Coeliac disease, gluten and oats

There is no consistent answer among experts in different countries about whether you can safely eat oats if you have Coeliac disease or gluten intolerance, with some saying it is safe all the time, some saying safe for the majority and others yet saying it needs to be avoided.  Coeliac Australia has a position statement recommending that oats be avoided, so let’s have a look at oats, gluten and why there is disagreement.

What is gluten?

Most people think of gluten as the protein component of wheat, which is true, but that is a bit too simplistic.  The first point to clarify is that gluten is not a single protein or the only protein, but rather it is a mixture of cereal proteins, and there are other types of cereal proteins as well.  (Note: when I am talking about cereals here I mean grain, or grasses of the Poaceae family, not a boxed breakfast cereal.) Chemist Thomas Burr Osborne first classified plant proteins into 4 families in 1907 and that classification is still used today, and these are as follows:

  1. Albumins: soluble in water.
  2. Globulins:  soluble in salt solutions; e.g. avenalin of oat.
  3. Glutelins, insoluble in water and neutral salt solutions, but soluble in acidic and basic solutions; e.g. glutenins of wheat.
  4. Prolamins:  soluble in 70% alcohol solution, but not in water or absolute alcohol.  They include:
  • avenin of oats
  • gliadins of wheat
  • hordein of barley
  • kafirin in sorghum
  • orzenin in rice
  • secalin of rye
  • zein of corn

So when people say ‘gluten’, they are often referring to prolamins and specifically to gliadins as this is what is involved in Coeliac disease and gluten sensitivity.

Let’s have a look at the grass plant family and see if that helps make things clearer.

 

For most people, it is the Triticeae tribe which includes wheat, barley and rye that causes the problem.  The prolamins in oats (from the Avenae tribe) are a slightly different structure and that is why it is thought they may be safe.  However, go one level up and you can see the Triticeae tribe and the Avenae Tribe are both in the Pooideae subfamily and the promalins from all of this subfamily may induce Coeliac disease in those with a genetic predisposition and cause damage to the small intestine in those who already have Coeliac disease.

The amount of avenin in oats is lower than the amount of gliadin in wheat, and this, along with the different structure of avenin, may be the reason most people don’t have significant symptoms with oats.  The estimated percentage of grain protein that is made up of prolamins:

  • Wheat – Gliadin 69%
  • Barley – Hordein 46-52%
  • Rye – Secalinin 30-50%
  • Oats – Avenin 16%

In wheat the gliadins are further categorised into 4 types: alpha, beta, gamma and omega.  The gliadins are not of great nutritional value and the structure of the amino acids in the protein is what causes the immune reaction in Coeliac disease, and hence they are the most widely studied prolamin.  The gliadins link with each other and with the glutenins and this gives gluten the texture and stability to stretch and not fall apart.

So how do you know if you react to oats if you don’t have symptoms? (Remembering not everyone will have symptoms even when the villi lining their small intestine are being actively damaged.)

You don’t.  there isn’t a specific blood test for it and the only other option would be to oat lots of oats for 6 weeks and then have an endoscopy and small intestine biopsy, which seems a little extreme!

There is no test for gluten in oats (which is the prolamin, and in oats is called avenin – it’s ok, there isn’t a test at the end of this).   The current tests for gluten in food can measure gliadin, hordein, and secalin but not avenin, because it is that slightly different structure.  Accordingly, the Australian Food Standards Code prohibits the use of a ‘gluten free’ claim on oat containing products.

What happens in Australia is different to some countries such as in Europe and the USA where oats can be labelled and promoted as being gluten-free.    The other issue is that the oats may have been cross-contaminated with wheat, rye and barley, so that even if the oats are safe themselves, this now makes them unsafe.

The recommendation from Coeliac Australia is:

Evidence shows that uncontaminated oats are well tolerated by most people with coeliac disease. However, in
some people with coeliac disease, oat consumption can trigger a potentially harmful immune response.

Please note that the absence of symptoms when consuming oats does not necessarily indicate they are safe – bowel damage can still occur despite the absence of symptoms.

Short version: oats are not recommended if you have Coeliac disease.  If you have gluten sensitivity you may be able to enjoy oats or they may cause symptoms – a trial and error may help to work out if oats are right for you.

Okay, probably a good time for a lie-down or a bit of a hike to clear the head.

 

Further information

  • Coeliac Australia http://www.coeliac.org.au/
  • Shewry PR, Halford NG. Cereal seed storage proteins: structures, properties and role in grain utilization. J Exp Bot 2002;53:947-58. PMID__ 11912237.
  • Plant family chart:  Tanner, G. (2014). Gluten, Celiac Disease, and Gluten Intolerance and the Impact of Gluten Minimization Treatments with Prolylendopeptidase on the Measurement of Gluten in Beer. Journal of the American Society of Brewing Chemists 72(1):36-50 · 
  • Images: muesli – Alisha Hieb and hiking – Ali Inay
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Categories: Holistic health

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