Are you on the fence about adding soybeans to your diet? There is so much conflicting information about the health benefits of soybeans and their potential dangers. Soybeans (scientifically referred to as Glycine max and colloquially as soya beans) have been cultivated and consumed for thousands of years, and they are a staple protein source for vegetarians and vegans. Nutritionally speaking, soybeans are rich in protein, vitamins, minerals, omega-3 fatty acids, and dietary fiber. But soybeans and soy products such as soybean oil are not without controversy.
Chinese farmers first cultivated soybeans around 1100 BC, but it wasn’t until 1851 that soybean seeds from East Asia arrived in the United States. Classified as an oilseed crop, U.S. soybeans were first used as livestock feed. The United States Department of Agriculture (USDA) began testing the safety and efficacy of soybeans as animal feed around 1900.
In 1904, George Washington Carver identified that soybeans were a good source of both protein and oil. Mr. Carver also found that soybean plants benefited the soil by replenishing nitrogen and minerals extracted by cotton farming. He urged farmers to rotate their crops by growing cotton for 1 year and growing soybeans for 2 years.
Through the next 80 years, soybean production in the U.S. grew, and in 1996, Monsanto introduced Roundup Ready soybean, a GMO crop engineered to resist the herbicide glyphosate. Now, the Roundup Ready trait is present in nearly 90% of all soybeans grown in the United States according to a 2010 article in The New York Times. Today, 31 states east of the Rocky Mountains grow soybeans, but Brazil soybean producers are set to exceed U.S. soybean production within the next decade.
In a surprising decision, the European Commission approved the import of Monsanto’s Roundup Ready genetically modified soybean in 2016 in addition to Bayer’s CropScience soybean variety. The decision allows for the import of soybeans for food and animal feed, but this ruling does not allow for the planting of genetically modified soybeans within the boundaries of the European Union.
In India, China, Paraguay, and Argentina soybeans are genetically modified products, and by current estimates at least 80% of the global soybean crop is genetically modified. It is becoming more and more difficult to find non-GMO soy food products in stores.
What Are Soybeans?
Soybeans are small edible legumes native to the Asian continent. Soybean plants grow quickly and produce healthy crops harvested in late September or early October. Soybean farmers harvest soybeans when the moisture level reaches 13% to 15% and the foliage on the plant has dried.
Here’s a popular question: are edamame beans and soybeans the same thing?
Edamame is picked earlier during a period called the “green shell stage.“ Essentially, edamame pods are immature soybeans that retain a tender and more vegetable-like texture similar to that of green beans or peas.
What are soybeans used for? According to the University of Arizona’s Cooperative Extension, soybeans are used for food, animal feed, and the following industrial products:
- Body lotion
Soybean meal is the byproduct created after soy oil is extracted from a mature soybean. Soy oil is used for cooking and a variety of industrial purposes including biodiesel. Soybean meal is a valuable commodity and used to make soy flour and some brands of soy milk—but the vast majority of this soy byproduct is used as animal feed.
In fact, according to a 2010 report from the Canadian International Grains Institute, approximately 2% of soybean meal is used for human consumption, while the remaining 98% is used as animal feed. Here is an estimated breakdown by animal species; however, it should be noted that feeding soybean meal to lamb is becoming more popular, even though it is not included in the breakdown.
- Poultry: 48%
- Swine: 26%
- Beef cattle: 12%
- Dairy cows: 9%
- Fish feed (farmed fish): 3%
- Pet food: 2%
Soybean Nutrition Facts
For thousands of years, soybeans and soybean products have been consumed by vegans and meat-eaters alike. Soybeans are most noted for their high protein content. In fact, soybeans contain all nine essential amino acids, which makes soybeans a complete protein and a great substitute for animal protein for those with dietary restrictions.
In addition, soybeans contain high levels of manganese, iron, phosphorus, vitamin K, and magnesium, as well as health-boosting phytochemicals like isoflavones and saponins. And soybeans are the only legume that contains omega-3 fatty acids, including the inflammation fighter alpha-linolenic acid.
