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September 2014

Soy Linked to Potential Breast Cancer Concerns

A new study raises concerns about the potential effects of soy on breast cancer-related genes in women with breast cancer.

Soy contains protein, isoflavones, and fiber, all thought to provide health benefits. Isoflavones such as genistein are believed to have estrogen-like effects in the body, and as a result are sometimes called "phytoestrogens."

In a recent study, researchers randomly assigned 140 women with early-stage breast cancer to receive soy protein supplementation or placebo for 7 to 30 days. Changes in breast-cancer related genes and cancer cell growth were evaluated throughout the study.

The researchers found that blood levels of isoflavones rose in women in the soy group. Soy supplementation affected the expression of 21 breast cancer-related genes. Gene expression, including the FGFR2 gene, which is known to increase cancer cell growth, was doubled. Several other genes known to affect cancer cell growth were also increased.

The authors concluded that these findings raise concerns about the potential effects of soy in women with breast cancer. Further research is warranted.

For information about soy, please visit Natural Standard’s Food, Herbs & Supplements Database.


  1. Natural Standard: The Authority on Integrative Medicine.
  2. Shike M, Doane AS, Russo L, et al. The effects of soy supplementation on gene expression in breast cancer: a randomized placebo-controlled study. J Natl Cancer Inst. 2014 Sep 4;106(9).

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