Singh P, et al. - Using enzyme-linked immunosorbent assays and irritable bowel syndrome-symptom severity scale, researchers measured serum zonulin and intestinal fatty acid binding protein levels in diarrhea-predominant irritable bowel syndrome and constipation-predominant irritable bowel syndrome and compared with healthy controls and celiac disease. In irritable bowel syndrome, serum zonulin is upregulated and levels are comparable to those in celiac disease. In diarrhea-predominant irritable bowel syndrome, zonulin levels related to the severity of bowel habits. The levels of intestinal fatty acid binding protein in patients with irritable bowel syndrome did not increase. No significant increase in enterocyte death was suggested.