Gluten is the name for the protein in grains. All grains contain protein that is theoretically gluten but people with celiac disease and most other gluten allergies only react to the form of gluten found in wheat (including spelt, kamut, triticale and all varieties of wheat), barley, and rye.
While it’s not really correct to refer to other grains as “gluten-free,” they are free from the form of gluten found in varieties of wheat, barley, rye, and their derivatives and are safe for people with celiac disease and most gluten intolerances.
Products that may be used in a “gluten-free” diet include amaranth, arrowroot, buckwheat, chickpea (garbanzo) flour, corn, flax, millet, potato starch or flour, quinoa, rice (rice bran and flour), sago, sorghum, soy, tapioca, and teff. While oats do not contain the form of gluten that can not be used by people who are sensitive to the gluten in wheat, barley, and rye, it is often processed on the same equipment as is wheat so it is important to look for oatmeal that is labeled gluten-free.
Grains and grain products that should not be included in a “gluten-free” diet because they contain the form of gluten not safe for people with celiac and most gluten intolerances or have a high chance of cross contamination in their production include barley, barley malt or extract, bran, bulgur, couscous, durum, farina, faro, kamut, malt, matzo flour or meal, orzo, panko, rye, seitan, semolina, spelt, triticale. udon, wheat, wheat bran, wheat germ, or wheat starch. It is always important to read product labels. Some products such as soy sauce and other seasonings and sauces contain wheat.
Whole grains are an important part of a healthy diet and a gluten-free diet has no health-related benefit for people who do not have celiac disease or a gluten intolerance.