Soy is one of the more controversial foods. While it is inherently more compassionate and sustainable to eat plants than it is to eat animals, and soy has been eaten for centuries in Asian countries and more recently by people pursuing a plant-based diet, soy’s purported health impacts are an area of fierce debate.
With so much conflicting information out there, it’s easy to get confused. Let’s take a look at some of the arguments about whether or not soy is bad for you and what its potential health benefits may be.
Best known for its edible beans, soy is a flowering plant belonging to the legume family (also
referred to as the pea or bean family). Although they are primarily grown to feed farmed animals, soybeans can be turned into a vast array of appetizing plant-based foods for humans. Soy was first domesticated in China, and whole soy and fermented soy foods have long been staples of many Asian cuisines.
Whole soy products are unprocessed or minimally processed nutrient-dense soy-based foods with few or no additives. These include edamame—young, green soybeans that can be cooked and either added to meals or eaten as a tasty snack—as well as soy nuts, soy milk, and tofu.
Soy can be cultured using bacteria, yeast, or mold to make traditional fermented foods such as tempeh, miso paste, and tamari sauce. The fermentation process is thought to boost soy’s nutritional quality.
Many soy-based processed foods are ideal replacements for animal-based foods. Soybeans can be defatted, shaped, and dried out to make textured vegetable protein (TVP), a versatile ingredient that, once rehydrated and cooked, can be used in the same way as ground meat.
While soy is packed with protein and other nutrients, it’s worth noting that a meal is not automatically good for your body just because it is made from TVP or soy protein isolate. The health-conscious consumer should be wary of ultra-processed foods that have low nutritional quality but contain high levels of salt, sugar, fat, and other additives.
As well as being used for food, soy is commonly sold in the form of protein powder that some people add to their smoothies and other foods as an additional source of protein in their diets. However, although many studies have confirmed the health benefits of soy consumption, there have not been enough studies looking at the potential long-term health effects of consuming more concentrated soy supplements.
Soy provides us with all of the nine essential amino acids that the human body requires from food, and this makes it a nutrient dense source of protein. Not only that, but it is also rich in numerous vitamins and minerals, including B vitamins, magnesium, calcium, and iron. Unlike meat and dairy, soy is low in saturated fats and high in heart-healthy polyunsaturated fats.
The nutritional value of soy varies between food products, but whole soy and fermented soy are generally considered to be the most nourishing. An 84-gram serving of tempeh, for example, will provide you with 15 grams of protein, 12 percent of the recommended daily intake (RDI) of iron, and nine percent of the RDI of calcium. It is also high in riboflavin (vitamin B2), niacin (vitamin B3), manganese, and other nutrients.
Many people find that soy in its various forms makes it easier for them to reduce, or even eliminate, their intake of unhealthy animal products. In and of itself, soy has a variety of potential health benefits. When eaten on a regular basis, this legume may help lower cholesterol, improve fertility, and reduce menopause symptoms.
Around 38 percent of adults in the U.S. have high cholesterol levels, a health problem that does not necessarily cause any symptoms but can lead to a dangerous buildup of fat in the blood vessels. Both red and white meat can raise your levels of low-density lipoprotein (LDL), or “bad” cholesterol. Soy protein, on the other hand, has been found to reduce LDL cholesterol levels in adults by around three to four percent in some studies. (Researchers note that soy may be more effective at lowering LDL cholesterol levels in real life than it is in studies, especially if it’s eaten instead of animal-based foods.)
Soy consumption has also been linked to a lower risk of cardiovascular disease, stroke, and coronary heart disease.
Some research suggests that regularly eating soy may help women who are trying to conceive. In one study involving 315 women who were receiving treatment for infertility, those who ate soy were between 1.3 and 1.8 times more likely to have a child than those who did not.
Research suggests that the isoflavone compounds found in soy may help to relieve menopause symptoms. In a 2021 study, postmenopausal women who switched to a low-fat, plant-based diet that included eating half a cup of cooked soybeans every day for 12 weeks saw an 84 percent reduction in moderate and severe hot flashes. Participants who followed this diet also reported better overall health.
Proponents of animal agriculture make a variety of claims about the negative health impacts of soy, many of which are not supported by strong scientific evidence. A lot of controversy surrounding the healthiness of soy is because it is notably rich in isoflavones, a form of naturally occurring phytoestrogen (or plant estrogen). These compounds act like human estrogen in some ways but are far less powerful and have been shown to actually bind to and block estrogen receptors, in effect lowering estrogen levels and having a neutral or protective effect against estrogen-linked cancers (like breast cancer).
A A growing number of human studies suggest that eating healthy soy-based foods either has no effect on, or may actually lower, the risk of people developing breast cancer. Breast cancer rates are particularly low in Asian communities where women consume high amounts of soy from a young age.
In people whose thyroid glands do not produce enough hormones, eating soy may affect the absorption of synthetic thyroid hormone medication. However, for people who have a normally functioning thyroid gland and get enough iodine from their diet, soy consumption should not be a problem. Animal-free sources of iodine include seaweed and iodized salt.
Contrary to popular belief, there is no credible evidence to suggest that eating soy has a feminizing effect on men. A meta-analysis of clinical data that looked at 41 studies involving a total of 1753 men suggests that consuming soy protein or isoflavones does not lower men’s testosterone levels or affect estrogen levels.
While it is true that most soy in the U.S. contains genetically modified organisms (GMO), let’s not forget that the majority of this soy is fed to farmed animals. This means that many meat-eaters who are critical of GMO soy indirectly consume it on a regular basis without even realizing it.
Don’t let the thought of GMO soy turn you away from perfectly wholesome plant-based foods you might enjoy. Instead of boycotting soy altogether, you can look out for soy products that are certified organic or carry a Non-GMO Project verification label.
Some concerns about the impact of soy on digestive health arise from the fact that it contains anti-nutrients, natural compounds found in many animal-and-plant-derived foods that can make it more difficult for your body to take in vitamins and minerals from food. Contrary to what we might assume though, many anti-nutrients are actually good for our health as long as we don’t consume them in excessive quantities. Processing and cooking soy generally brings its anti-nutrient content down to safe levels.
Health experts recommend eating a wide variety of fruits, vegetables, legumes, nuts, seeds, and whole grains in order to get all of the important nutrients that our bodies need to work properly. Soy can safely be consumed daily in moderation as part of a well-balanced, plant-based diet. Up to 50 grams of soy protein per day is generally considered healthy.
Soy products are delicious and are a staple throughout the world. There is no reason to avoid soy unless you have a soy allergy. Packed with vital nutrients, soy is not only safe to consume but has the potential to boost human health in a number of ways. As a source of high-quality animal-free protein, soy could play an important role in the necessary shift towards a plant-based food system that is healthier, more environmentally friendly, and ultimately far kinder to the animals we share our planet with.