Both a low-carbohydrate diet and a combined low FODMAP/traditional irritable bowel syndrome (IBS) diet were linked to greater symptoms reduction compared with optimized medical treatment alone in patients with IBS, according to findings from a randomized, controlled trial presented at Digestive Disease Week (DDW), held from May 21 to 24, 2022, in San Diego, California.

“Our findings support the current guidelines in the treatment of IBS [in which] general lifestyle and dietary advice are considered the first-line treatment options in managing symptoms of IBS,” said lead author Sanna Nybacka, RD, PhD, of the Department of Molecular and Clinical Medicine University at Gothenburg in Sweden. “Medical treatment should be guided by the patient’s symptom profile and preference, as a second-line treatment option.”

Components of the Low-Carbohydrate and FODMAP Diets

A total of 302 adults with moderate or severe IBS symptom severity were randomly assigned to 1 of 3 treatments:

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  • Low total carbohydrate diet (10% carbohydrates, 67% fat, and 23% protein)
  • Low fermentable oligosaccharides, disaccharides, monosaccharides, polyols (FODMAP) diet and traditional IBS dietary advice (50% carbohydrates, 33% fat, and 17% protein)
  • Optimized medical treatment strategy

Patients in both diet groups ate 2350 kcal/day and food was delivered weekly. Seven subjects were excluded from the trial, leaving 295 patients in the intention to treat analysis, according to the study authors.

Severity of IBS Reduce by All 3 Interventions

Patients in all 3 treatment arms experienced a reduction in symptoms as measured on the Irritable Bowel Syndrome Severity Scoring System (IBS-SSS); however, the change in symptoms severity was significantly greater in the dietary intervention arms than in the medical treatment arm (Table). Outcomes were not significantly different among the low-FODMAP and low-carbohydrate groups (P =.29).

Patients in the diet groups were significantly more likely to meet the primary endpoint of a greater than 50-point reduction in IBS-SSS.

Table. Response Rates Based on IBS-SSS

MeasureLow-Carb DietLow FODMAP + traditional IBS dietOptimized Medical TreatmentP valuea
Change in IBS-SSS-131-147-76<0.001
Proportion with ≥50 decrease in IBS-SSS72%75%58%0.025
aP values between the 3 groups
IBS-SSS, Irritable Bowel Syndrome Severity Scoring System

“Several different treatment options are effective in alleviating symptoms of IBS and patients’ preferences should be taken into account when deciding on treatment strategy,” Dr Nybacka said in an interview. More research is needed to identify pretreatment factors that predict a positive outcome with the various interventions to better optimize treatment selection, the study authors noted in their presentation.

“We have also conducted a 6-month follow-up of this study that we are currently analyzing,” Dr Nybacka said. “We need to evaluate that the treatments are safe, effective, and applicable to patients. We will also need to elucidate which pretreatment factors can predict a positive treatment outcome to give more personalized treatment to patients.”

Read more research from DDW 2022 here.


Nybacka S, Törnblom H, Josefsson A, et al. Both a low carbohydrate diet and a combined low FODMAP/traditional IBS diet are superior to optimized medical treatment in irritable bowel syndrome (IBS): a randomized controlled trial. Presented at: DDW 2022; May 21-24, 2022; San Diego, CA. Abstract 684.