UPDATED 7/8/13 TO REFLECT FURTHER RESEARCH
This keeps coming up in discussions here, so I'm hoping I can clarify some things about clarity ferm and "reduced-gluten" beers, such as Omission and Daura.
Background: I'm an acupuncturist in California, where an acupuncture license requires a 4-year education, culminating in a Master's of Science, which covers enough mainstream medicine to allow us to be licensed as primary care providers. We can order and read lab tests, and refer appropriately to specialists. I'm not a doctor, but I know an awful lot about pathophysiology, and I've spent a long, long time surveying the scientific literature on gluten testing, gluten sensitivity, and specifically gluten in beer. I am always continuing my research, and expect that I may need to update this periodically.
So, for starters, let me say that "gluten intolerance" is a tremendous and unfortunate misnomer, as the intact gluten and gluten-like proteins are NOT the culprit in any known pathology included under this umbrella term. Rather, the culprit is prolamine molecules like gliadin, hordein, secalin, and occasionally avenin, and in the case of celiac disease, specific peptide sequences found in those molecules.
Let's break down the variety of pathophysiological mechanisms by which proteins from wheat, barley, rye, etc. can cause gastrointestinal symptoms. Celiac disease is the best-known and most-studied. While it is commonly stated that celiac disease is caused by a reaction to gluten and gluten-like compounds called prolamines, it is ultimately caused by a handful of peptides within those proteins. Specifically it appears to be a handful of "glutamine residues" being acted upon by tissue transglutaminase, an enzyme naturally occuring in the gut, turning them into a compound that provokes an immune response. All prolamines contain both proline and glutamine--that is the source of their name, PROline-glutAMINE. In other words, it's not the whole gluten molecule that is the problem, it's a small component of it. Sources: http://jem.rupress.org/content/195/5/643.abstract
But I'm getting ahead of myself. Celiac disease is but one of a few pathologies responsible for wheat/barley-related gastrointestinal distress. Non-celiac gluten intolerance is another one, which is studied and understood rather poorly compared to celiac disease. One thing is known for certain, and that is that gliadin--a component of gluten--does alter the permeability of intestinal mucosa in certain patients, which can increase exposure to any number of antigens that may be present in the diet (but which would not be problematic were the intestinal barrier functions intact). There are also as-of-yet untested hypotheses that gluten can alter intestinal motility in sensitive patients and generate IBS-like symptoms. Alcohol is known to exacerbate these effects.
However, there is another pathology--the allergic response--which is an important consideration as well. While gluten and gliadin specifically can trigger allergic responses to wheat, the main protein in barley that seems to trigger the allergic response is known as Lipid Transfer Protein 1--the same protein that is responsible for rendering barley-based beers "heady". If you get a rash following shortly after consuming a barley-based beer, and it goes away within a day, that is a sign of an allergic reaction. The rash associated with celiac disease, dermatitis herpetiformis, does not come and go that quickly, and can take up to two years to resolve after the adoption of a gluten-free diet.
Now, what does all this have to do with Brewer's Clarex, aka ClarityFerm? ClarityFerm is what is known as a "proline-specific endoprotease", meaning it is an enzyme that hydrolyzes ("cuts apart") proline specifically, while sparing other proteins. Proline is the main protein implicated in the formation of "chill haze" in beer, and Brewer's Clarex hit the market originally as a way to ensure beer remains clear after sitting in the fridge for a long time. It hydrolyzes hordein by breaking apart the proline into its component peptide groups--break the proline, break the hordein. Simple. So far in my research, nothing I've read suggests that a proline-specific protease will hydrolyse glutamine. HOWEVER, malted barley itself contains an enzyme capable of hydrolyzing glutamine, EP-B2, which has been isolated and marketed as a supplement "Glutenase" to help protect celiac sufferers from inadvertent exposure (see here
). Why this enzyme does not naturally render all beer safe for celiacs, I haven't figured out yet; I suspect it has something to do with temperature and/or the solubility of prolamines. But it is the case that compared to unmalted barley flour, flour made with barley malt is SIGNIFICANTLY lower in hordein. This is explained in greater detail in this study
. In any case, it seems as though a long protein rest should have comparable effect to using Brewer's Clarex.
Hydrolysis of gliadin, hordein, and secalin can render them undetectable under certain testing methods--namely, the once-popular R5 sandwich
ELISA test--and this has caused controversy in the past as studies have demonstrated that this form of ELISA test can give false negatives, thus allowing a "gluten-free" label to go on a harmful product. See this study
. The more recent R5 competitive
detect hydrolyzed fragments of hordein, and specifically the peptide sequences known to trigger an autoimmune response in celiac sufferers. This is the test that Omission uses.
To make their beer, Omission uses a combo of a special cultivar of barley with a very low production of hordein, as well as brewer's clarex, producing the beer on equipment that has been fully sanitized. See here
. No mention about centrifuges or anything, so I think we can put to rest the myth that they somehow "centrifuge out" the gluten. In any case, nothing in their methodology explains to me how their beers can pass the R5 competitive ELISA, but apparently they do, as every bottle is tested.
However, It is worth noting that while the R5 competitive ELISA is theoretically sound, it is not to my knowledge clinically verified. That is to say, clinical trials have yet to be done to show that any food which passes the test will be safe for celiacs. The test's threshold is 3 PPM of the relevant peptides, and Omission admits that the safety of their product is not guaranteed (though they happily still label it "gluten-free" in the state of Oregon--a bit hypocritical, if you ask me).
It is also worth noting that on the spectrum of gastroenterological disorders that can be associated with consumption of certain cereal grains, celiac disease is the only one for which it has been decisively proven that the pathogenic antigen lies within the gluten molecule. If you have a barley allergy, then the antigen of interest is NOT in the gluten molecule, and is not going to be affected *AT ALL* by Brewer's Clarex. In fact, that's one of the selling points of Brewer's Clarex, that it does not denature the LTP1 protein responsible for head formation. In the case of non-celiac gluten sensitivity, it has not been established which peptides are the culprit in provoking a response, or if it is in fact the gluten that is responsible at all, since grains contain a host of additional proteins.
So what's the take-away here? When it comes to barley-related gastroenterological disorders, there is much we still don't know. If you have a barley allergy, your problem is not gluten and beers like Omission are decidedly NOT safe. Some people, including myself, continue to have mild-to-moderately-severe reactions to beers like Omission and Daura; whether our symptoms are due to allergy, to a response to some other protein, to psychosomatics, or to some as-yet undiscovered pathology, no one can say. On the other hand, some people can drink Omission without any symptoms at all. Further studies and clinical trials must be conducted, but in the meantime the only way to be 100% safe is to avoid anything made with wheat and barley, regardless of how it is processed. Experiment at your own risk, and do so under a doctor's supervision, as your disease may return asymptomatically at first.