What Is Soy? Is It Good for You?

Edamame

Soybeans are a staple ingredient in many cuisines across the globe, and have been for millennia. Yet most of the world’s soy isn’t eaten by humans. The livestock sector uses an estimated 80 percent of global soy as feed for the animals that are raised to produce meat, dairy, eggs and other products. When cultivated for people, soy is a far more efficient use of resources and an excellent source of nutrition and protein. 

What Is Soy?   

Soy is a protein-rich legume native to East Asia that is widely grown worldwide thanks to its many uses as an ingredient. Soy is an ancient crop, and botanists believe it was domesticated in central China as early as 7000 B.C. Soy can be used to describe both soybeans and products derived from them, such as soy sauce and soy milk.

Soy is a highly versatile plant that can be processed into many forms, including milk, sauce, tofu, beans and burgers. As a meat and milk substitute, soy can be used in a large number of dishes, making it a valuable staple for anyone reducing or eliminating animal products from their diet.

Types And Uses

As a nutrient-dense protein source, soy is used to feed humans and animals. Soy is also used for industrial purposes, including in biofuels and lubricants.

Green Soybeans

Green soybeans, called edamame in Japanese, are immature soybeans harvested about 80 days after sowing. They are known for their crunchy, vegetable-forward flavor.

Yellow Soybeans

Yellow soybeans are fully ripened. Perhaps the most ubiquitous variety used in cooking, yellow soybeans form the basis of soy milk, soy sauce, tempeh, tofu, tamari and many meat alternatives.

Black Soybeans

Black soybeans are a rarer variation of soybean found in East Asia, used as a cooking ingredient and in traditional medicine formulations. Their black color derives from a high concentration of anthocyanins in their seed coat. The high anthocyanin count means black soybeans also contain powerful antioxidants, which are beneficial for your health.

What Is Soy Lecithin?

Lecithins contain fatty acids, and are found in animal and plant tissue, including in soy. Soy lecithin is used as an emulsifier in products like dietary supplements, infant formulas, bread and ice cream. It is also a source of the essential nutrient choline. Though it is sometimes touted as a way to reduce cholesterol, there are only very limited studies testing these claims.  Most people with soy allergies can safely consume lecithin, though it should be avoided by anyone with extreme allergic reactions or high sensitivity to soy.

What is Soy Protein

Vegetarians and vegans often rely on soy foods as a source of protein, vitamins and minerals. The protein content of soy products differs depending on the preparation. For example, 1/2 cup of tofu contains 22 grams of protein, while 1 cup of soy milk contains just 6.5 grams. Soy protein products offer various health benefits, including improved cardiovascular health if eaten in place of animal protein, lowered risk of certain types of cancer, improved bone density following menopause, and obesity prevention for diabetics.

Soy Nutrition

Soy is highly nutritious. It is one of the best complete plant-based protein sources as it contains all nine essential amino acids. Soy protein can help you meet the daily recommendation of 0.8 grams of protein per kilo (.36 grams per pound) of your body weight.

10 Products Made From Soybeans

Most people associate soy with soy milk or tofu, but many other foods also include soy. 

Edamame

Edamame is a dish made from immature soybeans. The beans are boiled or steamed while still encased in their pod, before being served with salt or other condiments such as chili or garlic. Edamame can accompany soups, stews, salad or noodle dishes, or be eaten alone as a snack. Edamame is rich in protein, vitamins and minerals, containing far more vitamin K and folate than mature soybeans.

Meat Alternatives

Soy is often the main ingredient of meat alternatives including veggie burgers, ground or mince meat and sausages because of its high protein content and convincing texture. Meat alternatives made from soy originated in China many centuries ago.

A more recent ingredient is texturized vegetable protein (TVP), a vegan meat substitute produced by removing oil from soy flour. TVP is also known as textured soy protein (TSP), soy meat or soya chunks, and was developed by the food processing company Archer Daniels Midland in the 1960s.

