Digestive Diseases and Sciences, Vol. 49, No. 1 (January 2004), pp. 73–77 ( C  2004) A 14-Day Elemental Diet Is Highly Effective in Normalizing the Lactulose Breath Test MARK PIMENTEL, MD, FRCP(C), TESS CONSTANTINO, RN, YUTHANA KONG, MPH, MEERA BAJWA, MD, ABOLGHASEM REZAEI, MD, and SANDY PARK, BA Treatment of small intestinal bacterial overgrowth is frustrated by the low efficacy of antibiotics. Elemental diets have been shown to reduce enteric flora. In this study, we evaluate the ability of an elemental diet to normalize the lactulose breath test (LBT) in IBS subjects with abnormal breath test findings. Consecutive subjects with IBS and abnormal LBT suggesting the presence of bacterial overgrowth underwent a 2-week exclusive elemental diet. The diet consisted of Vivonex Plus (Novartis Nutrition Corp., Minneapolis, MN) in a quantity based on individual caloric requirement. On day 15 (prior to solid food), subjects returned for a follow-up breath test and those with an abnormal LBT were continued on the diet for an additional 7 days. The ability of an elemental diet to normalize the LBT was determined for days 15 and 21. A chart review was then conducted to evaluate any clinical benefit 1 month later. Of the 93 subjects available for analysis, 74 (80%) had a normal LBT on day 15 of the elemental diet. When those who continued to day 21 were included, five additional patients normalized the breath test (85%). On chart review, subjects who successfully normalized their breath test had a 66.4 ± 36.1% improvement in bowel symptoms, compared to 11.9 ± 22.0% in those who failed to normalize ( P < 0.001). An elemental diet is highly effective in normalizing an abnormal LBT in IBS subjects, with a concomitant improvement in clinical symptoms. KEY WORDS: bacterial overgrowth; enteral nutrition; elemental diet; irritable bowel syndrome. Bacterial overgrowth is a condition whereby the bacte- ria of the normally colonized colon are now also colo- nizing the relatively sterile small intestine. The resulting displacement of bacteria into the small bowel produces a constellation of symptoms including altered bowel habits, abdominal pain, bloating, gas, and distention (1). Clas- sically, bacterial overgrowth is observed in subjects with altered bowel anatomy (2–8). However, recent data sug- gest that the majority of subjects with IBS may also have an abnormal lactulose breath test (LBT) to suggest bac- Manuscript received June 21, 2003; accepted September 30, 2003. All from the GI Motility Program, Division of Gastroenterology, Department of Medicine, Cedars-Sinai Medical Center, CSMC Burns & Allen Research Institute, Los Angeles, California 90048, and School of Medicine, University of California, Los Angeles, California 90024, USA. Address for reprint requests: Mark Pimentel, MD, Cedars-Sinai Med- ical Center, 8635 West 3rd Streets, Suite 770 W, Los Angeles, California 90048, USA; mark.pimentel@cshs.org. terial overgrowth in the absence of underlying bowel dis- ease (9, 10). Although there remains some argument as to whether the abnormal LBT in IBS represents accelerated transit or abnormal small bowel flora, IBS symptoms re- spond to a normalization of the breath test with antibiotics and the LBT abnormality in IBS is significantly different from controls (10). One major problem in the management of bacterial overgrowth is the poor success of antibiotics in elimi- nating the large variety of organisms present. In fact, re- cent studies show that, at best, norfloxacin and ampicillin- clavulanate have a 30 and 50% success in normalizing the LBT to indicate eradication of bacterial overgrowth, respectively (11). This and other experiences lead clini- cians to use rotating antibiotics, prolonged courses, and repeated treatment that potentially lead to bacterial re- sistance. In the case of IBS, neomycin is successful in normalizing the LBT in only 20% of subjects receiving Digestive Diseases and Sciences, Vol. 49, No. 1 (January 2004) 73 0163-2116/04/0100-0073/0 C  2004 Plenum Publishing Corporation