Author: Dr. Bonnie Brock, NMD, RD, MPH
As a Registered Dietitian working in oncology, the question I was asked most often concerned the relationship between soy and breast cancer. Many people are under the (false) impression that consuming soy increases breast cancer risk and they would actively avoid it. I understand the confusion because there is a connection between soy and estrogen and there is a separate connection between estrogen and breast cancer, so people sometimes connect those dots mentally. Soy contains a high concentration of isoflavones, a plant derived estrogen-like compound, referred to as a phytoestrogen. While this compound mimics the action of human estrogen in the body because of its ability to “sit on” and stimulate the estrogen receptor, it does so with a much weaker effect. I typically explain this phenomenon with this analogy: “imagine you have 100 seats on a bus and 100 loud kids. If every seat has a loud kid in it, you have a pretty noisy bus. But imagine you replaced 50 of the loud kids with 50 quiet kids, well when they all sit down, the bus is less loud. In this scenario, estrogen receptors are the seats, human estrogen the loud kids and phytoestrogen the quiet kids.” As long as each type of estrogen (human and plant-derived) has the same affinity for each receptor, then the overall estrogen effect is weaker with plant-derived phytoestrogen present and the estrogen + cancer risk is lower. Understanding this phenomenon, researchers have found foods high in isoflavones to be breast cancer protective. In fact, the Shanghai Women’s Health Study followed more than 73,000 Chinese women and determined that women who ate the most soy had a 59% lower risk of pre-menopausal breast cancer and women who ate large amounts of soy when they were adolescents had a 43% lower risk of breast cancer later in life. That being said, consuming phytoestrogens after a breast cancer diagnosis and/or while undergoing cancer treatment may be discouraged and one should always consult with their oncologist.
This soy effect can also be used to ease menopause symptoms. Back to our bus analogy: in menopause, the loud kids are dropping off and lots of bus seats are left empty. By eating foods with isoflavones or taking soy-derived supplements, the phytoestrogens can help “fill in” the seats (receptors) that would otherwise go empty and mitigate the menopausal symptoms.
As always, make sure the soy you are eating is organic and non-GMO for the best impact on your health and wellness. Check back here throughout the month for a soy-recipe!
