Effect of miso soup containing Natto on the composition and metabolic activity of the human faecal flora

Abstract

This study investigated the effect of consumption of miso soup containing natto (natto miso soup) over 14 days on the bacterial flora and metabolic activity of the faeces of healthy volunteers (age range 21-59 years). No marked change in the number of total bacteria was observed throughout the experimental period. During intake, the numbers of Bacillus and Bifidobacterium were increased (p <0.05), whereas numbers of Enterobacteriaceae were decreased (p <0.05) and numbers of lecithinase-positive clostridia (including Clostridium perfringens) tended to decrease. Faecal acetic and propionic acids were increased (p <0.05) while faecal indole, p-cresol, ammonia and sulfide were lowered (p <0.05) during the intake period. Faecal moisture was increased and faecal pH was decreased during the intake period, although they were not significantly different. These results indicate that consumption of natto miso soup improved the intestinal environment of the volunteers. © 2006 Taylor & Francis.