Investigators explored the increased FODMAP-induced gastrointestinal (GI) symptoms in patients with irritable bowel syndrome (IBS) compared to healthy controls (HCs), despite FODMAPs yielding comparable small bowel water and colonic gas production in both populations. The article, published in Alimentary Pharmacology & Therapeutics, confirmed that fructans increase small bowel motility and colon gas and volume comparably in patients with IBS and HCs.
However, the investigators further reported that, “increased symptom responses to fructans in IBS co-vary with altered brain responses in pain-related regions, indicating that gut-brain axis dysregulation may drive FODMAP-induced symptom generation in IBS.”
The randomized study included 13 patients with IBS and 13 HCs, all of whom attended 3 visits where they received intragastric infusions of fructans (40 g/500 mL saline), glucose (40 g/500 mL saline), or saline (500 mL) during a 1-hour magnetic resonance imaging (MRI) brain scan, with abdominal MRI conducted before and after infusions.
In patients with IBS, fructans led to greater cramps, pain, flatulence, and nausea vs glucose (p =.03, .001, .009, and <.001) compared with HCs, with between-group differences observed for cramps and nausea (p =.004; p =.023). As noted, fructans increased small bowel motility and ascended colonic gas and volume equally between the groups (between-group p >.25). Additionally, colonic gas differences between fructans and saline “covaried with differences in bloating and cramps in IBS.” Finally, pain-related brain regions, including the cerebellum, supramarginal gyrus, anterior/midcingulate cortex, insula, and thalamus, exhibited differential responses to fructans in patients with IBS compared to HCs.
In short, the authors concluded that more severe fructans-induced symptoms in patients with IBS may be related to gut-brain axis dysfunction rather than increased GI parameter measures.