If you’ve cut out gluten to ease digestive symptoms, you’re not alone. But according to a new study, you might not need to.
Researchers from McMaster University have found that many people with irritable bowel syndrome (IBS) who believe they’re sensitive to gluten or wheat may not actually be reacting to those ingredients. The study, published in The Lancet Gastroenterology & Hepatology, used a randomized, double-blind, placebo-controlled crossover trial, widely considered the gold standard in clinical research.
In the trial, participants with clinically diagnosed IBS who felt better on a gluten-free diet were given cereal bars that either contained gluten, whole wheat or were gluten-free placebos. Neither the participants nor the researchers knew which bar was which during the test.
The result? Symptom flare-ups occurred just as often with the gluten-free placebo as they did with the bars containing gluten or wheat.
“Not every patient who believes they are reacting to gluten actually does,” said senior author Dr. Premysl Bercik, a professor in McMaster’s Department of Medicine. “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”
That phenomenon is known as the nocebo effect, when negative expectations alone cause real symptoms. Even after participants learned which bars contained gluten, most didn’t change their beliefs or diets, according to the study.
The findings highlight an often-overlooked aspect of gut health: psychological stress and expectation can be just as powerful as what we eat. Bercik emphasized that this doesn’t mean symptoms aren’t real, just that the root cause might not be the ingredient people expect.
“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.”
The study also notes that social media and peer stories can reinforce beliefs that gluten is harmful, even without clinical evidence. That can lead people to unnecessarily restrict their diets, potentially missing out on important nutrients or food enjoyment.
Before cutting out gluten, or any major food group, it’s worth consulting with a health care provider. What feels like a food sensitivity might actually be more about how your brain and gut are communicating.
This study was funded by the Canadian Digestive Health Foundation and the Society for the Study of Celiac Disease.