Details

Autor(en) / Beteiligte

• XIA XU
• DUNCAN, A. M
• WANGEN, K. E
• KURZER, M. S

Titel

Soy Consumption Alters Endogenous Estrogen Metabolism in Postmenopausal Women

Ist Teil von

• Cancer epidemiology, biomarkers & prevention, 2000-08, Vol.9 (8), p.781-786

Ort / Verlag

Philadelphia, PA: American Association for Cancer Research

Erscheinungsjahr

2000

Quelle

MEDLINE

Beschreibungen/Notizen

• Isoflavones are soy phytoestrogens that have been suggested to be anticarcinogenic. Our previous study in premenopausal women suggested that the mechanisms by which isoflavones exert cancer-preventive effects may involve modulation of estrogen metabolism away from production of potentially carcinogenic metabolites [16α-(OH) estrone, 4-(OH) estrone, and 4-(OH) estradiol] (X. Xu et al. , Cancer Epidemiol. Biomark. Prev., 7: 1101–1108, 1998). To further evaluate this hypothesis, a randomized, cross-over soy isoflavone feeding study was performed in 18 healthy postmenopausal women. The study consisted of three diet periods, each separated by a washout of ∼3 weeks. Each diet period lasted for 93 days, during which subjects consumed their habitual diets supplemented with soy protein isolate providing 0.1 (control), 1, or 2 mg isoflavones/kg body weight/day (7.1 ± 1.1, 65 ± 11, or 132 ± 22 mg/day). A 72-h urine sample was collected 3 days before the study (baseline) and days 91–93 of each diet period. Urine samples were analyzed for 10 phytoestrogens and 15 endogenous estrogens and their metabolites by a capillary gas chromatography-mass spectrometry method. Compared with the soy-free baseline and very low isoflavone control diet, consumption of 65 mg isoflavones increased the urinary 2/16α-(OH) estrone ratio, and consumption of 65 or 132 mg isoflavones decreased excretion of 4-(OH) estrone. When compared with baseline values, consumption of all three soy diets increased the ratio of 2/4-(OH) estrogens and decreased the ratio of genotoxic:total estrogens. These data suggest that both isoflavones and other soy constituents may exert cancer-preventive effects in postmenopausal women by altering estrogen metabolism away from genotoxic metabolites toward inactive metabolites.