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

AIMS/INTRODUCTION: 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. MATERIALS AND METHODS: 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). RESULTS: 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). CONCLUSIONS: Our study findings showed that postmenopausal women had a low proportion of equol producers with diabetes and dyslipidemia.