Can blood samples from active-CD patients be used to detect residual gluten-fragments in beer?
Sue Cane discusses new research by Laura Allred and colleagues which uses blood samples from coeliacs to test whether or not gluten-free beer genuinely is gluten free.
Unless you’re a scientist involved in testing food for allergens or someone with a particular interest in coeliac disease, you probably won’t have read of a small study on gluten-free beer that’s been published in the US.
The Celiac Patient Antibody Response to Conventional and Gluten-Removed Beer, funded by the Gluten Intolerance Group, might not have achieved a large amount of attention, but it has important implications, both in methodology and the detail of its findings.
There is much contention over the question of whether we have a scientifically-acceptable test that can accurately quantify the gluten content of fermented foods like beer (1,2), even though the competitive R5 ELISA, which is commonly used, is approved for this purpose by several international associations.
In this new study, Laura K. Allred et al obtain ground-breaking results by using blood samples from 31 people with coeliac disease (and a non-coeliac control group of 29), to see if their antibodies identify the residual gluten-fragments found in gluten-free beer.
Why is this research important?
The research is important for two reasons. Firstly, it validates the method of using coeliac-patient antibodies to assess the safety of hydrolysed and fermented products that can’t otherwise be tested in an accurate way; secondly, its findings could force us to re-evaluate the current declaration of barley beer as ‘gluten-free’, based as it is on the use of unsuitable methodology. (3)
Ordinary beer is difficult to test for gluten because during brewing, hydrolysation (4) and fermentation (5) break up gluten proteins so they become hard to identify. Usually characterised by long chains of amino acids, these proteins are broken into small fragments. Not only is their toxicity not fully understood (6), we know that some are not even identified by the common, commercially-available lab tests, which use a single antibody to look for a particular sequence of amino acids.
Why testing gluten-free beer is even more difficult
The gluten content of gluten-free beer (see note below) is even more problematic to quantify, as after fermentation it undergoes additional hydrolysis with an enzyme that specifically targets the protein sequence for which the test antibody is looking, breaking up the former, thus rendering the test useless. (3)
But this particular protein-sequence is by no means the only culprit in coeliac disease. Multiple amino-acid sequences can trigger a coeliac response and this can vary between individuals. What we don’t know is which they are in beer, or even how many types there are, which is why it’s so hard to design a test that identifies them (2).
In the US the FDA has not validated a test for use on hydrolysed or fermented foods, and in addition, the TTB (Alcohol and Tobacco Tax and Trade Bureau) does not allow the use of the term ‘gluten-free’ to describe beer made with barley (7). But in the EU it is common practice to use the R5 ELISA method to test beer (8), and despite its limitations it has been used in the UK in the gluten-free declaration of over 100 beers to date.
A new way?
Against this status quo, the Allred et al study might offer a new way forward.
Participants with untreated CD were chosen as only those consuming gluten make antibodies to it. This response goes away on a GF diet (which is why a gluten challenge is needed before diagnosis, if you’ve already given it up).
Participant serum was checked before the study to make sure it would demonstrate an antibody response to barley. Of the 7 patients who showed a response to hordein, 2 also reacted to the gluten-free beer, leading to the conclusion ‘a strong response from CD patients in the absence of equivalent reactions from normal control subjects would suggest that there are residual peptides in the product that may be specifically recognized by persons with CD.’ In lay terms, it’s likely these reactions are evidence of a CD-specific response to gluten-free beer.
The implications for coeliacs
This has implications for coeliacs who drink beer, particularly those who show no outward immunological-response to the ingestion of gluten. Anaemia and osteoporosis are often hidden signs of active, untreated CD (10) and the lack of perceived symptoms after drinking beer is categorically no guarantee of safety. It could indeed be the case that the preliminary findings from this study lead us to challenge the status of gluten-free beer and raise questions over whether it is indeed safe for coeliacs to drink.
In addition to this application to beer the Allred et al study offers new methodology for assessing the safety of other hydrolysed or fermented foods - products like soy sauce, which has so far resisted current methods of testing and is widely used throughout the food industry.
There are two types of ‘gluten-free’ beer. The first is naturally gluten-free and is brewed from grains such as sorghum and quinoa, which do not contain gluten. The second is made from barley, generally treated with an enzyme, and declared gluten-free after testing, in line with current FSA Guidance in the EU. It is only this barley-based beer, called ‘gluten-removed’ in the US, which is the subject of this article.
Thanks to Adrian Rogers of Romer Labs for help with the science.