Duncan A M, Merz-Demlow B E, Xu X, Phipps W R, Kurzer M S
Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota 55108, USA.
Cancer Epidemiol Biomarkers Prev. 2000 Jun;9(6):581-6.
Increased urinary excretion of equol, a metabolite of the isoflavone daidzein, has been associated with a reduced risk of breast cancer. This risk reduction has generally been presumed to be a consequence of increased isoflavone consumption. However, only 30-40% of the population excretes more than trace amounts of equol, regardless of isoflavone intake. Accordingly, we hypothesized that the observed apparent protective effect of equol is at least in part attributable to hormonal differences between equol excretors and non-excretors, and that these differences are largely independent of isoflavone intake. We measured plasma hormone and sex hormone binding globulin (SHBG) concentrations in 14 normally cycling premenopausal women during each of three diet periods in which they consumed differing isoflavone doses (0.15, 1.0, and 2.0 mg/kg of body weight/day) as a component of soy protein isolate. The plasma hormone and SHBG concentrations of equol excretors (n = 5) were then compared with those of the non-excretors (n = 9). Results showed that even at the lowest dose, urinary equol excretion values for excretors far exceeded those for non-excretors consuming the highest dose. At all doses, equol excretors generally had lower concentrations of estrone, estrone-sulfate, testosterone, androstenedione, dehydroepiandrosterone (DHEA), DHEA-sulfate, and cortisol and higher concentrations of SHBG and midluteal progesterone, a hormonal pattern overall consistent with lowered breast cancer risk. In conclusion, the association of equol excretion and lowered breast cancer risk may largely reflect the tendency of equol excretors to have more favorable hormonal profiles, as opposed to merely reflecting increased isoflavone intake. Equol may be a marker for the presence of colonic bacterial enzymatic activity that increases fecal steroid excretion. Alternatively, equol itself, even with very modest isoflavone intake, may exert beneficial effects on the regulation of endogenous hormones.
异黄酮大豆苷元的代谢产物雌马酚的尿排泄量增加与乳腺癌风险降低相关。这种风险降低通常被认为是异黄酮摄入量增加的结果。然而，无论异黄酮摄入量如何，只有30%-40%的人群排泄的雌马酚超过微量。因此，我们推测，观察到的雌马酚明显的保护作用至少部分归因于雌马酚排泄者和非排泄者之间的激素差异，而且这些差异在很大程度上与异黄酮摄入量无关。我们测量了14名正常月经周期的绝经前女性在三个饮食阶段中每个阶段的血浆激素和性激素结合球蛋白（SHBG）浓度，她们食用不同剂量的异黄酮（0.15、1.0和2.0毫克/千克体重/天）作为大豆分离蛋白的组成部分。然后将雌马酚排泄者（n = 5）的血浆激素和SHBG浓度与非排泄者（n = 9）的进行比较。结果显示，即使在最低剂量下，排泄者的尿雌马酚排泄值也远远超过食用最高剂量的非排泄者。在所有剂量下，雌马酚排泄者的雌酮、硫酸雌酮、睾酮、雄烯二酮、脱氢表雄酮（DHEA）、硫酸脱氢表雄酮和皮质醇浓度通常较低，而SHBG和黄体中期孕酮浓度较高，这种激素模式总体上与降低乳腺癌风险一致。总之，雌马酚排泄与降低乳腺癌风险之间的关联可能很大程度上反映了雌马酚排泄者具有更有利的激素谱的倾向，而不仅仅反映异黄酮摄入量的增加。雌马酚可能是结肠细菌酶活性增加粪便类固醇排泄的一个标志。或者，即使异黄酮摄入量非常少，雌马酚本身也可能对内源性激素的调节产生有益影响。
