Is Soy Gluten-Free? Why Do I React To It?

I'm gluten-free and react to soy. What's going on?

soybeans
Soy is heavily cross-contaminated with gluten. Lauren Burke/Getty Images

Pure soybeans do not have gluten in them, since the gluten protein responsible for reactions in celiac disease and non-celiac gluten sensitivity only occurs in the grains wheat, barley, and rye.

But unfortunately, that's not the end of the story for soy and gluten... and the rest of the story may explain why you react to soy, even though it's supposed to be naturally gluten-free. You also need to be cautious with products that have soy as a main ingredient, since many of those products also include gluten ingredients.

Why Soy May Not Always Be Gluten-Free

Soy is everywhere in our food supply, since it's a common ingredient in many processed food products.

Generally speaking, you'll only encounter plain soybeans as edamame, which are plain soybeans steamed in their pods. Edamame is popular at restaurants featuring Japanese cuisine, such as sushi restaurants. But soy is used as an ingredient in foods such as soy sauce, soymilk, candy bars and as a meat substitute.

Soy can be subject to gluten cross-contamination—in some cases, lots of gluten cross-contamination—as a result of how it's grown.

Farmers commonly grow soybeans in rotation with wheat crops. That means the farmers use the same fields to grow soy and wheat, along with the same combines to harvest them, the same storage facilities to keep them and the same trucks to transport them to market. As a result, bits of wheat get mixed in with the soy harvest.

A 2010 study by celiac dietitian Tricia Thompson on gluten in so-called 'gluten-free' grains found that soy was one of the most cross-contaminated grains—in fact, one sample of soy flour contained a whopping 2,925 parts per million of gluten. For comparison, less than 20 parts per million generally is considered "gluten-free," although many people react to even less gluten than that.

Do You React to Soy Like You React to Gluten?

Many people report reacting to soy in a similar fashion as they do to wheat and other gluten grains.

Now, soy is a pretty allergenic food—it's one of the top eight allergens in the U.S. So there's no question that you could have a true allergy to soy. Lots of people do.

Still, I suspect that one reason so many celiacs and gluten-sensitive people report "soy intolerances" (not true allergies) is due to high levels of gluten cross-contamination in the soy... not necessarily due to a problem with the soy itself.

If you think this might be the case with you, you'll probably have your best luck looking for soy products that are certified gluten-free. Gluten-free certification programs require food manufacturers to follow strict sourcing guidelines for their raw materials, which means the end products will contain less cross contamination, too—in fact, the gluten-free certification programs in the U.S. require products to test at less than at least 10 parts per million of gluten.

You might be wondering whether soy lecithin—an ingredient found in many processed foods—is gluten-free. Soy lecithin is used as an additive to enhance flavor and make foods seem creamier.

Because soy lecithin is so highly processed, it's unlikely to contain any gluten, even if the soy used to make it was highly cross-contaminated. 

A Word from Verywell

Fortunately for those who can't have gluten, there are plenty of options out there for gluten-free soy sauce, soy flour, and soy milk.

Let's start with soy sauce. Almost every conventional soy sauce you'll find on supermarket shelves and in restaurants contains wheat. For gluten-free soy sauce, you'll need tamari, which is a richer-tasting, slightly thicker soy sauce that's made in a traditional way with no wheat. Make certain to buy one of the various gluten-free soy sauce brands, some of which are certified gluten-free.

San-J soy sauce is a good choice.

When it comes to gluten-free soy milk, you can't just pick up any carton of soy milk and assume it's gluten-free, since a few contain gluten ingredients. Silk soy milk, Pacific Natural Brands soy milk, and 8th Continent soy milk all are good choices (although you always should check the label, since ingredients can change at any time).

If you want soy flour or soy protein to use in baking or for other cooking projects, both Bob's Red Mill and Arrowhead Mills have gluten-free-labeled soy products that contain less than 20 parts per million of gluten.

Source:

Thompson T, Lee AR, Grace T. Gluten Contamination of Grains, Seeds, and Flours in the United States: A Pilot Study. J Am Diet Assoc. 2010;110:937-940

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