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When it comes to eating a gluten-free diet, most of the information out there about which grains to avoid is pretty cut and dried (see our comprehensive list of gluten-free foods). Maybe you've noticed, though, that oats are a little bit of a gray area. For example, a gluten-free oat recipe will call specifically for gluten-free oats, which begs the question: are oats naturally gluten-free?
The short answer is, oats are naturally gluten-free, but they're often grown in a way that leads to cross-contamination. "Oats are considered a naturally gluten-free grain," says Tricia Thompson, M.S., R.D., author of Celiac Disease Nutrition Guide. The problem, she says, is that they're often grown in fields alongside wheat, barley and rye, all of which are gluten-containing grains.
"It is likely that there will be errant wheat, barley or rye grain growing in the oat field that will be harvested along with the oats," Thompson says. "And, the same harvesting, transporting and storing equipment and facilities may be used for oats as well as for wheat, barley and rye. All of these factors contribute to the presence of wheat, barley and rye grain in standard oats." There's research to back this up too—a 2011 study of 133 commercial oat samples found that 88 percent of them contained a level of gluten above 20 parts per million, which is the FDA's limit for foods labeled gluten-free and considered safe for those with celiac disease.
"Folks with celiac disease and gluten-related disorders should avoid oats and oat products not labeled gluten-free," Thompson warns. But there are plenty of gluten-free options available, likely at your local grocery store. "Oats labeled gluten-free must contain a level of gluten below 20 parts per million," she says. These oats are grown according to a purity protocol that keeps them separate from gluten-containing grains from the time they're planted to when they're packaged. So, oats labeled gluten-free are a safe bet.
That said, if you have celiac disease and find that even gluten-free oats trigger symptoms like abdominal pain and bloating, it might be that you're reacting to avenin, another protein found in oats. A 2016 study found that only a very small percentage of people with celiac disease have any negative reaction to avenin, but if you do find that you react badly to oats, bring it up with your doctor or a registered dietitian.
Like conventionally grown oats, gluten-free oats come in several forms (get our best tips for making oatmeal the right way). Steel-cut oats are oat groats that have simply been cut into pieces; these take about half an hour to cook on the stove and have lots of texture. Rolled or old-fashioned oats are oat groats that have been cut into pieces, steamed and then flattened; these take about five minutes to cook on the stove, and are what most recipes call for. Quick or instant oats are the most processed kind, and are basically old-fashioned oats that have been chopped so they cook faster; they only take about a minute to cook on the stove, but they don't have much texture.
Whatever type of oat you like best, you can find it gluten-free. Thompson recommends Avena Foods, GF Harvest, Montana Gluten-Free and Glanbia Nutritionals because they have strict processing and testing standards. Thrive Market and Bob's Red Mill are two other widely available brands that you can look for. Even Quaker Oats makes gluten-free oat products—but you'll need to specifically look for gluten-free on the label.
If you're worried about eating oats on a gluten-free diet, don't be. Just look for the gluten-free label (as always) and cook your oats as usual.