From the Journals

Microbiota may predict success on low FODMAP diet



Setting the stage for focused studies

The low FODMAP diet has demonstrated effectiveness for symptom relief in IBS, although potential risks include exacerbation of disordered eating, nutrition deficiencies, and disrupting gut microbiota, wrote Peter R. Gibson, MD, and Emma P. Halmos, MD, of Monash University and Alfred Health, Melbourne, in an accompanying editorial. However, the current study takes a new step on the journey to identifying patients most likely to respond to a low FODMAP diet, they said.

The editorialists noted three key takeaway points. First, the fecal microbiome may predict response to a low FODMAP diet. Second, the correction of the microbiome through the low FODMAP diet appeared to continue even after the diet was discontinued. “The other intriguing finding was that trehalose metabolic pathways were ‘activated’ in those with dysbiosis,” suggesting that trehalose might be an unrecognized FODMAP, the researchers noted. Trehalose has not been well studied but has been associated with pathogenicity, they said.

Although the study may overemphasize the impact of the low FODMAP diet given the relatively poor assessment of FODMAP intake, “the beauty of Vervier’s work is not in its definitive nature but in that it enables the creation of feasible innovative hypotheses that can be examined by focused studies,” they concluded.

The current study is important because IBS and related disorders of gut-brain interaction are common and greatly impact the quality of life of affected individuals, Jatin Roper, MD, of Duke University in Durham, N.C., said in an interview. Although the mechanisms for improvement are unknown, he said, “The low FODMAP diet is widely used to treat IBS, based on the hypothesis that this diet modifies the gut microbiome in a beneficial way.”

The study authors made two important discoveries, said Dr. Roper. “First, they found that they were able to distinguish IBS versus household controls based on their gut microbial signatures as well expression of key metabolic genes,” he said. “Second, they identified a unique microbiota subtype that was associated with a significant clinical response to the low FODMAP diet in IBS patients; IBS patients with a ‘pathogenic’ microbiome consisting of high Firmicutes and low Bacteroidetes responded to a greater degree to the low FODMAP diet compared to IBS patients with a ‘healthy’ microbiome that was similar to controls,” he explained. “Furthermore, after time on the low FODMAP diet, the IBS patients with pathogenic microbiome signatures developed a microbiome with low Firmicutes and high Bacteroidetes, which is thought to be healthy,” he added.

“These findings are exciting because they suggest that a patient’s microbial signature might be used clinically to predict response to the low FODMAP diet,” said Dr. Roper. “The surprising aspect of these results is that the microbial signature alone was able to predict response to a low FODMAP diet, despite the complex effects of the diet on host physiology and metabolism and the multifactorial etiology of IBS,” he noted.

However, larger clinical studies are needed to confirm the study findings results in larger patient cohorts and to show that standardized clinical assays can be used to prospectively predict response to dietary interventions such as low FODMAP in IBS, Dr. Roper emphasized.

“This paper provides preliminary and provocative findings that suggest that gut microbiota metabolites may play a role in the pathogenesis of IBS,” said Dr. Roper. “Future basic science and translational research is needed to study the mechanisms by which specific bacterial metabolites regulate intestinal function and disorders such as IBS. I hope that this research will eventually lead to metabolite-based therapies for IBS and other gastrointestinal disorders,” he said.

The study received no outside funding. Lead author Dr. Vervier had no financial conflicts to disclose. Dr. Gibson disclosed authoring two educational/recipe books on the low FODMAP diet, and Monash University financially benefits from the sales of a digital application, booklets, and online courses on the low FODMAP diet. Dr. Halmos had no financial conflicts to disclose. Dr. Roper had no financial conflicts to disclose.

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