil,andleafyvegetables. Whatmakesomega-3fatsspecial?Theyareanintegralpartofcellmembranesthroughoutthebodyandaffectthefunctionofthecellreceptorsinthesemembranes.Theyprovidethestartingpointformakinghormonesthatregulatebloodclotting,contractionandrelaxationofarterywalls,andinflammation.Theyalsobindtoreceptorsincellsthatregulategeneticfunction.Likelyduetotheseeffects,omega-3fatshavebeenshowntohelppreventheartdiseaseandstroke,mayhelpcontrollupus,eczema,andrheumatoidarthritis,andmayplayprotectiverolesincancerandotherconditions. Omega-3fatsareakeyfamilyofpolyunsaturatedfats.Therearethreemainomega-3s: Eicosapentaenoicacid(EPA)anddocosahexaenoicacid(DHA)comemainlyfromfish,sotheyaresometimescalledmarineomega-3s. Alpha-linolenicacid(ALA),themostcommonomega-3fattyacidinmostWesterndiets,isfoundinvegetableoilsandnuts(especiallywalnuts),flaxseedsandflaxseedoil,leafyvegetables,andsomeanimalfat,especiallyingrass-fedanimals.ThehumanbodygenerallyusesALAforenergy,andconversionintoEPAandDHAisverylimited. Thestrongestevidenceforabeneficialeffectofomega-3fatshastodowithheartdisease.Thesefatsappeartohelptheheartbeatatasteadyclipandnotveerintoadangerousorpotentiallyfatalerraticrhythm.(1)Sucharrhythmiascausemostofthe500,000-pluscardiacdeathsthatoccureachyearintheUnitedStates.Omega-3fatsalsolowerbloodpressureandheartrate,improvebloodvesselfunction,and,athigherdoses,lowertriglyceridesandmayeaseinflammation,whichplaysaroleinthedevelopmentofatherosclerosis.(1) Severallargetrialshaveevaluatedtheeffectoffishorfishoilsonheartdisease.IntheGruppoItalianoperloStudiodellaSopravvivenzanell’InfartoMiocardio(knownastheGISSIPreventionTrial),heartattacksurvivorswhotooka1-gramcapsuleofomega-3fatseverydayforthreeyearswerelesslikelytohavearepeatheartattack,stroke,ordieofsuddendeaththanthosewhotookaplacebo.(2)Notably,theriskofsuddencardiacdeathwasreducedbyabout50percent.InthemorerecentJapanEPALipidInterventionStudy(JELIS),participantswhotookEPAplusacholesterol-loweringstatinwerelesslikelytohaveamajorcoronaryevent(suddencardiacdeath,fatalornonfatalheartattack,unstableangina,oraproceduretoopenorbypassanarrowedorblockedcoronaryartery)thanthosewhotookastatinalone.(3) MostAmericanstakeinfarmoreofanotheressentialfat—omega-6fats—thantheydoomega-3fats.Someexpertshaveraisedthehypothesisthatthishigherintakeofomega-6fatscouldposeproblems,cardiovascularandotherwise,butthishasnotbeensupportedbyevidenceinhumans.(4)IntheHealthProfessionalsFollow-upStudy,forexample,theratioofomega-6toomega-3fatswasn’tlinkedwithriskofheartdiseasebecausebothofthesewerebeneficial.(5)Manyotherstudiesandtrialsinhumansalsosupportcardiovascularbenefitsofomega-6fats.AlthoughthereisnoquestionthatmanyAmericanscouldbenefitfromincreasingtheirintakeofomega-3fats,thereisevidencethatomega-6fatsalsopositivelyinfluencecardiovascularriskfactorsandreduceheartdisease. Researchersaretakingahardlookatadifferentsortofbalance,thisonebetweenpossibleeffectsofmarineandplantomega-3fatsonprostatecancer.ResultsfromtheHealthProfessionalsFollow-upStudyandothersshowthatmenwhosedietsarerichinEPAandDHA(mainlyfromfishandseafood)arelesslikelytodevelopadvancedprostatecancerthanthosewithlowintakeofEPAandDHA.(6)Atthesametime,some-butnotall-studiesshowanincreaseinprostatecancerandadvancedprostatecanceramongmenwithhighintakesofALA(mainlyfromsupplements).However,thiseffectisinconsistent.IntheverylargeProstate,Lung,Colorectal,andOvarian(PLCO)CancerScreeningTrial,forexample,therewasnolinkbetweenALAintakeandearly,late,oradvancedprostatecancer.(7) Recipesforhealth Here’sadeliciouswaytogetyouromega-3s:TryPanRoastedSalmonwithMintySnapPeas. Giventhewide-rangingimportanceandbenefitsofmarineomega-3fattyacids,itisimportanttoeatfishorotherseafoodonetotwotimesperweek,particularlyfatty(darkmeat)fishthatarericherinEPAandDHA.Thisisespeciallyimportantforwomenwhoarepregnantorhopingtobecomepregnantandnursingmothers.Fromthethirdtrimesteruntilthesecondyearoflife,adevelopingchildneedsasteadysupplyofDHAtoformthebrainandotherpartsofthenervoussystem.Manywomenshyawayfromeatingfishbecauseofconcernsthatmercuryandotherpossiblecontaminantsmightharmtheirbabies,(9)yettheevidenceforharmfromlackofomega-3fatsisfarmoreconsistent,andabalanceofbenefitvs.riskiseasilyobtained.