Soybeans have been one of the major food allergens in the United States since the Food Allergen Labeling and Consumer Protection Act took effect in 2006. Soy allergy is most common in young children. FARE estimates it affects about 0.4% of US infants, and a long-term study at Johns Hopkins found that roughly half of soy-allergic children had outgrown it by age 7, and about 69% by age 10.
For families still living with it, the hard part is how widely soy is used. It is cheap, high in protein, and useful to food manufacturers in a dozen different ways, so it shows up in foods that seem to have nothing to do with soybeans.
What Is Soy, Exactly?
Soybeans are legumes, in the same plant family as peanuts, peas, and lentils. Whole or lightly processed, they become edamame, tofu, tempeh, miso, natto, and soy milk. Processed further, they become ingredients: soy protein isolate, textured vegetable protein, soy flour, soybean oil, and soy lecithin.
The whole foods are easy to recognize. The ingredients are where most surprises come from.
Where Soy Hides
- Baked goods. Soy flour and soy lecithin are common in packaged breads, buns, and cookies.
- Canned soups and broths. "Vegetable broth" in some canned products, including some canned tuna, can contain soy.
- Protein bars and shakes. Soy protein isolate is one of the most common protein sources in bars and powders.
- Plant-based meats. Many meat alternatives use soy protein as their base. The Impossible Burger, for example, contains soy protein concentrate and soy leghemoglobin.
- Processed meats. Some sausages, deli meats, and burgers use soy protein as a filler or binder.
- Chocolate and candy. Soy lecithin is a standard emulsifier in chocolate.
- Asian sauces. Soy sauce, tamari, teriyaki, hoisin, and miso are all soy based. (Soy sauce also usually contains wheat, which we covered in an earlier article.)
- Medications and supplements. FARE lists these as a possible source too, so ask your pharmacist.
Why It's So Easy to Miss
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It goes by many names. Edamame, miso, tempeh, tofu, natto, textured vegetable protein (TVP), and soy lecithin all mean soy. US labels have to state soy plainly in the ingredient list or a "Contains" line, so the "Contains" line is the quickest check.
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Some soy ingredients are exempt. Under FDA's allergen labeling rules, highly refined soybean oil is exempt from allergen labeling because refining removes almost all of the protein. It still appears in the ingredient list as "soybean oil." Cold-pressed or expeller-pressed soy oils keep more protein and are treated as allergens. FARE notes that most soy-allergic people tolerate highly refined soy oil and soy lecithin, but this is a question for your allergist, since sensitivity varies.
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It's in so many processed foods. Soy can do the job of a protein, a fat, an emulsifier, and a texture agent. A single trip through a grocery store will turn up dozens of products that list it.
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Recipes change. A manufacturer may switch from one emulsifier or protein source to another without changing the front of the package.
Two Questions People Often Ask
If I'm allergic to peanuts, should I avoid soy? Both are legumes, and allergy tests often show a positive result for both. True reactions are much less common. In one study, about 6.5% to 7% of peanut-allergic children reacted to soy during a supervised food challenge. Your allergist can tell you whether testing makes sense for you.
Can soy allergy show up in adults? Yes, and one form is linked to birch pollen. Some people with birch pollen allergy develop reactions to a soy protein called Gly m 4, which resembles a birch protein. European researchers have described serious reactions, especially after soy drinks or protein powders and often during pollen season. If you have birch allergy and notice symptoms after soy milk or shakes, bring it up with your allergist.
How to Protect Yourself
- Check the "Contains" line first, then the full ingredient list. The "Contains" line catches the major allergens. The full list tells you about exempt ingredients like refined soybean oil.
- Ask about fillers and binders in burgers, sausages, and meatballs when eating out.
- Read every label, every time. Soy is one of the ingredients manufacturers swap most often.
- Ask your allergist about refined oil and lecithin. Many people with soy allergy can include them, which makes daily life much easier, and your allergist can tell you whether you are one of them.
- Use ForkSure for a quick check on dishes and packages. ForkSure flags soy as one of the Big 9.
The Bottom Line
Soy is one of the most useful ingredients in the modern food supply, which is exactly why it turns up in so many places. Most of the work of avoiding it comes down to learning its other names and getting into the habit of checking labels. The good news is that many children outgrow soy allergy, and many people who still have it can safely eat some highly refined soy ingredients with their allergist's guidance.
Stay safe, and when you need help, scan it with ForkSure.