9 Hidden Sources of Gluten You Definitely Need to Know About

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February 28, 2020

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Shopping for gluten-free foods is one of those things that isn’t as clear-cut as you might think — whether you have celiac disease, are gluten intolerant, or are simply avoiding gluten for a time. Sure, you can look for certified gluten-free seals, but what about all those products that aren’t certified gluten free? It comes down to knowing about hidden ingredients and cross contaminants.

"Eating a gluten-free diet is lifelong challenge," says Emily Rubin, RD, director of clinical nutrition in the division of gastroenterology and hepatology at Thomas Jefferson University Hospital, in Philadelphia. Make sure to read package labels not only for the ingredients themselves but also to find out about the manufacturing process. Some products that are gluten free, for example, are processed on equipment that also processes wheat and therefore wouldn’t be safe for someone with celiac disease.

We chatted with registered dietitians specializing in gluten-free eating about the top surprise gluten-containing foods to look out for at the grocery store — and replacements to consider.

These grains are tricky because technically, they’re gluten-free. "However, many oat products are contaminated with gluten during processing," says Edwina Clark, MS, RD, CSSD, a dietitian in San Francisco. That processing includes growing time, when oats are often grown alongside wheat. It also includes the time that oats spend in a factory — meaning they could be processed in the same place or on the same equipment that processes wheat or rye. "Because some protocols for ensuring that oats are pure are questionable, it’s best to purchase products that have been certified gluten free by a third-party certifier," adds Rachel Begun, MS, RDN, a culinary nutritionist in Los Angeles who has celiac disease. One Degree Organic Foods Sprouted Rolled Oats are certified by the Gluten-Free Certification Program.

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Corn Flakes sound like they’re just corn and Rice Krispies sound like they’re just rice, right? Not necessarily. These types of cereals often contain malt flavoring, which is derived from barley. Thankfully, several gluten-free options exist. Barbara’s Organic Brown Rice Crisps Cereal contains just brown rice, cane sugar and sea salt.

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Spices are just spices, right? Actually, not always. "Spice and seasoning blends with more than one ingredient can have binding agents that contain gluten," says Begun. "Seasoning blends are really easy to make, so I recommend purchasing certified gluten-free, single-ingredient herbs and spices — and mixing the blends yourself." You can make a homemade pizza spice, for example. "And if your butcher or fish monger can’t tell you with confidence whether his pre-seasoned items are gluten free, then it’s best to buy plain cuts of meat and fish and season them at home," she adds. Spicely Organics sells spices that are certified gluten-free.

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"Wheat flour is often used as a thickener in creamy sauces and gravies," says Clark. "To give homemade gravy a gluten-free makeover, use cornstarch as a thickener instead of wheat flour." Some gluten-free gravy mixes exist, often in the form of mixes. Tomato-based sauces, fruit chutneys, hummus and mustard also serve as good gluten-free alternatives, adds Clark. Simply Organic Turkey Flavored Gravy Mix is certified gluten free.

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"Many people don’t realize that soy sauce is one of the top hidden sources of gluten contaminants," says Rubin. "The ingredient hydrolyzed vegetable protein can be made from either soy or gluten, which is confusing." You can shop for gluten-free soy sauce, Bragg Liquid Aminos, or tamari. "Tamari is a Japanese-style soy sauce made from fermented soybeans and miso paste," she says. "It does not contain any wheat."

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Hash browns aren’t always just potatoes. "Wheat flour is sometimes added to hash browns to bind the potato together and create an extra-crisp coating," says Clark. "For a gluten-free alternative, make your own hash browns with grated potato and egg, or look for a frozen product that's purely potatoes." Cascadian Farms Premium Organic Hashbrowns contain just one ingredient: potatoes.

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Love heat-and-eat soup? Just make sure to read the ingredients list before you buy. "Many canned soups and bouillon packets contain gluten additives," says Rubin. "Cream-based soups usually contain gluten-containing flours and grains to thicken the soup." As well, bouillon cubes are often made with autolyzed yeast extract, which can be derived from barley. Progresso sells many gluten-free soups, including its Vegetable Classics Lentil soup.

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"Pre-packaged and deli-counter processed meats including cold cuts, liverwurst, hot dogs, sausages, bologna and pepperoni can contain gluten," says Rubin. "You may not realize that there are more ingredients than just turkey in sliced turkey." Meat can be marinated with a teriyaki glaze made with gluten-containing soy sauce, for instance. "Plus, cross contamination can sneak in from the slicer," says Rubin. "When shopping for deli meat, I usually recommend discarding the first and last piece of deli meat after being sliced or purchasing the deli meat when the store opens to prevent cross contamination." Applegate Farms notes that most of its products are gluten free, including its deli meat and dinner sausages.

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Undistilled Vinegars

"Many vinegars are safe to eat, including balsamic, apple cider, pure rice wine and distilled options," says Begun. "However, undistilled vinegars derived from gluten-containing grains are not safe." This includes malt vinegar, which is made from malted barley. "If you are unsure of the ingredient that the vinegar is being made from, always opt for distilled," she says. "The distillation process removes the protein that triggers the immune response." Bertolli Balsamic Vinegar of Modena is free of gluten-containing ingredients.

Amy Gorin, MS, RDN, is a plant-forward registered dietitian nutritionist and owner of Amy Gorin Nutrition in the New York City area. She’s a regular contributor to many publications, including EverydayHealth.com, ReadersDigest.com, NBCNews.com, and more. She also pens a recipe-focused blog, Amy’s Eat List, where she shares easy, healthy recipes.

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