Oats: Do They or Don’t They Belong in a Gluten-Free Diet?

By Jodi Friedlander, N.C.
November 10, 2013

Are you confused as to whether oats, even those that are certified gluten-free, can be tolerated by people with celiac disease and other forms of gluten sensitivity? If so, you’re in good company, as there’s quite a bit of controversy surrounding this topic. No matter where one looks, whether it’s some of the online gluten forums or the scientific research, there is little agreement and a lot of confusion. Some people with celiac disease tolerate oats very well; some do not. The same holds true for others who experience non-celiac gluten sensitivity (NCGS), which is in itself a confusing and only recently acknowledged medical entity. In fact, despite how much we hear about it in the media, very little is known about NCGS, and research into it is in its early stages. As for oats, there’s much to be learned here, too.

First, let’s take a quick look at why gluten itself can be so problematic. Comprised of two protein groups—gliadin and glutenin—gluten gives wheat its strength, malleability, and the elasticity that allows it to rise. The gliadin portion, which is a type of prolamin (a group of simple proteins), is the source of the intestinal damage seen in celiac disease—the autoimmune reaction to gluten. Gliadins are subdivided further into four groups—alpha, beta, gamma, and omega. All can elicit immune responses, though the alpha portion is considered to be the most inflammatory. However, the other gliadins, and glutenin too, have all demonstrated the ability to elicit the autoimmune reactions seen in celiac disease. It is currently not known which component(s) elicit reactions in NCGS.

Prolamins are basic grain-derived proteins and most notably are found in wheat (including kamut and spelt), barley, and rye, and to a lesser extent in oats. Though they have their own specific names (the prolamin in oats is called avenin), they are often all referred to as gluten. This is, however, technically incorrect, as prolamins constitute only a fraction of what we call gluten. There are several different strains of oats, as there are with all grains. These strains differ in their content of avenin and, therefore, in their effects on celiac patients. Oats are currently divided into three categories based on these effects: non-toxic, medium-toxicity, and high-toxicity (Real et al., 2012).

Oat and wheat prolamins vary quite a bit, but they also have much in common. Avenin proteins are comprised of both gliadin-like and glutenin-like peptides (chains of amino acids), though these comprise only 12-14% of the total protein content of the grain. While the total prolamin content of the cultivars of oats in the study by Real et al. (2012) was similar, some of them contained far more alpha and gamma gliadin-like proteins, closely resembling those of wheat. So, some celiac patients who react to oats may be reacting to avenin’s similarity to wheat gluten; others have indeed been shown to be sensitive to the avenin itself (Real et al., 2012). But even in these people, oats may or may not affect them, depending on the levels of avenin in their chosen strains of oats (non-celiacs have not been tested).

And then, what if some reactions are not about gluten at all? FODMAPs stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols, all of which represent food components (short-chain carbohydrates) that are poorly absorbed and rapidly fermented by gut bacteria. They can cause gastrointestinal discomfort, such as gas and bloating and stool changes, and are often associated with the symptoms that are typical of irritable bowel syndrome (IBS), for which a low-FODMAPs diet has proven to be quite effective (Staudacher, Lomer, Anderson, Irving, & Whelan, 2011). The maldigestion and malabsorption that ensue can also lead to symptoms of fatigue and brain fog, as well as to nutrient deficiencies from malabsorption (Food Intolerance Diagnostics, 2012). This constellation of symptoms is also typical of gluten sensitivity of any type.

