Gluten sensitivity – we hear it everywhere these days, and with good reason. It is estimated that one in every 250 people in the Western world suffers from celiac disease, defined as “a condition in which the small intestine fails to digest and absorb food due to sensitivity of the intestinal lining to gluten, and causes atrophy of the digestive and absorptive cells of the intestine.”
There are many more individuals without this “official” diagnosis who are sensitive to gluten, either clinically or sub-clinically. At this point, it is common practice to tell gluten-sensitive people to avoid gluten-containing grains such as wheat, barley, rye and sorghum.
As gluten awareness has grown in recent years, so has the controversy over one common grain: oats.
The question of whether or not oats are a safe option for gluten sensitive people has been a subject of debate for over 20 years. Conflicting information also exists in scientific literature and among practitioners as to whether or not oats actually contain gluten.
The honest answer is, "it depends." There are wide range of different oat cultivars, each with its own profile of starches and proteins, to which people may or may not be sensitive. Some cultivars appear to be safe, even for people with frank celiac disease. Others induce strong reactions. The problem is that for the most part, it is difficult for anyone to know which types are being used in a given oat-containing product.
A brief scan of professional opinion underscores the confusion. For example, Liz Lipski, PhD, a well known expert on digestive disorders and director of the Nutrition & Integrative Health programs at Maryland University of Integrative Health, holds that oats themselves contain no gluten but are subject to cross contamination during harvest and processing.
Contamination or Cross-Reactivity?
She goes on to say that people with celiac or even non-celiac gluten intolerance typically have a leaky gut, and may experience cross reactivity to other foods and grains….whether they are gluten-containing or not.
Peter Osborne, DC, known popularly as the Gluten Free Warrior, states on his website that oats are a problem because they do contain gluten, albeit a different kind of gluten than wheat, barley, and rye, but gluten nonetheless.
Yet a 2011 FDA publication, “Health Hazard Assessment for Gluten Exposure in Individuals with Celiac Disease,” clearly states that gluten is found only in wheat (Office of Food Safety, Center of Food Safety and Applied Nutrition, Food and Drug Administration (FDA publication NUCM264150)).
Part of the problem is that gluten itself is loosely defined, and use of the term varies among researchers and health advocates.
This is the definition of gluten given in a 2012 study that isolated the proteins found in gluten: "Gluten is a mixture of polypeptides (proteins) found in cereal grains: wheat, barley, rye, oats. The gluten in wheat is made up of two components: gliadin which is ethanol-soluble, and glutenin which is insoluble."
There are ethanol-soluble components in barley called hordeins, and in rye called secalins. In oats, the ethanol-soluble components are known as avenins. Avenins, hordeins, and secalins are known as prolamins because they contain a large proportion of the amino acids proline and glutamine.
The divergent vocabulary add to the confusion surrounding oats and whether or not they are safe on a gluten-free diet. In addition, avenins have not been studied nearly as much as gliadins. For the purposes of this article, we will consider oats naturally gluten-free and gluten as the storage protein found only in wheat.
Why worry about oats, anyway? Can’t they just be eliminated from a gluten free diet, as are other grains?
Nutrient-Rich & Comforting
First there is a quality of life factor. Individuals who have had to give up bread and other familiar foods enjoy having a warm, filling bowl of oatmeal. Of greater importance may be the nutritional value of oats. Besides being a source of soluble fiber, oats are a good source of iron, thiamin, magnesium, phosphorous, and manganese. Oats also contain antioxidants and may help keep LDL-cholesterol at a healthy level (Fric P, et al. Nutr Rev. 2011: 69(2):107-15).
Because of these obvious health benefits, one may be tempted to recommend gluten-free oats to celiac patients. These are oats that are certified and tested by a third party as being free from contamination by gluten-containing grains.
Yet there is evidence that even gluten-free oats can cause celiac-like symptoms in gluten sensitive people. A randomized, double blind study was done in 2014 involving children with celiac disease. The goal was to determine the effect, if any, that gluten-free oats would have on gut bacteria.
Thirty-four of the children ate a standard gluten-free diet without oats for one year; the other group of thirty-seven children ate a similar diet but included oats that had been certified gluten-free. After a year, the levels of short chain fatty acids (SCFA) were measured in fecal samples from each group.
The kids eating the oats had significantly higher levels of SCFAs in their feces. Researchers concluded that, since SCFAs are produced by gut bacteria and that higher levels of SCFA indicate gut inflammation, the gluten-free oats negatively affected the gut bacteria of these children (Tjellstrom B, et al. Alimentary Pharmacology and Therapeutics, 2014 39(10):1156-1160).
Another 2014 study of similar design assessed the effect of gluten-free oats on the immune status of the intestines in children diagnosed with celiac disease. The group of 15 children who consumed gluten-free oats had a significant increase in natural killer cells and inflammatory cytokines in the intestinal mucosa over the group of 13 children who did not eat any oats. Intestinal biopsies showed that the group eating oats also had greater intestinal permeability (Sjoberg, V, et al. Clinical and Translational Gastroenterology. 2014:5(6); e58).
A 2004 study involved 39 adults diagnosed with celiac disease. Twenty-three consumed a gluten-free diet including 50 grams of oats daily, while 16 followed the same gluten-free diet minus the oats. The oat-eating group had more inflammatory intestinal symptoms and also an increase in lymphocytes in the small intestine (Peraaho, M, et al. Scand J Gastroenterol. 2004; 39(1): 27-31).
That said, several other studies on adults have shown that some celiac patients can eat oats for years and experience no adverse symptoms (Kaukinen, K., Collin, P., Huhtala, H., Maki, M. Nutrients. 2013 5(11): 4380-4389)
Diverse Cultivars, Different Effects
Conflicting studies and confusion among celiac patients as to oat safety may be due to differences in the oats themselves. This will be apparent in reviewing a 2012 analysis of oat cultivars. Researchers undertook a comprehensive analysis of different cultivated varieties of oats to determine which, if any, produced a response similar to gliadins in celiac patients.
The toxicity of the oat varieties may be determined by differences in their protein sequences. When wheat proteins are broken down in the gut, they bind to histocompatibility leukocyte antigen (HLA) molecules. The inflammatory response seen in the small intestine is caused by stimulation of the T-cells by these HLA molecules (Real A, et al. PLoS One. 2012;7(12).
During the analysis the researchers learned that one of the antibodies produced by the T-cells, known as the G12 antibody, recognized avenin in the oat varieties via cross-reactivity. The reactions of the T-cells to different cultivars were grouped in to high, medium, and no reactivity. This enabled researchers to classify different types of oats by level of toxicity to patients with celiac disease as low, medium, or high toxicity.
Therefore a patient would not only want gluten-free oats, he would need to somehow make sure he was eating only the cultivars of oats that showed low reactivity.
Unfortunately, right now there’s no simple way for consumers to know which oat cultivars are used in the various oat-containing foods on the market.
In theory, some types of oats may be perfectly safe for GF people, but practically, there’s no way to know.
Non-reactive varieties of oats will need to be produced on a large scale, and researchers will have to work with clinicians, patient advocates, regulators and food manufacturers to develop a labeling system based on protein sequencing may be developed.
Such a shift will require more research on sustainable methods for production, testing, and marketing of these oat strains. Until then, it may be advisable for practitioners to steer their celiac and gluten-sensitive clients away from oats entirely, even if they are certified gluten-free.
Cara Lynch is a systems analyst in the food industry, and recently completed her Masters of Science in Nutrition & Integrative Health at the Maryland University of Integrative Health.