Association between daidzein metabolism to equol and fecal bile acid profiles in young women

Abstract

The ability to produce equol varies considerably among individuals due to differences in gut microbiota. Bile acids exert strong selective pressure on the intestinal microbiota, and their profiles in feces are considered to reflect the overall intestinal environment. However, the relationship between fecal bile acid profiles and human equol production has not yet been established. In this study, we investigated the association between equol production and fecal bile acid profiles in 15 young Japanese women. Following approximately one year of 24 h urine analyses conducted at 1–2 month intervals, four participants were classified as equol producers, ten as non-producers, and one as a crosser. Although 14 participants exhibited stable equol production status during the interventional trial, the composition of individual urinary daidzein metabolites, including equol, varied over a relatively wide range. Cluster analysis classified fecal bile acid profiles into primary and secondary bile acid–dominant groups. No equol producers were included in the primary bile acid–dominant group, whereas all equol producers were included in the secondary bile acid–dominant group. Therefore, bile acids are likely one of the key factors influencing equol production ability in humans.