Tamari and soy sauce both add a rich, salty, and savory flavor to foods. Both soy sauce and tamari are fermented soy products, but soy sauce includes wheat or wheat flour. While the two products have a similar flavor, tamari is appropriate for a gluten-free diet, but soy sauce generally is not. You may also find tamari labeled "gluten-free soy sauce" in some markets.

Depending on the brand, soy sauce may contain only soybeans, wheat and water, or it may have a number of additives, including caramel color, corn syrup, and monosodium glutamate. While gluten levels may be low in naturally fermented sauces, individuals with celiac disease should avoid the potential contamination of soy sauce containing wheat.

Tamari sauces typically contain only fermented soybeans and many brands are certified gluten-free. If you're on a gluten-free diet, you should always double check that you are purchasing a gluten-free tamari. Reduced sodium versions are also available, and some companies produce travel packets, making it easy to enjoy a safe soy sauce flavor on the go. The flavor of tamari is slightly milder than soy sauce, but you can substitute tamari in equal amounts for traditional soy sauce. Use tamari as a dipping sauce, in stir-fries or to flavor your favorite dishes.

Alongside the regular soy sauce in your market, you may find gluten-free soy sauce. Unlike tamari, gluten-free soy sauce is not made with 100 percent soybeans. Gluten-free soy sauce relies on a combination of rice and soybeans to create a product that closely mimics the taste of naturally fermented soy sauce. If your market does not carry tamari, you may find gluten-free options made by mainstream soy sauce manufacturers on the shelf as alternatives.

Soy sauce is a common ingredient and flavoring in recipes, packaged foods and restaurant meals. If you're eating out and need to avoid gluten, check to see that the soy sauce is gluten-free, or opt to carry your own in packets or a small bottle. Assume processed foods containing soy sauce contain gluten, unless they are specifically labeled gluten-free.