Wheat gets most of the attention, but gluten also occurs naturally in barley, rye, and triticale (a rye-wheat hybrid). It shows up in ancient wheat relatives like spelt, kamut, and einkorn. And it hides in less obvious places: soy sauce, malt vinegar, beer, and certain medications. If you’re avoiding gluten, wheat is only the starting point.
Barley, Rye, and Triticale
Gluten is a family of storage proteins found in certain cereal grains. In wheat, those proteins are called gliadins and glutenins. Barley has its own version called hordeins, and rye contains secalins. These proteins are closely related to wheat gluten and trigger the same immune response in people with celiac disease or gluten sensitivity. Triticale, a cross between wheat and rye, contains gluten from both parent grains.
Barley is especially worth watching for because about 75% of its total protein is gluten. It appears in products you might not immediately connect to grain: malt extract, malt vinegar, malt flavoring, and most beer. Rye shows up in rye bread, pumpernickel, rye whiskey (though distilled spirits are a separate issue, covered below), and some cereals.
Ancient Wheat Relatives
Spelt, emmer (often sold as farro), einkorn, kamut, and durum wheat are all members of the wheat family. They’re sometimes marketed as healthier or easier-to-digest alternatives, but they all contain gluten. In fact, research from a multi-location growing study found that einkorn, emmer, and spelt had higher protein and gluten contents than modern common wheat, which is the opposite of what most consumers expect.
If a product is made with any of these grains, it is not gluten-free. The FDA’s labeling rule specifically lists spelt wheat as an example of a gluten-containing grain.
The Oats Question
Oats contain a protein called avenin, which is structurally different from wheat gluten. Avenin makes up only 10% to 15% of oat protein, compared to 80% to 85% for gluten in wheat. The known celiac-triggering sequences from wheat, barley, and rye are not present in oat avenins, and T cells that react specifically to avenin have been found very rarely in celiac patients. Long-term studies show that most people with celiac disease can safely eat up to 100 grams of uncontaminated oats per day.
The real problem with oats is contamination. Gluten-containing grains can mix in during sowing, harvesting, milling, and processing. Regular store-bought oats frequently test above the 20 parts per million (ppm) threshold that defines “gluten-free” under FDA rules. If you need to avoid gluten, look for oats specifically labeled gluten-free, which are produced under controlled conditions to stay below that 20 ppm limit.
Soy Sauce, Beer, and Other Processed Foods
Traditional soy sauce is brewed from a mixture of cooked soybeans and roasted wheat, fermented with a mold culture. The wheat is a core ingredient, not a trace contaminant. Tamari, a Japanese-style soy sauce, is typically made with little or no wheat, but you should check the label since some brands do include it. Coconut aminos are another wheat-free alternative.
Beer is brewed from barley malt in most cases, and standard lagers, ales, and stouts contain measurable gluten. Testing of more than 40 commercial Belgian beers found gluten levels ranging from below the detection limit up to 101 ppm. Some brewers use enzymes to break down gluten during production, and certain 100% barley malt beers can actually test below 20 ppm after this treatment. Beers made entirely from sorghum, rice, or millet are naturally gluten-free. Ciders and wines are also safe.
Other processed foods that commonly contain hidden gluten include:
- Soups and gravies: wheat flour is a standard thickener
- Salad dressings and marinades: may contain malt vinegar or wheat-based thickeners
- Processed meats: sausages, deli meats, and meatballs sometimes use breadcrumbs or wheat starch as binders
- Seasoning blends: some contain wheat flour as an anti-caking agent
- Communion wafers and croutons: made from wheat flour
- Couscous: often mistaken for a grain, it is actually tiny pasta made from wheat semolina
Medications and Lip Products
Wheat gluten itself is almost never intentionally added to medications. The FDA has confirmed it is aware of no oral drug products currently marketed in the United States that contain wheat gluten as an intentional ingredient. However, gluten can be present at low levels as an impurity in wheat-derived inactive ingredients like modified starch, pregelatinized starch, and sodium starch glycolate. Some ingredients, including citric acid and certain sugar alcohols (sorbitol, xylitol, maltitol, mannitol), may be produced through fermentation processes that use wheat-derived carbohydrates as a feedstock.
Lip balms and lip sunscreens are a special case because anything applied to the lips can be inadvertently swallowed. Wheat germ oil is sometimes used in these products. The FDA treats topical products applied near the mouth the same as oral products for gluten-safety purposes. Gluten in lotions, shampoos, or other products that don’t reach the mouth is not believed to cause harm to people with celiac disease, since gluten must be ingested to trigger an immune response.
Distilled Spirits
Distillation removes gluten proteins, so pure distilled spirits made from wheat, barley, or rye (vodka, gin, whiskey) are generally considered safe. The concern arises when flavorings or additives are introduced after distillation. Flavored vodkas, pre-mixed cocktails, and liqueurs may contain gluten-containing ingredients added post-distillation. Straight, unflavored distilled spirits are not a significant source of gluten.
Foods That Sound Like Grains but Are Gluten-Free
Several foods get lumped in with gluten-containing grains because of their names or how they’re used, but they belong to entirely different plant families. Buckwheat is not related to wheat at all; it’s a seed from a plant more closely related to rhubarb. Quinoa and amaranth are pseudocereals from the same family as spinach and beets. All three are naturally gluten-free and are widely used in gluten-free bread formulations.
Other naturally gluten-free grains and starches include rice, corn, millet, sorghum, teff, tapioca, potato, and arrowroot. These are safe in their whole, unprocessed forms. The risk with any of these comes from cross-contamination during processing if they’re milled or packaged in facilities that also handle wheat, barley, or rye.
Reading Labels Effectively
In the United States, a product labeled “gluten-free” must contain less than 20 ppm of gluten. That threshold applies whether the food is inherently free of gluten or has been processed to remove it. Wheat must be declared on U.S. food labels as a major allergen, but barley and rye are not required to be called out separately. This means a product could contain barley malt and not have a bold allergen warning, so scanning the full ingredient list matters.
Look specifically for: malt, malt extract, malt flavoring, brewer’s yeast, wheat starch, modified food starch (if the source isn’t specified), hydrolyzed wheat protein, and seitan (which is pure wheat gluten). When in doubt, a “gluten-free” certification seal from a third-party organization provides an extra layer of testing beyond what the FDA requires.