Objective: This study aims to evaluate the effects of soy isoflavones on breast tissue in postmenopausal women.
Methods: In this randomized, double-blind, placebo-controlled study, 80 women (aged ≥45 y and with amenorrhea >12 mo) with vasomotor symptoms were randomized to receive either 250 mg of standardized soy extract corresponding to isoflavone 100 mg/day (n = 40) or placebo (n = 40) for 10 months. Breasts were evaluated through mammographic density and breast parenchyma using ultrasound (US) at baseline and 10-month follow-up. Independent t test, analysis of variance, Mann-Whitney U test, and χ2 trend test were used in statistical analysis.
Results: Baseline clinical characteristics showed no significant differences between the isoflavone group and the placebo group, with mean (SD) age of 55.1 (6.0) and 56.2 (7.7) years, mean (SD) menopause duration of 6.6 (4.8) and 7.1 (4.2) years, and mean (SD) body mass index of 29.7 (5.0) and 28.5 (4.9) kg/m2, respectively (P > 0.05). The study was completed by 32 women on isoflavone and 34 women on placebo. The groups did not differ in mammographic density or breast parenchyma by US (P > 0.05). Within each group, the baseline and final moments did not differ in mammography or US parameters significantly (P > 0.05).
Conclusions: The use of soy isoflavone extract for 10 months does not affect breast density, as assessed by mammography and US, in postmenopausal women.
From the Department of Gynecology and Obstetrics, Botucatu Medical School, São Paulo State University (UNESP), São Paulo, Brazil.
Received November 8, 2012; revised and accepted December 27, 2012.
Funding/support: This investigation was supported by Ativus Farmaceutica, Brazil, and by grants from the Lucentis Foundation for Supporting Culture, Teaching, Research, and Extension.
Financial disclosure/conflicts of interest: None reported.
The authors have no commercial, proprietary, or financial interest in the products or instruments described in this article.
Address correspondence to: Eliana Aguiar Petri Nahas, MD, PhD, Department of Gynecology and Obstetrics, Botucatu Medical School, São Paulo State University (UNESP), Distrito de Rubiao Junior s/n Botucatu 18618-970, São Paulo, Brazil. E-mail: firstname.lastname@example.org