Phenotypic differences between equol-producing and non-equol-producing intestinal microbiota

Equol is an isoflavone produced by intestinal microbiota from daidzein. It has been assumed that individuals with equol-producing microbiota are those who mainly benefit from isoflavone consumption. However, no obvious genotypic differences can be found between the microbiota of equol-producing individuals and non-equol-producing individuals. The aim of this work was to find phenotypic differences in isoflavone metabolism between equol-producing and non-equol-producing intestinal microbiota. Of the 17 faecal samples used in this work, six produced equol from both daidzein and dihydrodaidzein (DHD); however, only equol-producing faecal samples produced 5-hydroxy-equol from genistein and dihydrogenistein (DHG). The equol producing microbiota metabolised most of daidzein, genistein, DHD and DHG present in the medium, while the metabolism of daidzein and genistein by non-equol producing microbiota is much lower, and they do not metabolise DHD and DHG. Moreover, equol-producing faecal samples produced lower concentrations of O-DMA than the non-equol-producing faecal samples. In addition, we demonstrated that most of the O-DMA is produced from daidzein. Therefore, there are important phenotypic differences between equol-producing and non-equol-producing intestinal microbiota, and these differences explain the differentiation between equol-producing and non-equol-producing individuals, and help to understand the metabolism of isoflavones by microbiota and how intestinal microbiota is responsible for the benefits of isoflavone intake.