Misleading presentations in functional food trials led by contract research organizations were frequently observed in Japan : meta-epidemiological study

[Objectives] The functional food market has experienced significant growth, leading to an uptick in clinical trials conducted by contract research organizations (CROs). Research focusing on CRO-managed trials and the communication of trial outcomes to the consumer market remains underexplored. This metaepidemiological study aims to evaluate the quality of randomized controlled trials (RCTs) facilitated by prominent CROs in Japan and to examine the quality of the representations used to convey their results to consumers. [Study Design and Setting] This study focused on the food trials that were registered in the University Hospital Medical Information Network Clinical Trial Registry or the International Clinical Trials Registry Platform by the top 5 CROs. Press releases of study results or advertisements of food products based on the study results were identified by conducting a Google search. The risk of bias in the RCT publications was independently assessed by 2 reviewers, who also evaluated the presence of “spin” in the abstracts and full texts. An assessment of “spin” in press releases/advertisements was undertaken. [Results] A total of 76 RCT registrations, 32 RCT publications, and 11 press releases/advertisements were included. Approximately 72% of the RCT publications exhibited a high risk of bias due to selective outcome reporting. “Spin” was present in the results of the abstract (72%), abstract conclusion (81%), full-text results (44%), and full-text conclusion (84%). “Spin” appeared in 73% of press releases/advertisements due to the selective outcome reporting. [Conclusion] Functional food presentations in Japan frequently contained “spin.” The Japanese government should more rigorously check whether food manufacturers report outcomes selectively.