Effect of dried-bonito broth on mental fatigue and mental task performance in subjects with a high fatigue score. 
Dried-bonito broth is commonly employed as a soup and sauce base in Japanese cuisine and is considered to be a nutritional supplement that promotes recovery from fatigue.  Previous human trials suggest that the ingestion of dried-bonito broth improves several mood states; however, its effect on fatigue has not yet been clarified.  The aim of this study was to clarify the effects of daily ingestion of dried-bonito broth on fatigue and cognitive parameters by a placebo-controlled double blind crossover trial.  Forty-eight subjects with fatigue symptoms ingested the dried-bonito broth or a placebo solution every day for 4 weeks.  Mood states were evaluated by the Profile of Mood States (POMS), and mental task performance was evaluated by the Uchida-Kraepelin psychodiagnostic (UKP) test.  Fatigue and total mood disturbance (TMD) scores on the POMS test decreased significantly during the dried-bonito broth ingestion (p<0.05), but did not change significantly during placebo ingestion.  The change in vigor score during dried-bonito broth ingestion was significantly higher than that during placebo ingestion at 2 weeks (p<0.05).  The results of the UKP test indicate that the numbers of both total answers and correct answers significantly increased during dried-bonito broth ingestion (p<0.05), while no significant changes were observed in the placebo ingestion.  These results suggest that the daily ingestion of dried-bonito broth may improve the mood states, may reduce mental fatigue and may increase performance on a simple calculation task.