Soy is the leggings-as-pants of the food world — people either love it or they hate it. What really makes it stand out more than, it seems, any other food is that the evidence for and against its effect on your health is all over the place.
“Soy is definitely a very controversial topic,” says Sara Vance, C.N., a nutritionist in San Diego and founder of Rebalance Life. “On the one hand, you have groups touting the health benefits — that it’s a low-calorie, complete source of protein, it can help reduce cholesterol and heart disease risk, and some studies have even found that the isoflavones in soy have anti-cancer benefits.” The result: Good things are said about soy, so people flood their diet with it.
On the flip side of that coin, there is also pretty substantial evidence to the contrary, says Vance. "[Some studies] say that soy can be quite detrimental to your health, and that the isoflavones can interfere with your endocrine system and hormone balance," she says. "This can possibly reduce fertility in women, contribute to premature puberty, and has even been linked to certain cancers and conditions like gyecomastia (male breast development) when consumed in large amounts.”
According to Amy Shapiro, R.D., a nutritionist and founder of Real Nutrition NYC, while the research regarding soy's estrogen-like compounds certainly raises a red flag, the kind found in soy are plant estrogens, not the exact same kind that humans make. What's more, they're far less potent, with approximately 1/1000th of the estrogen strength that the real-deal human estrogen has. “It’s not like when you eat soy, it’s exactly the equivalent of taking a hormone pill,” Shapiro says. “And, the research linking high quantities of soy to breast cancer was more related to those who already were diagnosed with the disease and therefore estrogen sensitive. So, yes, eating any soy would be a risk [for them], for sure.”
Let's take things back to the basics for a second — namely, what is soy, exactly? “Soy comes from the soybean plant — it’s a legume but actually considered an oilseed — and it’s rich in protein and fiber, as well as isoflavones, powerful antioxidants,” says Shapiro. So that yummy edamame app you're so fond of at your local sushi joint is basically a soybean in its purest form. It’s once you venture outside of that into the more processed foods that soy’s nutritional value typically starts to decline, she says. The exceptions, besides actual soybeans and fresh tofu, are the fermented versions such as miso, tempeh, soy sauce, and tamari.
So, what's all the fuss about? It's just a bean from a plant — how bad could it really be? Well, once you start ingesting an excessive amount of it, soy's not-so-great side pops up. And it’s easy to OD on soy and not even know it. The more processed foods you’ve got in your pantry, the more soy you are eating. “Soy is a cheap source of protein for many packaged and processed foods, so if you are eating protein bars, cereals, bottled dressings, mayonnaise, vegan meat substitutes, and fast foods, you are probably consuming soy,” says Vance. You’d be surprised by how many different forms that it can come in — you'll be able to identify it on a label as soy oil, soy protein isolates, soy protein, soy lecithin, and textured vegetable protein (TVP), among others.
Another possible downside: “Soy products are very high in phytic acid, which can interfere with mineral absorption,” says Vance. “So, despite claims that soy helps prevent osteoporosis, foods that contain phytic acid can actually interfere with the absorption of minerals, possibly leading to mineral deficiencies. Whereas soaking and sprouting other grains and legumes can remove the phytic acid, that does not work with soy, and the only way to neutralize the phytic acid in soy is to ferment it.”
Vance says that the only form of soy that she recommends her clients consume is organic fermented soy (such as miso and tempeh). “Fermented foods are beneficial to our digestion, and are helpful for boosting the healthy bacteria in our guts,” she says. Shapiro agrees: “When we move away from the actual soybean on to soy milk and the soy protein isolates in energy bars and veggie bars, that’s where it starts to become processed and a ghost of a nutrition food.”
Finally, soy is one of the most genetically modified foods (along with corn). “Unless it says non-GMO, or organic, it is safe to assume it is probably GMO soy,” says Vance. And when it comes to soy milk, make sure it’s unsweetened. “Only when it’s unsweetened are there less calories than regular milk, or skim,” says Shapiro. “When you add in all that sugar, it’s a whole new ball game nutritionally and not beneficial from a health or diet perspective.” Vance isn't a big fan of soy milk in general, noting that there are plenty of other dairy alternatives out there that won't put you at risk. She likes almond, coconut, or flax milk to drink, and So Delicious Coconut Milk Creamer for your coffee.
The bottom line: soy, in its purest form (edamame) can be a stellar source of protein and fiber, and having a splash of non-GMO plain soy milk in your coffee is no biggie, but enjoy your soy in moderation. (And, read the labels!) Being educated and aware of where and when the not-so-healthy versions of soy are lurking in your foods is the only way to truly know the source — and amount —in your diet.
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Illustrated by Emily Kowzan