Background: This study aimed to conduct a preliminary evaluation of the effects of 6-methylsulfinylhexel isothiocyanate (6-MSITC) contained in wasabi rhizomes on brain fatigue and sleep and examine its safety through overdose study.
Methods: A total of 20 healthy volunteers who were experiencing daily fatigue were given wasabi extract powder containing 6-MSITC (4.8 mg/day of 6-MSITC) for 4 weeks. Then, fatigue, sleep, autonomic nerves, stress, and immunity were evaluated. In addition, overdose safety study of the extract powder (up to 16 mg/day of 6-MSITC for 4 weeks) was performed with 30 healthy volunteers in double-blind placebo-controlled method.
Results: Wasabi extract powder containing 6-MSITC did not improve fatigue after mental task, but fatigue before mental task, sleep and mood were improved significantly after 4 weeks intake. No changes were observed in the autonomic nerve function, stress, or immune markers. In the overdose safety study, no changes in the parameters or side effects were observed, and the results showed that overdosing on wasabi extract powder containing 6-MSITC was safe.
Conclusion: This study confirmed the possibility that wasabi extract powder containing 6-MSITC may improve brain fatigue and sleep. However, since the effectiveness evaluation in this study was a single-arm, open-label study and there was no placebo control group, these points must be considered when interpreting the results. Safety was confirmed in an overdose study of more than three times the amount compared to that in the efficacy evaluation study. In the future, further research should be conducted on brain fatigue and sleep with wasabi extract powder containing 6-MSITC.
Trial registration: UMIN clinical trial registration system, UMIN000049913. Registered 27 December 2022 Retrospectively registered, https://center6.umin.ac.jp/cgiopen-bin/ctr/ctr_view.cgi?recptno=R000056818