With celiac disease, your immune system attacks the lining of your small intestine every time you eat gluten, a protein found in wheat, barley, and rye. Even tiny amounts (below what you can taste or see) cause damage. The foods to avoid go well beyond obvious bread and pasta. Gluten hides in sauces, seasonings, drinks, and processed foods under names you might not recognize.
How Gluten Damages Your Body
Your small intestine is lined with tiny, fingerlike projections called villi that absorb nutrients from food. When you have celiac disease and eat gluten, your immune system overreacts and damages those villi. Flattened or destroyed villi can’t absorb vitamins, minerals, or calories properly, no matter how much you eat. This is why even small, repeated exposures matter. There’s no safe threshold of gluten for someone with celiac disease; the goal is to stay under 20 parts per million, which is the lowest level that can be reliably measured in food and the cutoff the FDA uses for “gluten-free” labeling.
Grains and Starches to Avoid
The three primary grains that contain gluten are wheat, barley, and rye. But wheat goes by many names, and several ancient or specialty grains are actually wheat varieties. All of these must be eliminated completely:
- Wheat varieties: spelt, farro, kamut, durum, semolina, einkorn, emmer, triticale (a wheat-rye hybrid)
- Barley and its derivatives: malt extract, malt syrup, malt flavoring, malt vinegar, malted barley flour, malted milk
- Rye
- Brewer’s yeast: a byproduct of beer brewing with barley
Wheat starch is a gray area. Some manufacturers process it to remove gluten below 20 ppm, which meets the FDA’s standard for a gluten-free label. But wheat starch that hasn’t been processed to that level still contains enough gluten to cause damage. If you see “wheat starch” on a product that isn’t labeled gluten-free, skip it.
The Oat Question
Oats don’t naturally contain gluten, but conventional oats are almost always contaminated with wheat or barley from shared fields, transport trucks, and milling equipment. Regular oats that haven’t been specially produced to be gluten-free should not be eaten by people with celiac disease.
Purity protocol oats are grown, harvested, and processed using dedicated gluten-free equipment at every step, from the seed in the field through milling and packaging. These oats are then tested to confirm they contain less than 20 ppm of gluten (or less than 10 ppm for GFCO certification). Most people with celiac disease tolerate purity protocol oats, but a small number react to oats themselves, regardless of contamination. If you’re newly diagnosed, many gastroenterologists recommend getting stable on a gluten-free diet first before introducing certified gluten-free oats.
Processed Foods With Hidden Gluten
Gluten shows up in processed foods under ingredient names that don’t mention wheat, barley, or rye directly. These are the ones that catch people off guard:
- Soy sauce and teriyaki sauce: most conventional soy sauce is brewed with wheat
- Malt in any form: malt extract, malt syrup, malt flavoring (commonly found in cereals, candy, and chocolate drinks)
- Brown rice syrup: sometimes made using barley enzymes
- Starch or dextrin on meat and poultry products: these can come from any grain, including wheat, and manufacturers aren’t always required to specify the source
- Soups and gravies: flour is a common thickener
- Salad dressings and marinades: many contain wheat flour or malt vinegar
- Seasoning blends: some use wheat-based fillers or anti-caking agents
- Instant mashed potatoes and flavored rice mixes: may contain wheat-based thickeners
- Coated french fries: some frozen and restaurant fries are dusted with flour for crispiness
- Imitation bacon bits and meat substitutes: often contain wheat protein
The simplest rule: if a product doesn’t carry a “gluten-free” label and the ingredient list includes anything you can’t identify, check with the manufacturer before eating it.
Alcohol: What’s Safe and What Isn’t
Beer is the biggest risk. Traditional beer is brewed from barley malt and contains gluten. “Gluten-removed” or “gluten-reduced” beers start with barley and use enzymes to break down gluten proteins, but current testing methods can’t reliably verify that the gluten is fully removed. These beers should be avoided. Beers brewed from naturally gluten-free grains like sorghum or rice, labeled gluten-free, are a safer choice.
Distilled spirits are a different story. The distillation process removes proteins from the liquid, so even spirits made from wheat, barley, or rye (like most vodkas, whiskeys, and gins) are considered free of gluten protein by celiac disease experts. The risk comes from flavored spirits, which may have gluten-containing ingredients added after distillation. Wine and hard cider are naturally gluten-free.
Cross-Contamination in Your Kitchen
Avoiding gluten ingredients is only half the challenge. Cross-contamination, sometimes called cross-contact, happens when gluten-free food touches a surface, utensil, or oil that has been in contact with gluten. At home, the most common sources of cross-contact include:
- Toasters: crumbs from regular bread coat the interior and transfer to gluten-free bread. Use a dedicated toaster or toaster bags.
- Deep fryers and air fryers: oil used to fry breaded foods retains gluten particles. Gluten-free items need their own fryer with clean oil.
- Wooden utensils, cutting boards, and colanders: porous materials trap gluten and can’t be fully cleaned. Keep dedicated gluten-free versions.
- Non-stick pans with scratches: gluten can lodge in scratches. Use separate pans for gluten-free cooking.
- Convection ovens: the fan circulates particles, so avoid cooking gluten-free and gluten-containing foods at the same time.
- Shared grills: place foil underneath gluten-free food if you can’t use a separate grill.
- Dry lentils and legumes from bulk bins: errant wheat or barley grains often end up mixed in. Pick through and rinse them before cooking.
Shared condiment jars are another easy-to-miss risk. A knife that touched regular bread and then goes into the butter or jam jar leaves behind enough gluten to cause a reaction. Squeeze bottles or dedicated containers solve this.
Eating at Restaurants
Restaurants present the highest risk of accidental gluten exposure because you can’t control the kitchen. Some specific questions worth asking: Does the kitchen use a separate fryer for gluten-free items? Has the food been dusted with flour before sautéing? Does the sauce contain flour, soy sauce, or teriyaki? Are the mashed potatoes made from scratch or from a mix? Is the salad topped with croutons, wontons, or crispy noodles?
Restaurants with dedicated gluten-free menus or staff trained in gluten-free preparation are significantly safer than those that simply offer to “modify” a dish. Some chains and independent restaurants have completed gluten-free training programs. It’s worth asking whether the kitchen has any formal protocol before ordering.
Non-Food Products That Contain Gluten
Gluten doesn’t just show up in food. Anything that could end up in your mouth, even in trace amounts, matters. Lipstick and lip balm sometimes contain wheat germ oil or barley extract. Toothpaste and mouthwash can harbor gluten-based ingredients. Orthodontic rubber bands have been found coated in gluten-containing anti-caking agents.
Vitamins and supplements are another blind spot. Inactive ingredients like modified starch, pregelatinized starch, dextrin, and caramel coloring may be derived from wheat. The FDA’s gluten-free labeling standard applies to food but does not extend to prescription or over-the-counter medications, which can also use gluten-containing starches as fillers. Look for supplements that explicitly state “gluten-free” on the label, and check with your pharmacist before starting any new medication.
Safe Foods to Build Your Diet Around
The list of naturally gluten-free foods is long. All fresh fruits and vegetables, plain meats and fish, eggs, dairy, nuts, seeds, beans, and legumes are gluten-free in their unprocessed forms. Safe grains and starches include rice, corn, quinoa, millet, buckwheat (despite the name, it’s not related to wheat), amaranth, teff, sorghum, tapioca, and potato. Choosing whole, unprocessed foods and cooking at home gives you the most control and the lowest risk of accidental exposure.