Full disclosure: I’ve been a little tough on soy. I used to really, really hammer soy brutally, throwing in to the “avoid” category along with gluten, artificial sweeteners, and trans fats.
Truthfully, I — and many others in the natural health community — have probably been a little too tough on soy, oversimplifying a potentially healthy food (potentially with a lot of caveats). You can understand why, when soy dogs and countless other soy-based Frankenfoods become marketed as healthy.
Putting this into perspective, we’ve seen the examples of “soy dog” packaging, which claim to be “heart healthy” among other things.
The soy debate quickly becomes confusing, confounded by inconclusive studies, flawed research, and dogmatic experts determined to prove soy is either the perfect food or a culinary evil destined to make you fat, sick, and miserable.
The truth, as usual, lies somewhere in the middle.
“The pro-soy [public relations] effort has been so strong that most people simply accept that anything with soy in it is a health food,” writes Dr. Jonny Bowden in The 150 Healthiest Foods on Earth.
On the other hand, Bowden notes “the anti-soy contingent is sometimes so strident and angry (probably because it is frustrated with not being heard) that it sometimes tends to overstate some of the negatives (and the dangers) associated with soy, making that group easier to ignore.”
Dr. Kaayla Daniel is one such soy opponent. “Over the past two decades, soy has been widely promoted as a ‘miracle’ food that can prevent heart disease, fight cancer, fan away hot flushes and build strong bones and bodies in a myriad of ways,” she writes in her blog “The Dark Side of Soy.”
“Sales of soy foods topped $4 [billion] in the USA for the first time in 2004, with most segments of the industry reporting double-digit growth. Although such growth has mostly slowed, sales are not falling and the soy industry has been stepping up its marketing of products all over the world.”
Daniel continues by listing soy’s various problems; among them, it is an anti-nutrient linked to numerous problems from hypothyroidism to infertility.(1)
Then you’ve got the United States Food and Drug Administration (FDA), which argues 25 grams of soy protein daily could reduce your risk for heart disease.(2) And esteemed experts like Dr. Mark Hyman (in his book Eat Fat, Get Thin) suggest eating non-genetically modified (GMO) soy foods like tempeh or tofu.
Like complex nutrition topics like meat, studies sprawl all over the map about soy’s potential benefits and drawbacks. You could spend an afternoon on PubMed, America’s free science research engine, devouring studies about soy and feel more confused than when you began.
Take cancer: Some studies argue women in Asian countries who eat a significant amount of soy daily are less likely to die of breast cancer or experience cancer recurrence than women who consumed less soy. Other studies argue soy may interfere with anticancer drugs. Others suggest certain properties in soy mimic estrogen, which can fuel some breast cancers (so skip it).(3)
Likewise, some studies show soy improves cardiovascular health and memory while decreasing menopausal symptoms. Others show soy might damage thyroid function and potentially alter other hormone function.
Soy as Big Business
Part of this confusion stems from manufacturers. Soy is big business, and companies remain driven to capitalize on the “soy is healthy” mentality many health-conscious consumers still believe.
Between 2000 and 2007, American food manufacturers introduced more than 2,700 new soy-based foods including meat substitutes, soy cheese, soy mayonnaise, soy milk, and soy yogurt.(4) Most of these fall under the fake food or “Frankenfood” category, but still earn a health halo.
It isn’t just manufacturers who love soy. About 32 percent of the world’s total soybeans grow in America today (5), making this legume a serious cash crop.
The Soy Echelon
Soy comes in many forms, some more processed than others. One popular way to eat soybeans whole is edamame, or fresh green soybeans available individually or still inside the pod. You can eat edamame raw, boiled, or steamed. Many sushi and Japanese restaurants include boiled, steamed edamame as a staple appetizer.
Soy can also be fermented into foods like miso, natto, and tempeh. Daniel, author of The Whole Soy Story, says ancient Chinese and Japanese cultures knew soybeans must be soaked, cooked, and fermented to make them healthy and edible.
Fermenting enlists bacteria, fungi, and other beneficial microorganisms to help break down complex proteins, starches, and fats into highly digestible amino acids, simple sugars, and fatty acids.
When you hear about soy’s many wonders – for instance, that Japanese people live longer and have lower cancer rates compared than Americans because they eat soy – experts are mostly talking about fermented soy. Conversely, when experts condemn soy (such as Daniel’s comment), they’re referring to unfermented soy.
In his book Effortless Healing, Dr. Joseph Mercola breaks down fermented soy products, which include:
- Tempeh: a fermented soybean cake with a firm texture and nutty, mushroom-like flavor.
- Miso: a fermented soybean paste with a salty, buttery texture. You’ve probably had miso soup at a Japanese restaurant or sushi bar.
