Combined estrogenic effect of soybean food containing phytoestrogens and endocrine disruptor

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 17500546
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Eating habits, studies on eating habits
• Research Institution: Kyoto Prefectural University
• Principal Investigator: KAWAZOE Sadahiro Kyoto Prefectural University, Department of Food Sciences and Nutritional Health, Instructor, 人間環境学部, 助手 (00224783)
• Project Period (FY): 2005 – 2006
• Keywords: phytoestrogens / soybean food / endocrine disruptor / estrogenic effect / combined estrogenic effect

Research Abstract

Isoflavones, such as genistein and daidzein, are phytoestrogens present in soybean foods and have estrogenic activity. In this study, we examined the combined estrogenic effect of soybean extract (Nijiru) containing human intake dose level of isoflavones (10 mg/kg/day) as soybean food and endocrine disruptor.
Soybeans were boiled for 40 min at 120"C in water, and Nijiru was produced and was then freeze-dried to make a powder. Nijiru powder contained daidzin, glycitin, genistin, daidzein, glycitein, and genistein. Nijiru (1900-6600 mg/kg corresponding to dose of total isoflavone 10 mg/kg) was administered to ovariectomized ICR mice by oral gavage for 11 consecutive days. The synthetic endocrine-active hormone diethylstilbestrol (DES) (0.05 mg/kg) was then co-administered orally with Nijiru and continued for another 3 days. The relative uterine weight (% of body weight) of Nijiru+DES treatment was slightly higher than that of DES alone. Similarly, synthetic endocrine-active compound bisphenol A (BPA) (300 mg/kg) or pesticide methoxychlor (MX) (50 mg/kg) were co-administered orally with Nijiru and continued for another 3 days. Although Nijiru+MX treatment increased (vs. MX alone) the relative uterine weight, Nijiru+BPA treatment did not increase (vs. BPA alone) the relative uterine weight.