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Cut out FODMAPs, cut out IBS symptoms?

If you have IBS, you know that physicians often lack well-supported dietary recommendations, so new research can be extremely valuable. This study is the first meta-analysis on the low-FODMAP strategy for curbing IBS symptoms

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Study under review: Does a diet low in FODMAPs reduce symptoms associated with functional gastrointestinal disorders? A comprehensive systematic review and metaanalysis

Introduction

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder that affects approximately 11% of the global population[1]. It is associated with abdominal pain, bloating, excessive flatulence, and altered bowel habits, severely lowering a person’s quality of life. Functional gastrointestinal disorders like IBS are not caused by structural abnormalities such as ulcers or tumors. Rather, they occur as a result of an abnormally functioning GI tract. This makes it difficult to accurately diagnose a person because no biomarker can indicate whether or not someone is suffering from IBS. Thus, clinicians have to rely on the reports of patients and on a set of criteria that have evolved over time for diagnosis.

Although the cause of IBS is still not well understood, researchers have put forth several hypotheses. Some of these theories include infections of the GI tract[2], psychological stress[3], abnormalities in gut motility[4], and gut-brain axis problems. Unfortunately, no cures currently exist for IBS. It is managed through various treatments such as 5-HT agonists/antagonists, antispasmodics, and antidepressants. These drugs can improve primary symptoms in some people, but they are unable to fully resolve disorders like IBS that are characterized by multiple symptoms. In addition to their limited use, there are several side effects associated with these drugs, so long-term use is not ideal.

As a result of these issues, researchers have investigated several alternative treatments as potential treatments for IBS. Patients suffering from IBS often report that particular foods worsen their symptoms more than others. Therefore, researchers have investigated various dietary interventions.

Dietary interventions that restrict specific food components, such as low-FODMAP diets, have been explored in several trials. FODMAP is an acronym that stands for "Fermentable, Oligo-saccharides, Di-saccharides, Mono-saccharides, and Polyols." These are short-chain carbohydrates that are poorly digested and absorbed[5] in the small intestine. As a consequence, they travel to the large intestine, where they are fermented by the bacteria that colonize it. This breakdown of carbohydrates by bacteria results in the formation of gasses such as hydrogen and methane in all individuals. However, this phenomenon seems to be excessive in IBS sufferers. Therefore, restricting foods that are rich in these short-chain carbohydrates (some of these are listed in Figure 1) can potentially alleviate many of the symptoms prominent in people with IBS.

Figure 1: Food FODMAP content

Source: The Monash University Low FODMAP diet

A previous systematic review[6] conducted in 2015 showed that a low-FODMAP diet was somewhat effective in reducing the severity of symptoms associated with IBS. Six studies were included in that review and of those six, three were randomized controlled trials. The authors concluded that although a low-FODMAP was somewhat effective in treating IBS symptoms, more controlled trials with longer durations were needed to gauge the efficacy and safety of a low-FODMAP diet in treating IBS symptoms. The current study extends upon that review with further research, and also performs a meta-analysis to quantitatively summarize the findings.

Irritable bowel syndrome is a functional gastrointestinal disorder associated with abdominal pain, distension, and altered bowel habits. It is theorized to have a variety of causes. It is currently considered incurable by most medical practitioners, and is most commonly managed through the use of pharmaceuticals. Several alternative treatments have been explored as a result of this and one of these treatments, a low-FODMAP diet, has shown some effectiveness in reducing the severity of the symptoms associated with IBS.

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