Gluten is a protein found in wheat, barley, and rye. Those three grains are the starting point, but gluten shows up in a surprisingly long list of foods, drinks, and even a few non-food products because wheat and barley derivatives are used as thickeners, flavorings, and stabilizers across the food supply.
The Three Core Gluten Grains
Wheat is by far the most common source. It appears in bread, pasta, cereal, crackers, baked goods, tortillas, and pizza dough. But wheat also goes by less obvious names on ingredient labels: durum, semolina, bulgur, couscous, and graham flour are all wheat.
Barley is the second major source. You’ll encounter it most often as malt, which is sprouted barley used to add flavor and sweetness. Malt shows up as malt extract, malt syrup, malt flavoring, and malt vinegar. Barley is also the base grain for most beer.
Rye is the third. It’s found in rye bread, pumpernickel, some crackers, and certain whiskeys (though distillation removes gluten from spirits).
Ancient Grains That Still Contain Gluten
Spelt, kamut, einkorn, emmer, farro, and freekeh are all marketed as “ancient grains,” and some people assume they’re gluten-free alternatives. They are not. Every one of these is a variety of wheat or a closely related grain, and all contain gluten. Farro, for example, is actually a blanket term for three traditional wheat species: emmer, spelt, and einkorn.
A 2013 study confirmed that exposure to any of these wheat varieties still triggers the same immune response in people with celiac disease. The idea that ancient forms of wheat are somehow safer is a persistent myth with no scientific backing.
Processed Foods With Hidden Gluten
The obvious sources (bread, pasta, pastries) are easy to spot. The trickier ones are processed foods where wheat or barley derivatives serve as minor ingredients:
- Soy sauce: Traditional soy sauce is brewed with wheat as a primary ingredient.
- Hoisin sauce: Nearly all commercial versions contain wheat flour.
- Bean sauces: Chinese black bean garlic sauce and yellow or brown bean sauces typically use wheat as a thickener.
- Salad dressings and marinades: These may contain malt vinegar, soy sauce, or flour as thickeners.
- Corn flakes and rice puffs: Many contain malt extract or malt flavoring derived from barley.
- Potato chips: Some seasonings include malt vinegar or wheat starch.
- Shaoxing rice wine: Despite being made from rice, wheat is usually added during production.
- Gravy and cream soups: Flour is the standard thickener in both.
Brewer’s yeast is another hidden source. It’s a byproduct of beer brewing and carries gluten from the barley used in the process. Nutritional yeast, by contrast, is grown on molasses and is gluten-free.
Reading Labels for Gluten Ingredients
Some ingredient names are ambiguous. Modified food starch, maltodextrin, and dextrin can be made from wheat, but they’re most often derived from corn or potato. The key is the allergen statement at the bottom of the nutrition label. U.S. food labeling law requires manufacturers to declare wheat when it’s used. If wheat is not listed in the allergen statement, these starches are gluten-free.
Wheat-based glucose syrups, caramel color, and dextrin are allowed in products labeled “gluten-free” because the processing breaks down the protein to very low levels. The FDA requires any product carrying a “gluten-free” label to contain less than 20 parts per million of gluten, which is the lowest level that can be reliably measured with current testing methods. Most people with celiac disease tolerate foods below this threshold. Still, buying from trusted manufacturers matters, since completely separating wheat starch from wheat protein is difficult, and trace amounts can remain.
Beer, Spirits, and Other Drinks
Beer, ale, lager, and malt beverages are made from barley or wheat and are not distilled, so they retain gluten. This includes most craft beers and mainstream brands alike. Gluten-removed beers use enzymes to break down the protein, but testing their final gluten content is unreliable, and they can’t carry an FDA-compliant “gluten-free” label.
Distilled spirits are a different story. Vodka, gin, whiskey, and bourbon may start with wheat, barley, or rye, but distillation removes the gluten protein. The final distilled product is gluten-free. Problems arise only if gluten-containing flavoring is added after distillation.
Wine is naturally gluten-free. Hard ciders made from apples or pears are also gluten-free, though you should check for added barley-based flavorings in flavored varieties.
The Oat Problem
Oats themselves do not contain the same gluten proteins found in wheat, barley, and rye. But commercially grown oats are frequently contaminated because they’re planted in rotation with wheat and processed in shared facilities. One study testing 15 oat-only products labeled “gluten-free” found that 67% exceeded the 20 ppm gluten threshold. If you’re avoiding gluten for medical reasons, look for oats specifically certified as “purity protocol” or “gluten-free,” which are grown and processed in dedicated gluten-free facilities.
Non-Food Products
Lip balms, lipsticks, and communion wafers are common non-food items that may contain wheat starch or gluten-derived ingredients. Toothpaste and mouthwash occasionally use wheat-based ingredients, though this is uncommon.
Medications rarely contain gluten. The FDA has found very few oral drugs in the U.S. that use wheat starch, and none that intentionally add wheat gluten or wheat flour. Even in the rare cases where wheat starch appears, the estimated gluten content is no more than 0.5 mg per dose, a tiny fraction of what would be found in food. For nonprescription drugs, you can check the “inactive ingredients” section of the Drug Facts label. For prescriptions, ingredients are listed in the “Description” section of the package labeling.
Grains and Starches That Are Gluten-Free
Rice, corn, quinoa, millet, sorghum, teff, buckwheat (despite its name), amaranth, and arrowroot are all naturally free of gluten. Potatoes, cassava, and tapioca are also safe. These are the foundation of a gluten-free diet, along with all plain fruits, vegetables, meats, fish, eggs, dairy, legumes, nuts, and seeds. Gluten only becomes a concern with these foods when they’re processed with shared equipment or combined with gluten-containing additives.