Xu X, Duncan A M, Merz B E, Kurzer M S
Department of Food Science and Nutrition, University of Minnesota, St. Paul 55108, USA.
Cancer Epidemiol Biomarkers Prev. 1998 Dec;7(12):1101-8.
Isoflavones and lignans are soy phytoestrogens that have been suggested to be anticarcinogenic. The mechanisms by which they exert cancer-preventive effects may involve modulation of estrogen synthesis and metabolism. To evaluate this hypothesis, a randomized, cross-over soy isoflavone feeding study was performed in 12 healthy premenopausal women. The study consisted of three diet periods, each separated by a washout of approximately 3 weeks. Each diet period lasted for three menstrual cycles plus 9 days (averaging approximately 100 days), during which subjects consumed their habitual diets supplemented with soy protein powder providing 0.16 (control diet), 1.01, or 2.01 mg of total isoflavones per kg of body weight per day (10+/-1.1, 65+/-9.4, or 129+/-16 mg/day, respectively). A 72-h urine sample was collected during the midfollicular phase (days 7-9) of the fourth menstrual cycle in 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. Urinary excretion of isoflavonoids and lignans significantly increased with increased isoflavone consumption. Compared with the control diet, increased isoflavone consumption decreased urinary excretion of estradiol, estrone, estriol, and total estrogens, as well as excretion of the hypothesized genotoxic estrogen metabolites, 16alpha-hydroxyestrone, 4-hydroxyestrone, and 4-hydroxyestradiol. Of importance are the observations of a significant increase in the 2-hydroxyestrone/16alpha-hydroxyestrone ratio and a decrease in the genotoxic/total estrogens ratio. These data suggest that soy isoflavone consumption may exert cancer-preventive effects by decreasing estrogen synthesis and altering metabolism away from genotoxic metabolites toward inactive metabolites.
异黄酮和木脂素是大豆植物雌激素，被认为具有抗癌作用。它们发挥防癌作用的机制可能涉及雌激素合成和代谢的调节。为了评估这一假设，对12名健康的绝经前女性进行了一项随机交叉大豆异黄酮喂养研究。该研究包括三个饮食阶段，每个阶段之间间隔约3周的洗脱期。每个饮食阶段持续三个月经周期加9天（平均约100天），在此期间，受试者食用其习惯饮食，并补充大豆蛋白粉，每天每公斤体重提供0.16（对照饮食）、1.01或2.01毫克总异黄酮（分别为10±1.1、65±9.4或129±16毫克/天）。在每个饮食阶段的第四个月经周期的卵泡中期（第7 - 9天）收集72小时尿液样本。通过毛细管气相色谱 - 质谱法分析尿液样本中的10种植物雌激素、15种内源性雌激素及其代谢物。异黄酮摄入量增加时，异黄酮类化合物和木脂素的尿排泄量显著增加。与对照饮食相比，异黄酮摄入量增加会降低雌二醇、雌酮、雌三醇和总雌激素的尿排泄量，以及假定的遗传毒性雌激素代谢物16α - 羟基雌酮、4 - 羟基雌酮和4 - 羟基雌二醇的排泄量。重要的是观察到2 - 羟基雌酮/16α - 羟基雌酮比值显著增加，遗传毒性/总雌激素比值降低。这些数据表明，食用大豆异黄酮可能通过减少雌激素合成并将代谢从遗传毒性代谢物转向无活性代谢物来发挥防癌作用。
