The Real Truth About Oats and Gluten

Are oats gluten-free? And, if they are gluten-free does that mean that they are safe for those with Celiac Disease? There are so much confusion and controversy around oats in the gluten-free community. There are three reasons for this:

  1. Risk of cross-contact with gluten-containing grains
  2. Individual variability
  3. Differing food labeling regulations
Are Oats Gluten Free?
Are Oats Gluten-Free?

Chemical Make-Up of Gluten

Before we dive deeper into these three reasons, it is important for us to understand the scientific definition of gluten.

Gluten: the complex mixture of seed storage proteins found in cereal grains wheat, rye, barley, oats, and their hybrids (example: triticale—a hybrid of wheat and rye)

  • Wheat, rye, and barley are closely related to one another
  • Oats are not as closely related to wheat, rye, and barley.

Gluten is a protein. Proteins are made up of amino acids. There are 20 amino acids, which are known to be the building blocks of proteins. Gluten proteins are described to be prolamins because they contain a large amount of the amino acids—glutamine and proline in their chemical structure (1).

What is prolamin?

The term prolamin is used to group together the proteins found in plants that contain large amounts of the amino acid proline. But not all prolamin found in plants contain gluten. Other examples of non-gluten grains that contain prolamin include corn and rice (1).

Gluten Prolamins
The image shows that prolamin (plant storage proteins high in the amino acid, proline) can be divided into two categories—gluten prolamins and non-gluten prolamins. Wheat, barley, and rye are closely related to one another. Yet, the prolamins of oats are different than the prolamins of wheat, rye, and barley. Corn (maize) and rice contain non-gluten prolamins.

Image Courtesy of Balakireva et al., 2016

The specific gluten proteins found in each of the gluten prolamins differ (1).

  • Wheat: Gliadin
  • Rye: Secalin
  • Barley: Hordein
  • Oats: Avenin

Among people with Celiac Disease gluten proteins found in the prolamins of cereal grains wheat, rye, and barley contribute to the damage of the small intestine. In addition, wheat has another non-prolamin gluten protein, glutenin that contributes to the damage of the small intestine (1, 2).

Is the prolamin in oats similar to that of wheat, rye, and barley?

The prolamins, avenin, in oats, is structurally different than the prolamins found in wheat, rye, barley because of two reasons (1):

  1. The prolamins in oats are lower in the amino acid, proline.  
  2. The total prolamin content of oats is 10-15% of total oat protein but wheat, rye, and barley can contain anywhere from 30-50% prolamin in their total protein content.

Are oats gluten-free?

Research conducted among individuals with Celiac Disease indicated that they had an auto-immune reaction towards the prolamins founds in wheat (and glutenin), rye, and barley but not oats. This led to the conclusion that oats are gluten-free (1, 2).

But that doesn’t answer if oats are safe for those with Celiac Disease because there is the risk of cross-contact with gluten-grains and individual variability.   

Risk of Cross-Contact with Gluten-Grains

Oats and Cross-Contact
Oats and Cross-Contact: three types of available oats in the market.

The main issue with oats and their safety of consumption for those with Celiac Disease is cross-contact. Cross-Contact is the unintentional transfer of gluten proteins to food from other food and/or surfaces. Cross-Contact of oats can occur at any point from the field to the production facility.

Examples of Cross-Contact:

  • Crops-Rotation: farmers grow oats one year and gluten-grains the next year
  • Proximity to Gluten Grains: oats tend to be grown next to wheat, barley, or rye.
    • These tend harvested at the same time with oats leading to potential contamination.
  • Transportation: oats may be transported along with other gluten-grains
  • Stored: oats may be stored along with other gluten-grain

3 Types of Oats in the Market Place

  1. Commercial oats: oats tend to be produced with crop-rotation and/or close proximity to gluten-containing grains.
  2. Mechanically and/or optically sorted oats: commercially grown oats are mechanically sorted and/or optically (visually) to ensure gluten-containing grains are not present.
  3. Purity protocol oats: no standardized definition (check with each supplier/manufacturer) but usually implies that oats are produced without crop rotation and proximity of gluten-containing grains.

