Gluten Sensitivity

The differences between coeliac disease, gluten sensitivity and IBS

There is much discussion and debate extending from the food industry through the wellness industry, and into the fields of nutrition and health research about gluten. Not that long ago, maybe as little as 10 years in fact, gluten was discussed in all these fields only in the context of being toxic to those with coeliac disease. Through an almost uncanny set of coincidences, popular dietary culture has embraced the gluten-free diet. This gluten-free trend that has been welcomed with open arms by the food industry, has created the gluten-free food juggernaut that is evident in supermarkets across the Western world. If a person who does not have coeliac disease feels better on a gluten-free diet (with no other changes) it would be reasonable for them to assume that they are sensitive to gluten. So researchers have been busily investigating how gluten might cause symptoms such as lethargy, “brain fog”, bloating, wind and abdominal pain.

In parallel, the undigested carbohydrate in wheat (part of the FODMAP family) has been implicated as contributing to Irritable Bowel Syndrome (IBS) symptoms of bloating, abdominal pain and wind/gas. People who feel better on a gluten-free diet could therefore theoretically be feeling better NOT because they have reduced the gluten protein in wheat but the starchy carbohydrate component. The logical question for a person who knows they feel better when they don’t eat bread would be, which part of wheat am I sensitive to?

In order to fully understand what might be happening here, it might be helpful for me to define what (non-coeliac) gluten sensitivity actually is! That may sound simple and sensible, but in reality it is very, very difficult due to conflicting information, even in the highest level scientific literature. By definition, gluten sensitivity is self-reported gluten intolerance, with negative coeliac blood testing and /or biopsy results. It does seem that an unusually high proportion of people with diagnosed gluten sensitivity are predisposed to coeliac disease. Often termed ‘coeliac lite’ these people have first degree relatives with coeliac disease, the genetic marker for coeliac disease, and respond well to a gluten-free diet1. Alternately, some people who are classified as gluten sensitive might be actually pre-coeliac. They might have the genetic markers, the positive blood tests but their biopsy was negative. A proportion of these people eventually do develop coeliac disease at some stage in life.

There is some research being done in Europe to determine whether the symptoms of gluten sensitivity may be related the levels of the Zonulin in the body. This protein is a “tight junction regulator” as it controls the size of the gaps between the intestinal cells and this influences the movement of nutrients, water and cells into and out of the gut2. When Zonulin is present, the normally tight junctions between the intestinal cells remain open, creating bowel “leakiness” and initiating an inflammatory cascade that eventually damages the intestinal wall. Elevated levels of Zonulin have previously been found people with coeliac disease, and more recently it has been reported that those with gluten sensitivity have Zonulin levels close to those with coeliac disease and much higher than those with IBS or no gut problems. It is likely that some of the symptoms attributed to gluten sensitivity might relate to the influence of elevated Zonulin on the nervous and immune systems (fatigue, lethargy, “brain fog”) and some symptoms might be attributable to IBS (wind, pain, bloating, diarrhoea, constipation).

So we have a situation where about 1% of the population have coeliac disease and require a gluten-free diet, some of whom also have IBS and would benefit from trialling a low FODMAP diet (see image). Then there are about 15% of people who have IBS, some of whom think that a gluten-free diet has helped them but possibly only because this resulted in lower wheat and hence they would benefit from trialling a low FODMAP diet3. Finally, there are a small proportion of people who seem to be sensitive to gluten (often with a strong family history of coeliac, perhaps undiagnosed coeliac or pre-coeliac) but may also have IBS and this group may benefit from gluten-free, low FODMAP diet.

Let Kerith Duncanson know if you have any questions or if this has helped explain this tricky issue.


  1. Molina‐Infante, J., Santolaria, S., Sanders, D. S., & Fernández‐Bañares, F. (2015). Systematic review: noncoeliac gluten sensitivity. Alimentary pharmacology & therapeutics, 41(9), 807-820.
  2. Barbara, G. (2015) 23rd United European Gastroenterology Week (UEG Week 2015)
  3. Biesiekierski, J. R., Newnham, E. D., Shepherd, S. J., Muir, J. G., & Gibson, P. R. (2014). Characterization of adults with a self-diagnosis of nonceliac gluten sensitivity. Nutrition in Clinical Practice, 29(4), 504-509.