Fructose and Fructans and Irritable Bowel Syndrome: MRI Study of Underlying Mechanisms

The purpose of the study is to investigate if patients with Irritable Bowel Syndrome (IBS) who also report bloating are more likely to report clinically important gastrointestinal symptoms after consuming fructose or fructans than after consuming glucose. We will also use MRI imaging to investigate the mechanisms by which those symptoms might be caused.

We will also study a parallel group of age and gender frequency matched healthy volunteers to provide descriptive statistics on a likely reference range for the healthy population.

Irritable Bowel Syndrome (IBS) is a common chronic condition, the main features of which are pain in the abdomen, an erratic bowel habit and sometimes bloating. Recent research has found that certain carbohydrates (sugars) in the diet can cause symptoms such as discomfort, bloating and wind/gas in people with IBS. These sugars are not well digested in the small bowel. They move to the colon (large bowel) where bacteria act on them by fermentation, producing gas. Some of the gas is absorbed and breathed out through the lungs, where we can measure it. The rest is released as flatulence/ wind, or occasionally belching. People without IBS rarely get symptoms after consuming these sugars. We want to find out what is different in IBS sufferers.

We will study fructose and fructans, sugars found in fruit, vegetables and wheat. Fructose draws water into the small bowel but fructans do not so we can compare effects on the small bowel and colon. Participants will attend three times, and on each occasion consume a drink containing either fructose, fructans, or glucose - a sugar that does not cause symptoms. Neither they nor the investigators present will know which drink is which. They will record their symptoms over the next 5 hours. We will observe how many report a clinically important increase in symptoms.

To look at what is happening in the bowel we will use a technique called Magnetic Resonance Imaging (MRI). We want to see if more gas, or water, builds up in people with IBS than in healthy volunteers. We will also measure the amount of hydrogen released in the breath to see if this is could be a simple bedside test that agrees with the MRI findings

Finding differences between the response of participants to fructose, fructans and glucose could change the way we advise patients, and could lead to the use of MRI as a test for IBS.