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Author: Christian Maino-Vieytes, B.S. Nutritional Sciences, University of Maryland, College Park, M.S. Candidate, Division of Nutritional Sciences, University of Illinois at Urbana-Champaign


Irritable Bowel Syndrome (IBS) is a condition defined by continuous bouts of abdominal pain and altered bowel habits resulting in an abnormal stool. Unlike the inflammatory bowel diseases (IBD), IBS does not have a detectable disease origin or explanation. Also, IBS shares significant symptom-overlap with other illnesses, including lactose intolerance, which can make it difficult to diagnose. Consequently, many individuals routinely afflicted by IBS symptoms may be misdiagnosed or never diagnosed at all. However, there are a set of clinical criteria, called the Rome criteria, which are implemented by doctors, dietitians, or other providers to diagnose and classify IBS. Standards, such as the Manning criteria or the Kruis criteria can be used in place of or combined with Rome. On average, IBS affects younger and female individuals, and disturbed sleep patterns appear to play a role. IBS may present in tandem with other conditions including depression, anxiety, and fibromyalgia. In many cases, an imbalance between healthy and unhealthy bacteria in the gut is present. These facts highlight a hallmark of IBS, which is a compromised brain-gut connection.

IBS routinely presents as recurrent abdominal pain, described as cramping in nature, accompanied by diarrhea, constipation, or both. These symptoms inform the different categories of IBS:

  • IBS with predominant constipation (IBS-C)
  • IBS with predominant diarrhea (IBS-D)
  • IBS with mixed bowel habits (IBS-M)
  • IBS unclassified (IBS-U)

Symptoms are preceded by unique environmental “triggers” or foods that will cause symptoms to flare-up. Consequently, addressing food sensitivities through the management of these triggers features as the mainstay nutritional intervention for treating IBS.

FODMAPs and Nutritional Strategies for Those Living with IBS

The recently touted low-FODMAPs diet has been embraced by professionals and patients in the IBS community as suitable nutritional therapy. FODMAPs, which stands for fermentable oligo-, di-, monosaccharides, and polyols, are small, sugar-containing food components that are fermented by certain bacterial species residing within the gut. The chemical products of these fermentations, including different gases and water retention, are what precipitate the range of symptoms previously discussed (e.g. bloating, gas, abdominal pain, and altered stool). Clinical research has demonstrated that sticking to a diet low in FODMAPs can substantially lower the severity of symptoms for a majority of IBS patients. Despite this, a low-FODMAPs diet can be very restrictive and challenging to implement due to the pervasiveness of FODMAPs in the foods we consume regularly. Common high-FODMAP foods include fruits, vegetables, legumes, nuts/seeds, dairy, and sugar-alcohol sweeteners. The Institute for Functional Medicine provides further details on the pillars of the diet as well as a list of high-FODMAP foods and their low-FODMAP alternatives.

In addition to the low-FODMAPs diet, other evidence-based dietary strategies include supplementation with probiotics and consuming more fiber-containing foods. Gluten sensitivity, although frequently mentioned in the same sentence as IBS, has not benefited from the same degree of scientific support. What many confuse as gluten being a food-related trigger for IBS is, in fact, consumption of foods that contain FODMAPs in addition to gluten (wheat, rye, and barley all contain FODMAPs). Despite the broad scientific consensus on common food triggers for IBS, these food constituents will affect individuals differently. An individualized nutrition plan that carefully examines specific food triggers in one’s diet requires collaboration between patient and clinician and development with the guidance of a health care provider.


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