Urinary Disposition of the Soybean Isoflavones Daidzein, Genistein and Glycitein Differs among Humans with Moderate Fecal Isoflavone Degradation Activity

摘要

Glycitein metabolism was compared with other isoflavones to begin to understand the effect of this compound. Total isoflavones of 4.5 μmol/kg body weight from soymilk (high in genistein and daidzein) and soygerm (high in daidzein and glycitein) was fed to seven women and seven men. To minimize interindividual variation, only subjects with moderate fecal isoflavone degradation rates (half-lives of daidzein and genistein were 15.7 and 8.9 h, respectively) were included. The average 48-h urinary excretion of glycitein, daidzein and genistein was ～55, 46 and 29% of the dose ingested, respectively, which was significantly different from each other in men and women (P 0.001). Plasma isoflavone concentrations at 6 and 24 h after soymilk feeding paralleled relative amounts of isoflavones in soymilk (genistein daidzein glycitein) (P 0.05) in men and women, but plasma isoflavone concentrations after soygerm feeding did not parallel soygerm isoflavone concentrations in women because genistein and glycitein did not differ from each other at 6 h after feeding. Six hours after soygerm dosing, plasma isoflavone concentrations paralleled soygerm isoflavone levels in men. Based on plasma isoflavone concentrations at 6 h after dosing, the bioavailabilities of daidzein and genistein were similar in men and women. At the high glycitein dose (soygerm), plasma concentration at 24 h after dosing suggested a modest gender difference in glycitein bioavailability.