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# Breast cancer risk lower in women taking isoflavone supplements
- URL: https://www.foodconsumer.org/isoflavones_breast_cancer_0701131202/
- Published: 2013-07-02T01:01:00.000Z
- Updated: 2026-09-22T16:21:14.000Z
- Description: An Ontario study of 3,101 breast cancer cases and 3,471 controls found isoflavone supplement use associated with lower risk: 32% lower for women using three or more supplements and 25% for any supplement taken five years or longer. The reduction showed up only in postmenopausal women.
- Author: Food Consumer
- Tags: Supplements, Nutrition, #vivvo-import

Monday July 1, 2013 (foodconsumer.org) A new study in International Journal of Cancer suggests that taking isoflavone supplements may help prevent breast cancer.

Beatrice A. Boucher from Cancer Care Ontario in Toronto, Ontario, Canada and colleagues conducted the study and found that several individual isoflavone supplements were associated with reduced risk of developing breast cancer.

"Food-based isoflavones have been associated with reduced breast cancer risk," the authors say in their report. Their current study was intended to associate isoflavone supplements with the risk of breast cancer.

Enrolled in the study were 3101 cases of breast cancer identified in the Ontario Cancer Registry and 3471 controls without the disease identified randomly from the general population from 2002 to 2003\. 

Using any of the 28 isoflavone supplements was associated with 32% reduced risk of breast cancer when three or more supplements were used. If taken for five years, then any isoflavone supplement was associated with 25% reduced risk. Risk reduction was found in postmenopausal women only when they took individual or combined supplements.

Women who ever took three or more isoflavone supplements in high doses were 45% less likely to be diagnosed with breast cancer and again when taken for more than five years, any supplement reduced the risk by 53%.

The effectiveness does not seem to be influenced by the estrogen-progesterone tumor receptor status. 

The researchers concluded "isoflavone supplements were associated with decreased postmenopausal breast cancer risk."

Isoflavones are a class of naturally occurring organic compounds related to the isoflavonoids many of which act as phytoestrogens in mammals.

Isoflavone supplements act differently to exert an effect. Some are antioxidants, some like soy isoflavones were associated with lower incidence of breast cancer and other malignancies because they can influence sex hormone metabolism and enzyme activity, protein synthesis, growth factor functions, malignant cell proliferation, differentiation and angiogenesis. (reporting by David Liu, PHD)