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14 Things That Happen To Your Body When You Eat Soy

Some say it's a health food and others claim it's a dangerous science experiment. So which is right?

One glance at the literature and you'll see—researchers seem to be divided on the pros and cons of soy. For every study that finds a certain component of the legume can help relieve menopause symptoms, that same component is scrutinized for causing infertility. And despite thousands of studies on the topic, it seems like the jury is still out.

For a little bit of background, soybeans were initially used in the U.S. as a commercial crop during the early 1900s. It wasn't until fat and oil imports were blocked during World War II that we actually started to eat the beans. And once the FDA approved a health claim in 1999 that consuming 25 grams of soy protein could reduce the risk of heart disease—along with the rise of many plant-based animal and dairy alternatives—soybean production and consumption has blossomed. Now, soy is the U.S.'s second largest crop in cash sales, making America the leading soybean producer and exporter in the world, according to the American Soybean Association.

We may keep churning out production of this crop, but there is a limit to how much soy you can use to feed animals or make into tofu—so, manufacturers turned to food scientists. Now, soy has become the basis for many of the additives you find in processed foods, from artificial flavoring and hydrolyzed vegetable protein to soy lecithin and soybean oil, among countless others. As a result, researchers from the National Institutes of Health (NIH) estimate that soybeans currently account for an astonishing 10 percent of Americans' total calories, mostly due to processed and fried foods.

If almost all of us are eating this food, we should probably figure out if it's safe to eat or not. We combed through studies upon studies, and reached out to nutritionist Isabel Smith, MS, RD, CDN, registered dietitian and founder of Isabel Smith Nutrition, to determine if soy is a protein-packed, cholesterol-lowering, heart disease- and breast cancer-preventing, superfood or a genetically-modified, testosterone-lowering, fertility-decreasing, man-boob-producing health risk. Read on to find out.

You'll Probably Be Exposed To Carcinogens

Happen to your body soy GMO

Smith tells us that the major concern with soy products is that they're so over-produced and over-processed—and the numbers certainly back her up. An astounding 94 percent of soybeans are genetically engineered in the US, according to the Center for Food Safety, which makes it the number one GM crop plant in the world. The issue here is that almost all genetically modified soybeans are designed to be "Roundup ready" (i.e. they're engineered to withstand heavy doses of herbicides that basically kill any and every unwanted vegetation without killing the soybean plant itself). And after the FDA classified the main active ingredient in Roundup, glyphosate, as "probably carcinogenic to humans," this means some seriously bad news for your health.

According to a study published in Food Chemistry, researchers found that genetically engineered soybeans accumulate and absorb (you can't just rinse it off) high levels of glyphosate (up to 8.8 mg/kg) upon being sprayed during their growing season—they also have poorer nutritional profiles compared to organic soybeans. And even though the maximum residue level (MRL) in the US is 20 mg/kg, countless studies in animals and using human cells have found serious negative health effects at concentrations far below the MRLs, including causing miscarriages and abnormal fetal development by interfering with hormone productions.

It May Cause Chronic Inflammation

Soybean oil

For years, the popular additive and cooking oil was considered a better alternative to health-harming saturated fats, but new research suggests that when it comes to weight gain, soybean oil may be just as bad. Our bodies evolved on a near equal balance of omega-6 fatty acids and omega-3 fatty acids; however, over the last century, our diets have shifted completely to omega-6s. In fact, according to a study in Nutrients, most Americans are getting 20 times the amount of omega-6s than we really need—a big problem considering omega-6s are inflammation-causing, fat-storing, and weight-gain-inducing whereas omega-3s are anti-inflammatory. One of the primary causes for this shift? High consumption of foods that have been fried in soybean oil, which has an omega-6 to omega-3 ratio of 7.5:1. (For your reference, a neutral oil alternative like canola oil is only 2.2:1.)

It Can Make Your Throat Itchy

Happen to your body soy allergies

If you have birch pollen allergies, that is. Oral allergy syndrome (OAS) occurs when your body mistakes proteins in certain raw foods for the same allergenic proteins in pollen, confusing your immune system and making existing allergy symptoms worse. A Japanese study found that about 10 percent of patients with birch pollen allergies exhibited sensitivity (described as an "abdominal burning sensation" and itchy throat) to soy milk. Even though soy milk is processed, and wasn't thought to be able to evoke an OAS response, researchers speculate the symptoms might be due to the fact that soy milk's proteins are not broken down that much during processing, leaving these allergy-inducing compounds apparent in the milk.

