Soy and Breast Cancer: Is There a Connection?
In the United States, breast cancer remains the most commonly diagnosed cancer among women. Although advancements in treatment have improved survival rates and overall outcomes, there is a strong emphasis on healthy lifestyle changes for those at risk or in remission, including nutrition. Soy has been a controversial food when it comes to breast cancer, even as our understanding of it has evolved over the past several decades - so let’s explore the latest recommendations.
Is Eating Soy Dangerous?
One of the early concerns with soy was its natural content of isoflavones, which are plant-based estrogens. It was thought that because soy contains plant-based estrogens, it could increase risk of estrogen-dependent breast cancer. Although plant estrogens can seem similar to human estrogen because of their chemical structure, their activity is actually different. While elevated estrogen levels are known to increase breast cancer risk, the isoflavones in soy foods do not have the same effect. Instead, they are known for their anti-estrogenic properties, as they compete with and bind to estrogen receptors, ultimately reducing overall breast cancer risk.
Some misunderstandings about the safety of soy also stem from the fact that studies on humans and animals can yield different results. In certain animal studies, rodents exposed to high doses of isoflavones showed an increased risk of breast cancer.
However, rodents metabolize soy differently than humans, and these findings have not been replicated in human studies. Additionally, the doses of isoflavones used in animal studies are much higher than what humans typically consume. In human research, soy's estrogenic effects either show no impact or seem to reduce breast cancer risk, particularly in Asian countries where lifelong soy intake is higher than in the U.S.
Best Soy Foods to Eat
Traditional, minimally processed soy foods should be prioritized as a protein choice on your plate. You can opt for both fermented and unfermented soy foods:
Fermented: miso, cooked tempeh, natto
Unfermented: edamame, tofu, edamame, soy milk
Fermented choices tend to have more isoflavones. However, both kinds are great and you can try to get a mixed variety. In addition to isoflavones, soy products can be great sources of protein, B vitamins, potassium, fiber, and other nutrients.
Ready to try some soy recipes? Click here for a free collection I curated - simply enter your name and email, and you can download a Soy Recipe booklet.
Recommendations from the American Institute for Cancer Research
The American Institute for Cancer Research generally recommends including soy in the diet of patients with or at risk for breast cancer. Although research is still ongoing, soy provides valuable antioxidant and anti-estrogenic benefits that contribute to a healthy diet. Different soy sources also offer various nutrients that can support those at risk for or living with breast cancer.
If you’re wondering if soy is a good choice for you and how to fit it into your diet, or if you need support through a cancer journey, speak with your Dietitian to develop a treatment plan that is tailored to your specific needs.
