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Among adults with moderate or severe symptoms of irritable bowel syndrome (IBS), more than 70% of those who followed either of 2 dietary interventions had a statistically significant reduction in symptoms after 4 weeks compared to 58% of those receiving optimized pharmacotherapy, according to study findings published in The Lancet Gastroenterology and Hepatology.1
After 6 months, when participants in the dietary change groups had partially returned to previous eating patterns, nearly two-thirds continued to report significant relief of symptoms, prompting study authors to suggest that dietary interventions might be an effective approach to first-line IBS treatment.1
IBS is described as a disorder of gut-brain interactions that affects approximately 4% of the adult population. While symptoms include chronic or recurrent abdominal discomfort and irregular bowel habits, results of routine clinical tests and investigations are normal, study authors wrote.1 Specific dietary modifications are typically used as first-line treatment with appropriate pharmacologic interventions chosen to target a most bothersome symptom.1
When more restrictive dietary measures are needed, a regimen low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) is often prescribed or one that has high fiber content, low total carbohydrates, and high proportions of protein and fat.1 Study authors, led by Sanna Nybacka, PhD, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden, described a dearth of research either comparing dietary approaches to IBS symptom management or comparing dietary approaches to medical treatment of the predominant gastrointestinal (GI) symptoms. Their study was designed to compare 3 options: a FODMAP diet plus traditional IBS dietary advice (FODMAP+); a low-carbohydrate diet, and pharmacologic treatment.1
For the single-center, single-blind randomized controlled trial Nybacka and fellow researchers enrolled individuals at a specialized outpatient clinic at the Sahlgrenska University Hospital, screening those aged 18 years and older with moderate-to-severe IBS (Rome IV criteria, IBS Severity Scoring System (IBS-SSS) score of 175 or greater, and no reported serious diseases or food allergies.
A total of 1104 individuals were assessed for eligibility between January 2017 and September 2021. The modified intention-to-treat cohort numbered 294 participants (18% men, mean age 38 years) who were randomly assigned in a 1:1:1 ratio to receive dietary or medical intervention as follows: FODMAP+ diet (n = 96); low carbohydrate diet (n = 97); and optimized medical therapy (n = 101). Participants followed the assigned regimens for 4 weeks. All were masked to the dietary intervention, but medication was open label.
The primary end point of interest was the proportion of participants in each group with a response to the 4-week intervention, defined as a reduction of 50 or more in IBS-SSS relative to baseline score.
Researchers reported that after 4 weeks, 73 (76%) of 96 participants in the FODMAP+ diet group, 69 (71%) of 97 participants in the low-carbohydrate diet group, and 59 (58%) of 101 participants in the optimized medical treatment group experienced the reduction of 50 or more in IBS-SSS vs baseline with a statistically significant difference between groups (P =.023).1
Participants in the 2 dietary intervention groups returned to their habitual dietary habits over the next 6 months. When investigators followed up with them, 68% in the FODMAP+ group and 60% in the low-carbohydrate group still had clinically significant symptom relief.1
Nybacka et al had hypothesized that the diet combining FODMAP, and traditional IBS dietary advice would be superior to the low-carbohydrate diet and to medical intervention, which was borne out by the findings. But as they point out, while the 2 dietary interventions proved more effective than medical therapy, all 3 reduced IBS symptom severity. Further, all 3 approaches also improved quality of life symptoms of depression and anxiety, and non-GI somatic symptoms.1
“With this study, we can show that diet plays a central role in the treatment of IBS, but that there are several alternative treatments that are effective,” Nybacka said in a University of Gothenberg press release.2 “We need more knowledge about how to best personalize the treatment of IBS in the future and we will further investigate whether there are certain factors that can predict whether individuals will respond better to different treatment options,” concluded the author.2