Things that bug me: gluten


As I sift through the ruins of organized skepticism, I recall something that always bugged me.

Celiac disease is an autoimmune disorder that causes a bunch of chronic gastrointestinal problems.  The treatment to celiac disease is to switch to a completely gluten-free diet.  However, people with celiac are not by themselves the cause of the many gluten-free products sold in stores.  Many people buy those because they believe they have a different condition, Non-Celiac Gluten Sensitivity (NCGS).  They believe that when they go on a low-gluten or gluten-free diet, they have fewer gastrointestinal symptoms (e.g. they feel less bloated).  I say “believe”, because there is no consensus that NCGS exists.

The standard skeptic’s line on NCGS is that there is no evidence that it exists, and there is no reason for people to go on gluten-free diets unless they think they have celiac disease.  One study that has been used in support of this position, is a paper from 2013, which says in the title “No effects of gluten in patients with self-reported non-celiac gluten sensitivity“.

The interesting thing about this paper is that it says that people who report NCGS do experience a significant reduction in symptoms when they change their diet.  However, the important change in their diet is not the elimination of gluten, but the elimination of another category of chemicals, known as FODMAPs.  FODMAPs are generally present in the same grains that include gluten, so it’s easy to get them confused without having a study designed specifically to separate them.  In other words, it is possible that people who believe they have NCGS are correct about having symptoms that improve with a change in diet, but incorrect about the source of those symptoms.

I recall that back in 2013, skeptics were saying, “This is another confirmation of what we’ve been saying all along: NCGS doesn’t exist.”  And I recall reading the news reports and thinking, wait.  This means we were wrong.  People who thought they had NCGS were correct to change their diets.  We were wrong.  Why weren’t skeptics acknowledging that they had been wrong?

A few caveats.  The 2013 study only involved 37 participants who self-reported NCGS.  I wouldn’t take its conclusions for granted without further study.  Since I do not follow this literature, all I can say is that I’m unaware of further studies that either reproduced or overturned the conclusions.  If any readers are aware of such studies, you are welcome to share in the comments.  But as far as I’m concerned, the idea that self-reported NCGS can be attributed to FODMAPs rather than gluten, is merely a hypothesis with some support.  I should also mention that the study did in fact find a non-zero effect of gluten:

Gluten-specific effects were observed in only 8% of participants.

In other words, they did in fact measure gluten sensitivity in a few of the participants, but it happened in so few cases that it was not statistically significant enough to reject the null hypothesis.  While I agree with the authors that this does not constitute evidence of NCGS, I think it drives home the point that 37 participants isn’t really enough.  If it were true that <8% of people who think they have NCGS really do have it, then you’d need a more powerful study to detect evidence of that.

But for the moment, let’s take for granted the conclusions of the study (just as skeptics did).  The study suggests that in ordinary circumstances, people who believe they have NCGS can improve their health by eliminating wheat and other grains from their diet.  Furthermore, the effect is so significant that it can be detected in a clinical study with only 37 participants.  However, there are some changes in diet which will not help.  In particular, if you somehow eliminate gluten-containing grains, while maintaining a high FODMAP diet, there may be no improvement at all.

There’s an important followup question.  While avoiding gluten-containing grains will also lead to a low-FODMAP diet that will improve some people’s health, it is less clear to me that products advertised as “gluten-free” would do the same.  For all I know, these products have substituted gluten-containing grains for some ingredient that does not contain gluten but is high in FODMAPs.  I have no idea if this is remotely true, but it seems like such a basic question.

Anyway, the study suggests that people who claim to have NCGS don’t really have it.  They aren’t sensitive to gluten, they’re sensitive to FODMAPs.  So skeptics who said NCGS doesn’t exist were technically vindicated.  But that’s missing the point.  Changing the name from NCGS to Non-Celiac Wheat Sensitivity (or whatever) is easy.  Changing diets is hard.  Skeptics can feel vindicated about a technical point of minor significance, and gluten-free dieters can feel vindicated on the part that actually matters: the benefits of the diet itself.

I have not read any of the literature on the subject and acknowledge the possibility that I have drawn the incorrect conclusion on NCGS.  However, if that is the case, then it just shows that skeptics failed to present the relevant evidence, and instead promoted a study that clearly disconfirmed their stated position.

Comments

  1. anothersara says

    Personally, I’m grateful that gluten-free diets have become a fad, because it makes life easier for people with Celiac disease. My cousin was diagnosed with celiac disease some time around 1990 (I don’t know the exact year) and back then it was significantly harder to maintain a gluten-free diet.

    It’s also worth noting that many people who switch to a gluten-free diet also eliminate dairy from their diet (including people with Celiac disease, since lactose intolerance is a common symptom), and most dairy products are also high in FODMAPs. However, given that there are so many foods high in FODMAPs which contain neither grains nor dairy (apples for example), and a few foods which are high in gluten but low in FODMAPs (spelt) that someone who is sensitive to FODMAPs but not gluten is probably better off knowing that.

  2. says

    I did not know that foods with FODMAPs but not gluten were so common.

    I had a friend with celiac who once complained to me that foods advertised as gluten-free were not always following sufficiently stringent standards to actually be safe for her. Since many people seeking gluten-free foods can’t actually detect small quantities of gluten, the waters were a bit muddied. But that was many years ago, and maybe standards have changed today.

  3. Mano Singham says

    That is interesting. I know people who have switched to gluten-free diets and have said they felt better even though they did not have celiac disease. I had never heard about the FODMAP hypothesis but will pass it. on.

  4. kestrel says

    It’s amazing how many products are now being labeled as “gluten free” that never would have had gluten in them to start with. And for the strangest example I have personally seen, last time I was at the Sally’s Beauty store, the manager proudly showed me a new line of hair care products that were gluten free. !!! Fortunately for me I do not eat hair care products so even if they put tons of gluten in there AND I had celiac disease, I’d be OK.

  5. says

    kestrel@#4:
    It’s amazing how many products are now being labeled as “gluten free” that never would have had gluten in them to start with

    Yeah, pure sugar candies – good for you now, because they are gluten free!

  6. says

    I’ve seen gluten free recipes recommended for diabetics. Whether they are useful depends on what is substituted for wheat and the like. Nut flours are ok. Rice, corn, potatoes? Not good, they are just as high in carbohydrates.
    I imagine the same thing can happen with FODMAPS as with carbohydrates.

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