Effect of a Low FODMAP Diet on SIBO Breath Test Positivity

Overview

Bloating is the most common symptom associated with disorders of brain-gut interaction (i.e., functional bowel disorders) such as irritable bowel syndrome, a disorder characterized by abdominal pain and altered bowel habits which affects up to 11% of world population. A common cause of bloating is small intestinal bacterial overgrowth (SIBO), a condition defined by excessive and/or abnormal type of bacteria in the small bowel. The potential role of SIBO for irritable bowel syndrome (IBS) was initially proposed by Pimentel et al. Using lactulose breath tests (LBTs), 78% of patients with IBS were also diagnosed with SIBO. After antibiotic therapy, 48% of patients no longer met the Rome criteria for IBS. A recent systematic review and meta-analysis concluded that the prevalence of SIBO is increased in IBS.

Despite the clinical efficacy of LFD in improving symptoms of IBS-D, its mechanism of action is not clear. Recently, Zhou et al have shown FODMAPs induce colonic tight junction dysfunction and visceral hypersensitivity in rat models, both of which are reversible when rats were fed an LFD. They further showed that this effect of FODMAPs is mediated by microbial dysbiosis and elevated fecal lipopolysaccharide level. However, studies evaluating the effect of LFD on colonic permeability of humans are lacking. Studies have shown significant differences in intra-individual luminal and mucosal microbiome of patients with functional gastrointestinal disorders as well as an increase in Prevotella abundance in IBS patients with SIBO as compared with IBS patients without SIBO. Thus, the exact effect of FODMAP on intestinal permeability and mucosal microbiome in humans is not clear and needs further evaluation.