- Natto: fermented soybeans with a sticky texture and strong, cheese-like flavor.
- Soy sauce: traditionally made by fermenting soybeans, salt and enzymes. Many varieties on the market today are made artificially using a chemical process.
Tofu didn’t make that list because it’s not fermented.(6) Instead, manufacturers make tofu by adding a curdling agent to soy milk, which then separates into curds and whey (much like cow’s milk).
Tofu digests easier than modern soybean products because many unwanted components, including flatulence-producing oligosaccharides, concentrate in the soaking liquid rather than the curd.
That makes tofu better, but it still carries traditional problems. According to Dr. Jonny Bowden in The 150 Healthiest Foods on Earth, those problems include anti-nutrients like:
- Potent enzyme inhibitors that block the action of enzymes needed for protein digestion. (He notes these same protease inhibitors could also have cancer-protective effects.)
- Haemagglutinin, a clot-promoting substance that causes red blood cells to clump together
- Goitrogens, substances that suppress thyroid function.
- High levels of phytates, which block absorption of minerals (though fermentation reduces these phytates).
The Biggest Losers: Soy Protein Isolate and Soybean Oil
In the soy echelon, fermented foods would probably rank tops; next would be tofu; furthest down the list, on the very very bottom, are Frankenfood soy products, prevalent in health food stores because of their profit margin and pseudo-healthy aura.
Americans seldom consume soybeans in their whole natural form. Instead, manufacturers process soybeans by using hexane or other solvents to remove the oil, which can be sold as cooking oil or oil to be added to other processed foods. (More on that in a minute.)
They take what’s left over (defatted soy flour) after they extract oil and combine it with other proteins to make animal feed or wash it with water to create soy protein concentrate.
Soy protein concentrate becomes two even more processed soy sources: textured soy protein that can be produced through a process called extrusion, or more popularly, soy protein isolate that can be produced by stabilizing soy protein concentrate.
Soy protein isolate lurks in many processed foods, including protein powders, protein bars, and those ubiquitous Frankenfoods.
According to the Soyfoods Association of America, soy protein isolate is a dry powder food ingredient separated or isolated from the other components of the soybean, making it 90 to 95 percent protein and nearly carbohydrate and fat-free.(7)
In other words, soy protein isolate becomes a far, far different “food” than traditional soybeans: A heavily processed protein that often ends up in heavily processed foods.
Equally ranking in soy ubiquity is soybean oil, which is extracted using the chemical solvent hexane. Over 90 percent of soy produced in the U.S. is genetically modified and sprayed with the herbicide Roundup.(8)
Soybean oil is cheap, which explains why nearly any restaurant will use it and many processed foods contain it. According to Dr. Mark Hyman in Eat Fat, Get Thin, two big problems with soybean oil are its inflammatory omega-6 oils (the number one oil source, in fact) and its harmful residues of the herbicide glyphosate.
Hyman notes in the early 1900s, an abundance of soy and a butter shortage led manufacturers to solidify soybean oil into margarine. The result was nothing short of disastrous for our health.
“Thanks to farm subsidies and the power of Monsanto’s global soybean monopoly, Americans now consume about 18 billion pounds of soybean oil a year,” he writes in Eat Fat, Get Thin. “About 20 percent of our calories come from soybean oil, which is 50 percent linoleic acid, an inflammatory omega-6 fat. Check your grocery store labels; soybean oil is in almost everything.”
Wonder why our modern diet contains way more (some experts argue up to 50) times the amount of omega 6s compared with anti-inflammatory omega 3s? You might start by blaming soybean oil.
An Upside to Soy?
So if soy creates all these problems, why did it ever get any health praise? Among its benefits, soy contains bioactive compounds called isoflavones (including genistein and daidzein), commonly known as phytoestrogens. These isoflavones have hormone-like activity due to their structural similarity with estrogen.
Soy isoflavones can mimic the effects of estrogen in some tissues and block the effects of estrogen in others. (9)
Even that can have a downside though: Crops vary in phytoestrogens(10), and some people metabolize phytoestrogens more efficiently than others.(11) To further complicate matters, your gut bacteria varies, which can impact your ability to benefit from phytoestrogens.(12)
Is Soy an Ideal Protein Source?
Vegans and vegetarians frequently use soy as a protein source. While soy contains all the essential amino acids, it isn’t considered a high-quality protein source because two essential amino acids – lysine and methionine – exist in low amounts.
Many processed foods also contain the aforementioned heavily processed soy protein isolate. High-heat processing can damage soy’s fragile amino acids, making soy protein even less bioavailable.(13)
What you’ve ultimately got is a merely adequate protein source. You can do much better with quality animal protein or if you’re a vegan or vegetarian, plant protein sources and non-soy plant protein powders.
