Is Soy Good or Bad For You?

Soy is a plant-based source of protein that is in many favorite dishes. But there are also questions about soy. Does it contain estrogen? Has soy been linked to breast cancer? To determine if soy is good or bad for you, we got in touch with Julie Garden-Robinson, Ph.D., R.D., L.R.D. She is a professor and food and nutrition specialist with North Dakota State University Extension.

What nutrition does soy and soy foods provide?

Dr. Garden-Robinson: “Soy foods are rich in many nutrients, including protein, which makes them important for people interested in focusing on a plant-based diet, especially a vegetarian or vegan diet.  Soy foods also provide fiber, calcium and iron. As with any plant-based foods, soy contains no cholesterol and is low in saturated fat. The fat found in soy includes heart-healthy polyunsaturated and monounsaturated fats, including essential fatty acids.

“Soy provides B vitamins, which are necessary for producing energy from the foods we eat, and soy foods also provide potassium, phosphorus and iron.  Potassium is important to maintain a healthy blood pressure, while phosphorus is needed for cell growth. Iron is crucial for the production of red blood cells and hemoglobin.”

What are the health benefits of eating soy?

Dr. Garden-Robinson: “Soy may help build strong bones because of isoflavones and other components, including calcium, found naturally in soy. Some researchers have reported that consuming soy foods may reduce LDL (“bad”) cholesterol without affecting HDL (“good”) cholesterol. Others have stated that consumption of soy protein and isoflavones may help reduce blood pressure.

“More recently, researchers have noted that soy’s effect on blood cholesterol may be more moderate than what was reported in prior research. Therefore, in 2017, after reviewing the scientific evidence regarding the relationship between soy protein and heart disease, the U.S. Food and Drug Administration proposed revoking the allowable health claim. The health claim states that “consuming 25 grams of soy protein a day may reduce the risk for heart disease.”  As of May 2019, a final decision had not been made.

“Other researchers have reported that soy may help lower the risk of various types of cancer, including prostate, colon and breast cancer. In addition, some research teams have noted the potential for soy products and a favorable effect on kidney function, skin health and mental health. More recently, researchers are focusing on gut health and the influence of soy fiber on the microbiome.  The research continues, so watch for updates and consult with a dietitian and/or medical care provider before making major dietary changes.”

What are some good options for soy foods?

Dr. Garden-Robinson: “Soy foods have used widely for centuries, especially in Asian diets, so there are numerous types of soy foods available throughout a typical supermarket. Soymilk, tofu, edamame (immature “green” soybeans), soynuts and fermented foods such as tempeh are just a few of the wide range of available soy foods. Soy also is used to create “meat-like” products ranging from soy-based “burgers” to crumbles to use in taco filling.”

Is soy milk healthy? Find out here.

Does soy contain estrogen? Is it something to be concerned about?

Dr. Garden-Robinson: “Sometimes information is shared that soyfoods are “feminizing” for men because of estrogen; however, soy foods do not contain the hormone “estrogen.” They contain isoflavones, which are “phytoestrogens” (“phyto” = plant) that are structurally similar to estrogen but function more weakly.  According to epidemiological studies, Asian women, who consume a higher amount of soy foods, have a lower incidence of the bone-weakening disease, osteoporosis.”

Is it okay for women (and men) to eat soy?

Dr. Garden-Robinson: “We might see some alarming information shared on social media about soy from time to time, but the most recent Dietary Guidelines for Americans stated that “a healthy eating pattern can include a variety of soy food products.”  As we know, anyone can share both positive and negative information online very easily. Many researchers have reported that soy foods may have a variety of health benefits. The research continues to build, so the best advice is to look for reputable sources of nutrition and health information. Be sure to follow the advice of your medical care provider.

Is there a link between soy and breast cancer?

Dr. Garden-Robinson: “Some research has shown breast cancer survivors may reduce their risk of reoccurrence with a fairly small amount of soy (e.g. 1/2 cup of soymilk per day). Other research has shown that having soy foods early in life may decrease the risk of breast cancer later in life.”

Are there any potential health concerns of eating soy?

Dr. Garden-Robinson: “Soy foods are among the common allergens, so any foods that contain soy must list “Contains Soy” with the ingredient statement on food labels.  Sometimes, allergies to soy can be fairly mild, with symptoms such as hives, itching, nausea or vomiting. For some people, eating soy may produce life-threatening symptoms. If people suspect they have an allergy to soy, they should visit with their healthcare providers for further testing.”

Is it possible for someone on a plant-based/vegetarian diet to consume too much soy?

Dr. Garden-Robinson: “As with any diet, variety is important. If you focus too much on a particular food, you may miss nutrients that you need in an overall healthy diet.”

Anything else you’d like to add?

Dr. Garden-Robinson: “If you have never tried certain soy foods, consider exploring the options. Soy foods are located throughout grocery stores. For example, you can find soy foods in the frozen food aisle as soy crumbles, soy ice cream and edamame, among others. You can find soy foods in canned form, as soy flour and in snack mixes or soy nuts.”

Soy contains protein, as well as fiber, calcium and iron. Soy has been shown to have health benefits including building strong bones, reducing the risk of certain types of cancer and lowering cholesterol. Soy contains plant estrogens that do not affect humans.

For more information:

Is soy consumption good or bad for the breast?

Soy and health update: Evaluation of the clinical and epidemiologic literature

U.S. Food and Drug Administration Statement