A great source of complete plant protein, soy has been a staple in Asian diets for thousands of years. There’s no debating it — soy can be found in pretty much anything these days. And we’re not talking about tofu and soy sauce here. From protein bars and veggie burgers to chicken noodle soup, soy has become ubiquitous in the food system in one form or another. It’s inexpensive, packed with protein and relatively tasteless. Additionally, some soy foods are made with calcium sulfate, which makes them good sources of calcium, too.
However, some fear that these foods may not be safe because soy contains certain estrogenlike compounds — and high levels of estrogen have been linked to increased breast cancer risk. Let’s dig a little deeper to find out whether or not this is true.
Understanding the Soy-Cancer Connection
The question around the safety of soy stems from isoflavones, a group of estrogenlike compounds made by certain plants that can mimic the actions of estrogen. While high levels of estrogen have been associated with an increased breast cancer risk, interestingly enough soy actually seems to protect against breast cancer, prostate cancer and even heart disease in human studies. This cancer-fighting effect likely comes in part from other phytochemicals in soy that reduce inflammation and prevent activation of proteins that promote cell growth commonly seen with certain cancers. As an added bonus for women, soy may also provide relief from menopausal symptoms, though the jury is still out on whether or not soy protects against osteoporosis.
Since Americans don’t eat large quantities of soy, it’s not easy to conduct observational studies comparing how various intakes link to cancer risk. In Asia, where soy is a staple and women consume 1–2 servings per day, population studies link regular consumption with lower breast cancer risk. (One serving being equivalent to 1/3 cup tofu, 1 cup soy milk, 1/2 cup edamame or 1 ounce soy nuts.)
What about cancer survivors? According to the American Institute for Cancer Research, consuming moderate amounts of soy does not increase a woman’s risk for poorer outcomes. In fact, consuming moderate amounts of soy appears to reduce recurrence and increase survival rates. The same goes for prostate cancer survivors — trials show that consuming soy food may be beneficial while none demonstrated harm.
Is there more to this debate? Yes. Opponents of soy consumption question its impact on male fertility, its anti-nutrients (Think: phytic acid, lignans and phytoestrogens — compounds that can interfere with absorption of certain minerals), and the long-term health effects of consuming modern forms of highly processed soy. Regarding fertility, some studies show no impact of soy consumption on male fertility and reproductive hormones while some show a negative effect. If you eat a varied diet of nutrient-rich whole foods, anti-nutrients shouldn’t be a concern; however, soaking, fermenting and heating soy may help mitigate the impact anti-nutrients may have on absorption.
The Takeaway
Our take? The impressive anti-cancer benefits of soy outweigh the possible concerns. To maximize the benefits, consume moderate amounts of soy in whole-food (minimally processed) forms. More research is needed to know the long-term health effects of consuming the highly processed versions of soy foods lining the shelves today. Lastly, be wary of anti-soy studies that rely heavily on animal rather than human research studies.
To enjoy your tofu without worry, here are a few tips to get the most nutritional benefit from soy foods in your diet.
- Stick to whole soy foods. Getting 1–2 servings of tofu, tempeh, edamame, miso and soymilk daily can be wonderful additions to a healthy diet. When possible, avoid soybean oil and soy protein isolate, a highly processed form of soy found in protein bars, frozen veggie burgers, canned soup and other processed foods. Those isolated, super-processed forms of soy don’t boast the health benefits of the whole soybean.
- Opt for organic when possible. It’s estimated that a whopping 93% of soy crops in the U.S. come from genetically modified seeds also treated with pesticides. If available and the budget allows, choose organic soy products.
- Look for fermented forms of soy. Fermented soy products like tempeh, miso and soy sauce are the cream of the crop thanks to the health-promoting benefits of gut-friendly bacteria. Fermenting soy may also help reduce its allergenic properties and increase the availability of amino acids.