Whole soybeans do contain minerals including calcium, iron, magnesium, manganese, phosphorus, zinc, and potassium.
At the same time, soybeans are much higher in inflammatory omega 6s than omega 3s. In fact, one cup contains 637 mg of omega 3s but almost five grams of omega 6s.(14)
Keep in mind those nutrients entail the entire soybean. Whole soy foods such as edamame, tofu, and tempeh contain the most nutrients. Soy protein isolate contains the least.
Years ago, celebrity nutrition and fitness expert JJ Virgin lived in Japan. She noticed while Asians indeed eat soy, they eat more fermented soy such as miso soup, some tofu in a stir-fry, or a little soy sauce with sushi. They weren’t eating tofu burgers or soy-cheese pizza. Further, they used soy is a condiment, not a replacement for animal protein. And unlike most American soy, theirs is organic and non-GMO.(15)
Soy and Particular Health Benefits: Here’s Some (Murky) Science
Particular health benefits generally entail whole soy sources, not the processed Frankensoy found in fake-food products. Most glowing (or not-so-glowing, for that matter) studies are not using Tofurkey or Beyond Meat (particular meat substitute brands) as their soy sources.
From this small study sampling, you can begin to understand why soy becomes so confusing. Among purported health benefits include:
- Soy and heart health.
Studies regarding soy and heart health yield mixed results. One review in Circulation found little to no effect to benefit heart health.(16) Soy seems to slightly reduce low-density lipoprotein (LDL) in folks with very high levels of cholesterol, yet experts like Bowden (in his book The Great Cholesterol Myth, co-authored with Dr. Stephen Sinatra) argue particle size, not LDL itself, cause many cardiovascular problems. Several large studies (mainly with Asian populations) that looked at large soy consumption and heart health also found mixed results. In the Japan Public Health Center-based Study, soy foods created a reduced risk of stroke in women but not men.(17) The Singapore Chinese Health Study also found no link with soy consumption and cardiovascular benefits.(18)
- Soy and menopause.
A Cochrane review found isoflavones isolated from whole soybeans and consumed as a supplement significantly reduce the frequency of hot flashes, yet soy from whole food sources didn’t decrease those hot flashes.(19) Another review published by the Linus Pauling Institute that examined over 60 studies on soy and menopause found soy could potentially cut down on hot flashes in menopausal women.(20) Likewise review published in the journal Menopause found isoflavone supplements reduced hot flashes by 17 percent.(21) Overall, isoflavones seem to help with hot flashes as a supplement but not from food. Looking at this collection of studies, the results go against my personal philosophy that whole foods are almost always better than isolated compounds and processed ingredients, or, at least, that whole foods would provide some of the same benefits as their concentrated extracts. But, sometimes an exception exists to the rule — and perhaps there is more to the story that we have yet to discover.
- Soy and bone health.
One review published in the Journal of Women’s Health found no effect of soy on bone mineral density (BMD.(22) Another study published in Clinical Nutrition showed postmenopausal women had significant increases in BMD with supplemental soy isoflavones.(23)
- Soy and cancer.
Since soy isoflavones resemble natural estrogens, they might help protect against hormone-associated cancers. Clinical trials again show variable results. A few case studies conclude soy exposure during childhood and adolescence might mean a lower risk for breast cancer later in life.(24) One study in the Journal of Human Reproduction found no effect of soy on breast density.(25) Overall, little evidence shows soy decreases breast cancer risk. Ditto for endometrial cancer. Some studies found no effect of soy risk factors for this cancer, yet others showed some protective effects of soy on the risk factors.(26) Studies regarding soy and prostate cancer found no positive or negative effects on prostate cancer risk factors.(27) These and other studies prove contrary what anti-soy folks argue, soy might not reduce cancer risk, but neither does it seem to increase it. Again, quality and source matter.
- Soy and brain health.
Soy can potentially improve brain health. Researchers using cognitive function tests – including tests for memory, attention, verbal fluency, motor control, and dementia – show improvements in cognitive function.(28)
The Darker Side of Soy
The aforementioned studies overall present a very mixed, potentially confusing review about soy. Others present a darker perspective:
- Breast cancer.
Not all cancer studies show soy’s beneficial effects, especially with breast cancer. According to a review in the Journal of Nutrition, the isoflavone genistein promotes growth of human breast cancer cells sensitive to presence of estrogen.(29) Until the issue becomes clearer, many doctors recommend women who take hormonal therapy or who have estrogen-receptor-positive breast cancer avoid soy supplements such as soy isoflavones and soy isolates because they contain high concentrations of isoflavones.(30)
If you’re a guy who regularly eats soy, you risk developing gynecomastia (male breasts). One study found 20 men consumed approximately 36 servings of soy for 84 days. Two men experienced hot flashes and one developed a mild case of gynecomastia that returned to normal once the soy was no longer consumed.(31) According to Daniel, many boys and young men are growing breasts. In fact, surgeons report a booming business in breast reduction operations. Not only that; soy can trigger premature puberty in girls and delayed or arrested puberty in boys. Daniel contributes this increase to environmental estrogens in plastics, pesticides, drinking water, supermarket meats, poultry, and soy products. In other words, there isn’t just one culprit, but soy could contribute to that problem.
