The growth of the flavonoid-degrading intestinal bacterium, Eubacterium ramulus, is stimulated by dietary flavonoids in vivo

Abstract

A human study was performed to investigate the influence of different dietary flavonoids on the faecal population of the flavonoid-degrading bacterium Eubacterium ramulus. Twenty-eight healthy subjects, divided into five groups, consumed for 6 days a flavonoid-free diet. On day 4 of this intervention period the study participants ingested a single dose of quercetin (14 mg kg(-1) body mass (bm)), rutin (pure or as buckwheat leaves, 28 mg kg(-1) bm) or a placebo. During the first 3 days of the intervention period the total faecal flora decreased by 61-88% and the population of E. ramulus by 40-75%. The oral intake of the flavonoids resulted in a dramatic increase in the faecal E. ramulus population. The relative proportion of E. ramulus rose from minimally 0.2% (on day 1) to maximally 6.9% of the total flora on day 8. The faecal concentrations of degradational products were highly variable but reflected the bacterial breakdown of the flavonoids.