Evidence-based Dietary Management of Functional Gastrointestinal Symptoms: The FODMAP Approach

Peter R Gibson; Susan J Shepherd


J Gastroenterol Hepatol. 2010;25(2):252-258. 

In This Article

Mechanistic Basis for Dietary Intervention

The physiological basis for the genesis of many functional gut symptoms is luminal distension. Evidence for this comes from barostat and gas infusion studies.[2,3] Luminal distension not only induces the symptoms of pain, the sensation of bloating and visible abdominal distension, but may also lead to secondary motility changes. Thus, minimizing the consumption of dietary factors that can distend the intestine would theoretically lead to improvement in global symptoms that characterize FGID. In the case of two of the most common types of FGID involving the intestine, irritable bowel syndrome (IBS) and functional bloating, the distal small and proximal large intestine would be the target regions of the gut.

The intestinal lumen can be distended by solids, liquids and gas. Solids can be altered in the proximal large intestine by changing the dietary fiber content both directly and indirectly via expansion or contraction of the bacterial mass. The liquid content in the distal small intestine will be dictated by the osmotic load in the lumen, and in the proximal large intestine by the osmotic load and the absorptive ability of the epithelium. The gas content will include a component of swallowed nitrogen, but the majority will be locally produced by bacterial fermentation. The volume that the gas creates will depend upon the number of molecules and its diffusion capacity across the epithelium and into the circulation. Dietary components that will putatively lead to luminal distension in the regions of interest will therefore be poorly absorbed in the proximal small intestine, will be small molecules (i.e. osmotically active), will be rapidly fermented by bacteria (with the potential to be fermented by small intestinal as well as cecal bacteria and to expand the bacterial population), and will be associated with hydrogen rather than methane production. Dietary FODMAP are the best fit for these principles.


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