First things first: coeliac disease* is a real thing, where eating food containing gluten causes an adverse reaction.
But gluten intolerance in the absence of coeliac disease is starting to look a little more suspect.
Peter Gibson, a scientist at Monash University in Melbourne, Australia, was one of the authors on a key scientific paper that established evidence of non-coeliac gluten sensitivity in 2011.
But last year Gibson published a follow up paper based on a new, much more detailed and controlled, study that contradicts his previous findings.
That doesn't mean the symptoms people who think they're gluten intolerant are experiencing are all in their head. It just means it could be something other than gluten that's causing them.
Gluten sensitivity could be a misnomer for allergies related to things other than gluten in wheat.
"There are many people that feel that they have gluten sensitivity because when they go on a gluten-free diet they feel well, and when they eat wheat they feel poorly," Gibson told the Gastroenterology podcast last year. But the question is whether it's really the gluten or another part of wheat that is making people feel unwell.
Wheat has both protein and carbohydrate components, and either could be to blame.
"FODMAPs" are carbs that are rapidly fermented in the gut.
It's an acronym that stands for "Fermentable Oligo-, Di-, Mono-saccharides and Polyols." FODMAPs are found in many different foods, including some grains, fruits and vegetables, and you shouldn't try to cut them out without first consulting with your doctor or dietitian.
Gibson's new study tested 37 self-identified gluten-sensitive people.
Participants each spent a week on three different diets: high-gluten, low-gluten, and gluten-free (they didn't know which they were on at any one time, and neither did the scientists in charge of the experiment). 95% of the food the participants ate was provided by the scientists, and the rest was "carefully controlled", says Gibson.
In the run up to the experiment, patients were on a low FODMAP diet, and continued on that throughout.
While they were on the high-gluten diet, participants experienced the pain and other symptoms they blamed gluten for. But, curiously, they also experienced symptoms on the low-gluten and the gluten-free diet, too.
In contrast to our first study, we could find absolutely no specific response to gluten [...] We found that yes, the gluten did induce symptoms, but it was exactly the same as the symptoms when they didn't have the gluten.
At present there is no strong evidence to recommend a gluten free diet to treat IBS [irritable bowel syndrome] symptoms. However a low FODMAP diet has evidence for providing symptomatic relief for IBS.
Nutritional research is difficult, because restricting one food type often cuts intake of another. If symptoms improve, you don't know what caused the problem in the first place.
In this case, says Martin, reducing gluten could improve patient's symptoms because it's also reducing another component of the foot i.e. FODMAPs. Or it could be that gluten does not trigger symptoms when you also reduce FODMAPs.