Biological effects of a diet of soy protein rich in isoflavones on the menstrual cycle of premenopausal women

• Published in: The American journal of clinical nutrition Vol. 60; no. 3; pp. 333 - 340
• Main Authors: Cassidy, A, Bingham, S, Setchell, KD
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 01.09.1994; American Society for Clinical Nutrition; American Society for Clinical Nutrition, Inc
• Subjects: Adult; Biological and medical sciences; breast cancer; Diet; Dietary Proteins - administration & dosage; Dietary Proteins - pharmacology; Estradiol - blood; Female; Follicle Stimulating Hormone - blood; Glycine max; Gynecology. Andrology. Obstetrics; hormonal status; Hormones; Humans; isoflavones; Isoflavones - administration & dosage; Isoflavones - pharmacology; Isoflavones - urine; Luteinizing Hormone - blood; Mammary gland diseases; Medical sciences; menstrual cycle; Menstruation; Menstruation - drug effects; Menstruation - metabolism; Plant Proteins, Dietary - administration & dosage; Plant Proteins, Dietary - chemistry; Plant Proteins, Dietary - pharmacology; Premenopause - metabolism; Progesterone - blood; Proteins; Sex Hormone-Binding Globulin - metabolism; Soy; Soybean Proteins; Soybeans; tamoxifen; Tumors; Women; breast cancer; hormonal status; isoflavones; Soy; tamoxifen; menstrual cycle; Human; Soy protein; Prevention; Mammary gland diseases; Menstrual cycle; Premenopause; Supplemented diet; Biological effect; Mammary gland; Malignant tumor; Isoflavone derivatives
• DOI: 10.1093/ajcn/60.3.333
• ISSN: 0002-9165

The influence of a diet containing soy protein on the hormonal status and regulation of the menstrual cycle was examined in six premenopausal women with regular ovulatory cycles. Soy protein (60 g containing 45 mg isoflavones) given daily for 1 mo significantly (P < 0.01) increased follicular phase length and/or delayed menstruation. Midcycle surges of luteinizing hormone and follicle-stimulating hormone were significantly suppressed during dietary intervention with soy protein. Plasma estradiol concentrations increased in the follicular phase and cholesterol concentrations decreased 9.6%. Similar responses occur with tamoxifen, an antiestrogen undergoing clinical trial as a prophylactic agent in women at high risk for breast cancer. These effects are presumed to be due to nonsteroidal estrogens of the isoflavone class, which behave as partial estrogen agonists/antagonists. The responses to soy protein are potentially beneficial with respect to risk factors for breast cancer and may in part explain the low incidence of breast cancer and its correlation with a high soy intake in Japanese and Chinese women.