Low FODMAP Gluten-Free Diet Improves Gut Bacteria and Symptoms of Irritable Bowel Syndrome

Celiac.com 08/04/2021 - Dietary restriction of fermentable carbohydrates (a low-FODMAP diet) is getting a good deal of attention as a potential method for reducing symptoms in patients with irritable bowel syndrome (IBS), particularly in combination with a gluten-free diet. 

Several studies have associated IBS with dysbiosis in the gut microbiota. Additionally, a few studies have reported inflammation in the gastrointestinal (GI) system of adults with IBS. A team of researchers recently set out to  investigate the effects of a low FODMAP-gluten free diet (LF-GFD) on clinical symptoms, intestinal microbiota diversity, and fecal calprotectin (FC) level in Iranian patients with IBS.

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The research team included Kaveh Naseri, Hossein Dabiri, Mohammad Rostami‑Nejad, Abbas Yadegar, Hamidreza Houri, Meysam Olfatifar, Amir Sadeghi, Saeede Saadati, Carolina Ciacci, Paola Iovino, and Mohammad Reza Zali. They are variously affiliated with the Celiac Disease Department, Gastroenterology and Liver Diseases; the Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran; and the Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Shahid Arabi Ave., Yemen St., Velenjak, Tehran, Iran.

In their clinical trial study, the team put 42 IBS patients, with Rome IV criteria, on a low-FODMAP, gluten-free diet for 6 weeks and assessed symptoms using the IBS symptom severity scoring (IBS-SSS), and collected and analyzed fecal samples by quantitative 16 S rRNA PCR assay at baseline, and after the gluten-free diet. They compared gut microbiota diversity at baseline and after 6 weeks of dietary intervention, and analyzed all fecal calprotectin using the ELISA method.

Thirty patients, ranging in age from about 25 to 49 years old, completed the six-week diet. After the diet, they showed substantially reduced IBS-SSS overall, compared to the baseline scores. The team noted significant microbial differences in fecal samples taken before and after the dietary period. They found a significant increase in Bacteroidetes, and a decrease in the ratio of Firmicutes to Bacteroidetes (F/B) after the dietary intervention, and also noted decreased FC values.

The team's results suggest that IBS patients on a low FODMAP-gluten-free diet show marked reduction in IBS symptom severity, along with reduced FC level after normalization of gut microbiota. 

The team advocates for more rigorous trials to better assess long-term efficacy and safety of a a low FODMAP-gluten free diet for personalized nutrition in IBS.

Read more in BMC Gastroenterol (2021) 21:292