In a recent review published in the journal Dr nutrients, Italian researchers discuss the possible pathophysiological mechanisms of a low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) diet in the management of irritable bowel syndrome (IBS). They provide an overview of the current evidence, exploring the optimal application of the diet as well as the challenges associated with implementing a low FODMAP diet for IBS.
Revaluation: The role of the FODMAP diet in IBS. Image credit: Marharyta M/Shutterstock
IBS is a common gut-brain interaction disorder, affecting 3.8% to 12% of the population and is more prevalent in women. Diagnosis involves the exclusion of organic causes through specific tests. IBS manifests as chronic abdominal pain associated with bowel movements and altered bowel habits, which are classified into subtypes. Recent insights highlight immune activation and compromised intestinal barrier in its pathophysiology. Traditional drug therapy shows limited efficacy, prompting patients to explore alternative approaches, with more than 80% targeting food linkage. The low FODMAP diet has emerged as an evidence-supported intervention with two approaches to implementation: top-down and bottom-up. In the current review, researchers provide a comprehensive guideline for the FODMAP diet in IBS, discussing mechanisms, optimal settings, and potential pitfalls, with the goal of helping clinicians improve clinical outcomes and quality of life.
Low FODMAP Diet
The term FODMAP was coined to categorize fermentable carbohydrates associated with gastrointestinal symptoms, particularly in people with IBS. Evidence prior to this idea linked poorly absorbed short-chain carbohydrates to IBS symptoms. The first trial confirming the efficacy of a low fructose/fructan diet was conducted in 2006, demonstrating symptom relief and fructose malabsorption in people with IBS. Mechanistic investigations in 2010 explored FODMAP effects in an ileostomy model while measuring breath hydrogen levels and revealed that the osmotic and fermentative properties of FODMAPs contribute to symptoms.
The latest low FODMAP diet consists of six carbohydrates and aims to reduce overall FODMAP consumption. FODMAPs show three common functional properties: low absorption in the small intestine, rapid bacterial fermentation and osmotically active molecules. Proposed mechanisms for FODMAP-induced symptoms include luminal distension by gas and water, visceral hypersensitivity, increased intestinal permeability, microbiota changes, SCFA production, and motility changes. However, the precise interplay of these mechanisms in the context of IBS and the low FODMAP diet remains a complex and evolving area of research, requiring further exploration to further our understanding of the role of FODMAPs in IBS pathophysiology and dietary management.
Improvement of symptoms with diet
The low FODMAP diet has gained popularity over the years as a dietary intervention for IBS due to the positive results observed in many trials. Implementation of the method involves restricting fermentable carbohydrates. Studies show the effectiveness of this method in reducing symptoms such as bloating, pain and changes in stool frequency. About 65% of patients with carbohydrate malabsorption, especially fructose intolerance, show improvement in symptoms after one month of dietary restriction. Several international guidelines recommend the low FODMAP diet as second-line treatment for IBS, acknowledging its potential benefits. Comparative studies indicate the superiority of the low FODMAP diet over other dietary approaches and suggest its efficacy in improving overall gastrointestinal symptoms.
However, complications, cost, and concerns about nutritional adequacy require the involvement of trained dietitians in the implementation of a low FODMAP diet for IBS. Personalization and stepwise reintroduction of FODMAPs may increase adaptability and long-term adherence, providing patients with a tailored approach to managing IBS symptoms.
Studies on the effectiveness of low FODMAP diets in IBS initially report success rates of 50-75%. Efforts to increase effectiveness and identify predictors of response included a recent crossover trial, which suggested that responders had more severe IBS profiles and higher anxiety levels at baseline. Possible predictors include breath test results, a positive FODMAP food challenge test that shows promise in predicting food reactions. Analyzing the microbiota reveals associations between specific bacterial taxa and positive responses, emphasizing the role of the gut microenvironment. Faecal and urinary metabolites, particularly volatile organic compounds, show promise in differentiating responders, but further research is needed for validation and clarity.
Despite its effectiveness in relieving symptoms, the low FODMAP diet is associated with several challenges and limitations. Given the social and lifestyle disadvantages, including the impact on costs and quality of life, traditional dietary advice is considered more cost-effective and practical. Nutritional deficiencies, especially fiber and vitamins, increase anxiety, requiring monitoring by healthcare professionals. Microbiota changes are notably reduced Bifidobacterium, posing potential long-term risks. Additionally, there are challenges such as accurately measuring FODMAP content, potential increase in constipation, links to eating disorders, and limited long-term data. Although some studies have reported sustained benefits, more research is needed on the long-term efficacy and safety of the diet.
In conclusion, the low FODMAP diet is a promising strategy for managing IBS symptoms. Although the approach is effective and customizable, research gaps exist, particularly on microbiome effects and long-term effects. Researchers highlight the importance of carrying food under medical guidance. More research is needed to confirm the long-term effects and benefits of a low FODMAP diet.