Effect of Soy-Derived Isoflavones on Hot Flashes, Endometrial Thickness, and the Pulsatility Index of the Uterine and Cerebral Arteries

Abstract

Females in Asian countries seem to have fewer and milder menopausal symptoms than those in Western countries. Dietary differences could be responsible. The traditional Asian diet is rich in substances of vegetable origin that resemble estrogen structurally. Soy, a dietary staple, is a source of isoflavones, including genistine and daidzine, the metabolic products of which appear to have weak estrogenic as well as antiestrogen activity. This randomized, double-blind, placebo-controlled trial examined the effects of soy-derived isoflavones in 62 postmenopausal women 45 to 60 years of age who were in good general health. Actively treated women received two 1-g tablets daily containing a total of 72 mg of soy-derived isoflavones and were followed up along with placebo recipients for 6 months. Endometrial thickness was measured by ultrasound, and Doppler studies were done of blood flow in the uterine, internal carotid, and middle cerebral arteries on either side. The number of daily hot flushes decreased significantly by approximately 40% in both groups after 30 days and did not change appreciably after that time. There were no significant between-group differences or variations over time for the pulsatility index (PI) in the uterine arteries or for endometrial thickness. None of the participants had uterine bleeding during 6 months of follow up. In addition, there were no differences in the PI of the internal carotid or middle cerebral arteries. Soy-derived isoflavones had no apparent advantage over placebo in reducing hot flushes in postmenopausal women in this randomized 6-month trial. There were no substantial differences in endometrial thickness or blood flow in the uterine, internal carotid, or middle cerebral arteries between the actively treated and placebo groups.