- Thyroid health.
Soy’s effect on thyroid function shows mixed data and opinions. One review published in the journal Thyroid found soy does not impact thyroid function,(32) yet experts like Dr. Mercola believe soy can block synthesis of thyroid hormones and interfere with iodine metabolism, thereby interfering with thyroid function.
- Health concerns among children with soy.
“The Israeli Health Ministry strongly recommended that consumption of soy foods be limited for young children and adults and that soy formula be avoided altogether by infants,” said Daniel. “This is a giant step forward. I hope that Israel’s action will encourage other government agencies to alert their citizens to the fact that it is a myth that soy is a ‘health food’ and that there are very real dangers from making soy a staple of their diets.” Daniel noted that there are hundreds of studies linking soy foods and soy infant formula to digestive problems, thyroid dysfunction, ADD/ADHD, dementia, reproductive disorders and even cancer.(33)
What’s the Take-Home?
Nutrition can be a messy field, and few complex issues present concise, clear-cut answers. Researchers and experts often have their own biases, and studies can’t possibly account for every variable.
Take soy and cancer, usually a multifactorial disease. Let’s say a study argues women who consume more soy have more breast cancer. What other factors might contribute to those increased rates? Those women might have more toxic exposure, live in polluted cities, have stressful jobs, and make poor eating decisions. Those and many other thing play a role in that increased breast cancer. From that perspective, saying eating soy increases breast cancer vastly oversimplifies a very complex issue.
Ditto for the pro-soy agenda: What other factors might potentially increase improve cognitive function among soy eaters?
Ultimately, clinical studies and expert advice leave us in murky, conflicting waters regarding soy. Some studies show negative effects, others show positive effects, and others show no effects at all.
Even if you’re a non-soy eater, you’ll likely encounter this ubiquitous food in more places than you might initially suspect (see rule #1). With that in mind, remember these seven rules about soy.
1. Beware of sneaky sources.
Look at your protein powder; does it contain soy? Ditto your beloved protein bar. Atkins Bars, a favorite among low-carbers who might otherwise avoid soy, contains soy protein isolate or soy nuggets (soy protein isolate and oat flour) among their first ingredients. Really, any processed food might have soy among its ingredients. You might be eating more soy than you realize.
2. Soy isn’t always a bad word.
Besides the aforementioned fermented soy foods that are perfectly healthy for most people, don’t freak out if your supplement container says “soy phytosomes.” Phytosomes are a phospholipid (fat) that help your body better absorb a particular nutrient like curcumin.
3. Demand better oil.
You’re probably not using soybean oil to cook with, but if you’re eating out, you’re almost certainly getting it. Some restaurants have upgraded, and more health-conscious places will use other oils. If in doubt, ask; and if they use soybean oil, ask the owner to switch.
4. Find better vegan/vegetarian alternatives.
If you’re a vegan or vegetarian, you might rely more on soy, especially as the gazillion fake foods that still line many health food stores. Vegetarians have better protein sources including pasture-raised eggs and goat cheese. Vegans can utilize sources like nuts, seeds, legumes and pea/rice protein powders.
5. Find better alternatives.
Whether you’re vegan or Paleo, you can easily substitute unsweetened coconut or almond milks for soy milk (or cow’s milk, for that matter). Coconut Aminos makes an easier (and in my opinion, better tasting) option than soy sauce. Translation: Soy almost never needs to make an appearance in your diet, if you don’t want it there.
6. For most folks, the occasional soy isn’t going to be a problem.
Regardless whether you’re vegan or not, a once-in-a-blue-moon tofu in your stir-fry probably isn’t going to hurt you. Only when you start making soy a daily staple – especially several times each day – can this food become a problem. And how would you know if you’re one of those people for whom soy could be a problem? Always work with your health practitioner to assess your comprehensive health picture based on testing — not only on your shopping list.
7. Put those critics into perspective.
“Let me be clear: In a world of French fries, fast food, trans fats, and high-fructose corn syrup, I hardly think a few servings of soy protein is the worst thing in the world,” Bowden says. “We have bigger battles to fight in the food arena. But I also don’t think soy products are among the healthiest foods on the planet, for all the reasons mentioned above.” I agree.