Pilot study on the effect of reducing dietary FODMAP intake on bowel function in patients without a colon

Poorly absorbed short-chain carbohydrates (FODMAPs) in the diet should, by virtue of their osmotic effects, increase fecal output following colectomy and ileal pouch formation or ileorectal anastomosis (IRA). The aim was to perform a proof-of-concept evaluation of this hypothesis.

Fifteen patients (13 pouch, 2 IRA) had dietary and symptomatic evaluation before and during a low FODMAP diet. Carbohydrate malabsorption was evaluated by breath tests. Pouchitis was assessed clinically/endoscopically or by fecal lactoferrin.

Of 8 patients with a breath hydrogen response to lactulose, 7 had fructose malabsorption, 3 with lactose malabsorption, and 1 had lactose malabsorption alone. Five of 7 studied retrospectively improved stool frequency (from median 8 to 4 per day; P = 0.02), this being sustained over 0.5-3 years of follow-up. Five of 8 patients completed a prospective arm of the study. One patient had sustained improvement in stool frequency and 1 had reduced wind production. Overall, none of 8 patients who had pouchitis improved. In contrast, median daily stool frequency fell from 8 to 4 (P = 0.001) in the 7 without pouchitis. The degree of change in FODMAP intake also predicted response. There was a tendency for pouchitis to be associated with low baseline FODMAP intake.

There is a high prevalence of carbohydrate malabsorption in these patients. Reduction of the intake of FODMAPs may be efficacious in reducing stool frequency in patients without pouchitis, depending on dietary adherence and baseline diet.