If you’re trying to eat more plant-based meals, you may find yourself filling up on a lot of soy. It seems like an easy choice, but soy is one of many heavily-debated ingredients. Its impact on health is still somewhat up for grabs. Minimally processed soy, such as tofu or tempeh, can be a great alternative to animal protein. It serves as a good source of fiber and omega-3 fatty acids. However, some studies indicate potential risks, such as an increased link to breast cancer or allergies. Our experts break down the benefits and risks of soy in your diet.
Is soy healthy?
“Soy can be part of a balanced, healthy diet for many individuals,” notes Registered Dietitian Elizabeth Shaw. “Soy is an excellent plant-based complete protein source. It can provide nutrients like folate and potassium. Research has shown the cholesterol-lowering effects of soy protein: 25 grams a day may reduce the risk of heart disease. Soy has also shown promise in lowering one’s risk for osteoporosis [and] colon and other cancers.”
Shaw advises those who are allergic to soy to check labels. She recommends refraining from eating food with soy proteins to accommodate individual sensitivities.
Does soy increase the risk of breast cancer?
According to Dr. Sherry Ross, OB-GYN, women’s health expert at Providence Saint John’s Health, the research is complicated. “Soy contains isoflavones, which mimic similar effects to estrogen. These have generated much concern in the safety of soy products to women at high risk for breast cancer. Or those women currently with breast cancer,” she says. “Not all soy products contain isoflavones, and this information is often not available on the food label. For example, soy oil does not contain isoflavones, but soy flour does. It’s thought that if you have an estrogen-sensitive breast cancer, then you need to be careful consuming soy isoflavones.”
Not all experts agree, though, and findings have varied over the years. Some research links soy to the growth of breast cancer cells. Other studies indicate a reduced risk of breast cancer due to the intake of dietary soy.
“The controversy with soy actually arises from the phytoestrogens that have some similarities with the estrogen that naturally occurs in our bodies,” says Dr. Priya Khorana, New York City-based nutritionist and exercise physiologist. “However, research shows that phytoestrogens don’t always mimic estrogens. In some tissues, they can actually block the action of estrogen. If soy’s estrogen-blocking action occurs in the breast, then eating soy could, in theory, reduce the risk of breast cancer. [This is] because estrogen stimulates the growth and multiplication of breast and breast cancer cells. But studies so far haven’t provided a clear answer. Some have shown a benefit between soy consumption and breast cancer, while others show no association.”
All in all, Dr. Khorana points back to the benefits of soy, especially for your heart. It can help lower blood pressure and cholesterol, and the fiber found in soy can help regulate blood sugar. Additionally, it’s said to aid in weight loss and prevent obesity.
Is there a difference between processed and unprocessed types of soy?
“The nutritional benefits of soy depend on if it is processed or not,” Dr. Ross says. “The healthiest and most nutrient-rich form of soy is when it’s unprocessed. Unprocessed soy contains all the essential amino acids—fiber, potassium, magnesium, B vitamins, calcium, iron—and the good fats, omega-3 and -6 fatty acids. In the United States, the majority of soy that is consumed is in the form of processed soy, which has less nutritional value.”
Jessica Cording, registered dietitian and health coach, recommends sticking with whole forms of soy, such as edamame, tofu, tempeh, and miso. She advises avoiding processed forms commonly used as “fillers” in snack foods and protein bars. Dr. Ross warns against other processed but popular foods, such as soy meats and cheeses. Dr. Khorana also considers soy milk and soy flour healthy options and reinforces the approach of eating minimally processed, non-GMO sources of soy.
Shaw says, “We are fortunate enough to live in a society today where a lean toward plant-forward eating is very present. With that, there are many soy-based products becoming available on the market. Soy can add a flavorful boost to your favorite recipes that you may assume have to be made with an animal-based option. As with everything, I always remind my clients to practice moderation with whatever they enjoy consuming and, whenever possible, [to] try to consume the source of the food they enjoy in the form that is closest to nature.”
What’s the smartest way to add soy to your diet?
“In general, for someone who wants to include soy in their diet, I recommend going for the whole, minimally processed forms. Keep it to about one serving per day or capping at 25 grams of soy protein per day,” Cording advises. “Mixing up the different varieties over the course of the week helps you enjoy a range of nutrients without overdoing it on any one thing. Organic and non-GMO sources are also options to consider.”
“Soy is one of those foods that seemingly saves us from disease one day and then causes it the next,” says Registered Dietitian Mitchell Zandes. “With a decent amount of protein, a good mix of unsaturated fat, and desirable levels of calcium and iron, I recommend tofu to anyone interested in moving toward a plant-based diet. Or [someone] at least willing to try something other than beef or chicken. When it comes to soy, the advice I give for most food applies. Try to get the least processed form, and go organic if you can.”
If you have an existing condition that requires medication, then consider talking to your doctor about soy consumption. Make sure there’s no interference with the absorption of your medication. It is always best to connect with your health care provider or nutritionist if you have specific concerns about eating soy. Talk with them to figure out an approach that works best for your needs.