• Posted July 22, 2025

For Some, Gluten Intolerance Is Psychological, Study Says

Gluten intolerance might be all in the minds of some people with irritable bowel syndrome (IBS), results from a small-scale experiment indicate.

People with the common digestive disorder reported worse GI symptoms after eating a cereal bar, even though the bar contained no gluten or wheat, according to results published July 21 in The Lancet Gastroenterology and Hepatology. 

Their symptoms after noshing a gluten-free bar were similar to those they experienced after eating cereal bars containing either gluten or whole wheat, results show.

This indicates that suggestions and beliefs, rather than the ingredients themselves, might be driving an IBS patient’s GI symptoms in many cases, researchers said.

“Not every patient who believes they are reacting to gluten actually does,” senior researcher Dr. Premysl Bercik, a professor of medicine at McMaster University in Ontario, Canada, said in a news release.

“Some truly have a sensitivity to this food protein, but for many others, it’s the belief itself that’s driving their symptoms and subsequent choices to avoid gluten-containing foods,” he continued.

Gluten is a protein found in grains like wheat, barley and rye. It can cause GI problems for some people who are either allergic to the protein or in whom it causes an immune response that can be damaging to the gut, according to the Harvard T.H. Chan School of Public Health. 

For the study, researchers recruited 28 patients with diagnosed IBS who said their symptoms had improved when they followed a gluten-free diet.

In a lab experiment, each person was given a cereal bar to eat at three separate times. The three bars were different – one contained gluten, one contained wheat and one had neither.

The number of people who felt worse after eating the cereal bar was the same across all three types of bars, researchers report.

After each snack, 26 of the 28 participants reported worse GI symptoms even when the bar was free of gluten and wheat.

This could be due to what researchers call the “nocebo effect,” in which negative expectations alone can trigger real physical symptoms, Bercik said.

In particular, social media and online communities could be fueling ideas that gluten is harmful, even though it might not be the true cause of some patients’ IBS symptoms, he said.

“There is strong influence from the internet,” Bercik said. “Many patients post how bad they feel about gluten. Of course, it influences others.”

Some IBS patients also might feel that avoiding gluten is a way to take control of their situation, rather than feeling helpless.

Bercik said continuing the gluten-free diet might provide patients with an actionable method to try to control their symptoms, even though it means unnecessary diet restrictions.

In fact, many of the study’s participants didn’t change their beliefs or their diets even after they were later told which bars caused their GI symptoms, researchers said.

Therapy and coaching might be needed to help these folks move past their gluten hangups, Bercik said.

“What we need to improve in our clinical management of these patients is to work with them further, not just tell them that gluten is not the trigger and move on,” he said. “Many of them may benefit from psychological support and guidance to help destigmatize gluten and wheat and reintroduce them safely in their diet.”

More research is needed to test these findings in larger groups of people, and to determine why beliefs about gluten might drive some IBS symptoms, researchers said.

More information

The Harvard T.H. Chan School of Public Health has more on gluten.

SOURCE: McMaster University, news release, July 21, 2024