Perspective:USDANutritionEvidenceSystematic ReviewMethodology:GradingtheStrengthof EvidenceinNutrition-andPublicHealth–Related SystematicReviews

Abstract

TheUSDA’sNutritionEvidenceSystematicReview(NESR)teamconductsfood-andnutrition-relatedsystematicreviewsusedtoinformUSFederal guidelinesandprograms,includingtheDietaryGuidelinesforAmericans.NESR’ssystematicreviewmethodologyincludesasteptogradethestrength oftheevidenceunderlyingconclusionstatements,whichiscriticalforensuringthatendusersunderstandthelevelofcertaintyinconclusionswhen usingthemtomakedecisions.Overtime,NESRhasensureditsgradingprocessnotonlyremainsstateoftheartbutisalsodesignedspecificallyfor systematicreviewsthatinformFederalguidelinesandprogramsonnutritionandpublichealth.TheNESRgradingprocessusedbythe2020Dietary Guidelines Advisory Committee included 5 grading elements: risk of bias, consistency, directness, precision, and generalizability. Evidence was groupedbystudydesignandassessedagainsttheseelements,andthegradeassignedtotheentirebodyofevidencetookintoconsiderationthe strengthsandlimitationsofeachdesign.Basedonthisassessment,1of4gradeswasassigned:strong,moderate,limited,orgradenotassignable. The grade was clearly communicated by integrating specific language into each conclusion statement (e.g., “strong evidence demonstrates”or “limited evidence suggests”), and supported by rationale documented in the review. NESR’s grading process aligns with approaches used by otherorganizationsthatconductsystematicreviews,whileretainingaspectsuniquetoNESR’sroleininformingFederalnutritionandpublichealth guidelines and programs. It provides a framework that promotes consistency in grading across food- and nutrition-related reviews, while offering flexibility that allows for thorough consideration of the body of evidence underlying an individual conclusion statement. NESR’s rigorous and transparentmethodsforgradingthestrengthofevidenceinfood-andnutrition-relatedsystematicreviewsensurethatdecisionsrelatedtonutrition andpublichealtharebasedonthestrongestavailableevidence