Association between equol producers and type 2 diabetes mellitus among Japanese older adults

Equol, which is produced by enteric bacteria from soybean isoflavones, has a chemical structure similar to estrogen. Both in vivo and in vitro studies have shown the beneficial metabolic effects of equol. However, its effects on type 2 diabetes remain unclear. We investigated the association between the equol producers/non-producers and type 2 diabetes.

The participants included 147 patients with type diabetes mellitus aged 70-89 years, and 147 age- and sex-matched controls. To ascertain the equol producers or non-producers, we used the comparative logarithm between the urinary equol and daidzein concentrations (cut-off value -1.75).

The urinary equol concentration was significantly lower in the diabetes group compared with the non-diabetes group (P = 0.01). A significant difference in the proportion of equol producers was observed among all participants (38.8% in the diabetes group and 53.1% in the non-diabetes group; P = 0.01). The proportion of equol producers among women was significantly lower in the diabetes group (31.4%) than in the non-diabetes group (52.8%; P < 0.01). Additionally, the frequency of dyslipidemia in female equol producers was significantly lower than that in female non-equol producers (P < 0.01). Among men, no such differences were observed. We found a significant positive correlation between the urinary equol and daidzein concentrations among equol producers (r = 0.55, P < 0.01).

Our study findings showed that postmenopausal women had a low proportion of equol producers with diabetes and dyslipidemia.