Almost daily, I see clients who know that gluten is an issue for them. They tell me that they have gone to heroic lengths to be gluten free. They are strict and dedicated to this path, and yet, mysteriously (and most unfairly) they still have symptoms. Then I review their diet details, and find that they are eating oats every day for breakfast, and sometimes also eating oat based "gluten free" snacks. I point out the presence of oats in their daily diet. They reply "that's OK, they are gluten free! It says so on the label!"
I groan inwardly, close my eyes, take a deep breath. This is not a fun conversation.
But it IS a frequent one. It is made necessary by the unfortunate marketing and labeling laws in the United States, as well as some basic misconceptions about what defines gluten and how the body responds to it.
Here's the deal. There is no such thing as a gluten free oat. All oats, no matter how they are processed or labeled, contain oat gluten. All spelt, no matter how it is labeled, contains spelt gluten. All barley, no matter how it is labeled, contains barley gluten. How can this be? Let me explain.
What is Gluten?
Gluten is the name of a group of proteins found in a wide variety of grains. Technically, gluten is made up of two proteins called gliadin and glutenin. These proteins are part of a larger chemical family called prolamins.
Ref: A.Balakireva, A. Zamyatnin. Properties of Gluten Intolerance: Gluten Structure, Evolution, Pathogenicity and Detoxification Capabilities. Nutrients 2016, 8(10), 644.
Most of the grains we eat are seeds from closely related varieties of grasses. Wheat, oats, barley, rye, spelt, triticale, kamut, and farina are all very closely related. If you see them in their unprocessed form, they are all tan colored, ellipsoid shaped grass seeds. They all contain gluten prolamins unique to their species (wheat gluten, oat gluten, barley gluten, spelt gluten, etc).
What makes this extra confusing is that the prolamins in different grains are named different things, even if they are in the gluten family. In wheat the gluten prolamins are called gluten, but in barley the gluten prolamins are called hordein, and in rye they are called secalin. As you can see above, oats are one step away from the main gluten containing group, but still make a prolamin (called avenin) that falls into the gluten prolamin category.
Oat Labeling loophole
In the United States, a product is allowed to be labeled "gluten free" if it contains less than 20ppm (parts per million) of wheat gluten. Gluten Free labeling laws are different in other countries. For example, oats are not allowed to carry a "gluten free" label in Australia or New Zealand.
Oats labeled "gluten free" are simply not contaminated with wheat gluten beyond the level of 20ppm. They are not avenin-free (that would be just as impossible as wheat being gluten free). Just like all wheat contains gluten, all oats contain avenin (aka. oat gluten).
So, there is no such thing as a gluten free oat.
There are oats that are contaminated with wheat gluten during processing and there are oats that are free from wheat gluten contamination. This is highly relevant for some folks, but less so for others, as we will discuss below.
Gluten Sensitivity and Celiac Spectrum
So what is the big deal with gluten anyway? Some people develop antibodies to gluten. There is often (but maybe not always) a genetic component to this. When a person has antibodies to gluten, consuming gluten will cause an immune mediated inflammatory response in the gut. Celiac disease is a severe version of this. In the case of Celiac, exposure to even small amounts of gluten causes so much inflammation that the microvilli of the intestines actually break off. This causes the loss of up to 75% of the absorptive surface of the intestines, leading to inadequate nutrient uptake. It is also possible to have other immune / inflammatory responses to gluten that do not cause detectable microvilli damage.
Interestingly, inflammatory responses to consuming gluten do not always cause intestinal symptoms. Gluten sensitivity reactions can manifest as skin rashes, headaches, psychological issues, fatigue and joint pain. Some people with gluten sensitivity experience digestive pain, some get diarrhea, some get heartburn, some get constipation or bloating. Some people have gut symptoms AND symptoms in other areas (joints, brain, skin), some only experience skin, brain or joint symptoms.
Is this really a problem for everyone?
No, not everyone is sensitive to gluten, wheat or grains. True Celiac disease is relatively rare, and is estimated to affect between 0.5 - 1% of people worldwide. I do see a LOT of people in my practice that have health issues that improve or resolve when removing gluten from their diet, so I would consider this gluten sensitivity. In my practice gluten sensitivity is very common (though still not universal). I think it is important to point out that I do not see a random sample of the population in my practice. I see people who are sick with difficult to diagnose or complex illnesses (these people are much more likely to have food sensitivities as part of their health issue). Knowing this, I would assume that half or less of the general population has some level of noticeable gluten sensitivity. I am always suspicious of gluten when people have chronic mood issues, chronic skin issues, chronic joint issues (in multiple, symmetrical joints), or chronic digestive issues.
In my clinical experience (and based on studies I've seen out of Australia and New Zealand) I would guess that about 50% of people with Celiac or that have non-celiac gluten intolerance, have a similar inflammatory reaction to avenin in oats. For those people, they must avoid oats just like they avoid wheat. The best way to determine this is to remove oats from the diet for 4-6 weeks, see if the symptoms resolve, then do a food challenge by eating "gluten free" oats to see if symptoms return. If you know you are gluten sensitive, but pass this test, then gluten free oats are probably safe for you. If your symptoms resolve when taking gluten free oats out of your diet, and return when you start eating oats again, then you are sensitive to avenin in the same way that you are sensitive to wheat gluten.