Non-Celiac Gluten Sensitivity? Nuance Be Damned!

The debate over non-celiac gluten sensitivity (NCGS) is back (did it ever go away?), and personalities with clout are weighing in: Michael Pollan.  Shauna James Ahern.  Jimmy Kimmel.  It's a hugely complicated issue, and I almost don't know where to start because there's so much to say.  However, as a dietitian who has successfully treated her own IBS by eliminating gluten, the issue is personally important to me, so I feel that I have to try and clarify the situation a bit.

First, the majority of studies on NCGS are done on participants with gut issues, primarily irritable bowel syndrome (IBS).  To say there are a myriad of causes for gastrointestinal issues is the understatement of the century - give me 20 people with IBS, and I'll give you 20 different etiologies.  After all, it's a syndrome, a collection of symptoms rather than a specific pathological cause-and-effect relationship.  The wide spectrum of IBS causes makes it very difficult to pinpoint the clinical effects of any single intervention in a group with the syndrome, and this complicates studies that want to test for gluten intolerance (or lack thereof).

The latest round of gluten-free bashing seems to have originated from a study recently published in the journal of Nutrition in Clinical Practice, which evaluated participants with self-diagnosed gluten-intolerance.  This is the abstract:

Characterization of Adults With a Self-Diagnosis of Nonceliac Gluten Sensitivity

Background: Nonceliac gluten sensitivity (NCGS), occurring in patients without celiac disease yet whose gastrointestinal symptoms improve on a gluten-free diet (GFD), is largely a self-reported diagnosis and would appear to be very common. The aims of this study were to characterize patients who believe they have NCGS. Materials and Methods: Advertising was directed toward adults who believed they had NCGS and were willing to participate in a clinical trial. Respondents were asked to complete a questionnaire about symptoms, diet, and celiac investigation. Results: Of 248 respondents, 147 completed the survey. Mean age was 43.5 years, and 130 were women. Seventy-two percent did not meet the description of NCGS due to inadequate exclusion of celiac disease (62%), uncontrolled symptoms despite gluten restriction (24%), and not following a GFD (27%), alone or in combination. The GFD was self-initiated in 44% of respondents; in other respondents it was prescribed by alternative health professionals (21%), dietitians (19%), and general practitioners (16%). No celiac investigations had been performed in 15% of respondents. Of 75 respondents who had duodenal biopsies, 29% had no or inadequate gluten intake at the time of endoscopy. Inadequate celiac investigation was common if the GFD was initiated by self (69%), alternative health professionals (70%), general practitioners (46%), or dietitians (43%). In 40 respondents who fulfilled the criteria for NCGS, their knowledge of and adherence to the GFD were excellent, and 65% identified other food intolerances. Conclusions: Just over 1 in 4 respondents self-reporting as NCGS fulfill criteria for its diagnosis. Initiation of a GFD without adequate exclusion of celiac disease is common. In 1 of 4 respondents, symptoms are poorly controlled despite gluten avoidance.

Two big takeaways:

1. The authors found that ~3/4 of the respondents didn't meet the criteria for non-celiac gluten intolerance, but this doesn't indicate that they do not have it.  It is more meaningful to note that only 1/4 of the respondents reported that their symptoms hadn't abated on a gluten-free diet; this indicates that NCGS isn't the cause of their particular digestive issues.  Just to be clear, that's only a quarter of the respondents.  That isn't strong evidence that NCGS is bunk, as has been so widely touted.

Mostly (62%), the responses indicated that these people hadn't ruled out celiac disease.  Please, if you think you have a reaction to gluten, get tested.  Celiac causes serious long-term harm left untreated.

2.  Another 1/4 of the respondents (27%) weren't actually following a gluten-free diet, but they reported feeling better anyway!  This has also been talked up; it looks like the placebo effect, or possibly the nocebo effect, where gluten acts as the nocebo.  Keep in mind, some of these people presumably overlap with the ones whose symptoms hadn't abated, which makes any conclusion about those individuals' NCGS status impossible.

However, there's another serious interpretation problem: NCGS may have a threshold level of gluten sensitivity greater than zero, beneath which there is no harm.  Many individuals who have followed strict gluten-free diets to good effect report that they can introduce varying levels of gluten back into their diets with little or no detriment to their health.  We in the medical community are so conditioned by celiac disease to think in terms of zero tolerance (celiac sufferers have a reaction to even tiny amounts of the protein), that we may have erroneously assumed NCGS works the same way, when it does not.

Still, we have to conclude that a significant number of people who self-report NCGS are talking themselves into feeling better.  Anyone shocked that people claim benefits of a trendy but meaningless dietary change?  Raise your hand.  Anyone?

According to this study, the diagnosis and treatment of NCGS, either self-diagnosed or by a health care provider, is a red hot mess.  There is no established path to diagnosis and treatment, so people are feeling their way through, trying to come up with a solution to their health issues.  What I found terribly concerning was that 29% (22) of the 75 people who had a duodenal biopsy to rule out celiac disease had not consumed enough gluten beforehand to make the test accurate.  If a patient is going through the rigamarole of having a biopsy, the health care provider responsible for their care should make darn sure that the patient has been consuming large amounts of gluten for at least 6 weeks prior to the test!

My conclusion?  Gut issues are not cut-and-dried, and new research is coming out every single day.  Each of those studies has the potential to help, but only if we read it for what it says rather than what we want it to say.

It also looks to me like both patients and health care providers are woefully undereducated about NCGS. When a patient comes to me looking for an answer for their nausea/vomiting/diarrhea/ constipation/gas/bloating/belching, etc, I have a checklist of questions I ask myself and the patient to determine the cause.  Are they not chewing their food?  When and how much are they eating?  Do they have enough stomach acid?  Have they been evaluated for celiac disease?  Assuming NCGS is the cause of a person's digestive issues before evaluating them thoroughly is bad medicine.

And the study that everyone keeps referencing that was published in Gastroenterology in August 2013?  The small study that contradicts the other small study published by the same authors in 2011 that established the existence of non-celiac gluten sensitivity?

Yeah, I'm going to tackle that one next week.

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