Getting Closer to Gluten-Free Oats
By: Peter Olins, Ph.D. on June 18, 2011
People with celiac disease are continually asking if there is such a thing as “gluten-free oats”. The answer given by dietitians, doctors and scientists is “maybe”. While this is obviously an unsatisfactory answer for the individual seeking a gluten-free diet, it is based on different results from a large number of research studies.
In this article, I describe exciting results published in the latest issue of the scientific journal, Gut, which shed light on this controversy. This work should aid in the selection of oats for cultivation which have the best safety profile for the celiac patient.
For about the past 20 years, there has been a debate about whether oats are a safe food for celiacs, and a large number of clinical studies (Refs. 1,2) have given oats either a thumbs-up or a thumbs-down, based on whether a toxic response was observed after consuming oats.
According to the Canadian Celiac Association, 1/2 to 3/4 cup of “pure and uncontaminated” oats may be eaten daily by most celiacs, but a small number of patients may not be able to tolerate even this amount. The US Celiac Sprue Association is more cautious, and excludes oats from its recommended list of foods suitable for celiacs. This is unfortunate, since oats are a rich source of a variety of nutrients, plus they provide soluble and insoluble fiber, which can be lacking in a typical gluten-free diet.
There are many reasons why the clinical results may not be clear:
- Different sources/varieties of oats
- Too few patients were studied for a rare toxic reaction to be observed
- Measurements of “safety” differed from study to study
- People vary widely in their degree of reaction to gluten
- Contamination with other grains in the field
- Contamination during processing
Ref. 1: The molecular basis for oat intolerance in patients with celiac disease. PLos Medic. 2004;1:84-92. Arentz-Hansen, H., et al.
Ref. 2: Introduction of oats in the diets of individuals with celiac disease: a systematic review. Adv Food Nutr Res 2009;57:235-85. Pulido, O., et al.
No cross-contamination with other grains
This article describes recent work by Comino et al. (Ref. 3), a collaborative study from seven laboratories in Spain and Australia, designed to identify a variety of oats with the least risk of toxicity to celiacs. Previous studies suggested that the toxicity of oats in celiac patients may have actually resulted from contamination with wheat, barley, or rye, either during cultivation or processing. To eliminate such concerns, the authors used a sensitive DNA test to ensure that the oat samples were not contaminated with other grains. It may be useful to use similar DNA tests in future oat-toxicity research.
Ref. 3: Diversity in oat potential immunogenicity: basis for the selection of oat varieties with no toxicity in coeliac disease. Gut 2011;60:915-922 doi:10.1136/gut.2010.225268. Comino, I., et al.
Study comparing the immune-reactivity of nine varieties of oats
The authors used an antibody called G12 which binds strongly to the most toxic peptide in wheat gliadin (a component of gluten). Oats are a distant cousin of wheat, and the oat protein closest to wheat gliadin is called “avenin”. Avenin peptides were prepared from nine different oat varieties, and tested for how strongly they bind to the G12 antibody. A very wide range of binding strengths was observed; remarkably, avenin peptides from one oat variety (OF720) were over 250-fold less reactive with the antibody than the most reactive oat variety. In fact, the strength of binding was below the limit of detection. Likewise, OF720 peptides were over 10,000 times less reactive than those from wheat gluten.
Similar results were obtained using the “R5″ antibody, which is commonly used for measuring gluten contamination in foods. Using the R5 ELISA assay, the OF720 oats had a level of less than 5 ppm “gluten” which is well below the commonly accepted cutoff of 20 ppm for a gluten-free food.
Immunotoxicity of different varieties of oats
Avenin peptides were then tested for their ability to stimulate T-cells from the blood of celiac patients. This is a measure of how strongly these peptides are recognized as being “foreign”. Remarkably, avenin from oat variety OF720 showed no significant activity on the T-cells. Indeed, the activity of oat avenin was comparable to protein obtained from rice (a common part of a gluten-free diet). This may help explain some of the seemingly contradictory results from previous toxicity studies; clearly, the particular variety of oats chosen can have a profound effect on T-cell reactivity.
The G12 antibody described in this study should be a useful tool for testing which variety of oats may have the lowest chance of causing an immune response. The next step will be to give their best variety of oats to patients on a gluten-free diet to see if they are non-toxic.
How close are we to having oats that are safe for celiacs?
When someone asks is it possible to find “gluten-free oats”, for now, the answer is still “maybe”. Careful culture and processing will still be required, but the results of this latest study are very encouraging, and suggest that oat varieties such as OF720 should allow us to get closer to the goal of gluten-free oats in the future.