“An IgG-guided elimination diet improves IBS symptoms.”

The 2025 trial enrolled adults with IBS at 8 centers who tested positive for at least 1 of 18 foods on an IBS-specific IgG test. Of 238 people randomized, 223 were analyzed after 8 weeks. Neither the patients nor the study staff knew who had the real diet, and the fake diet cut the same number of foods, just not the ones the test flagged. The trial's public registry lists a different main measure, the change in daily belly pain, from the responder measure the paper reports. Benefit looked largest in people with constipation-type and mixed-type IBS, but those were smaller subgroups. In the 2004 trial, the true diet most often cut yeast, milk, egg, wheat and cashews, while the fake diet most often cut potato, rice and tomato. Milk and wheat are common IBS triggers, so the trials cannot tell whether the test found each person's problem foods or simply steered people away from common ones. The British Society of Gastroenterology (2021) strongly recommends against IgG-based elimination diets for IBS, citing a modest benefit and concerns that the test flags many foods that do not cause symptoms; for example, 87% of patients in the 2004 trial had IgG to yeast, which rarely causes symptoms. The American College of Gastroenterology (2021) advises against routine food allergy and food sensitivity testing in IBS unless a person has repeated reactions that suggest a true food allergy, and it recommends a limited trial of a low-FODMAP diet. The American Gastroenterological Association calls low-FODMAP the diet with the most evidence for IBS. The British guideline also backs it, as a second-line step after general diet advice, with supervision by a trained dietitian. Low-FODMAP means cutting back for a few weeks on certain carbs that ferment in the gut, then adding foods back one at a time to find personal triggers. All three sets of guidance were written before the 2025 trial was published.