Reporting completeness and outcomes of the diet- and nutrition-related systematic review planning process: protocol...

Dietary recommendations should be based on scientific evidence, and ideally, systematic reviews (SRs) are conducted as part of the guideline development process. The usability of SRs for decision-making is primarily determined by the quality of the evidence from available primary studies, as well as the quality of the SRs themselves. A comprehensive SR protocol ensures high-quality implementation and minimises bias, while making these protocols publicly accessible, promotes transparency and prevents redundancy. The PROSPERO database offers valuable insights into planned methodologies. The aim of this study is to investigate the completeness of reporting in SR protocols for diet- or nutrition-related trials, determine how this has changed over time, and examine the publication of completed SRs by comparing their content with those described in the corresponding protocols.

We developed a systematic search strategy for PROSPERO to identify nutrition- or diet-related SR protocols registered at two different time points (2019 and 2024). Following a screening process to identify eligible protocols, relevant predefined data will be extracted. Subsequently, a structured search will be conducted to identify potential journal publications of the selected protocols, as well as publications describing the results of the SRs, from which relevant predefined data will be also extracted. The methodology of the published articles will be compared with the corresponding a priori protocols registered in PROSPERO. The PROSPERO records registered in 2019 will be compared with those registered in 2024. The results will be evaluated by descriptive statistics, the reporting completeness of PROSPERO records will be assessed based on Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P), the planned use of any approaches to assess certainty of evidence will be investigated, and the adherence of published SRs to the methodological details outlined in their corresponding PROSPERO entries will be examined.

Since both databases and publications used in this study are publicly available, ethical approval is not required. Results of the study will be submitted for publication in an international, peer-reviewed journal.

The present study has previously been registered with the Open Science Framework (https://osf.io/8fsx7).