The notion that people not diagnosed with coeliac disease can become sick from ingesting gluten — an idea that has spawned billion-dollar businesses and a myriad of diet fads — is being challenged by some researchers, who suggest that the real culprit behind the gut-wrenching symptoms reported by some consumers might not be gluten after all. 

Research from the University of Melbourne has demonstrated that individuals who claim to be gluten-sensitive but do not have coeliac disease — known as non-coeliac gluten sensitivity, or NCGS — may be barking up the wrong dietary tree.

The new study, published in the United European Gastroenterology Journal, put gluten — a protein naturally found in grains like wheat, barley, and rye — on trial. Researchers analyzed 16 people with self-diagnosed gluten sensitivity against 20 healthy participants. The gluten group was provided with goodies to test their gut reaction — yogurt with a side of gluten and gluten-laden muffins — while the non-gluten group had plain yogurt and gluten-free muffins.

The results? Those who thought gluten was their digestive arch-nemesis experienced bloating, pain, and fatigue regardless of whether gluten was present. Their symptoms didn’t change, regardless of whether their treats were gluten-free or not. Tests on blood, saliva, and urine found no evidence that gluten was doing anything nefarious. 

“Acute and sub-acute symptoms in individuals with [non-coeliac gluten sensitivity] are not gluten-specific, suggesting other mechanisms are involved,” the researchers said.

The researchers speculate that there may be “nocebo effect,” when the expectation of something being bad ends up making it bad. Essentially, participants’ fear of gluten seemed to amplify their symptoms, the researchers said.

“These findings reveal that [non-coeliac gluten sensitivity] is characterised by baseline differences in affect, and higher acute fatigue and subacute gastrointestinal symptoms that are not gluten-specific,” the researchers wrote. “This may be explained by nocebo effects, warranting research into novel mechanisms and re-evaluating the NCGS definition.”

About 10 percent of the population claims to be “gluten-sensitive,” but coeliac disease — a well-defined autoimmune condition — affects only about 1 percent of the population. For people with coeliac disease, avoiding gluten is non-negotiable. 

Simply giving up gluten isn’t a good call in some cases, one of the study’s authors, associate professor Jessica Biesiekierski, told the Guardian. “Gluten is actually a complex mixture of proteins found in wheat, and related proteins are also present in rye, barley and sometimes oats. When you follow a gluten-free diet, you’re excluding an entire group of cereals and grains. Over the long term, this can lead to nutritional inadequacies and is often more costly.”

The researchers suggested that fructan, a type of carbohydrate found in wheat and other foods, could actually be the culprit behind the bloating and belly aches. Other pesky dietary culprits, such as high FODMAP foods — short for fermentable oligosaccharides, disaccharides, monosaccharides and polyols-types of carbohydrates, which could cause gas and bloating — might actually be to blame. 

Not everyone’s on board the “gluten isn’t guilty” bandwagon just yet, however. A research dietitian from the University of Newcastle, Dr. Kerith Duncanson, found the study promising but highlighted its small sample size. “Much larger numbers are needed for definitive conclusions and application to clinical practice,” she told the Guardian.