Objective: Equol (Eq) , a metabolite produced from soy isoflavone daidzein by intestinal bacteria, exhibits estrogen activity and may exert effects on glucose metabolism. Eq levels vary extensively depending on the capability for Eq production and amounts of daidzein consumed. We examined the relationship between Eq levels and type 2 diabetes mellitus.

Research Design and Methods: Among 1,395 outpatients with diabetes at our hospital, 147 subjects (age: 70-89 years) were recruited (DM group) . Also, 147 age-/sex-matched non-DM subjects were recruited from 1,113 individuals who underwent routine health examinations (non-DM group) . As the estrogenic effect of Eq becomes apparent after menopause, the subjects were age restricted. Eq producers (EqPr) were determined based on the logarithm of the ratio of urinary Eq to the concentration of daidzein with a cut-off value of −1.75.

Results: Urinary daidzein (p=0.03) and Eq concentrations (p=0.01) were significantly lower in the DM group versus the non-DM group. The proportion of EqPr differed significantly between the groups (38.8% and 53.1%, respectively; p=0.01) . However, analyses with sex-based stratification showed such difference only in women; the proportion of EqPr was 31.4% and 52.8%, respectively (p<0.01) . Reversely, there were significantly fewer DM subjects among EqPr versus non-EqPr (p=0.01) . Among women, EqPr had significantly less DM than non-EqPr (p<0.01) . However, such differences were not observed in men. Correlation analyses showed a significant positive correlation between urinary Eq and daidzein concentrations only in EqPr (r=0.55, p<0.01) .

Conclusion: In postmenopausal women, EqPr were less diabetic; this status appears to be protective against DM. Eq levels increased in parallel with the amount of daidzein consumed in EqPr, but not in non-EqPr. Therefore, Eq supplements and/or enteric bacteria transplantation, rather than dietary intervention, may be effective in preventing DM in non-EqPr.


K.Hamaura: None. H.Murakami: None. A.Tamura: None. Y.Nishiya: None. S.Mizushiri: None. M.Daimon: None.

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