Soy Isoflavones and Breast Cancer Risk: A Meta-analysis

Abstract

Background/aim: Soy contains genistein and daidzein isoflavones. Isoflavones are phytoestrogens, with a similarity in structure to human 17-β estradiol hormone. They imitate the action of estrogen on organs by binding and activating estrogen receptors. Numerous studies have examined the relationship between soy consumption and breast cancer but not the amount of consumption itself. We performed a systematic review of the literature in order to determine whether the amount of soy and isoflavones consumed has a positive effect in pre- and post-menopausal women.

Materials and methods: Data gathering was performed following PRISMA guidelines. Narrowing down the result set for all relevant data was performed via title, abstract, full-text evaluation and the snowball procedure. The selected articles had all relevant data extracted. Analysis of the data was performed using Cochrane's Review Manager statistical analysis tool in order to draw conclusions regarding the positive effect for the amount of soy and isoflavones consumed.

Results: Significant results were found when statistically analyzing data from prospective studies which compared soy isoflavones consumption, breast cancer risk and occurrence. The data were indicative of a clear inverse correlation between the amount of isoflavones consumed and breast cancer occurrence in pre- and post-menopausal women.

Conclusion: The consumption of soy isoflavones can reduce the risk of breast cancer in pre-menopausal and post-menopausal women.

Keywords: Soy; breast cancer risk; isoflavones; meta-analysis; review.