I hear that soy contains estrogen and too much of it can cause cancer. Is it safe to consume?
Soy’s reputation is complicated and controversial — some people avoid soy for rumors of its link to cancer, while others swear by their daily soy-latte fix. The conflicting opinions (and seemingly questionable coverage of the research) make it difficult to know what’s best for your health.
The fact is, untangling the truth about soy is much more complex than what one-sided reports (or your Instagram feed full of vegan tofu salad bowls) might suggest.
Soy contains estrogen-like compounds (phytoestrogens) called isoflavones, which were once thought to act as endocrine disruptors and raise the risk of hormone-related cancers like breast cancer. However, according to the American Institute for Cancer Research, this link has been disproven. In fact, isoflavones, along with other phytonutrients found in soy, may actually help reduce risk of some cancers. A study from earlier this year also adds to the evidence that whole-food forms of soy (more about those below) are safe, and possibly even beneficial, for women with some types of breast cancer to consume. (Though women with breast cancer should always talk with their doctor about what is best for their specific case.) Research also shows similar conclusions for men with prostate cancer. In more good news, soy contains many phytonutrients (beyond isoflavones) that may reduce risk of cancer and provide other health benefits.
If you’re waiting for the catch, here it is: Frozen meatless meatballs probably won’t offer the same health benefits that miso soup will. The difference between heavily processed versions of soy such as soy protein isolate and whole soy foods is key.
Let’s go back to the basics. Soy-based foods are made from soybeans. Whole-food sources of soy such as tofu, tempeh, edamame, (most) soy milks, and miso (which is fermented soy) are good sources of protein and most offer other nutrients including fiber, potassium, magnesium, copper, and manganese as well as phytonutrients. For the average person, consuming 1-2 servings of soy is safe and can be beneficial, especially when following a plant-based diet (a serving is defined as about 1/3 cup of tofu, 1/2 cup edamame, or 1 cup of soy milk).
On the other hand, heavily processed forms of soy, such as soy-protein isolate, are often lacking in fiber and the other various nutrients that whole soy foods provide. Soy protein isolate is often used to boost the protein content in packaged foods such as vegetarian burgers and meat substitutes, cereals, energy/protein bars, and even breads. Processed soy doesn’t provide the same health benefits as whole soy foods and the foods it fortifies often have many other undesirable ingredients or high amounts of sodium, so it’s best that they aren’t the main source of protein in your diet. However, healthy people should not be afraid of the occasional soy-fortified food. Some research does suggest that women with breast cancer (and survivors) should limit soy-protein isolate, so for these populations, avoiding the processed soy products may be best.
The final verdict? Soy is safe* — and potentially beneficial — in moderation for the average healthy person. So, enjoy that soy-milk latte or grilled tofu power bowl — your body might even thank you. (Cue a sigh of relief.)
*Research on the effects of soy is still ongoing. If you or a loved one have any questions regarding your health, cancer, or a medical condition, it is best to consult your physician or other healthcare provider to find the best solution for you.
At Bon Appétit, we know there’s a lot on your plate that you worry about. That’s why we have a team of registered dietitian nutritionists ready to answer your nutrition questions about which food choices will help you avoid unwanted pounds, work or study (and sleep!) better, and form long-lasting healthy eating habits. Email your questions and feedback to firstname.lastname@example.org