Improvement of menopausal symptoms by soy isoflavones: a randomized double-blind study

Introduction: Despite promising results from recent placebo-controlled double-blind studies [1,2] the effects of soy extracts on menopausal hot flushes required confirmation from a robust clinical trial.

Method: 192 pre- to postmenopausal Caucasian women with European style diet (basically lacking soy products) who suffered from vasomotor symptoms were included in a 12-week, double-blind, placebo-controlled study (part I), followed by a 12 week open observational period under verum (part II). They were supplemented with one tablet/day of a soy extract preparation containing 100mg of isoflavones (calculated as aglycones) or placebo. Participants were keeping a diary on hot flushes. In addition, changes in the Greene Climacteric Scale (GCS) were evaluated. Safety parameters included haematology and biochemical parameters (including liver and thyroid function tests and hormonal levels), and vaginal cytology.

Results: Hot flush diaries were available from a total of 136 participants (verum: n=54), whereas the ITT population for GCS and safety consisted of 192 women (verum: n=97), with 12 drop-outs in study part I (verum: n=7). At the end of part I hot flushes were reduced by 43.3% with verum, and by 30.8% with placebo/verum (group difference p<0.001). Significant group differences in favour of verum were also obtained for all 21 items of the GCS (p<0.001). Two dropouts occurred in study part II. Hot flushes incidence was further reduced to 67.8%, with no more statistical significance between the verum and placebo groups of part I. Over the entire study period of 24 weeks no changes were found for safety parameters and vaginal cytology.

Conclusions: Soy extract with 100mg of isoflavones per day safely and effectively reduces menopausal vasomotor symptoms.

References: 1. Nahas, E. et al. (2007) Maturitas 58:249–258.

2. Khaodhiar et al. (2008) Menopause 15:125–132.