People who report being gluten intolerant but do not have coeliac disease may be experiencing gut symptoms unrelated to gluten intake, new research suggests.

A study involving individuals with self-reported gluten sensitivity has found that they experienced gut symptoms such as bloating and abdominal pain regardless of whether or not they consumed gluten.

Assoc Prof Jessica Biesiekierski of the University of Melbourne, one of the study’s senior authors, said the findings were significant in light of popular blame on gluten as a trigger for various symptoms.

Only about 1% of people in western countries have coeliac disease, an autoimmune condition in which gluten causes an inflammatory reaction in the small bowel.

“Coeliac disease is a well-defined medical condition. It has a clear diagnostic pathway,” Biesiekierski said. For people with coeliac disease, a gluten-free diet is the only effective treatment option.

However, about 10% of the population self-report being gluten sensitive. “We’ve got this large number of people who are following a gluten-free diet, possibly unnecessarily,” Biesiekierski said.

“Gluten is actually a complex mixture of proteins found in wheat, and related proteins are also present in rye, barley, and sometimes oats,” she said. “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 study involved 16 participants with non-coeliac gluten sensitivity and 20 healthy controls. Researchers gave participants yoghurt containing either 16g of gluten or whey protein. For five days, the participants also consumed two muffins daily, which each contained either 8g gluten, or no gluten.

After a two-week period, participants were then switched to the other intervention but were not aware of which they were ingesting.

Individuals with gluten-sensitivity reported increased fatigue after both the gluten and placebo yoghurt compared to healthy controls. They also reported increased pain and bloating with both the gluten and gluten-free muffins.

Urine, blood and saliva samples taken for cortisol levels and markers of inflammation showed no differences after gluten ingestion.

“Participants continued to report gastrointestinal symptoms, but these symptoms didn’t appear to be specifically triggered by gluten,” Biesiekierski said. Researchers believe the response to gluten may be explained by a nocebo effect, the opposite of the placebo effect, in which a negative outcome results from an expectation that the treatment will be harmful.

At baseline, the gluten-sensitive participants had a higher negative effect, the researchers noted.

“From working with these patient groups for more than 15 years, I can say their symptoms are real. It’s just that, for many of them, gluten may not be the specific cause,” Biesiekierski said.

Previous research has suggested that fructan, a type of carbohydrate, may be the culprit for abdominal symptoms in people with self-reported gluten sensitivity.

Rather than immediately turning to a gluten-free diet, the researchers suggest people should a consult a dietitian to explore whether other dietary triggers such as high Fodmaps (Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols) foods may be involved.

“We have strong evidence supporting psychological treatments like cognitive behavioural therapy and gut-directed hypnotherapy,” Biesiekierski added. “These approaches help to rewire the gut-brain pathways that may be contributing to the symptoms.”

Dr Kerith Duncanson, a research dietitian at the University of Newcastle who was not involved in the research, described the study as “very nicely designed” but said the main limitation was its small sample size.

“Much larger numbers are needed for definitive conclusions and application to clinical practice,” she said.

“While the study progresses understanding … it does not provide evidence that non-coeliac gluten sensitivity does not exist,” Duncanson added. “As a dietitian working clinically in this field, the reality is that people who present with suspected non-coeliac gluten sensitivity may have had considerable medical investigations and procedures or may simply have noticed they felt better when not eating wheat, and been following a gluten-free diet.”

Assoc Prof Jason Tye-Din, head of the coeliac research lab at the Walter and Eliza Hall Institute of Medical Research, who was not involved in the study, said despite the small sample size the study added to evidence “that non-celiac gluten sensitivity is most likely not driven or caused by gluten”.

“I think it’s a very positive and important study,” he said. “Future studies hopefully will be larger and explore this concept further.”

The research was published in the United European Gastroenterology Journal.