For years, I second-guessed every block of tofu I ate because someone's uncle read something online about hormones.
Remember that first time you heard someone say soy would "mess with your hormones"?
I do. It was at a barbecue about six years into my vegan journey, and a well-meaning uncle pulled me aside to warn me about my tofu burger. He'd read something online, he said. Something about estrogen. Something about men growing breasts.
I laughed it off then, but the seed of doubt was planted. For weeks afterward, I found myself second-guessing the tempeh in my stir-fry, wondering if there was truth to the fear.
Turns out, there wasn't. And I'm not alone in having been misled.
Soy has been consumed safely for over 2,000 years across Asia, yet somehow in the past few decades it became one of the most misunderstood foods in the Western diet. The myths spread faster than the science could keep up, leaving even longtime plant-based eaters confused about whether their morning soy latte was helping or hurting them.
But here's the good news: science has caught up. And it's debunking these myths one by one.
1) Soy increases estrogen levels and feminizes men
This is probably the most widespread myth about soy, and honestly, the one that causes the most unnecessary anxiety.
The concern stems from isoflavones, plant compounds in soy that can weakly mimic estrogen in the body. Because of this, people assumed soy would raise estrogen levels in men and lead to feminization, including breast growth.
But here's what the research actually shows: isoflavones are phytoestrogens, not actual estrogen. They're structurally similar, but they don't function the same way in human bodies.
Multiple studies have confirmed that soy consumption doesn't affect testosterone levels or circulating estrogen in men. A comprehensive review published in Fertility and Sterility found no feminizing effects even at isoflavone levels significantly higher than what a typical Asian male consuming a soy-rich diet would eat.
The few cases of gynecomastia linked to soy involved men consuming around 15 to 20 servings per day, which is nowhere near normal consumption. That would be like eating 15 blocks of tofu daily.
As one nutrition professor told The Washington Post in 2024, there's simply no data to confirm that normal soy milk consumption leads to feminization in men. And no major health organization warns against it for this reason.
2) Soy causes breast cancer in women
This myth kept me from recommending soy to friends for years, even after I'd gone vegan myself.
The logic seemed sound: soy contains phytoestrogens, estrogen can fuel certain breast cancers, therefore soy must increase breast cancer risk. Simple, right?
Wrong.
The research tells a completely different story. Studies involving over 46,000 women found that those with the highest soy consumption actually had a 30 percent reduction in endometrial cancer risk.
And when it comes to breast cancer specifically, multiple research reviews have found no association between soy consumption and increased risk. In fact, some studies suggest it may have a protective effect, particularly when consumed during adolescence.
A 2024 meta-analysis involving more than 900,000 participants found that people with higher soy intake had a 31 percent lower risk of cancer overall, with particularly significant reductions in gastrointestinal, ovarian, and upper aerodigestive cancers.
The confusion likely stems from early rodent studies, but rats metabolize isoflavones differently than humans. What happens in a lab rat doesn't necessarily translate to your tofu scramble.
3) Soy products cause thyroid problems
When I first heard this one, it gave me pause. Thyroid health is serious business, and the idea that my daily tempeh could be messing with my hormones was concerning.
The myth suggests that soy interferes with thyroid function and can lead to hypothyroidism or make existing thyroid conditions worse.
But here's what the science actually says: soy doesn't adversely affect thyroid function in healthy adults. The European Food Safety Authority evaluated isoflavone safety and found no evidence of harm to thyroid function at typical supplementation levels.
A comprehensive review examining 417 reports based on human data found that isoflavone intake does not negatively impact thyroid function.
There is one caveat worth noting: if you have hypothyroidism and take medication for it, soy can interfere with the absorption of that medication. The solution isn't to avoid soy entirely, though. Just wait a few hours after taking your thyroid medication before consuming soy products.
For everyone else? Your thyroid and your tofu can coexist peacefully.
4) All soy is genetically modified and therefore dangerous
This one had my partner worried for a while. She'd read somewhere that 93 percent of soybeans grown in the U.S. are genetically modified, and she wasn't sure if that made them unsafe.
Yes, it's true that the vast majority of soybeans in the U.S. are GMO. But here's what that actually means: genetic modification makes crops more resistant to herbicides, making weed control easier for farmers.
What it doesn't mean is that GMO soy is inherently dangerous or unhealthy. Despite decades of consumption, there's no scientific evidence linking GMO soy to health problems in humans.
And if you want to avoid GMO soy anyway? That's easy. Look for products labeled "non-GMO" or "organic." Certified organic products aren't allowed to use genetically modified ingredients.
