Objectives: The primary aim was to assess whether the use of an isoflavone extract containing 40 mg or 160 mg of total isoflavones affects the frequency of menopausal flushes and other symptoms. The secondary aims were assessments of possible effects on menopause symptom scores and biological measures of estrogen activity.
Methods: A randomized, double-blind, placebo-controlled prospective trial of 37 postmenopausal women with symptoms of estrogen deficiency was performed over a 12-week period. The women were randomized to three treatment groups: placebo, 40 mg or 160 mg, delivered in tablet form.
Results: There was no significant difference in the incidence of flushes between the three groups at trial conclusion. There was no difference between the groups in Greene Menopause Symptom Scores, vaginal pH, levels of follicle stimulating hormone (FSH), sex hormone binding globulin (SHBG) or total cholesterol, liver function or blood parameters. A statistically significant increase in high-density lipoprotein (HDL) cholesterol of 18.1% (p = 0.038) occurred in the 40-mg group.
Conclusion: A large placebo response and inadvertent use of dietary isoflavones in the placebo group may have obscured a significant change in flushing frequency. Previous uncontrolled studies claiming a beneficial effect of foods with a high isoflavone content on menopausal symptoms may have been confounded by a large placebo response.