High Fiber Diet Supplemented with Rice Bran Hemicellulose May Reduce Daidzein Absorption in Mice

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Much attention has focused on the health benefits of isoflavone. Investigating the absorption and metabolism of isoflavonoids is essential for understanding their biological activity. We explored the effect of a high fiber diet containing rice bran hemicellulose on the plasma and cecal isoflavonoids in mice. Mice were fed a 5% rice bran hemicellulose and 5% cellulose-0.1% daidzein diet (RBI diet) or a 5% cellulose-0.1% daidzein diet (CI diet) for 30 days. After the 30-day feeding period, the mice were sacrificed and blood and cecal contents were collected. The plasma isoflavonoids and plasma total cholesterol concentrations were measured. The plasma daidzein concentrations were significantly lower in the RBI group compared to the CI group. In contrast, there were no significant differences in the plasma equol concentrations or plasma total cholesterol concentrations between the RBI and CI groups. Binding affinity against isoflavonoids and/or the bulking effect in the gut might be related with the reduction in plasma daidzein concentration in the RBI group.