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Superfood or Seriously Scary? The Truth About Soy

Say it sin't soy–learn the facts about this controversial nutrient. 

My best friend, Alex, was sixteen when she decided to stop eating meat. Her love of animals and her distaste for the sinewy feeling of meat between her teeth left her seeking vegetarian alternatives to her old steak and chicken staples. When she discovered soy products, she quickly became a fan; not only could she continue to make her beloved “beef” tacos, but soy substitutes were also a good protein supplement. “The taste wasn’t too different,” Alex says. “It helped me feel like I was still eating substantial meals.” 

But how healthy is soy, really? The plant has been a dietary staple in East Asian cultures for thousands of years, and Americans have jumped on the bandwagon recently—between 1992 and 2008, soy-product sales increased from $300 million to $4 billion in the U.S. Whereas soy used to be relegated to health-food stores, now we can find it in just about every supermarket. Are we on our way to longer, healthier lives? 

Not exactly. “The bulk of soy products that you can buy in the States are processed and altered so much that the original East Asian consumers wouldn’t even recognize them,” says Alex, who recently earned a degree in nutrition science. 

Some studies have linked soy to infertility, breast cancer, thyroid problems, and other health issues. How true are these claims? Is soy a truly healthy alternative to dairy? What are our other options? I dove into the research surrounding some of these questions to see what scientists have really discovered—sans spin and sensational headlines. 

All Soy Isn’t Created Equal
Luckily, conflicting claims about soy are mostly reconcilable—we just have to get a little more specific. Jenny Geyser, a San Diego–based personal trainer, cautions people on eating overly processed soy in particular, which she claims has “lately been shown, through many studies, to be harmful.” Avoiding this potential harm means steering clear all processed soy products, including the “soy protein isolate” found in powders, bars, and those soy hot dogs, ice creams, protein shakes, and meats you see. 

We’ve taken soy to a whole new level—just think about all the new soy products you see in grocery aisles (we’re not talking just miso soup and tofu anymore). All those studies touting the benefit of soy are correct—the fermented soy present in traditional Asian diets does have great health benefits. But tofurkey? Not so much. 

What Is Unprocessed Soy?
In The Whole Soy Story, Dr. Kaayla Daniel discusses the differences in Eastern and Western cultures’ soy consumption. Traditional Asian eaters consume highly digestible, fermented soy, like miso, tamari, tofu, tempeh, and soy sauce—not fancy versions of America’s favorite junk foods. The main disparity, Daniel writes, is that people in Asia eat small amounts of whole-soybean products, while Western processors separate the beans into the protein and the oil. Traditional Asian products also use whole beans that are fermented for at least three months; this important part of the process makes the bean more digestible. High-tech processing does just the opposite—it increases the beans’ toxic and cancer-causing residues with high temperatures, pressures, and chemicals. Without fermentation, soy provides far fewer health rewards—it actually inhibits calcium, iron, and zinc absorption. 

This means that all of our newfangled, “healthy” soy products actually fall into the processed-food category. And, as we’ve now been told millions of times, processed food is one of those things that we should make the exception, not the rule, in our diet. 

Does Soy Lead to Infertility?
Some studies have shown that eating high levels of soy protein does have harmful effects on our ability to reproduce—but only when we’re taking in much, much more soy than average over a long period of time. So breathe easy, Silk Milk lovers—a glass of soymilk a day and the occasional tofu salad probably aren’t going to leave you childless, according a study published by Wake Forest Baptist University Medical Center. Researchers found that subjects who took soy supplements containing twice the amount of that eaten by most women in Asia over one year didn’t cause any negative changes in menstrual cycles or ovarian function. 

When we consume extremely high levels of soy, on the other hand, scientists have discovered some slightly scary effects. One study, published in the American Journal of Clinical Nutrition, showed that consuming the equivalent of about three twelve-ounce glasses of soymilk daily did cause subjects to experience hormonal changes after only a month. So if you’re downing this much soy every day, it’s probably smart to cut back if you want children someday. 

