Examining concordance and trustworthiness of bodies of evidence from randomized controlled trials and cohort studies in nutrition research and developing new guidance to their integration in future evidence syntheses

• Applicant: Privatdozent Dr. Lukas Schwingshackl
• Subject Area: Nutritional Sciences ; Public Health, Healthcare Research, Social and Occupational Medicine
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 459430615

Suboptimal diet is recognized as a leading modifiable risk factor for non-communicable diseases. This insight is predominantly based on bodies of evidence (BoE) from cohort studies (CSs), though evidence from randomized controlled trials (RCTs) exists as well. CSs are prone to risk of bias (RoB) such as residual confounding and measurement error. RCTs, if well-designed and well-conducted, give robust answers to the research questions they address, however dietary RCTs also suffer from inherent methodological limitations. In nutrition research, there are several examples of discordance between findings of RCTs and CSs. Yet, to date, there has been no systematic evaluation of the discordance between the BoE from RCTs and CSs, and potential reasons such as PI/ECO (population, intervention/exposure, comparator, outcome) differences or RoB has not been investigated. This is of major importance, since BoE from CSs can complement BoE from RCTs, and vice-versa. To inform for example dietary guidelines, new approaches and guidance for integration of both BoE in prospective nutrition evidence syntheses is highly needed. Therefore, in this project we aim: (i) to identify and compare empirical data to determine the extent to which diet-disease effect estimates of BoE from RCTs and CSs are concordant or discordant; (ii) to determine the trustworthiness of different BoE (based on RCTs and CSs) and to explore and understand reasons of concordant and discordant effect estimates between the different BoE; (iii) to explore approaches of integration of evidence from RCTs and CSs in nutrition evidence syntheses, and (iv) to provide evidence-based guidance how to integrate different BoE in future evidence syntheses. This project will provide novel insights into the controversial field of nutrition research by comparing the concordance between effect estimates of the outcome-specific BoE from RCTs and CSs, and will help us understand the reasons behind those discrepancies. Ultimately, this project will establish guidance on how to best optimize the integration of RCTs and CSs in prospective evidence syntheses in human nutrition.

• DFG Programme: Research Grants