FODMAPs are found in foods that contain:

  • Lactose, in dairy products
  • Fructose, in its free form, so generally in sweeteners such as high fructose corn syrup and agave nectar
  • Fructans in certain grains, onions, and garlic
  • Galactans, in beans and lentils
  • Sugar alcohols (polyols), such as mannitol, maltitol, sorbitol, and xylitol

People with IBS can be sensitive to all groups, but sensitivity can also occur to a single group and to anyone, not just those with IBS. Of particular interest to the topic of gluten is the fructan group—a subset of fructose—which includes wheat, barley (in large quantities), rye, kamut, and spelt, as well as several other plant foods, the greatest amounts provided by the onion family, artichokes, and garlic. Supplemental inulin fructo-oligosaccharides, marketed as a food source for our beneficial gut bacteria, are also a type of fructan. For most people, when consumed in average daily dietary amounts of 20-60 grams, fructans do not cause symptoms. However, approximately 70% of IBS sufferers are fructan-sensitive, as are about 30% of healthy adults (Food Intolerance Diagnostics, 2012). Oats reportedly do not contain fructans, nor are they restricted on the low-FODMAPs diet. If someone appears sensitive to gluten but not to oats, it’s not going to be clear whether the reaction is to gluten or to fructans. Only a food elimination and re-challenge protocol will make this clear.

A recent study demonstrated that in a group of IBS patients with self-reported non-celiac gluten sensitivity, all study subjects noted significant symptom reduction when eating a low-FODMAPs diet. All had symptom recurrence when challenged with gluten, as expected, but they all also reacted to whey protein, which contains lactose; their symptoms could not be traced to gluten (Biesiekierski et al., 2013). This alerts us to the possibility that non-celiac gluten sensitivity symptoms may sometimes be related to other factors (carbohydrate fractions, not proteins) and that deeper investigation may be warranted.

Let’s return to the question of whether oats can be consumed by people with celiac disease and NCGS. Unfortunately there’s no pat answer, as oats can present their own set of problems, and as of now, there’s no way to ascertain how much avenin is in even certified gluten-free oats. The more prudent choice would be to simply stay away from oats until such time as non-toxic-verified varieties are made available. Alternately, one could initiate a test with a one-month complete elimination of oats, followed by a challenge of eating two to three servings of oats in one day. Wait up to three days for symptoms to emerge. If you don’t experience symptoms, your current batch of oats is probably just fine for you to eat, but remember that each batch can be different, and that the next one may not be so benign. Keep in mind that there are plenty of delicious grains available that can replace those morning oats. Quinoa, buckwheat, brown rice, and millet are all as satisfying at breakfast as they are at dinner. Eating for Health invites us to include diversity in our food choices to increase our nutrient intake and to help us reduce the likelihood of creating new food sensitivities. Who knows? Another grain may become a new favorite, eliminating the need to worry about those questionable oats.


Biesiekierski, J.R., Peters, S.L., Newnham, E.D., Rosella, O., Muir, J.G., & Gibson, P.R. (2013, Aug). No effects of gluten in patients with self-reported non-celiac gluten sensitivity after dietary reduction of fermentable, poorly absorbed, short-chain carbohydrates [PDF]. Gastroenterology, 145(2): 320-8,e1-3. doi:10.1053/j.gastro.2013.04.051

Food Intolerance Diagnostics. (2012 copyright). Fructose (fruit sugar), fructan and other fructo-oligosaccharide intolerances. Retrieved from http://www.foodintolerances.com.au/food-intolerances-fructose.aspx

Real, A., Comino, I., de Lorenzo, L., Merchán, F., Gil-Humanes, J., Giménez, M.J., … Pistón, F. (2012). Molecular and immunological characterization of gluten proteins isolated from oat cultivars that differ in toxicity for celiac disease [Full text]. PLoS One, 7(12): e48365. doi:10.1371/journal.pone.0048365

Staudacher, H. M., Lomer, M. C. E., Anderson, J. L., Irving, P. M., & Whelan, K. (2011, Nov). Impact of a diet low in fermentable carbohydrates on gastrointestinal symptoms, stool output and faecal pH in patients with irritable bowel syndrome: A randomised controlled trial [PDF]. Proceedings of the Nutrition Society, 70(OCE5): E293. doi:10.1017/S0029665111003788

University of Arizona (UAW). (2011, Jul, revised). The Low FODMAPs Diet. Retrieved from http://www.health.arizona.edu/health_topics/nutrition/handouts


The University of Arizona reference contains a valuable chart of high-FODMAPs foods and alternative choices: http://www.health.arizona.edu/health_topics/nutrition/handouts