Advising patients with irritable bowel syndrome to cut their intake of fermentable short-chain carbohydrates improved GI symptoms as much as “traditional” recommendations to reduce meal size, gas-producing foods, insoluble fiber, fat, and caffeine, investigators reported in a randomized, multicenter, single-blinded study that appears in the November issue of Gastroenterology.
“Combining elements from these two strategies might further reduce symptoms of IBS,” said Lena Böhn, a registered dietician at the University of Gothenburg (Sweden) and her associates. Clinicians, however, should be aware that patients may cut calories in response to dietary advice even if they do not need to do so, which could eventually lead to malnutrition. “Monitoring calorie and nutrient intake in patients who follow dietary advice seems important,” the investigators wrote.
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Fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) such as apples, beans, white bread, and milk are poorly absorbed in the small intestine, which can trigger bouts of gas from colonic bacterial fermentation and diarrhea because of osmotic water transfer into the lumen of the colon. Several recent studies had linked FODMAPs to GI symptoms in IBS, but no prior randomized controlled trial had compared real-world recommendations to follow either a low-FODMAP or traditional IBS diet, the researchers noted (Gastroenterology 2015. doi: 10.1053/j.gastro.2015.07.056).
For the study, they randomized 75 patients who met Rome III IBS criteria to either the low-FODMAP or traditional IBS diet for 4 weeks. They used the IBS severity scoring system (Aliment Pharmacol Ther. 1997;11[2]:395-402) to assess symptomatic response and studied food diaries completed before and after the interventions to understand how closely patients followed the dietary advice.
A total of 67 patients completed the study, including 56 women and 14 men, Ms. Böhn and her associates reported. Both diets led to similarly significant (P < .0001) decreases in IBS symptoms, with no clear differences between them. Half the patients in the low-FODMAP group experienced at least a 50-point improvement in their IBS severity score, compared with 46% of patients in the traditional IBS diet cohort (P = .72).
Food diaries showed that patients adhered well to their diets, the investigators said, but “an unwanted and somewhat surprising finding” was that patients cut their caloric intake – by an average of 442 kcal/day on the low-FODMAP diet and almost 200 kcal/day on the traditional diet. “We hypothesize that even though patients were not advised to reduce calorie intake, receiving detailed dietary advice [to] limit intake of certain food constituents may result in this unwanted effect,” said the investigators. “In the short term, this should not be harmful, but a lesson from this trial is that calorie and nutrient intake needs to be supervised in order to avoid malnutrition if long-term dietary changes are initiated.”
The study was supported by the Swedish Medical Research Council and by the University of Gothenburg’s Marianne and Marcus Wallenberg Foundation, Centre for Person-Centered Care, and Faculty of Medicine. The investigators declared no competing interests.