Ingestion of dried-bonito broth ameliorates blood fluidity in humans

Abstract

To elucidate a physiological function of dried-bonito broth (DBB) on blood fluidity and oxidative stress, we performed a randomized double-blind placebo-controlled study in twenty-four healthy adult subjects. The subjects ingested DBB or a placebo for four weeks, and blood fluidity and oxidative stress were measured before and after ingestion. Blood fluidity was measured using a microchannel array flow analyzer by the passage time of 100 μl of heparinized whole blood through the microchannel array, while oxidative stress was evaluated as a level of derivative of reactive oxygen metabolites (d-ROMs) by a free radical analysis system (FRAS). DBB ingestion significantly shortened the blood passage time from 55.4 ± 3.4 to 47.6 ± 2.0 sec (mean ± SEM, p < 0.05), while no significant change was observed in the placebo group (52.4 ± 3.4 to 51.4 ± 2.6 sec, mean ± SEM) indicating that DBB ameliorated blood fluidity. The level of d-ROMs, known as a biomarker of oxidative stress, significantly decreased after DBB ingestion from 337.2 ± 18.5 to 316.5 ± 12.9 Carrotelli units (Carr. U.) (mean ± SEM, p < 0.05), suggesting that DBB reduced oxidative stress. Among subjects with a d-ROMs score > 320, regarded as being in a state of oxidative stress, changes in blood fluidity tended to correlate with changes in d-ROMs score (? = 0.55, p = 0.06), showing that blood fluidity may have improved in subjects whose oxidative stress was markedly decreased. These results also showed a possibility that DBB ingestion improved blood fluidity by decreasing oxidative stress. In previous studies, daily DBB ingestion improved various fatigue-related symptoms, so we investigated the effect of DBB on fatigue-related symptoms via a questionnaire survey in the present study. The result of this survey showed that symptoms of shoulder stiffness and visual fatigue were improved only in the DBB group (p < 0.05, p < 0.1, respectively). Insufficient blood circulation is considered to lead to the development of shoulder stiffness, visual fatigue, and other fatigue-related symptoms. Based on these findings, we considered that dietary intake of DBB may improve blood fluidity by reducing oxidative stress and thus might protect against fatigue.