(Tolearnmoreaboutthecontroversyovercontaminantsinfattyfish,readFish:FriendorFoe.) Thistablelistscommonfishandseafoodproductsandtheiromega-3fattyacidcontent. TypeofSeafood ServingSize Omega-3FattyAcids (mg/serving) Anchovy 2.0oz 1,200 Catfish(farmed) 5.0oz 253 Clams 3.0oz 241 Cod(Atlantic) 6.3oz 284 Crab 3.0oz 351 Fishsticks(frozen) 3.2oz 193 Halibut 5.6oz 740 Lobster 3.0oz 71 Mahimahi 5.6oz 221 Mussels 3.0oz 665 Oysters 3.0oz 585 Pollock(Alaskan) 2.1oz 281 Salmon(wild) 6.0oz 1,774 Salmon(farmed) 6.0oz 4,504 Sardines 2.0oz 556 Scallops 3.0oz 310 Shrimp 3.0oz 267 Swordfish* 3.7oz 868 Trout 2.2oz 581 Tuna(albacore)** 3.0oz 733 Tuna(light,skipjack) 3.0oz 228 SOURCE:MozaffarianD,RimmEB.JAMA.2006;296:1885-1899. *Swordfishcontainshighlevelsofmercury,asdoesshark,kingmackerel,andtilefish(sometimescalledgoldenbassorgoldensnapper).Womenwhoareormaybecomepregnant,nursingmothers,andyoungchildrenshouldavoidthesehigh-mercuryspeciesoffish,butcaneatupto12ounces(twoaveragemeals)aweekofavarietyoffishandshellfishthatarelowerinmercury. **Albacoretunacontainsmoremercurythancanned,lighttuna.Womenwhoareormaybecomepregnant,nursingmothers,andyoungchildrenshouldlimitalbacoretunatooneservingperweek. References 1.LeafA.Preventionofsuddencardiacdeathbyn-3polyunsaturatedfattyacids.JCardiovascMed.(Hagerstown).2007;8Suppl1:S27-29. 2.Dietarysupplementationwithn-3polyunsaturatedfattyacidsandvitaminEaftermyocardialinfarction:resultsoftheGISSI-Prevenzionetrial.GruppoItalianoperloStudiodellaSopravvivenzanell’Infartomiocardico.Lancet.1999;354:447-55. 3.YokoyamaM,OrigasaH,MatsuzakiM,etal.Effectsofeicosapentaenoicacidonmajorcoronaryeventsinhypercholesterolaemicpatients(JELIS):arandomisedopen-label,blindedendpointanalysis.Lancet.2007;369:1090-98. 4.WillettWC.Theroleofdietaryn-6fattyacidsinthepreventionofcardiovasculardisease.JCardiovascMed.(Hagerstown).2007;8Suppl1:S42-5. 5.MozaffarianD,AscherioA,HuFB,etal.Interplaybetweendifferentpolyunsaturatedfattyacidsandriskofcoronaryheartdiseaseinmen.Circulation.2005;111:157-64. 6.LeitzmannMF,StampferMJ,MichaudDS,etal.Dietaryintakeofn-3andn-6fattyacidsandtheriskofprostatecancer.AmJClinNutr.2004;80:204-16. 7.KoralekDO,PetersU,AndrioleG,etal.Aprospectivestudyofdietaryalpha-linolenicacidandtheriskofprostatecancer(UnitedStates).CancerCausesControl.2006;17:783-91. 8.EilanderA,HundscheidDC,OsendarpSJ,TranslerC,ZockPL.Effectsofn-3longchainpolyunsaturatedfattyacidsupplementationonvisualandcognitivedevelopmentthroughoutchildhood:areviewofhumanstudies.ProstaglandinsLeukotEssentFattyAcids.2007;76:189-203. 9.OkenE,KleinmanKP,BerlandWE,SimonSR,Rich-EdwardsJW,GillmanMW.Declineinfishconsumptionamongpregnantwomenafteranationalmercuryadvisory.ObstetGynecol.2003;102:346-51.   TermsofUseThecontentsofthiswebsiteareforeducationalpurposesandarenotintendedtoofferpersonalmedicaladvice.Youshouldseektheadviceofyourphysicianorotherqualifiedhealthproviderwithanyquestionsyoumayhaveregardingamedicalcondition.Neverdisregardprofessionalmedicaladviceordelayinseekingitbecauseofsomethingyouhavereadonthiswebsite.TheNutritionSourcedoesnotrecommendorendorseanyproducts. Explore: HealthyOils Usehealthyoils(likeoliveandcanolaoil)forcooking,onsalad,andatthetable.Limitbutter.Avoidtransfat. HEALTHY OILS Water Drinkwater,tea,orcoffee(withlittleornosugar).Limitmilk/dairy(1-2servings/day)andjuice(1smallglass/day).Avoidsugarydrinks. WATER Vegetables Themoreveggies—andthegreaterthevariety—thebetter.PotatoesandFrenchfriesdon’tcount. VEGETABLES Fruits Eatplentyoffruitsofallcolors FRUITS HealthyProtein Choosefish,poultry,beans,andnuts;limitredmeatandcheese;avoidbacon,coldcuts,andotherprocessedmeats. HEALTHY PROTEIN WholeGrains Eatavarietyofwholegrains(likewhole-wheatbread,whole-grainpasta,andbrownrice).Limitrefinedgrains(likewhitericeandwhitebread). WHOLE GRAINS StayActive Incorporatephysicalactivityintoyourdailyroutine. Createhealthy,balancedmealsusingthisvisualguideasablueprint. AmonthlyupdatefilledwithnutritionnewsandtipsfromHarvardexperts—alldesignedtohelpyoueathealthier.Signuphere. 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