Dietary poorly absorbed, short-chain carbohydrates increase delivery of water and fermentable substrates to the proximal colon

Aliment Pharmacol Ther. 2010 Apr;31(8):874-82. doi: 10.1111/j.1365-2036.2010.04237.x. Epub 2010 Jan 22.


Background: Functional gut symptoms are induced by inclusion and reduced by dietary restriction of poorly absorbed short-chain carbohydrates (FODMAPs), but the mechanisms of action remain untested.

Aims: To determine the effect of dietary FODMAPs on the content of water and fermentable substrates of ileal effluent.

Methods: Twelve ileostomates without evidence of small intestinal disease undertook two 4-day dietary periods, comprising diets differing only in FODMAP content in a randomized, cross-over, single-blinded intervention study. Daytime (14 h) ileal effluent was collected on day four of each diet. Patients rated effluent volume and consistency on a 10-cm visual analogue scale. The FODMAP content of the diet and effluent was measured.

Results: Ingested FODMAPs of 32% (range 6-73%) was recovered in the high FODMAP diet effluent. Effluent collection weight increased by a mean of 22% (95% CI, 5-39), water content by 20% (2-38%) and dry weight by 24% (4-43%) with the high compared to low FODMAP diet arm. Output increased by 95 (28-161) mL. Volunteers perceived effluent consistency was thicker (95% CI, 0.6-1.9) with the low FODMAP diet than with the high FODMAP diet (3.5-6.1; P = 0.006).

Conclusions: These data support the hypothetical mechanism; FODMAPs increase delivery of water and fermentable substrates to the proximal colon.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Colon / metabolism*
  • Cross-Over Studies
  • Dietary Carbohydrates / pharmacokinetics*
  • Dietary Proteins
  • Feces / chemistry
  • Humans
  • Intestinal Absorption / physiology
  • Intestine, Small / metabolism
  • Male
  • Middle Aged
  • Single-Blind Method
  • Water / metabolism*


  • Dietary Carbohydrates
  • Dietary Proteins
  • Water