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

Abstract

Glycitein metabolism was compared with other isoflavones to begin to understand the effect of this compound. Total isoflavones of 4.5 micromol/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 approximately 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.

Increased probiotic yogurt or resistant starch intake does not affect isoflavone bioavailability in subjects consuming a high soy diet

“…Previous studies also report no effect of either probiotic (37) or dietary fibre (52) supplementation with soy consumption on equol-producing capacity, suggesting genetics may contribute to this ability (59). In the current study, equol occurrence varied greatly between individuals and within subjects on different occasions, as has been previously reported (60)(61)(62). This large variability, combined with a small numbers of subjects, was a clear limitation.…”

Nutritional flavonoids impact on nuclear and extranuclear estrogen receptor activities

“…However, in a breast cancer case-control study in Shanghai, breast cancer patients had lower urinary levels of the two major isoflavone metabolites, O-DMA and equol, as well as of the three major soy aglycones, in comparison with matched controls (Zhang et al, 1999). The affinity of the daidzein and genistein aglycones for ER are 10-and 40-fold higher, respectively, than those of the respective glucuronides, but the glucuronides still show weak estrogenic activity at physiologic concentrations (Zhang et al, 1999). Spencer and coworkers (2001) showed the inability of 5-and 7-Oglucuronides of epicatechin to protect fibroblasts and neuronal cells from oxidative stress in vitro, whereas epicatechin and methylepicatechin were protective.…”

Optimization of a yeast estrogen screen and its applicability to study the release of estrogenic isoflavones from a soygerm powder.

“…Considerable attention has been focused on the estrogenic effects of genistein (14,16,33,34). However, much less is known about the effect of daidzein and glycitein, which are present in significant quantities in soy products (35,36). To our knowledge, no estrogenic responses of daidzein and glycitein in yeast assays have been reported.…”