Irritable bowel syndrome (IBS) is a common gastrointestinal condition characterized by abdominal cramping, bloating, and changes in bowel habits. Some individuals experience constipation, others diarrhea, and some alternate between the two. IBS is more common in women than in men, and symptoms often worsen during periods of stress.
Although the exact cause of IBS is considered unknown, research has identified several factors that may contribute to symptoms in at least a subset of patients. A study published in Gastroenterology (April 1992; Volume 102, Issue 4) examined 242 patients with IBS and found that approximately two-thirds had a positive hydrogen breath test. This test measures hydrogen produced in the breath when undigested carbohydrates are fermented by intestinal bacteria. In this study, a positive test indicated lactose intolerance. When lactose was restricted in the diet, 43% of patients experienced complete symptom remission and 41% experienced partial improvement. The authors concluded that hydrogen breath testing may be useful in evaluating IBS patients, even though lactose intolerance does not account for all cases.
Other research suggests that IBS-like symptoms may sometimes reflect an underlying condition. A study published in Gastroenterology (June 2004; Volume 126, Issue 7, Pages 1721–1732) reported that celiac disease can initially present with symptoms indistinguishable from IBS. The authors suggested that testing for celiac disease in patients diagnosed with IBS may be worthwhile.
Small intestinal bacterial overgrowth (SIBO) has also been linked to IBS. An article published in the Journal of the American Medical Association (August 18, 2004; Volume 292, Issue 7, Pages 852–858) proposed that excessive bacterial growth in the small intestine may play a role in IBS. Supporting this idea, a study published in the American Journal of Gastroenterology (December 2000; Volume 95, Issue 12, Pages 3503–3506) evaluated 157 IBS patients with evidence of bacterial overgrowth and found that 48% experienced remission of symptoms after antibiotic treatment. Additional research in the same journal (2000; Volume 95, Issue 5, Pages 1231–1238) found that supplementation with probiotic bacteria was associated with symptom improvement in IBS patients.
Dietary factors have also been proposed as contributors to IBS. Elaine Gottschall, a biochemist and cell biologist, suggested that diets high in complex carbohydrates may promote bacterial overgrowth, contributing to IBS as well as inflammatory bowel conditions. Her book, Ending the Vicious Cycle, outlines a dietary approach that eliminates lactose, gluten, starches, and refined sugars with the goal of reducing bacterial fuel and allowing intestinal function to normalize. While this approach does not work for all patients, many individuals with chronic intestinal symptoms report benefit.