It Can Cause Mineral Deficiencies

Happen to your body soy sad

Soybeans possess a notoriously high concentration of phytic acid. In fact, soybeans have a higher phytate content than any other grain or legume that has been studied. This anti-nutrient binds to important minerals like iron, calcium, magnesium, and zinc and limits their absorption. Adequate levels of zinc are especially important for anxious people, as deficiencies are common and have shown to induce anxious behavior and depression. Unfortunately, soybeans have been found to be highly resistant to traditional phytate-reducing techniques like cooking, soaking, and sprouting (which works for other legumes and whole grains that also have phytates), and the only way to significantly reduce the phytate content of soybeans is through fermentation.

It May Block Protein Digestion


Soy is like that date who demands affection while refusing PDA and cuddling. Even though soy is packed with lean protein, it's also packed with trypsin and protease inhibitors—enzymes that make the digestion of protein incredibly difficult, causing some gastric distress along with a deficiency in amino acid uptake if soy is eaten in excess. The only way to destroy these anti-nutrients is by soaking and cooking the beans.

It'll Make You Fart

Happen to your body soy fart

If you're new to the whole plant-based meat alternative thing, you'll notice that people may start migrating away from you after meals. That's because soy is loaded with fiber and oligosaccharides, prebiotic compounds that help feed our healthy gut bacteria, but are also known to cause flatulence and bloating.

So Can I Eat It?

Whats the deal

So with all these negative health effects out of the way, what's the bottom line here? Should you be eating soy? Smith reiterates that there isn't really any hard evidence that soybeans are unhealthy, so the only reason she personally doesn't recommend it is because many people are already eating it in excess (which is never a good thing) in processed foods and because the most common source of soy "is really processed and genetically modified"—that's the whole problem.

What's the solution? Go organic and GMO-free! "People can certainly consume soy but try to make it whole soy products (tofu, edamame and fermented products in moderation) and stay away from heavily processed proteins and soy products—just like you would other heavily processed items," she continues, "when soy is organic and not overly processed (or processed at all) it can play a healthy role." So with that in mind, if you cut out the junk, you can keep organic soy in your diet. Here are some of the benefits you'll get from eating this misunderstood food.

Fermented Soy Will Heal Your Gut

Miso Soup

Toss the fart-y processed tofu and veggie burgers, and stick to fermented varieties like tempeh, miso, and natto, which are easier to digest. Smith explains that "Fermented soy is generally thought of as 'better' than regular soy because the fermenting process reduces 'anti-nutrients,' such as phytic acid and sapoinin, and also because isoflavones are thought to be more available for our bodies to use in this form." Not to mention fermented foods are also a great source of gut-healthy probiotics which can promote healthy digestion. Natto, in particular, is touted for its unique benefits due to its high levels of vitamin K2—which is important for cardiovascular and bone health—as well as the presence of nattokinase, an enzyme found in the fermented food which has been shown to dissolve blood clots.

It Can Prevent Postmenopausal Symptoms

Happen to your body soy menopause

Hot flashes are no fun. Studies link the debilitating symptoms of peri- and postmenopause to declining levels of estrogen. And according to a review of 16 studies published in the British Journal of Clinical Pharmacology, soy isoflavones can aid with your menopause symptoms—albeit they only provide half of the maximum effect and work 10 weeks slower than traditional hormone replacement therapy (HRT) drug, estradiol, in terms of reducing hot flash frequency. Isoflavones are a class of phytoestrogens, plant versions of human estrogen. In other words, they nearly mimic estrogen's structure, allowing them to function in the same estrogen pathways which can help relieve hot flash symptoms. Chickpeas also contain phytoestrogen, which makes them one of the healthiest foods for women.