One cup of boiled mature whole soybeans contains:
- Calories: 298
- Total carbohydrates: 17.1 grams (6% DV)
- Total fat: 15.4 grams (24% DV)
- Protein: 28.6 grams (57% DV)
- Manganese: 1.4 milligrams (71% DV)
- Iron: 8.8 milligrams (49% DV)
- Phosphorus: 421 milligrams (42% DV)
- Vitamin K: 33.0 micrograms (41% DV)
- Magnesium: 148 milligrams (37% DV)
- Copper: 0.7 milligrams (35% DV)
- Riboflavin: 0.5 milligrams (29% DV)
- Potassium: 886 milligrams (25% DV)
- Folate: 92.9 micrograms (23% DV)
- Vitamin B6: 0.4 milligrams (20% DV)
- Thiamin: 0.3 milligrams (18% DV)
- Calcium: 175 milligrams (18% DV)
- Selenium: 12.6 micrograms (18% DV)
- Zinc: 2.0 milligrams (13% DV)
- Total omega-3 fatty acids: 1029 milligrams
- Total omega-6 fatty acids: 7681 milligrams
Soybeans are not a good source of vitamin A, vitamin B, vitamin C, or vitamin D.
Soybean Health Benefits
The micronutrients, protein, dietary fiber, and healthy fats in soybeans may provide health benefits according to scientific studies.
According to a meta-analysis of randomized controlled trials, soy reduces LDL cholesterol levels, and in some studies, significantly. In the analysis published in the British Journal of Nutrition, the authors of the study note that soy foods appear to be more beneficial than soy supplements, as isoflavone supplements had “no effect on the lipid profile.” If you have high cholesterol, consuming non-GMO soy milk, soy nuts, and other products may be beneficial in reducing LDL and total cholesterol levels.
Improve Fertility for In Vitro Fertilization Patients
Phytoestrogens naturally occur in food, including soybeans. Researchers from Rome, Italy conducted a controlled, randomized trial that looked at the effects of 1500 milligrams daily of phytoestrogens against a placebo on women undergoing in vitro fertilization treatments. Researchers found that the women who received phytoestrogens during the luteal phase had “statistically significant higher values for implantation.” The authors of the study state that further research is needed to support their results.
The hormone estrogen is necessary for helping maintain bone density. As women enter perimenopause the risk for progressive loss of bone-mineral density and bone fracture increases. Researchers have studied phytoestrogens for their potential as a way to preserve or increase bone density. Some studies have found a minimal association between increased consumption of soy isoflavones and improved bone density, but one study published in the Journal of the American College of Nutrition found supplementation with soy isoflavones may inhibit postmenopausal osteoporosis.
Prevent Cardiovascular Disease
A recent review from Canadian researchers published in the journal Nutrients has identified micronutrients in soy that may protect the heart. The authors of the review note that soy protein and isoflavones “appear to improve blood pressure, glycemic control, obesity, and inflammation” and may reduce overall cardiovascular disease risk. At one time, soy was believed to support blood vessel health, but new research indicates that is incorrect.
Isoflavones vary dramatically from soy species to soy species and the areas in which they grow. For example, the isoflavones in soybeans from Canada can range from 360 milligrams to 2,241 milligrams per kilogram while soybeans from the U.S. may contain 1,176 milligrams to 3,309 milligrams per kilogram. Sadly, it is virtually impossible to find the isoflavone levels on any soy products sold in the U.S. High-quality soy products can be part of a heart-healthy diet.
There is limited research on the effect of soy on weight loss—but the research that exists is mostly positive. According to a study published in the American Journal of Clinical Nutrition, obese men were assigned either to a soy-based diet or a meat-based, high-protein diet. Both diets resulted in weight loss and the scientists concluded that eating soy-based diets may improve insulin resistance and reduce appetite.
Soybean Products—Are They Healthy?
Is all soy good for you? The short answer is “no.” Soy products, just like other processed foods, can contain harmful chemicals, pesticides, added sugars, and other unhealthy ingredients. Let’s take a look at the different types of soybean products available and if they are good for you. Remember, the vast majority of soy is genetically modified (GMO), so if that is a concern, choose only organic, non-GMO verified soy products.
