Association between soy isoflavone intake and breast cancer risk for pre- and post-menopausal women: a meta-analysis of epidemiological studies

• Published in: PloS one 2014-02, Vol.9 (2), p.e89288-e89288
• Main Authors: Chen, Meinan, Rao, Yanhua, Zheng, Yi, Wei, Shiqing, Li, Ye, Guo, Tong, Yin, Ping
• Format: Article
• Language: English
• Subjects: Angiogenesis inhibitors; Breast cancer; Breast Neoplasms - prevention & control; Cancer; Cancer research; Case-Control Studies; Cohort analysis; Confidence intervals; Epidemiologic Studies; Epidemiology; Female; Health aspects; Health risk assessment; Health risks; Humans; Isoflavones; Isoflavones - administration & dosage; Medical ethics; Medicine; Menopause; Meta-analysis; Odds Ratio; Post-menopause; Postmenopausal women; Risk; Risk Assessment; Risk factors; Soy products; Soybean Proteins - pharmacology; Statistical analysis; Studies; Womens health
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0089288

Conclusions drawn from meta-analyses on the association between soy isoflavone intake and breast cancer risk for pre- and post-menopausal women are not fully consistent. These meta-analyses did not explore the influence of different study designs on the pooled results on the basis of distinguishing between pre- and post-menopausal women. We performed a meta-analysis of 35 studies which reported results of association between soy isoflavone intake and breast cancer risk for pre- and/or post-menopausal women, calculated pooled odds ratios and their 95% confidence intervals of pre- and post-menopausal women respectively, and further explored soy isoflavone-breast cancer association on the basis of considering different study regions and designs. Summary results suggested that soy isoflavone intake has a protective effect against breast cancer for both pre- and post-menopausal women. However, they are influenced by study design and region. Pooled ORs of studies carried out in Asian countries suggested that soy isoflavone's protective effect exist in both pre- and post-menopausal women (OR = 0.59, 95%CI: 0.48-0.69 for premenopausal women; OR = 0.59, 95%CI: 0.44-0.74 for postmenopausal women). However, there are some differences between the results pooled from different study designs for women in Asian countries (test for consistency, P = 0.04). Pooled OR of studies on postmenopausal women in Western countries suggested that soy isoflavone intake has a marginally significant protective effect (OR = 0.92; 95%CI: 0.83 ∼ 1.00), but further analyses stratifying by study design found no statistically significant association. We meta-analyzed more and newer research results, and separated women according to menopausal status to explore soy isoflavone-breast cancer association. We founded that soy isoflavone intake could lower the risk of breast cancer for both pre- and post-menopausal women in Asian countries. However, for women in Western countries, pre- or post-menopausal, there is no evidence to suggest an association between intake of soy isoflavone and breast cancer.