Soy Foods After Breast Cancer

The University of Pennsylvania School of Nursing
Last Modified: December 13, 2011

Question

I do not eat soybeans, tofu, tempeh, flax seeds. I do not consume any soy supplements. I am looking for a complete list of those foods that are no-no's for ER 100% patients re: estrogens, phytoestrogens, xenoestrogens. I have a list from www.dietaryfiberfood.com, which lists foods high in phytoestrogens and lignans (content and amounts included for both). Please recommend any resources that list no-no's as I listed above for ER 100% patients.

Answer

Karen Wagner, RD, Registered Dietitian at Penn Medicine, responds:

The literature surrounding phytoestrogens and estrogen receptor positive (ER +) breast cancer can be confusing. Based on the majority of the evidence it seems that phytoestrogens from soy foods and flax are safe and may even be protective for women with ER + tumors. Many major organizations, including the American Institute for Cancer Research and the American Cancer Society have issued statements that moderate consumption of soy foods (1-3 servings per day) should be safe for women with ER + breast cancer. Much of the confusion surrounding soy and breast cancer comes from studies done on cell cultures, animal models and some very small human studies done with high doses of soy isoflavones. The debate still continues as to whether genetic factors play a role in the relationship between soy and breast cancer. Also debated is whether or not the timing of soy intake plays a role in the development of breast cancer. For instance, some scientists are examining if is soy more protective early in life. While we certainly recommend that women with ER + tumors not consume large amounts of isolated soy protein, at this time, we do not have any lists of foods that absolutely must be avoided by women with ER + tumor type. For more information on this topic, please see www.aicr.org or www.cancer.org .

Xenoestrogens are a different issue altogether. These are chemicals that can enter the food supply and may be present in varying amounts in a wide variety of foods. The relationship between xenoestrogens and breast cancer is being studied, but at this time there is not enough data, either about the effects of xenoestrogens, their safety or the foods they are in to make definitive statements about what foods to avoid to avoid xenoestrogens.

This question and answer was part of the OncoLink Brown Bag Chat. Series, View the Life After Breast Cancer transcript.