Are Fermented Foods Gluten-Free? A Comprehensive Guide

November 10, 2025 •

4 min read

According to the FDA, foods labeled "gluten-free" must contain less than 20 parts per million (ppm) of gluten, and this rule also applies to fermented or hydrolyzed products. So, are fermented foods gluten-free? The answer depends entirely on the ingredients and production process, not on the fermentation itself.

Quick Summary

The gluten-free status of fermented foods depends on their initial ingredients and risk of cross-contamination. Many are naturally gluten-free, but some require careful label-checking for safety.

Key Points

Fermentation Doesn't Remove Gluten: The fermentation process does not eliminate gluten from foods that started with gluten-containing grains.
Check the Ingredients: A fermented food's gluten-free status depends entirely on its initial ingredients, not the fermentation process itself.
Safe Options Exist: Many fermented foods, like plain yogurt, water kefir, sauerkraut, and kimchi, are naturally gluten-free.
Be Wary of Hidden Gluten: Added flavorings, thickeners, or grains can introduce gluten to otherwise safe fermented foods. Examples include some miso, flavored yogurts, and soy sauce.
Beware of Cross-Contamination: For severe sensitivities, always choose products with a 'Certified Gluten-Free' label to avoid risks from shared manufacturing equipment.
DIY for Control: The safest way to ensure a fermented food is gluten-free is to make it yourself at home, with careful control over all ingredients and equipment.

The world of fermented foods is a treasure trove of flavor and gut-supporting probiotics, but for those with celiac disease or gluten sensitivity, navigating this landscape requires careful consideration. Simply because a food is fermented does not automatically make it gluten-free. The final product's status hinges on two primary factors: the original ingredients used and the risk of cross-contamination during manufacturing.

Fermentation Doesn't Eliminate Gluten

One of the most important facts to understand is that fermentation does not reliably eliminate gluten from products made with gluten-containing grains like wheat, barley, or rye. While fermentation involves microorganisms breaking down compounds, this process does not guarantee the complete degradation of gluten proteins to a level considered safe for those with celiac disease (below 20 ppm). In fact, testing fermented and hydrolyzed products for residual gluten is notoriously difficult because the proteins are broken into fragments that current testing methods may not accurately detect. This is why the FDA requires manufacturers to verify that the ingredients were gluten-free before fermentation took place if they want to label the final product as such.

Naturally Gluten-Free Fermented Foods

Fortunately, many popular fermented foods are naturally gluten-free because they are not made from gluten-containing grains. These are generally safe for a gluten-free diet, provided there is no cross-contamination.

Kombucha: Made from sweetened tea and a SCOBY (Symbiotic Culture of Bacteria and Yeast), kombucha is naturally gluten-free. Always check the label for any added flavorings that might contain gluten.
Yogurt and Kefir: Plain dairy-based yogurt and kefir are gluten-free as milk contains no gluten. Be cautious with flavored varieties or mix-ins, which might contain gluten-based thickeners or additives.
Sauerkraut and Kimchi: These are traditional fermented cabbage dishes. As long as the ingredients used are just vegetables, salt, and spices, they are naturally gluten-free. Soy sauce or other gluten-containing seasonings are a potential risk in some commercial brands.
Water Kefir: Made with kefir grains and sugar water, this bubbly beverage is another safe option.
Tempeh: While traditionally made from soybeans, some versions may include grain fillers like barley or wheat. Always check the packaging to confirm it is a pure soy or gluten-free grain variety.

Fermented Foods to Approach with Caution

Some fermented products require extra vigilance due to their ingredients or processing methods. These are not inherently gluten-free and can be dangerous for someone with celiac disease.

Sourdough Bread: Traditional sourdough uses wheat flour. While the fermentation process does break down some gluten, it does not eliminate it completely to safe levels. Only sourdough made with certified gluten-free flours like rice, buckwheat, or millet is safe.
Beer: Most beers are made from malted barley, a gluten-containing grain. Unless specifically labeled and certified as "gluten-free," beer is not safe. "Gluten-removed" beers use enzymes to break down gluten but are not safe for celiacs as residual fragments may remain.
Miso: Traditional miso is made from fermented soybeans and barley, so it contains gluten. Only miso made exclusively from rice or chickpeas (check labels!) is safe.
Traditional Soy Sauce: Most soy sauce is fermented using soy and wheat. Always opt for a gluten-free alternative like tamari, which is traditionally made with only soy, though checking labels is still prudent.

