Low FODMAPs linked to altered metabolome, improved IBS symptoms

SAN DIEGO — Patients with irritable bowel syndrome who adhered to a low fermentable oligo-, di-, and mono-saccharides and polyols, or FODMAP, diet experienced reduced symptoms and corresponding changes in the metabolome, according to randomized controlled trial data presented at DDW 2016.

FODMAPs “have been shown in many studies to cause symptoms in IBS but the mechanisms are not completely understood, and it’s becoming increasingly recognized that metabolomic measurements are a valuable tool to understand the impact of diet on the host,” David E. Reed, MD, from Queen’s University in Ontario, Canada, said during his presentation. “Therefore, the aim of our study was to examine changes in the metabolome following either a high FODMAP diet or a low FODMAP diet, and how these might underlie alterations of symptoms in IBS.

Reed and colleagues evaluated 37 patients with IBS, 19 of whom were randomly assigned to a low FODMAP diet and 18 of whom were randomly assigned to a high FODMAP diet for 3 weeks, through which they kept a food diary. Patients were unaware of what diet they were assigned.

The researchers evaluated symptoms using the IBS severity scoring system, and evaluated the metabolome before and after the diet intervention by using the lactulose breath test, direct infusion and gas chromatography mass spectrometry for urine metabolic profiling, and partial 16S rRNA gene profiling for stool microbiota analysis.

Patients in the low FODMAP group had reduced symptoms (P < .001), while the high FODMAP group did not. Urine metabolic profiles were comparable between groups at baseline, but changed significantly after the diet intervention (P < .01).

Three main metabolites differed between groups: histamine, p-hydroxybenzoic acid and azelaic acid. The low FODMAP group showed a six-fold reduction in histamine compared with the high FODMAP group (P < .05). In addition, the low FODMAP group showed nonsignificant reductions in H2 gas production based on lactulose breath test results, and after correcting for baseline differences, this reduction became significant (P < .05).

Alpha and beta diversity of the fecal microbiota did not differ before and after the diets, but those without IBS-C in the low FODMAP group showed increased bacterial richness after the diet intervention compared with the high FODMAP group (P = .047). The relative abundance of Propionibacteriaceae (Actinobacteria) and several butyrate-producing bacteria were decreased in the low FODMAP group after the diet intervention.

“The low FODMAP [diet] decreased IBS symptoms whereas the high FODMAP diet had no effect, and the low FODMAP diet was associated with significant differences in the metabolome compared to the high FODMAP diet,” Reed concluded. “One of these differences was alterations in urinary histamine levels, which may suggest that FODMAPs could be linked to immune activation in a subset of patients, and these findings can guide future translational studies of carefully phenotyped patients to elucidate pathophysiological mechanisms in IBS.” – by Adam Leitenberger

Reference:

Vanner S, et al. Abstract #258. Presented at: Digestive Disease Week; May 21-24, 2016; San Diego.

Disclosures: Reed reports no relevant financial disclosures. Please see the DDW disclosure list for all other researchers’ relevant financial disclosures.