Most of the soy products we actually eat, like tofu, tempeh, and soy milk, come from non-GMO soybeans. The GMO soy primarily goes to animal feed for factory farms, not human consumption.
Ironically, if you're eating meat and dairy, you're consuming far more GMO soy than a vegan eating tofu ever would.
5) Soy products are too processed to be healthy
This myth is a bit trickier because there's a kernel of truth hiding in there.
Not all soy products are created equal. Some, like soy-based chicken nuggets or sausages, are indeed highly processed. They're far removed from the original soybean and often packed with sodium, fat, and preservatives to mimic the texture and flavor of meat.
But lumping all soy products together is like saying all wheat products are unhealthy because some are refined white bread.
Whole and minimally processed soy foods like edamame, tofu, tempeh, miso, and plain soy milk are nutrient powerhouses. Just half a cup of whole soybeans contains 16 grams of protein, 5 grams of fiber, over half your daily iron requirement, and significant amounts of magnesium, copper, and manganese.
Tofu and tempeh require minimal processing. They're made by coagulating soy milk or fermenting soybeans, processes humans have used for thousands of years.
The key is reading labels and choosing whole or minimally processed soy foods most of the time. Those are the ones with proven health benefits.
6) Soy is bad for children and infants
This myth genuinely scared some parents I know away from soy-based formulas and foods for their kids.
The concern is that because soy contains isoflavones, it might interfere with normal development in children, particularly around hormones and sexual development.
But the research doesn't support this fear. The 2025 Dietary Guidelines Advisory Committee specifically highlights soy products as part of a healthy diet during childhood, emphasizing their role in providing high-quality protein and essential micronutrients critical for growth and development.
Multiple studies have found no negative effects of soy consumption in children. Australia's Dietary Guidelines include soy products as appropriate for children and adolescents, and Canada's guidelines list soy as a healthy food.
The American Academy of Pediatrics has stated that soy-based formulas are safe and effective for infants who need them, whether due to lactose intolerance, milk allergies, or family preference.
Cultures in Asia have been feeding soy to children for millennia, and there's no evidence of developmental problems as a result.
7) Soy consumption will lead to dementia
When my grandmother asked me about this one last Thanksgiving, I knew the soy myths had reached peak absurdity.
The claim is that soy can increase dementia risk, possibly due to its effects on the brain or hormones.
There is absolutely no evidence to support this concern. None.
In fact, the research points in the opposite direction. Studies suggest that consuming soy products may actually reduce dementia risk, possibly because of the anti-inflammatory and antioxidant properties of isoflavones.
A 2025 study published in The British Medical Journal looked at dietary factors and dementia risk and found that it's not soy people should worry about. The real culprits? Processed meats and ultra-processed foods were linked to potentially higher dementia risk.
Aging is the primary driver of dementia, along with factors like alcohol consumption, smoking, depression, and diabetes. Your tofu stir-fry isn't making the list.
8) Soy is destroying the rainforest
This last one isn't about health, but it's worth addressing because it stops people from choosing plant-based options.
The concern is valid: massive amounts of rainforest are being cleared to grow soybeans, particularly in South America. This is an environmental catastrophe.
But here's what most people don't realize: over 70 percent of soybeans produced globally go to animal feed for factory farms, not human consumption. We're talking about feed for poultry, hogs, cattle, and aquaculture.
I recently watched a fascinating video that traces soy's entire journey from ancient China to modern industrial agriculture. It explains how a crop that once healed soil and fed civilizations became the invisible engine of factory farming.
The historical context makes the environmental piece click in a way statistics alone can't. If you're curious about how we got here and what soy's 3,000-year story reveals about our relationship with food and land, it's worth your time.
Only a small percentage goes to making tofu, tempeh, and soy milk for humans.
So when you eat a burger made from cows, you're contributing far more to soy-driven deforestation than when you eat a tofu burger. The cow ate pounds of soy to produce that meat.
If you're genuinely concerned about the environmental impact of soy production, the most effective step you can take is to reduce or eliminate animal products from your diet. That directly reduces demand for the soy that's actually driving deforestation.
Conclusion
Soy has been unfairly demonized for years, largely based on misunderstood science and rodent studies that don't apply to humans.
The reality is that whole and minimally processed soy foods are some of the healthiest options available. They're complete proteins, packed with nutrients, and linked to reduced risks of several types of cancer, heart disease, and other chronic conditions.
Does this mean you need to eat soy? No. There are plenty of ways to be healthy without it.
But if you've been avoiding soy out of fear, you can stop. The science is clear: soy is safe, nutritious, and has been consumed successfully by billions of people for thousands of years.
Next time someone warns you about your tofu, you'll know what to say.
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