2.1. Study Design
This intervention study was approved by the ethics committee of the Tohoku University Graduate School of Medicine on 23 March 2020 (Receipt number: 2019-1-957). Written informed consent was obtained from all subjects at the time of enrollment. The study was a 12-week randomized, double-blinded, placebo-controlled clinical trial among healthy regional older adults in Miyagi prefecture, Japan. The primary outcome of the study was the cognitive function, which was evaluated individually in-person at the Tohoku University. This RCT was registered at the University Hospital medical information network (UNIM) Clinical Trial Registry (UMIN000039901).