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Should You Eat Soy?

Five rules for consuming the controversial bean.

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In the typical meat-free diet, few foods are as controversial as soy. Fans say it’s a superfood that prevents osteoporosis, cancer, and heart disease. Critics say it’s a poison that causes cancer, impairs thyroid function, harms the gut, and diminishes immunity. The truth, as usual, lies somewhere in the middle.

Soy probably shouldn’t be your only source of protein, but eaten with a few rules in mind, it’s a good (and tasty) way to fill in nutritional gaps. Follow these guidelines for safe soy consumption:

1. Eat it whole.

Limit your consumption of fake meat, cheese, milk, ice cream, energy bars, and other processed foods. They’re often high in sugar, sodium, added fat, and other ingredients. Protein powders, soy-fortified foods, and some energy bars are high in isolated soy protein, a heavily refined ingredient that’s processed with very high heat and solvents. Isolated soy protein also has a high concentration of soy isoflavones, the potent compounds in soy that are responsible for both its health benefits and hazards. Focus instead on whole forms of soy, such as edamame (soy beans), tempeh (fermented soy cakes), tofu, or whole soymilk made without sugar, thickeners, or other additives.

2. Always buy organic.

Soy has one of the highest levels of pesticide residue of any food. Even more troubling, 93 percent of all soy grown in the United States is genetically modified. If you do eat soy, always choose organic varieties-regulations prohibit organically grown products from containing GMOs. Even better, look for the Non-GMO Verified seal. It’s an assurance that the product has been tested and certified free of GMOs.

3. Stick with tradition.

Soy contains physic acid, a compound that prevents the body from absorbing minerals, including calcium, magnesium, zinc, and iron, and can cause deficiencies in these nutrients. When soy is fermented, as it is in traditional cultures, the acid content is dramatically reduced. Fermenting soy also makes it easier for the body to digest, and promotes the growth of probiotics, beneficial bacteria that support immunity and digestion. Fermented soy products include tempeh, miso, tamari or soy sauce, and natto, a rather pungent soy product that’s used in grain dishes or spread on toast.

4. Eat in moderation.

The typical Asian diet contains very moderate amounts of soy, about 9 grams a day. That’s the equivalent of half a cup of soymilk, a handful of edamame, or a few tablespoons of tofu. By contrast, if you’re drinking a cup of soy milk a day, eating a tofu pup or two, and enjoying an energy bar in the afternoon, you may be eating as much as 100 grams of soy protein-most of it in a highly processed form. Studies don’t yet show the implications of that kind of consumption. Another argument for moderation: studies suggest that small quantities of soy do not significantly affect hormone levels in men, but higher quantities can lead to estrogenic and feminizing activities in men.

5. Check in with your body.

One problem that many people have with soy: it’s hard to digest. This is primarily because soy contains protease inhibitors, compounds that block the action of enzymes critical for the digestion of protein. Some studies have also tentatively linked trypsin inhibitors with intestinal damage and increased susceptibility to disease. Additionally, soy is a highly allergenic food; even if it doesn’t result in anaphylaxis, it may cause significant gastric distress.