Miso   

Miso is a fermented food paste made from a mixture of soybeans, salt and grains, including barley or rice. The paste can range in taste from very salty to very sweet, but it is most commonly known for adding the fifth taste — umami — to dishes. Miso is a traditional ingredient in Japanese and Chinese cuisines and is often used to flavor savory dishes such as soups.

Soy Nuts

Soy nuts are made by roasting or baking ripe soybeans that have been soaked in water. Their taste is similar to other soy products, but they have a texture that resembles nuts. Soy nuts can be put into salads, smoothies, cereal, stir-fries and pasta dishes. 

Soy Sauce

Soy sauce is a traditional Asian condiment made from fermented soybeans, roasted grain, brine and fungi. Soy sauce is used to flavor dishes and marinate meat or meat substitutes and is often offered by sushi restaurants as a condiment at the table.

There are different varieties of soy sauce, including Chinese and Japanese soy sauces that have unique flavors and strengths. Tamari, a Japanese soy sauce, does not include wheat flour, making it suitable for gluten-free consumers.

Soy milk   

Soy milk is a beverage made from soybeans that have been soaked, ground and boiled. Soy milk can be a good alternative to dairy. It has a high protein content and is often fortified with vitamin B12 and calcium to make it closer in nutrition to cow’s milk. 

Tempeh

Tempeh is made from cooked and fermented soybeans. Cooked properly, it has a nutty, earthy flavor. 

Textured Soy Protein

Textured soy protein (TSP) is made by removing oil from soy flour. Products made from textured soy protein, such as soya chunks, are soaked in hot water for a few minutes, drained and seasoned before cooking to achieve a meat-like texture and flavor.

Tofu

Tofu was first discovered by the Chinese at least two millenia ago, though the exact origins are  heavily debated by historians. Tofu is made by boiling soybeans in water, mixing in a coagulant and adding salt to taste. Tofu can also be made by curdling soy milk, using a process that is very similar to that which turns cows’ milk into cheese. It has grown in popularity in the West since the 1960s, when interest in healthy foods began to grow. Tofu is a staple of cuisines across East and Southeast Asia and is often used as a meat substitute. It can come in firm, soft or crispy textures.

Whole Soybeans

Although they are not very common in the West, whole soybeans are highly nutritious and can be eaten like any other bean. It’s simple to boil them, as described here, and eat them with rice. You can also add them to pasta sauce or a stew and benefit from their high protein and nutrient contents.

Is Soy Good for You?

Bone Health

Women experiencing menopause can sometimes develop osteoporosis after low estrogen levels cause calcium to leach from their bones. There is some limited evidence that taking daily soy isoflavone supplements can increase bone mineral density.

Long-Term Kidney Disease

Some evidence shows that substituting soy for animal protein can improve renal function in patients with chronic kidney disease, possibly because it has a lower sodium and phosphorus content. However, more research is needed.

Blood Pressure

Evidence suggests that soy can help lower blood pressure to a small degree in subjects who have high blood pressure. This effect is thought to occur because of soy’s high arginine content, an amino acid believed to regulate blood pressure.   

Blood Sugar

Several studies have linked consuming soy to lower blood sugar, with the best evidence relating to menopausal women. Tofu consumption has also shown some effectiveness in treating Type 2 diabetes and metabolic syndrome. However, other studies failed to link soy consumption and blood sugar control in those with Type 2 diabetes.

Cholesterol Levels

In some studies, soy has been shown to lower the rates of LDL (bad) cholesterol and increase the levels of HDL (good) cholesterol in humans. Soy products that have been minimally processed, like soybeans, tofu, edamame or tempeh, were shown to have the most significant effect. A high-soy diet has the most positive impact on those with existing indicators for heart disease, like high cholesterol, obesity or Type 2 diabetes.

Obesity

Soy products can help manage obesity and weight loss in general. One study on non-Asian postmenopausal women described a significant improvement in weight loss attributed to the presence of isoflavones in soy. Meta-analyses covering soy and obesity in humans and animals strongly suggest that soy consumption favors weight loss and works against obesity.