It Lowers Cancer Risk

Happen to your body soy cancer

Soy and its influence on breast cancer have long been a source of concern. Soy contains phytoestrogens, naturally occurring hormone-like compounds with weak estrogenic effects, which—in the lab—have shown to fuel many cancers. However, human studies haven't found diets high in soy increase breast cancer risk. In fact, quite the opposite. A longitudinal study in the Cancer journal that followed over 6,000 breast cancer patients found that women who ate the most isoflavones had a 15 percent decrease in mortality. The American Cancer Society's dietary guidelines note that consumption of soy foods is not only safe but "may even lower breast cancer risk." Another study in the journal Nutrition & Metabolism has also shown that increased soy consumption correlates to a reduced risk of prostate cancer for men.

It Will Help Strengthen Your Bones

Happen to your body soy bones

Many soyfoods are good non-dairy sources of calcium, which is particularly important in aging populations who become increasingly lactose-intolerant. This mineral is essential for maintaining bone health and preventing both osteoporosis and cancer. Just a half a cup of tofu provides you with 43 percent of your DV. And even though one cup of edamame serves up 9 percent of your DV of calcium, this form of soy may still possess high levels of phytates, which could prevent your body's absorption of this mineral.

You'll Build Muscle

Happen to your body soy protein

Although all beans are rich in protein, soybeans are held in a high regard for both their quality and quantity of this macronutrient. For one, soybeans are one of the only plant-based complete proteins, which means they contain all 8 essential amino acids—including the branched chain amino acids, lysine, and arginine, which are preferentially turned into muscle. Soybeans are roughly 41% protein, and a half a cup of boiled soybeans provides nearly 15 g protein, which is about twice the amount found in other legumes. It not only has a high protein content, but this vegetarian protein is also of a quality similar to that of animal proteins. Based on the protein digestibility-corrected amino acid score (PDCAA), the quality of soy protein is just below 1.0, which put it on par with animal proteins that score a perfect 1.0. Because they're rich in the amino acid L-arginine, soybeans may help you burn more fat and carbs during workouts, according to a study printed in The Journal of the International Society of Sports Nutrition.

You Will Not Get Man Boobs

Happen to your body soy man boobs

Soy gets a bad rap because it contains plant estrogens, also called phytoestrogens. They mimic the same female hormone produced by women to cause the development of secondary sex characteristics like breasts. And claims that soyfoods exert feminizing effects are partially based on the premise that these foods lower testosterone levels. While high doses (read: above what people would typically ingest per day) of phytoestrogens have been shown to impair male rats' ability to produce offspring, the same effect hasn't been found in male humans. Many fertility concerns come from rat and mice studies, but it's important to note rodents metabolize soy isoflavones differently than humans, which makes many of these studies inapplicable. So when we look at human studies (in particular, the most recent meta-analysis in the journal Fertility and Sterility which looked at over 47 independent studies), we see that soy isoflavones do not exert estrogen-like effects in men, and they do not change the concentration of bioavailable testosterone. Soy may not decrease your sex drive, but these foods will.

It Can Lower Your LDL Cholesterol

Happen to your body soy LDL

Soy protein may reduce coronary heart disease risk by lowering LDL cholesterol (unfortunately, these health benefits are not passed along when defatted soy protein flour is baked, according to a study in The Journal of Nutrition. Authors speculate this is because the processing decreased levels of β-conglycinin, a soy protein that possesses the LDL-lowering-effects). According to a study in The Journal of Nutrition, just about 25 grams of soy protein daily can help lower LDL cholesterol and have a significantly favorable impact on decreasing risk factors for coronary heart disease.

It Can Help You Sleep


Who knew? Soybeans contain some of the highest concentrations of magnesium out of all food sources, at 54 mg of magnesium per ½ cup, or about 14 percent of your DV. But because processing and GM soybeans will typically contain less magnesium, it's best to eat organic sources of soybeans to reap the magnesium benefits. These include increasing protein synthesis and building lean muscle mass, as well as helping you fall asleep faster. In a study in the Journal of Research and Medical Sciences, magnesium had a positive effect on the quality of sleep in older adults with insomnia by extending the time they spent sleeping in bed (rather than just lying there) and making it easier to wake up. Check out what other foods can help you catch some ZZZs.


Olivia Tarantino
Olivia Tarantino is the Managing Editor of Eat This, Not That!, specializing in nutrition, health, and food product coverage. Read more about Olivia
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