Effect of dried-bonito broth (Katsuo-bushi dashi) on mental fatigue and stress caused by simple workload and task performance

The effect of dried-bonito broth on the mental fatigue and stress caused by simple workload and task performance is investigated. After a 1-week non-ingestion period, female subjects (n =31, 20.5+-0.6 years old) ingested dried-bonito broth (dry matter, 4.9g) daily for 1 week. The evaluation was performed after the non-ingestion and ingestion periods. For the simple workload, the Uchida-Kraepelin psychodiagnostic test (UKP) was administered. Profiles of Mood States (POMS) scores, flicker values and salivary cortisol were measured before and after UKP loading. After the non-ingestion period, post-loading flicker values were significantly lower than the preloading values, while there were no significant changes after the ingestion period. Pre-loading salivary cortisol concentrations significantly decreased during the ingestion period. Furthermore, UKP error rates after the ingestion period were significantly lower than after noningestion period. The results suggest that daily ingestion of dried-bonito broth for 1 week tends to lower the accumulation of mental fatigue and stress responses, and tends to suppress the lowering of task performance in a simple workload test.