Whole Soy Products
Soy foods that are the least processed are considered whole soy products. This category is likely the healthiest on this list. It includes edamame, minimally processed tofu, minimally processed soy milk, canned black soybeans, dried soybeans, and tempeh.
Fermented Soy Products
Fermented foods like probiotic-rich yogurt, kefir, and kimchi are known for their health benefits—and it is possible you are eating fermented soybeans without knowing it! Natto, tempeh, and miso are all fermented foods that have grown in popularity in recent years, and the good news is that the fermentation process increases vitamin K2 levels and makes the soy easier to digest.
Soy-Based Convenience Foods
“Soy” was once synonymous with health food, and soy-based processed foods began popping up in grocery stores across the country. Soy is often used as a meat alternative in products like Tofurky, veggie burgers, and vegetarian hot dogs. Foods in this category likely contain added sugar, artificial colors, and preservatives—read labels carefully.
Soy-Based Protein Foods
Soy protein isolate (SPI) is found in protein powders and energy bars. The protein is controversially extracted from the soybean using chemicals and byproducts from the gasoline industry. TVP, or textured vegetable protein, take soy protein isolate and process it further using high-pressure mechanisms to extrude it to create the texture. Read the labels of SPI and TVP soy products carefully before purchase to avoid unnecessary chemicals and additives.
Is soy sauce bad for you? The answer is complicated!
Originally, soy sauce was made by fermenting soybeans, wheat, and salt, and then pasteurized before it was bottled. Unfortunately today most soy sauce isn’t fermented and contains additives including artificial colors and flavors. Avoid soy sauce labeled “hydrolyzed soy protein.” You’ll also want to skip the soy sauce if you are sensitive to histamine, gluten, wheat, or soy.
Soybean Cooking Oil
Soybean oil is the most popular vegetable oil in the United States, and nearly 62 million tons were produced globally between 2018 and 2019.
Soybean oil that is organic, non-GMO, and not hydrated does have some healthy benefits courtesy of soya's nutrients. It's high in an omega-6 fat called linoleic acid, which makes up about 50% of soy oil. So, if your diet is low in linoleic acid, soybean oil might be a good fit. However, the majority of Americans are low in omega-3s, not omega-6s, and when this balance is off kilter in favor of omega-6 then inflammation may be running the show.
Polyunsaturated fats such as omega-3 and omega-6 are also more unstable and likely to oxidize when used for cooking in high heat. Saturated fats and monounsaturated fats, such as those found in olive and avocado oils, can hold up better to high smoke points.
Soy supplements and soy isoflavone supplements appear on health food store shelves across the country. Should you take them? It depends. Some research points to soy assisting with menopausal symptoms—especially hot flashes. But research also shows, as you will see below, that soy can increase the risk of breast cancer in postmenopausal women.
Additionally, long-term use of soy isoflavone supplements may increase the risk of endometrial hyperplasia according to the National Center for Complementary and Integrative Health. Before taking any soy supplements speak to your doctor or wellness professional about your risk factors and potential benefits.
Soybeans have been consumed safely for thousands of years in Asia. However, serving sizes of soy in Asian countries are significantly smaller than serving sizes of soy in the Western world. Scientists have unveiled some potential dangers of eating soy-based foods and taking soy supplements.
- Have had breast cancer or are at a heightened risk of breast cancer, consume whole soy products—not processed soybean products, or soy supplements.
- Have thyroid disease, avoid soy products, as it is a goitrogenic food. Individuals with compromised thyroid function or those who take iodine supplements may be at an increased risk of hypothyroidism when eating even minimal amounts of soy.
- Are pregnant, speak to your doctor before adding soy to your diet.
- Are seeking a non-dairy substitute for conventional dairy products, consider other nut-based beverages like almond milk, cashew milk, or rice milk if you have thyroid disease or are estrogen sensitive.
The takeaway: conservatively, 90% of the soybeans today are genetically modified, so look for non-GMO soy products verified through the Non-GMO Project.