Tofu, tempeh, and other soy-based eats are prime protein sources for many folks on a plant-forward diet. It’s pretty hard to argue against ’em from a strictly planet-warming perspective. On a gram-for-gram basis, the greenhouse emissions associated with making 100 grams of protein in tofu form are 1/25th those of making an equivalent of beef. Still, many Americans just aren’t into tofu. In fact, a new YouGov survey found that it’s the fourth most-hated food in the country—behind anchovies, liver, and sardines.
It’s hard to know exactly where those ill-feelings come from, because turning one’s nose up at tofu appears to be a problem of perception as opposed to taste. A recent study in the U.K. found that many consumers reject things like tofu and plant-based milks and cheeses without trying them first. But! That same study also found that more than half of consumers changed their mind after taking a bite.
Another potential reason for so much soy side-eye? The internet is peppered with anti-tofu sentiment—and a lot of misinformation suggesting that soy-based foods aren’t necessarily great for people or the planet. There’s the breast cancer myth, the “soy-boy” narrative, and the idea that soybean farming drives deforestation.
To set the record straight, we dug into the data and chatted with an accredited dietitian to separate what’s true from what’s false or misleading.
1. Soy feminizes men
Verdict: False. Soy does contain a form of estrogen, but it’s not the same as what occurs in the human body.
Explanation: Soybeans are legumes rich in isoflavones, a form of plant estrogen called phytoestrogens that to some degree mimic what’s in humans—though in a far less potent form. “People hear ‘phytoestrogen’ and it sounds similar to ‘estrogen,’ and there’s a fear about that,” says Elisa Bremner, a registered dietitian nutritionist and spokesperson for the New York State Academy of Nutrition and Science. “But it’s not having that kind of an impact. For most people, even daily soy is perfectly okay, because phytoestrogens are weak compared to our own natural estrogen.”
A 2021 meta-analysis of 41 separate studies found that soy showed no effect on hormone levels with normal consumption. Beware, though: Outliers might grab attention, but they’re often individual case studies and shouldn’t be confused with a norm. One man who drank more than a liter of soy milk every day for three years did see a dip in testosterone; when he stopped, things went back to normal.
2. Soy causes deforestation
Verdict: Misleading. Growing soy does drive some deforestation, but the vast majority goes to making livestock feed, not tofu.
Explanation: According to an analysis from the Food Climate Research Network, upwards of 75% of soy grown worldwide is fed to livestock; 5% goes to biofuel; and 20% is eaten by humans—mostly in the form of vegetable oil. The USDA estimates that only 6% of soy is used to make foods like edamame, tofu, tempeh, and soy milk.
Plus, when you zoom out and look at all drivers of deforestation, soy isn’t a primary culprit. According to data in the journal Science Advances, it’s historically been responsible for 6.5% of tree felling in the Amazon, while 52.4% traces back to clearing pastures for beef. The upshot? Reducing meat consumption is a more effective way to address deforestation than turning your nose up at tofu.
3. Soy isn’t a high-quality protein source
Verdict: False. As a source of the amino acids our bodies need, soy is as ‘complete’ as meat.
Explanation: Like beef, chicken, pork, or fish, soy contains all nine of the amino acids our bodies need to function but can’t make on their own (aka it’s a complete protein). Depending on the food you choose, its protein density can also be very high. Tempeh, a fermented cake of whole soybeans, is the most protein-rich, with 20 grams per 100-gram serving. That’s almost as much as the same amount of beef tenderloin.
No matter what the form, more of pretty much any soy product’s calories come from protein than any other macro. “It’s a great source of protein,” says Bremner. Firm tofu, which is made from soy milk, has close to 11 grams of protein per 100-gram serving, and shelled edamame also has about 11.
4. Soy increases breast cancer risk
Verdict: False. Some cancers are sensitive to hormones, but studies have found that eating soy may actually help lower the risk of recurrence.
Explanation: That soy contains phytoestrogens is understandably concerning to women with forms of breast cancer tied to estrogen. In these instances, hormones attach to receptors on cancer cells and spur growth, which is why people with these kinds of cancer take therapies that block or reduce estrogen. But many sources—including the American Cancer Society, the Mayo Clinic, and Memorial Sloan Kettering Cancer Center—say they don’t have to steer clear of soy.
While some older studies showed an increase in breast cancer in animals mainlining mega-doses of soy protein extracts (i.e., not edamame or tofu), subsequent human trials have found no evidence that ingesting phytoestrogens is cause for alarm. “When we look at populations of people who have soy-based diets, we’ve seen lower rates of cancer, especially in breast cancer,” Memorial Sloan Kettering Cancer Center oncologist Julia Brockway-Marchello says in an article on the hospital’s site. A 2020 study of 300,000 Chinese women in the European Journal of Epidemiology found no association between moderate soy consumption and breast cancer risk. In fact, higher soy intake might even help cut the chance of recurrence. Of course you should always run any concerns or major dietary changes by your doctor.
Additional reporting by Corinne Iozzio