Irritable bowel syndrome (IBS), a common chronic gastrointestinal disorder characterized by abdominal pain and alteration of bowel habits in the absence of structural abnormality, has a prevalence of approximately 15% in western populations1,2. Patients with IBS can be classified by their predominant bowel habits: diarrhea-predominant IBS (D-IBS), constipation-predominant IBS, or IBS with alternating bowel movements3. Although smooth-muscle relaxants, bulking agents, and anti-diarrheal agents are commonly used as conventional IBS treatments, many IBS patients turn to alternative treatments because of the lack of therapeutic advantages of these treatments4. Therefore, the development of a new therapy is necessary for IBS patients.