Yes, most traditional soy sauce contains gluten because it is made from fermented soybeans and wheat. However, gluten-free soy sauce options are widely available, made without wheat or with a gluten-free grain like rice.
What Is Soy Sauce Made Of?
Soy sauce is a liquid condiment of East Asian origin, traditionally produced by fermenting soybeans with roasted grain, water, and salt. The grain is almost always wheat, which serves as a food source for the fermentation culture (typically Aspergillus mold) and contributes to the sauce’s distinctive aroma, sweetness, and depth. The classic Japanese version, shoyu, uses roughly equal parts soybeans and wheat. Chinese light and dark soy sauces also commonly include wheat flour or wheat berries.
Because wheat is a primary ingredient, conventional soy sauce is not gluten-free. The fermentation process breaks down many proteins, but it does not eliminate the gluten proteins from wheat. Tests on regular soy sauce typically show gluten levels well above the 20 parts per million (ppm) threshold that the U.S. Food and Drug Administration (FDA) allows for a food to be labeled “gluten-free.�
How Gluten Gets Into Soy Sauce
Gluten enters soy sauce in two ways:
- As a primary ingredient: Wheat is intentionally added to the fermentation mash. This is the standard for most Japanese, Chinese, and Korean soy sauces.
- As an additive: Some cheaper or mass-produced sauces add wheat-based hydrolyzed soy protein or caramel color derived from wheat to speed up production or adjust flavor and color.
Even if a soy sauce is labeled “wheat-free,� it may still contain barley or rye, which also contain gluten. Always check the ingredient list and look for a gluten-free certification to be safe.
Gluten-Free Soy Sauce Options
Several types of soy sauce are naturally gluten-free or specially made without wheat:
- Tamari: A Japanese soy sauce made with little or no wheat. Traditional tamari is made with soybeans only, though many commercial tamari brands add a small amount of wheat. Look for “gluten-free tamari� on the label—major brands like San-J and Kikkoman offer certified gluten-free versions.
- Coconut aminos: A soy-free, gluten-free sauce made from fermented coconut sap. It has a similar salty-sweet flavor but is thinner and slightly less savory than soy sauce.
- Liquid aminos: Made from soybeans but not fermented; usually gluten-free, but check the label because some brands add wheat.
- Homemade or specialty gluten-free soy sauce: Some small producers make soy sauce from soybeans and rice, such as tamari made with rice koji.
When choosing a gluten-free soy sauce, always verify the label. Even a product that says “no wheat� may contain barley, and only a “gluten-free� claim or certification guarantees it meets the FDA standard of less than 20 ppm.
How to Choose a Safe Soy Sauce
If you have celiac disease or a gluten sensitivity, follow these steps:
- Check the ingredient list for wheat, barley, rye, or malt.
- Look for a “gluten-free� label. In the U.S., this means the product contains less than 20 ppm of gluten.
- Be aware that “low sodium� or “reduced sodium� soy sauces may have different ingredients; always check.
- When dining out, ask the restaurant what brand of soy sauce they use. Many restaurants use regular soy sauce, but some offer gluten-free tamari upon request.
Common Problems: Hidden Gluten and Cross-Contamination
The biggest risk for gluten-sensitive individuals is hidden gluten. Soy sauce is a common ingredient in marinades, salad dressings, sauces, and even some spice blends. A dish that seems safe, like a grilled chicken breast, may be brushed with soy sauce before cooking. Additionally, cross-contamination can occur in restaurants if the same oil or pan is used for gluten-free and regular soy sauce.
Another issue is that some products labeled “soy sauce� may be made with wheat-based hydrolyzed vegetable protein (HVP), which is a common flavor enhancer. HVP is often derived from wheat, so it contains gluten. Always read the full ingredient list, not just the front label.
Gluten-Free Soy Sauce Substitutes
If you need a gluten-free alternative to soy sauce, you have several options:
- Gluten-free tamari: The closest in flavor to traditional soy sauce, with a slightly richer taste.
- Coconut aminos: A good soy-free option, though it is sweeter and less salty. Use a bit more salt if needed.
- Fish sauce: Made from fermented fish, it is naturally gluten-free, but it has a strong, pungent flavor that is not a direct substitute in all dishes.
- Miso paste thinned with water: Miso is usually gluten-free (check the label), and when diluted, it provides a savory, umami-rich liquid.
When substituting, note that gluten-free tamari is the easiest 1:1 swap in most recipes. Coconut aminos are less salty, so you may need to adjust seasoning.
Cost and Availability
Gluten-free soy sauce and tamari are widely available in most grocery stores, especially in the Asian foods or health food sections. They are also easy to find online. The cost is typically 20–50% higher than regular soy sauce, but the price difference is modest for most home cooks. A 10-ounce (296 ml) bottle of gluten-free tamari usually costs between $3 and $6, while a similar size of regular soy sauce might cost $2–$4.
Safety and Storage
Soy sauce, whether gluten-free or not, is a fermented product and is shelf-stable until opened. Once opened, it should be refrigerated to maintain flavor and quality, though it will not spoil quickly at room temperature. The FDA does not require refrigeration, but most manufacturers recommend it. Unopened, soy sauce can last for years. Opened, it will keep for about 6 months in the refrigerator. Always check for off smells or mold, which are signs of spoilage.
Frequently Asked Questions
Is Kikkoman soy sauce gluten-free?
Kikkoman’s regular soy sauce contains wheat and is not gluten-free. However, Kikkoman makes a specifically labeled “Gluten-Free Tamari Soy Sauce� that is brewed without wheat and is certified gluten-free.
Can I use soy sauce if I have celiac disease?
You should only use soy sauce that is labeled gluten-free. Regular soy sauce contains wheat and can trigger symptoms in people with celiac disease. Gluten-free tamari is a safe alternative.
Is tamari always gluten-free?
No, not all tamari is gluten-free. Traditional tamari is made with only soybeans, but many commercial brands add a small amount of wheat. Always check the label for a gluten-free certification.
Does cooking soy sauce remove gluten?
No. Gluten proteins are heat-stable and are not broken down by cooking. If a sauce contains gluten, cooking it will not make it safe for someone with celiac disease.
What does “wheat-free� mean on a soy sauce label?
“Wheat-free� means the product does not contain wheat, but it may still contain barley or rye, which also contain gluten. Only a “gluten-free� label ensures it is safe for a gluten-free diet.
Is soy sauce gluten-free in Japan?
Traditional Japanese soy sauce (shoyu) contains wheat. However, gluten-free tamari is also produced in Japan and is available for those who need it. Always check the label, even when buying in Japan.
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