Treatment of functional bowel symptoms in IBD

Treatment options for functional bowel symptoms in IBD include those used in irritable bowel syndrome (IBS), e.g. antispasmodics, antidiarrhoeals and low-dose antidepressants; however, there is limited research on the safety and effectiveness of these treatments in IBD. 

From a dietary perspective, identification of dietary triggers is useful but is often difficult due to the complexity of diet and eating habits and a delay in symptom generation following consumption of the food or ingredients. Many patients with IBD alter their diet in an effort to control their symptoms, whether during periods of active disease or during remission. In fact, these self-induced dietary restrictions may be detrimental to patients’ nutritional status. In IBS, an alteration of dietary fibre, a reduction in fat intake and improvements in eating habits (e.g. regular meal pattern, taking time to eat) can be effective treatment strategies; however, there is limited research on the relation of these measures to functional bowel symptoms in IBD. A diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) has become recognised as a successful management strategy for functional bowel disorders like IBS. Some FODMAPs increase small intestinal luminal water (e.g. fructose) while others are incompletely absorbed and undergo colonic fermentation by the gastrointestinal microbiota (e.g. fructans). In susceptible individuals, FODMAPs induce functional bowel symptoms. Some FODMAPs are prebiotics [e.g. fructo-oligosaccharide (FOS) and galacto-oligosaccharide (GOS)] that presumably have a beneficial effect on the gastrointestinal microbiota. A low FODMAP diet in IBS is associated with a reduction in luminal bifidobacteria and F. prausnitzii, which may negatively impact the gastrointestinal microbiota. For this reason, the low FODMAP diet incorporates short-term FODMAP restriction for only 4–8 weeks to induce symptom control, followed by FODMAP reintroduction to personal tolerance using food challenges. Thus, in the long-term, only high FODMAP foods that trigger symptoms are avoided, maintaining long-term nutritionally adequacy. Whether the gastrointestinal microbial changes seen following FODMAP restriction return to normal in the long term is unknown. 

A small body of research has assessed the effects of FODMAPs and FODMAP reduction in IBD. In active Crohn’s Disease, FOS supplementation was found to significantly increase the incidence and severity of abdominal symptoms, although it was not known whether any of the patients had concomitant functional bowel symptoms. In a FODMAP challenge study in patients with inactive IBD and functional bowel symptoms who had responded to a low FODMAP diet, challenges with FOS, but not GOS or the polyol sorbitol, induced symptoms. 

In a service evaluation of 72 IBD patients who had previously received low FODMAP dietary advice, 56% reported overall symptom improvement. A prospective study of the low FODMAP diet in 88 IBD patients showed that 78% of patients reported satisfactory relief from their functional bowel symptoms at follow-up compared to only 16% at baseline. Abdominal pain, bloating, flatulence, belching, incomplete evacuation, nausea and heartburn also improved. 

Further research is needed to understand the mechanisms by which food-related functional symptoms in IBD develop and which dietary interventions are effective and safe for the management of functional symptoms in patients with inactive IBD.