Inter-individual variation in isoflavone absorption depends on gut microbial degradation and affects the efficacy of these compounds. We... » More

Inter-individual variation in isoflavone absorption depends on gut microbial degradation and affects the efficacy of these

compounds. We hypothesized that inter-individual variation in fecal isoflavone disappearance coincided with variation in

bacterial species. In vitro anaerobic fecal disappearance of isoflavones was measured from 33 participants by HPLC. Fecal

microbial 16S rRNA variable region PCR products were obtained from 4 participants with the greatest and least genistein

or glycitein degradation and were subjected to denaturing gradient gel electrophoresis. DNA bands with a homology of 90–

95% to Bacteroides uniformis and Faecalibacterium prausnitzii were present in greater intensities in fecal samples

showing a genistein disappearance rate constant of (1.47 +/- 0.14)/h compared with those with a genistein disappearance

rate constant of (0.15 +/- 0.030)/h (P < 0.05). Human fecal bacterial species with DNA sequences 90–100% homologous to

Tannerella forsythensis and 4 other species were present in greater intensities in fecal samples showing a glycitein

disappearance rate constant of (0.57 +/- 0.30)/h compared with fecal samples with a glycitein disappearance rate constant of (0.08 +/- 0.03)/h (P < 0.05). In high degraders, B. uniformis may be a candidate for genistein degradation and T.

forsythensis for glycitein degradation, based on fecal isoflavone degradation in the presence of these species. Bacteroides

acidifaciens increased isoflavone disappearance in anaerobic human fecal incubations under nutrient-rich and -depleted

conditions, suggesting this species as one responsible for the generally high degradation of isoflavones by humans. These

fecal microbes are candidate biomarkers for interindividual variation in isoflavone uptake and efficacy.

« Hide