Fertility

Consuming soy may improve success rates in fertility treatments for some women. Men, however, do not seem to experience similar benefits in fertility treatment success from eating soy. There is some evidence (primarily animal studies) suggesting that consuming very large amounts of soy may negatively impact fertility. However, even a “large” intake of up to four servings of soy per day will likely have no negative impact.

Heart Health   

Eating soy in place of red meat can improve heart health and reduce risk of heart disease by lowering bad cholesterol and raising good cholesterol in the body, though how much it impacts these levels can vary. 

Reduce Menopause Symptoms

Soy has been linked to the reduction of numerous menopause symptoms. Some studies have shown a reduction in the severity of hot flashes and night sweats, though more research is needed. Some limited studies have also shown decreasing incidences of vaginal symptoms.

Reduce the Risk of Breast Cancer

The isoflavones or phytoestrogens found in soy have been associated with a reduced risk of breast cancer. There has been some fear that isoflavones aggravate breast cancer, but these concerns were based on animal studies, which should not be extrapolated directly to humans. However, the Shanghai Women’s Health Study, which followed over 70,000 women over seven years, showed that those who consumed the highest amounts of soy had a 22 percent lower chance of getting breast cancer than those who consumed the least. 

The study had limitations however, primarily that the longstanding prevalence of soy in East Asian cuisine means that Asian people receive more benefits and experience fewer downsides from soy than Western populations. However, a study on an ethnically diverse group of breast cancer survivors from the U.S. revealed that those who consumed the most phytoestrogens had a 21 percent lower all-cause mortality rate than the rest of the cohort.

There have been objections to these findings, primarily that the long-lasting prevalence of soy in East Asian cuisine means that Asian people receive more benefits and fewer downsides to soy than Western populations. However, a study on an ethnically diverse group of breast cancer survivors from the U.S. revealed that those who consumed the most phytoestrogens had a 21 percent lower all-cause mortality rate than the rest of the cohort.

Risks of Other Types Of Cancer

Soy products also reduce the risk of prostate cancer for men. This has been validated by several studies detailed below.

Asian men experience the lowest rates of prostate cancer globally, and one study showed that the rates of prostate cancer increased in Asian men who moved to America and adopted a Western diet while staying the same in those who maintained their traditional diet. A meta-analysis of studies exploring this connection pointed to a link between eating soy and lower risk of prostate cancer.

Galactosemia

Galactosemia is a rare condition in which galactose, a type of sugar present in cows’ milk and most baby formulas, cannot be digested by the body. Soy milk can be used as an alternative to cows’ milk formula for children suffering from galactosemia. In the Netherlands, for example, it is the recommended treatment for galactosemic infants.

Risk Of Type 2 Diabetes

Some studies also show a link between consuming soy and the prevention of Type 2 diabetes. As discussed above, soy consumption may help treat kidney disease, improve heart health and can help to manage obesity, all of which are associated with Type 2 diabetes.

What Are The Dangers Of Soy?

Antinutrients

The term “antinutrients” refers to naturally occurring compounds found in many plant-based foods. Some scientists question whether this term is appropriate because these compounds are therapeutic agents for various conditions. Soy contains the antinutrients phytate, lectins, protease inhibitors, oxalates, and saponins — none of which are harmful to healthy individuals, according to dietitians, as long as soy is adequately prepared and eaten in moderation as part of a varied diet.

Phytate is one of the most common types of antinutrients, which binds strongly to iron and zinc and reduces the bioavailability of vitamins A, B12, D and E. However, there is no evidence that eating moderate amounts of soy leads to deficiencies. Further, phytate provides health benefits due to its antioxidant and anti-inflammatory properties. Studies indicate that phytate can help prevent cardiovascular disease, kidney stone development and some forms of cancer.

Cancer Risk

Many people are concerned that eating soy increases cancer risks. However, these concerns are based on animal studies, which do not always translate to people. The same results have not been observed in humans. On the contrary, studies found that a lifelong diet rich in soy actually reduces breast cancer risk. 

