Although estrogen replacement therapy effectively relieves menopausal symptoms, it has significant adverse effects and is not acceptable to many women. Alternative therapies include isoflavones that are found in many foods, particularly in soy products, and have estrogenic and antiestrogenic effects, depending on the target tissue. Studies of isoflavone supplementation to relieve menopausal symptoms have shown mixed results, possibly because of the type and dose of isoflavone used. Han and colleagues evaluated treatment of menopausal symptoms with 100 mg of soy isoflavone per day.
They recruited women 45 to 55 years of age who had been amenorrheic for at least 12 months but had not used any hormonal medications or herbal supplements during that time. Exclusions included hysterectomy, uncontrolled hypertension, and history of stroke, cancer, myocardial infarction, or transient ischemic attack during the previous five years. Blood levels of follicle-stimulating hormone (FSH) were required to be 25 U per L or greater, and estradiol levels of 20 pg per mL or less were required for participation in the study. Baseline screening included demographic and medical information, assessment of menopausal symptoms using the Kupperman index, review of medications and smoking status, and measurement of blood levels of FSH, luteinizing hormone (LH), estradiol, glucose, and lipids. Body mass index was calculated, baseline blood pressure recorded, and transvaginal sonography performed to evaluate the uterine cavity. The 82 patients were then assigned to receive 100 mg of isoflavone or an identical placebo daily and were followed for five months.
The two groups of patients were comparable in all important respects. One patient dropped out of each group, citing lack of effect or nausea. At the end of the study, patients receiving isoflavone showed significant improvement in menopausal symptoms over baseline and compared with the placebo group. Benefits were reported in all areas except urinary stress incontinence. No patients reported vaginal bleeding. Levels of total cholesterol and low-density lipoproteins (LDL) decreased significantly in the isoflavone group compared with the baseline and placebo groups. Triglycerides and high-density lipoproteins (HDL) increased in both groups. No changes occurred in blood glucose levels, blood pressure, or body mass index. Estrogen levels rose in the isoflavone group, but no proliferative effect occurred on the endometrium. Endometrial thickness, FSH, and LH levels were similar in placebo and treated patients.
The authors conclude that 100 mg per day of isoflavone effectively relieved menopausal symptoms, especially vasomotor instability. This is consistent with data from women who consume a high-soy Asian diet. They suggest that this relief of symptoms, combined with lack of endometrial effect and positive influence on LDL levels, could lead to wider use of isoflavones as an alternative therapy for menopausal symptoms.