Background: The Dietary Guidelines for Americans (DGA) are a set of recommendations that inform all federal nutrition programs in the U.S. The scientific rigour of U.S. dietary guidelines has raised questions on whether DGA recommendations are based on appropriate evaluation of scientific evidence and whether the systematic reviews (SRs) conducted by the Nutrition Evidence Systematic Review (NESR) team to inform these recommendations were sufficiently systematic. These questions have brought on a need for enhanced transparency, greater scientific rigour, and updates to the scientific methodology to the DGA process.
Objectives: The aim is to evaluate the following key questions (KQ): (KQ1) Do the SRs conducted by the NESR team report a transparent, complete, and accurate account of their SR process such that they can be replicated? (KQ2) If NESR’s SRs were replicated by a group external to the DGA, would any observed differences in SR reporting and methodology substantially impact any final conclusions made by NESR?
Methods: For KQ1, we will assess the overall methodological quality of the conduct of a random sample of SRs conducted by the NESR team using the AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews) critical appraisal tool. For KQ2, we will replicate a randomly selected SR using current Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidance for the report and conduct of SRs. We will discuss any differences between our replicated review and the NESR’s review using PRISMA 2020’s comprehensive checklist. Weaknesses identified from our AMSTAR 2 quality assessment will be used to discuss any observed differences in the conduct of our replicated SR. Following the results of our review, we will plan to evaluate the interpretation of results from the NESR team’s systematic reviews by reporting any spin bias. Expected Outcomes: Because DGAs are used to inform decision-making, it is imperative that the associated SRs are conducted with methodological rigour. We will use current methodological guidance to help determine the confidence the U.S. government can place in DGA dietary guideline recommendations. Patient, public, and/or healthcare consumer involvement: We will collaborate with patient partners and stakeholders to obtain feedback on our analyses, interpretation, and communication of findings.