ConsumptionofFishandω-3FattyAcidsand CancerRisk:AnUmbrellaReviewofMeta-Analyses ofObservationalStudies

Abstract

Multiplestudieshavesuggestedthat ω-3fattyacidintakemayhaveaprotectiveeffectoncancerrisk;however,itstrueassociationwithcancerrisk remains controversial. We performed an umbrella review of meta-analyses to summarize and evaluate the evidence for the association between ω-3 fatty acid intake and cancer outcomes. We searched PubMed, Embase, and the Cochrane Database of Systematic Reviews from inception toDecember1,2018.Weincludedmeta-analysesofobservationalstudiesthatexaminedassociationsbetweenintakeoffishor ω-3fattyacidand cancerrisk(gastrointestinal,liver,breast,gynecologic,prostate,brain,lung,andskin)anddeterminedthelevelofevidenceofassociations.Inaddition, we appraised the quality of the evidence of significant meta-analyses by using the Grading of Recommendations Assessment, Development and Evaluation(GRADE)system.Weinitiallyscreened598articles,and15articles,including57meta-analyses,wereeligible.Among57meta-analyses,15 reportedstatisticallysignificantresults.Wefoundthat12meta-analysesshowedweakevidenceofanassociationbetweenω-3fattyacidintakeand 1134 Copyright C TheAuthor(s)onbehalfoftheAmericanSocietyforNutrition2020. AdvNutr2020;11:1134–1149; doi:https://doi.org/10.1093/advances/nmaa055. riskofthefollowingtypesofcancer:livercancer(n=4of6),breastcancer(n=3of14),prostatecancer(n=3of11),andbraintumor(n=2of2). Intheother3meta-analyses,studiesofendometrialcancerandskincancer,therewerenoassessabledatafordeterminingtheevidencelevels.No meta-analysisshowedconvincing,highlysuggestive,orsuggestiveevidenceofanassociation.Inthesensitivityanalysisofmeta-analysesbystudy design,wefoundweakassociationsbetweenω-3fattyacidintakeandbreastcancerriskincohortstudies,butnostatisticallysignificantassociation incase-controlstudies.However,theoppositeresultswerefoundincaseofbraintumorrisk.Although ω-3fattyacidshavebeenstudiedinseveral meta-analyseswithregardtoawiderangeofcanceroutcomes,onlyweakassociationswereidentifiedinsomecancertypes,withseverallimitations. Considering the nonsignificant or weak evidence level, clinicians and researchers should cautiously interpret reported associations between ω-3 fattyacidconsumptionandcancerrisks