The role of dietary factors in the pathogenesis of IBS is still unclear. The aim of this study was to compare IgG4 levels to common food antigens between patients with IBS and healthy controls. Thirty-two patients diagnosed as IBS according to Rome III criteria (12 diarrhea subtype; 20 non-diarrhea subtype) and 32 sex and age-matched healthy controls participated in the study. Serum IgG4 titers to 90 common foods were measured in each subject. The number of subjects with positivity defined as the cut-off value ≥ 0.7 U/mL was compared. Patients with IBS had significantly higher IgG4 titers to wheat, leek, and taro compared to those of controls. Serum IgG4 titers to ginger, cocoa, walnut, white radish, onion, and lettuce in IBS patients tended to be higher than controls. IgG4 titers to wheat, gluten and gliadin in the diarrhea subgroup, and lettuce, leek, and taro in the non-diarrhea subgroup tended to be higher, compared with controls. The number of subjects with positivity to apple, orange, lettuce, and leek was significantly higher in IBS patients than controls. The number of subjects with positivity to apple, orange, gluten, and gliadin in the diarrhea subgroup, and egg white, pineapple, soybean, lettuce, and leek in the non-diarrhea subgroup was significantly higher, compared with controls. Serum IgG4 antibody levels to some common foods are abnormally elevated in IBS patients. The type of foods with abnormally elevated serum IgG4 titers in the diarrhea subgroup may be different from that in the non-diarrhea subgroup.