According to dietitians, soy foods don’t contain levels of isoflavones high enough to increase the risk of breast cancer. However, they recommend taking soy or isoflavone supplements with caution because these often contain higher levels of isoflavones.

Risk to Babies

Soy-based formulas have been used for babies with cows’ milk allergies since 1929. All baby formulas are required to fulfill certain criteria to ensure they safely meet a baby’s nutritional needs. As long as these criteria are met, soy-based formula is considered a good choice for vegan families and for babies with galactosemia or hereditary lactase deficiency. 

However, nutritionists warn against feeding soy-based formula to babies who are allergic to soy, are born prematurely, or who have a low birth weight, poor renal function or other health conditions. Parents choosing to feed their babies formula should consult with qualified healthcare providers to ensure their children’s nutritional needs are met.

Digestive Issues

Like most beans, soybeans contain insoluble fibers that may cause digestive symptoms. Animal studies suggest that the antinutrients in soy may reduce the gut’s barrier function, but human studies have not confirmed this finding. Those who experience bloating or other digestive issues after consuming soy products should consult with their doctor to determine if they are allergic or intolerant to soy. 

In people not affected by soy intolerance or allergy, digestive issues are rarely observed unless they consume enormous amounts of soy. People diagnosed with irritable bowel syndrome (IBS) may also consider avoiding soy products that trigger digestive issues.

Estrogen-Mimicking Effects

There is much controversy around the estrogen-like compounds found in soy. Many people worry that soy eating could negatively impact their health and increase the risk of breast cancer. However, the estrogen in human bodies is significantly more potent than the estrogen-like isoflavones included in soy.

Studies following large populations of healthy women for several years have found either no link between soy and breast cancer or that eating soy is associated with lower breast cancer risks. A 2022 study of the effects of soy on fertility found that soy has a negligible effect on the hormonal network, menstrual cycle length and fertility outcomes of healthy women and may even have beneficial effects in the case of endocrine diseases such as polycystic ovary syndrome (PCOS).

“Feminizing” Effects in Men

The myth that soy has feminizing effects on men persists despite scientific evidence to the contrary. Men’s Health published one of the articles contributing to this myth in 2009. However, following the release of new results, the magazine made a 180-degree turnaround, referring to soy as “the new king of protein.”

Most evidence indicates that isoflavones in soybeans do not adversely affect men’s fertility. A meta-analysis of clinical studies found that neither soy nor isoflavone intake affects male reproductive hormones.

Another study found that, contrary to animal studies, neither isoflavone supplements nor isoflavone-rich soy affects testosterone levels in humans. The study also found that soy does not cause increased breast tissue or fat in men.

GMOs

A large portion of soy grown worldwide has been genetically modified to improve the plant’s resilience and make it resistant to herbicide so that farmers can combat weeds without impacting their crops. According to the USDA Economic Research Service, 94 percent of soy grown in the United States is genetically modified to be herbicide-tolerant. Most genetically modified soy is used for farmed animal feed and soybean oil, along with some processed foods. There is no evidence of detrimental human health impacts from GMOs

Thyroid Function

According to a literature review, scientific findings provide little evidence of soy adversely affecting thyroid function in healthy individuals. The study, however, concluded that people who eat soy need to ensure that their intake of iodine is adequate. People on thyroid replacement medication need to be aware that soy can prevent optimal absorption, resulting in inconsistent medication effects.

What Is Soy Allergy?

Soy is one of the most common food allergies, with around 0.3 percent of people affected. Allergic reactions to soy can include symptoms like itchiness on the lips or in the mouth, facial swelling, wheezing, abdominal pain or red skin. Life-threatening allergic reactions to soy are rare but do exist. See a board-certified allergist or immunologist for an allergy diagnosis. If you are allergic to soy, check ingredient labels carefully, especially products like cereals and bread, which can contain soy. There are numerous other healthy plant-based protein sources if soy is not an option.

Final fact-check

Despite myths about soy’s environmental impact and health profile, soy protein is a highly versatile and nutritious food with many health benefits and rich culinary potential