Low-FODMAP Diet for Treatment of Irritable Bowel Syndrome

Abstract

Functional bowel disorders, including irritable bowel syndrome (IBS), are common disorders that have a significant impact on patients' quality of life. These disorders present major challenges to healthcare providers, as few effective medical therapies are currently available. Recently, there has been increasing interest in dietary therapies for IBS, particularly a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs). Since ingestion of FODMAPs increases the delivery of readily fermentable substrates and water to the distal small intestine and colon-which results in luminal distention and gas-the reduction of FODMAPs in a patient's diet may improve functional gastrointestinal symptoms. This paper will review the pathophysiology of IBS and the role of FODMAPs for the treatment of this condition.

Keywords: FODMAPs; Irritable bowel syndrome; food allergy; food intolerance; hydrogen breath testing; small intestinal bacterial overgrowth.

Figure 1.

Mean change in irritable bowel syndrome (IBS) symptom severity scores at 12 weeks according to degree of adherence to an elimination diet. The difference between the treatment and control groups with high adherence to the elimination diet is 101 units (95% confidence interval, 54-147). *P<.001.

Figure 2

Ingested fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) are poorly absorbed in the small intestine. Their small molecular size results in an osmotic effect, drawing water (H₂0) through to the large intestine. FODMAPs are then fermented by colonic microflora, producing hydrogen (H₂) and/or methane gas (CH₄). The increase in fluid and gas leads to diarrhea, bloating, flatulence, abdominal pain, and distension.

Figure 3.

Profiles of breath hydrogen production over 14 hours of each dietary period in healthy subjects and patients with irritable bowel syndrome (IBS) on high-FODMAP (fermentable oligosaccharide, disaccharide, monosaccharide, and polyol) diets (HFD) and low-FODMAP diets (LFD). Total breath hydrogen was significantly greater in patients on the HFD in both groups (P<.0001). Patients with IBS produced significantly more breath hydrogen over the 14-hour period than healthy controls. ppm=parts per million.