All oats are technically gluten-free but their cross-contact with gluten-containing grains pose a particular level of risk.

Assessing the Safety of Commercial Oats

Commercial oats are not considered to be safe for those individuals with Celiac Disease because of the high-level cross-contact that occurs from field to production.

  • Individuals following a gluten-free diet because of Non-Celiac Gluten Sensitivity (NCGS) and/or other autoimmune disorders may be able to consume commercial oats without the exacerbation of their symptoms on a case by case basis.
  • More sensitive individuals with Non-Celiac Gluten Sensitivity may need to opt-for mechanically and/or optically sorted or purity protocol oats.

Assessing the Safety of Mechanically Sorted Oats

There are individuals with Celiac Disease that report symptoms after the ingestion of mechanically sorted oats. General Mills uses mechanically sorted oats to make Gluten Free Cheerios and Gluten Free Lucky Charms.

  • If you had symptoms to mechanically sorted oats this could be because they are contaminated due to the limitations of mechanical and/or optical sorting. However, the absence of symptoms from ingestion of oats among individuals with Celiac Disease does not mean that there is no intestinal damage.
  • The safety of mechanically and/or optically sorted oats among individuals with Celiac Disease may vary from individual to individual. Confirmation with intestinal biopsy is needed to ensure there is no individual variability.

Assessing the Safety of Purity Protocol Oats

There aren’t a lot of purity protocol oats available in the U.S. market, which is why manufacturers have to rely on mechanically and/or optically sorted oats to make gluten products.

  • A large majority of individuals with Celiac Disease will tolerate purity protocol oats; however, a small minority may be intolerant to it due to unknown individual variability. Confirmation with intestinal biopsy is needed to ensure there is no individual variability.   

It is important to note that there’s no way of knowing if gluten-free oats are mechanically and/or optically sorted or pure oats unless it is disclosed by the manufacturer. Third-Party agencies that certify gluten-free product do not take into consideration if oats are mechanically and/or optically sorted.

Individual Variability

The scientific community has been extensively researching the safety of oats in a gluten-free diet among patients with Celiac Disease to provide evidence-based recommendations. The initial confusion and controversy started with conflicting clinical findings.

Clinic research conducted among individuals with Celiac Disease sometimes suggested intolerance oats (protein avenin) while others indicated tolerance (3).

Conflict in Scientific Research

These reason for these conflicting observations could be because of two reasons (3):  

  1. A proportion of individuals with Celiac Disease are intolerant to oats (protein avenin).
  2. The oats used in the conducted clinical research were contaminated with gluten-containing grains.

A large majority of the initial research conducted to determine the tolerance of oats among individuals with Celiac Disease were not effectively designed by scientist because the oats used were contaminated with gluten. This limits our ability to compare and contrasts the results of studies because the types of oats used in the research design differed. The types of oats they used included (3):

  • Using commercial oats [contaminated with gluten-grains]
  • Using gluten-free [defined as 200 ppm] oats in research between the year 1979-2008
  • Using gluten-free [defined as 20 ppm] oats in research from 2008 onwards

A large majority of the research conducted on the safety of oats in the gluten-free diet used commercial and/or gluten-free [defined as 200 ppm] oats (3). It is probable that the clinical research findings reporting intolerance to oats tended to be highly contaminated with gluten, which led to the symptoms observed in patients.

Another reason why it is difficult to compare the research studies is that the outcome of individuals with Celiac Disease ingesting oats varied (3, 4). Some investigators reported:

  • Patient’s symptoms.
  • Serological changes in patient’s antibody levels.
  • Histological changes in the patient’s small intestine by conducting a biopsy.

The Consensus Based on the Current Scientific Research

Based on the current findings and limitations of current research regarding the safety of oats among adults and children with Celiac Disease is that non-contaminated oats are tolerated by a large majority of individuals with Celiac Disease (4).

Yet, there have been case reports of certain individuals with Celiac Disease being intolerant to confirmed gluten-free oats. In fact, the intolerance of these individuals has been confirmed by a small biopsy screening of the small intestine (5). It is unknown why a minority of individuals with Celiac Disease react to uncontaminated gluten-free oats.