Does Soy Lead to Breast Cancer?
A diet high in soy actually appears to lower women’s breast-cancer risk. According to a study published in the Journal of the National Cancer Institute, the plant estrogens found in soy, called isoflavones, are protective, reducing our exposure to estrogen, which reduces the risk of cancer. Why, then, when I click over to the American Cancer Society’s Web site, does it urge me to avoid soy if I want to lower my cancer risk? 

I dug a little deeper. 

East Asian countries do experience far lower rates of breast cancer than the U.S. does—Japan and China have only about one-third to one-half as many incidences as we do. The difference lies in the type of soy found in traditional Asian diets (back to that whole fermentation thing). According to the American Journal of Clinical Nutrition, this kind of soy controls estrogen levels, thereby preventing cells from replicating (meaning cancer cells have a harder time reproducing) and zapping free radicals (which can lead to mutated, cancerous cells). So as long as someone living in China three hundred years ago could have recognized the type of soy you’re about to eat, it’s probably unlikely that you’ll develop cancer from it. 

Does Soy Lead to Thyroid Issues?
I ran across a ton of articles claiming that soy leads to thyroid troubles, but medical experts haven’t found any conclusive link yet. Here’s the gist of the claim: Hypothyroidism—a condition in which someone lacks the hormones necessary for the thyroid to keep his or her metabolism going strong—is treated with synthetic thyroid hormone. Experts have noticed that soy interferes with the body’s ability to absorb this remedy. But this doesn’t mean eliminating soy altogether is necessary. According to a Mayo Clinic article by endocrinologist Todd Nippoldt, “there’s no evidence that people who have hypothyroidism should avoid soy completely.” Instead, just avoid it when you take the actual hormone replacement—a four-hour window should be enough to prevent any negative effects. 

When it comes to cancer of the thyroid, opinions also vary. According to the Journal of the American Menopause Society, as with breast cancer, soy consumption doesn’t make us any more likely to develop thyroid cancer. Another study, published by the University of Illinois, found no convincing evidence that soy protein harms the thyroid—as long as people consume less than twenty-five grams per day, the equivalent of four eight-ounce cups of soy milk. In fact, this study also found that fermented soy can actually boost thyroid protection. 

Soy Alternatives
Soy used to be our go-to dairy alternative, but now that it’s become its own grocery-store category, we’ve developed some undeniably creative alternatives. As a lactose-intolerant girl, I’ve tried a bunch of ’em and have developed an arsenal of dairy-free faves. 

  • Almond Milk: Slightly sweet, high in healthy fats, and much lower in calories than soy; it also comes in chocolate flavor. Rice milk is another alternative that isn’t as thick as soy or dairy milk. 
  • Coconut Oil: This works well in baking (I promise) as a substitute for dairy or soy butter and has a slightly sweet, fruity taste. 
  • Vegetable Spread: This butter substitute works well in non-baking scenarios—plus, it’s spreadable and closer to butter’s texture. 
  • Cheese: There are lots of non-soy, non-dairy cheese options. My sister, also lactose-intolerant, is a fan of Teese Cheese: “It really satisfies any nachos or lasagna cravings I have,” she says. 
  • Craving Ice Cream? Try sorbet, coconut, or rice-milk ice cream. 

Besides making my eyes a bit blurry and my brain hurt a little, all this conflicting research showed me what should have been obvious—unprocessed soy, in moderation, likely poses no real health risk. In fact, it’s a nourishing way to add variety to your daily food routine. And since it’s too early to know what the real effects of Not Dogs, Veat, and nayonaise will be, it’s a no-brainer not to take those risks. But if you’re having a craving for processed soy, hey, it could be a lot worse—it’s not like you’re fiending for cigarettes. The occasional soy crisp never hurt anyone.

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