Comparison Table: Gluten-Free vs. Gluten-Risk Fermented Foods


Food Type	Naturally Gluten-Free?	Potential Gluten Risks	Key to Safe Consumption
Kombucha	Yes	Added flavorings or glutenous additives during secondary fermentation.	Read ingredient labels for additives.
Dairy Yogurt/Kefir	Yes (plain)	Added thickeners, fruits, or grains.	Choose plain and check mix-ins carefully.
Sauerkraut/Kimchi	Yes	Added seasonings like malt vinegar or traditional soy sauce.	Confirm ingredients are only vegetables and salt.
Traditional Sourdough	No	Made from wheat, barley, or rye.	Use only sourdough made with certified gluten-free flour.
Traditional Miso	No	Often contains barley; cross-contamination risk.	Select brands explicitly labeled 'gluten-free,' often made from rice or chickpeas.
Traditional Soy Sauce	No	Contains wheat used in the fermentation process.	Opt for a certified gluten-free tamari.
Tempeh	Depends	Some brands add gluten-containing grains as fillers.	Check the label for 100% soybean or certified gluten-free versions.
Beer	No	Typically brewed from barley. "Gluten-removed" not safe.	Only drink beer certified as gluten-free, made from naturally gluten-free grains.

The Importance of Avoiding Cross-Contamination

Beyond ingredient lists, those with severe sensitivities must also be aware of potential cross-contamination. This risk is especially high in facilities that produce both gluten-containing and gluten-free products. For example, some commercial brands of sauerkraut or pickles might be produced on the same equipment that processes other gluten foods. The safest choice is always to opt for products with a "Certified Gluten-Free" label, which guarantees they meet rigorous standards for both ingredients and production. For ultimate control, making fermented foods at home using dedicated equipment is a secure way to ensure their gluten-free status.

Conclusion: Navigate with Caution and Knowledge

While many fermented foods can be a healthy and delicious part of a gluten-free diet, a blanket assumption of their safety is a serious mistake. The key is to shift focus from the process of fermentation to the ingredients used. Always read labels, understand the base ingredients of your favorite fermented products, and be aware of cross-contamination risks. By doing so, you can safely enjoy the probiotic benefits and unique flavors that these foods offer without jeopardizing your health. When in doubt, search for products with trusted gluten-free certification or prepare them yourself to have full control over the process and ingredients.

Visit the Celiac Disease Foundation for more information on managing a gluten-free lifestyle.

Frequently Asked Questions

Yes, traditional kombucha is naturally gluten-free, made from tea, sugar, and a SCOBY. However, it's vital to check the label for any gluten-containing additives or flavorings, especially in secondary fermentation.

No, fermentation does not break down gluten to a reliably safe level (under 20 ppm) for individuals with celiac disease. Testing for gluten in fermented products is difficult, which is why the FDA requires pre-fermentation ingredient checks for gluten-free claims.

Traditional sourdough bread, made with wheat flour, is not gluten-free. You can, however, find or make sourdough bread using certified gluten-free flours, such as rice or buckwheat, which are safe for a gluten-free diet.

No, traditional miso is often made using a grain like barley, which contains gluten. To ensure it's gluten-free, purchase miso specifically labeled as such, as these are typically made from fermented rice or chickpeas.

The most reliable way is to look for a 'Certified Gluten-Free' label from a reputable organization. This indicates that the product and its manufacturing process have been verified to prevent gluten contamination.

You should avoid products made with gluten-containing grains or cross-contaminated ingredients. Specific examples include most beers, traditional soy sauce, and sourdough bread made with wheat flour. Always read labels carefully.

Plain yogurt is naturally gluten-free. Potential issues arise with flavored varieties that may use gluten-based thickeners or add-ins, so check the ingredient list carefully.