According to a new study, evidence was found that these dietary interventions were more efficacious at 4 weeks, suggesting their potential as first-line treatments.
“IBS is a disorder that may have different underlying causes, and it can manifest in different ways among patients. It is also likely that the most effective treatment option can differ in patients,” said lead author Sanna Nybacka, RD, PhD, a postdoctoral researcher in molecular and clinical medicine at the University of Gothenburg’s Sahlgrenska Academy, Gothenburg, Sweden.
“Up to 80% of patients with IBS report that their symptoms are exacerbated by dietary factors, and dietary modifications are considered a promising avenue for alleviating IBS symptoms,” she said. “However, as not all patients respond to dietary modifications, we need studies comparing the effectiveness of dietary vs pharmacological treatments in IBS to better understand which patients are more likely to benefit from which treatment.”
The study was published online in The Lancet Gastroenterology and Hepatology.
Treatment Comparison
Dr. Nybacka and colleagues conducted a single-blind randomized controlled trial at a specialized outpatient clinic at Sahlgrenska University Hospital in Gothenburg, Sweden, between January 2017 and September 2021. They included adults with moderate to severe IBS, which was defined as ≥ 175 points on the IBS Severity Scoring System (IBS-SSS), and who had no other serious diseases or food allergies.
The participants were assigned 1:1:1 to receive a low-FODMAP diet plus traditional dietary advice (50% carbohydrates, 33% fat, 17% protein), a fiber-optimized diet with low carbohydrates and high protein and fat (10% carbohydrates, 67% fat, 23% protein), or optimized medical treatment based on predominant IBS symptoms. Participants were masked to the names of the diets, but the pharmacological treatment was open-label.
After 4 weeks, participants were unmasked and encouraged to continue their diets.
During 6 months of follow-up, those in the low-FODMAP group were instructed on how to reintroduce FODMAPs, and those in the pharmacological treatment group were offered personalized diet counseling and to continue their medication.
Among 1104 participants assessed for eligibility, 304 were randomly assigned. However, 10 participants did not receive their intervention after randomization, so only 294 participants were included in the modified intention-to-treat population: 96 in the low-FODMAP group, 97 in the low-carbohydrate group, and 101 in the optimized medical treatment group. Overall, 82% were women, and the mean age was 38 years.
Following the 4-week intervention, 73 of 96 participants (76%) in the low-FODMAP group, 69 of 97 participants (71%) in the low-carbohydrate group, and 59 of 101 participants (58%) in the optimized medical treatment group had a reduction of ≥ 50 points in the IBS-SSS compared with baseline.
A stricter score reduction of ≥ 100 points was observed in 61% of the low-FODMAP group, 58% of the low-carbohydrate group, and 39% of the optimized medical treatment group.
In both the low-FODMAP group and the low-carbohydrate group, 95% of participants completed the 4-week intervention compared with 90% among the pharmacological group. Two people in each group said adverse events prompted their discontinuation, and five in the medical treatment group stopped prematurely due to side effects. No serious adverse events or treatment-related deaths occurred.
“We were surprised by the effectiveness of the fiber-optimized low-carbohydrate diet, which demonstrated comparable efficacy to the combined low-FODMAP and traditional IBS diet,” Dr. Nybacka said. “While previous knowledge suggested that high-fat intake could worsen symptoms in some individuals, the synergy with low-carbohydrate intake appeared to render the diet more tolerable for these patients.”
The authors noted that since all three treatment options showed significant and clinically meaningful efficacy, patient preference, ease of implementation, compliance, cost-effectiveness, and long-term effects, including those on nutritional status and gut microbiota, should be considered in personalized plans.