There are only two ways to know your tolerance to oats is to consume pure protocol gluten-free oats and monitor your symptoms as well as follow up with your physician to ensure there is no small intestinal damage.

Differing Food Labelling Regulations

Oats and Gluten Free Labeling
Oats and Gluten Free Labeling Regulations

United States: FDA position is that oats can be labeled as gluten-free if the presence of gluten levels in the final product does not exceed 20 ppm.

  • No specific mentioning that oats have to mechanically and/or optically sorted or purity protocol oats.

Canada: Health Canada’s position is that oats can be labeled as gluten-free if the presence of gluten levels in the final product does not exceed 20 ppm.

  • No specific mentioning that oats have to mechanically and/or optically sorted or purity protocol oats.

United Kingdom/European Union: European Commission position is similar to that of the U.S. and Canada in that that oats can be labeled as gluten-free if the presence of gluten levels in the final product does not exceed 20 ppm.

Australia and New Zealand: Food Standards Australia and New Zealand states that oats are considered to contain gluten and to protect the health of individuals with Celiac Disease they cannot be declared to be gluten-free. Why?

  • Current tests for gluten cannot measure the prolamin fraction of oats. They can only measure the prolamin fraction of wheat, rye, and barley.
  • Individual variability has been reported among certain individuals.

What do you do?

  • Majority of individuals will tolerate certified (by third-party) gluten-free oats.
    • Third-Party certification is necessary because a mere “gluten-free” label on a food package does not indicate that it has been tested, which puts you at risk for cross-contact. This is important to avoid because oats are often high in cross-contact with gluten-containing grains.
    • These may be mechanically and/or optically sorted or purity protocol oats.
    • You can contact the manufacturer to find out the type of oats used.
  • Australia and New Zealand have strict regulations in place because the absence of symptoms with the ingestion of certified (by third-party) gluten-free oats does not mean that there is no intestinal damage occurring.
    • Intestinal Damage is the hallmark symptom of Celiac Disease.
    • Working with your physician would be important to determine if ingestion of certified (by third-party) gluten-free oats are safe for you.

Summary

  • Gluten is a complex plant protein that is found in the prolamin fraction of wheat, rye, and barley and glutenin fraction of wheat.
  • Oats are gluten-free if they are not contaminated with gluten-containing grains.
  • There may be individual variability among individuals with Celiac Disease on whether they can tolerate uncontaminated gluten-free oats due to unknown reasons.
  • The United States, Canada, United Kingdom, and the European Union can label oats gluten-free if the final products contain less than 20 ppm of gluten. Australia and New Zealand never label oats as gluten-free.

References

  1. Balakireva, Anastasia, and Andrey Zamyatnin. “Properties of Gluten Intolerance: Gluten Structure, Evolution, Pathogenicity and Detoxification Capabilities.” Nutrients, vol. 8, no. 10, 2016, p. 644., doi:10.3390/nu8100644.
  2. Vieille, Sébastien La, et al. “Celiac Disease and Gluten-Free Oats: A Canadian Position Based on a Literature Review.” Canadian Journal of Gastroenterology and Hepatology, vol. 2016, 2016, pp. 1–10., doi:10.1155/2016/1870305.
  3. Fritz, Ronald D., and Yumin Chen. “Oat Safety for Celiac Disease Patients: Theoretical Analysis Correlates Adverse Symptoms in Clinical Studies to Contaminated Study Oats.” Nutrition Research, vol. 60, 2018, pp. 54–67., doi:10.1016/j.nutres.2018.09.003.
  4. Pinto-Sánchez, María Inés, et al. “Safety of Adding Oats to a Gluten-Free Diet for Patients With Celiac Disease: Systematic Review and Meta-Analysis of Clinical and Observational Studies.” Gastroenterology, vol. 153, no. 2, 2017, doi:10.1053/j.gastro.2017.04.009.
  5. Hardy, Melinda Y., et al. “Ingestion of Oats and Barley in Patients with Celiac Disease Mobilizes Cross-Reactive T Cells Activated by Avenin Peptides and Immuno-Dominant Hordein Peptides.” Journal of Autoimmunity, vol. 56, 2015, pp. 56–65., doi:10.1016/j.jaut.2014.10.003.
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