Dietary intervention is a common treatment among patients with irritable bowel syndrome (IBS). However, insufficient patient adherence, and essential need for ingredient restrictions limiting its use in this population. Immune assay guided diet may provide an individualized intervention, which may increase its effectiveness compared with non-personalized dietary strategies. We aimed to test the effectiveness of an individualized dietary intervention, based on Leukocyte activation to dietary components (Alcat, Germany), to improve patient compliance to diet modifications.