Gluten Could Be Wrongly Blamed for Americans' Stomach Troubles

Gizmodo

22-07-2025

For many of us, gluten is a dietary villain, capable of causing all sorts of gastrointestinal troubles. Research out this week looks to complicate that narrative, however, finding that people are sometimes wrongly blaming gluten for triggering their symptoms of irritable bowel syndrome.
Scientists at McMaster University in Canada conducted the study, a small, randomized trial of IBS patients. People became sicker just as often after eating food containing gluten or wheat as they did after eating food without the ingredient, they found. Gluten is likely safer to eat for those with IBS than commonly thought, the researchers say.
'These findings suggest that expectations played a major role in symptom generation and that only some of these patients could benefit from gluten or wheat restriction,' they wrote in their paper, published Monday in The Lancet Gastroenetrology and Hepatology.
IBS is a complex, chronic, and relatively common condition, estimated to affect between 5 and 10% of the population worldwide (including up to 45 million people in the U.S.). Its symptoms include stomach pain, bloating, and diarrhea or constipation. Unlike the closely named inflammatory bowel disorder, IBS isn't marked by physical changes or visible damage along the digestive tract, but it can still be a debilitating burden for many, with around 20% of sufferers experiencing severe bouts. The exact causes of IBS remain unclear, though scientists have speculated it can arise from a miscommunication between the nerves found in the gut and the brain.
People with IBS tend to report having specific triggers that can cause a flare-up of illness, gluten included, and often manage their condition by avoiding these triggers. The researchers behind the new study aimed to better understand gluten's potential role in IBS, so they recruited over two dozen people with IBS for their randomized, double-blinded trial, all of whom had reported improving after switching to a gluten-free diet.
At first, the volunteers were randomly assigned to one of three groups. All the groups were first told to eat cereal bars for a week. One group ate bars made with flour containing gluten, the second ate bars made with wheat flour, and the third ate bars made with gluten- and wheat-free flour. Afterward, the volunteers took a break for two weeks. Then they switched to eating the bars they hadn't eaten yet for another round of testing, a process repeated twice. By the study's end, all the volunteers had eaten all three kinds of bars, though on different schedules and without knowing which bars they had eaten on a given week.
A total of 28 people completed the trial. A significant percentage of people reported having worsening IBS symptoms after eating gluten or wheat bars, the study showed, but about just as often as they did after eating non-gluten/wheat bars (roughly a third experienced worsening IBS during each of the three conditions). 93% of participants also reported having adverse events after each scenario of bar-eating. Interestingly enough, tests of the participants' stool found that only a third strictly followed their diets as instructed, with likely many fearing they would get sick.
The findings are based on a very small sample size, so it's not yet certain that they apply to the general population of people with IBS tied to gluten. There are also, of course, digestive conditions clearly caused by an intolerance to gluten, particularly celiac disease. And the researchers aren't saying gluten can't sometimes be a genuine trigger for people's IBS. But they argue that in many cases, people's negative perception of gluten is causing a nocebo effect, the dark cousin of the placebo effect. In other words, someone's belief that gluten is bad for them can potentially spark or worsen the IBS symptoms seen after eating it, rather than gluten itself.
The researchers say better communication and follow-up care from doctors are needed for IBS patients, given the findings.
'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. Many of them may benefit from psychological support and guidance to help destigmatize gluten and wheat and reintroduce them safely in their diet,' said senior author Premysl Bercik, a professor at McMaster's Department of Medicine, in a statement from the university.
That may be easier said than done, though. The researchers note that most patients, upon learning the team's findings, staunchly refused to entertain the idea of gluten not being a trigger for their IBS symptoms. So it looks like gluten may need a promotional campaign to win back its reputation.