Differential effects of FODMAPs (fermentable oligo-, di-, mono-saccharides and polyols) on small and large intestinal contents in healthy subjects shown by MRI

Abstract

Objectives: The objective of this study was to investigate whether ingestion of fructose and fructans (such as inulin) can exacerbate irritable bowel syndrome (IBS) symptoms. The aim was to better understand the origin of these symptoms by magnetic resonance imaging (MRI) of the gut.

Methods: A total of 16 healthy volunteers participated in a four-way, randomized, single-blind, crossover study in which they consumed 500 ml of water containing 40 g of either glucose, fructose, inulin, or a 1:1 mixture of 40 g glucose and 40 g fructose. MRI scans were performed hourly for 5 h, assessing the volume of gastric contents, small bowel water content (SBWC), and colonic gas. Breath hydrogen (H2) was measured and symptoms recorded after each scan.

Results: Data are reported as mean (s.d.) (95% CI) when normally distributed and median (range) when not. Fructose increased area under the curve (AUC) from 0-5 h of SBWC to 71 (23) l/min, significantly greater than for glucose at 36 (11-132) l/min (P<0.001), whereas AUC SBWC after inulin, 33 (17-106) l/min, was no different from that after glucose. Adding glucose to fructose decreased AUC SBWC to 55 (28) l/min (P=0.08) vs. fructose. Inulin substantially increased AUC colonic gas to 33 (20) l/min, significantly greater than glucose and glucose+fructose (both P<0.05). Breath H2 rose more with inulin than with fructose. Glucose when combined with fructose significantly reduced breath H2 by 7,700 (3,121-12,300) p.p.m./min relative to fructose alone (P<0.01, n=13).

Conclusions: Fructose but not inulin distends the small bowel with water. Adding glucose to fructose reduces the effect of fructose on SBWC and breath hydrogen. Inulin distends the colon with gas more than fructose, but causes few symptoms in healthy volunteers.

Figures

Figure 1

Breath hydrogen (H2) concentrations throughout the study day for the 13 H2 producers after drinking each of the four drinks: glucose, fructose, fructan, and glucose+fructose mix. The time of drinking (t=0 min) is highlighted in the chart. Values are mean concentration (p.p.m.)±s.e.m.

Figure 2

Small bowel water content (SBWC) throughout the study day for 16 volunteers after drinking each of the four drinks: glucose, fructose, fructan, and glucose+fructose mix. The time of drinking (t=0 min) is highlighted in the chart. Values are mean volume (ml)±s.e.m.

Figure 3

A representative example of coronal images of the small bowel from a single volunteer at 75 min after drinking each of the test drinks: (a) glucose, (b) fructose, (c) glucose+fructose, and (d) fructan. The stomach and gall bladder are also visualized in these images.

Figure 4

The comparison between small bowel water content (SBWC) for 8 subjects who produced hydrogen (H2 positive) after fructose and 8 who did not (H2 negative) after drinking (a) fructose and (b) glucose+fructose. Values are mean concentration (ml)±s.e.m.

Figure 5

A representative example of coronal images through the large bowel of a single volunteer, comparing the visibility of gas in the colon at (a) baseline t= −45 min and (b) 255 min after drinking the fructan test meal.

Figure 6

Colonic gas volumes through the study day for the volunteers. The time of drinking (t =0 min) is highlighted in the chart. Values are mean volume (ml)±s.e.m.

Figure 7

The percent change from baseline of the small bowel diameters (SBDs) of the volunteers. The time of drinking is highlighted in the chart. Values are mean percent change ±s.e.m.