Over the years, there has been a lot of controversy surrounding soy products and their connection to estrogen-positive breast cancer. Will eating soy foods cause breast cancer? Could it increase the risk of breast cancer recurrence? The answer is a resounding NO! Let's explore why soy products are actually beneficial and how consuming soy can help reduce both the risk of developing breast cancer and the chance of recurrence.
Here are the basics:
Soybeans and soy products—such as soy milk, tofu, tempeh, soy sauce, miso, and edamame—contain phytoestrogens, specifically isoflavones, which have a chemical structure similar to human estrogen. This similarity has led to some confusion, as people might assume phytoestrogens function like estrogen in the body. However, it’s important to note that phytoestrogens are not the same as estrogen. Extensive research into soy products and cancer has clarified that they do not increase the risk of breast cancer. In fact, consuming soy products has been found to reduce the risk of developing breast cancer.
How are phytoestrogens different from estrogen? The human body has two types of estrogen receptors: alpha and beta. Human estrogen primarily binds to alpha receptors, while phytoestrogens—found in soy—preferentially bind to beta receptors. This distinction is important because alpha and beta receptors affect tissues differently. When different receptors are activated, they can stimulate or inhibit different pathways in the body. This is especially significant in breast tissue. Beta receptors, which phytoestrogens from soy bind to, have an anti-estrogen effect, meaning they work in opposition to estrogen.
Consuming soy products is also shown to reduce circulating estrogen in the body. Further research also indicates that soy products can inhibit the production of estrogen. All great news for estrogen-positive breast cancer. Soy does not “feed” the cancer but has the opposite effect.
Studies to back it up:
Five large studies have been performed on breast cancer survival and soy, involving more than 10,000 breast cancer patients. Among women affected by breast cancer, those who eat more soy live longer and have a reduced risk of recurrence. Looking at two of these studies: A study in the Journal of the American Medical Association reported that women with breast cancer who regularly consumed soy products had a 32% lower risk of breast cancer recurrence and a 29% decreased risk of death, compared with women who consumed little or no soy. An analysis of 14 studies, published in the American Journal of Clinical Nutrition, showed that increased intake of soy resulted in a 26% reduction in prostate cancer risk.
Conclusion:
Eat more soy!
Consuming soy foods after a breast cancer diagnosis (including estrogen-positive tumors) has been linked to improved survival rates and a reduced risk of recurrence. Furthermore, research indicates that higher soy intake during childhood and adolescence is significantly associated with a lower lifetime risk of developing breast cancer. Women who consume the most soy in their youth have nearly a 50% reduction in the risk of developing breast cancer compared to those who do not consume soy.
To incorporate more soy into your diet, focus on whole food sources of soy. Opt for options like whole soybeans, edamame, soy nuts, tofu, tempeh, and soy milk. Highly processed soy products—such as soy yogurt, protein powder, ice cream, cheese, and meat substitutes—can be included in moderation.