Biological effects of a diet of soy protein rich in isoflavones
on the menstrual cycle of premenopausal women
Cassidy A, Bingham S, Setchell KD.
Am J Clin Nutr 1994 Sep 60:3 333-40.
Abstract
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.
Author Address
Dunn Clinical Nutrition Centre, Cambridge, UK
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