Academic journal article The Journal of the Royal Society for the Promotion of Health

Randomised-Controlled Trial of a Fibre Supplement on the Symptoms of Irritable Bowel Syndrome

Academic journal article The Journal of the Royal Society for the Promotion of Health

Randomised-Controlled Trial of a Fibre Supplement on the Symptoms of Irritable Bowel Syndrome

Article excerpt

Key words

Dietary fibre; irritable bowel syndrome (IBS); non-starch polysaccharide (NSP); wheat bran


The aim of this study was to assess the effect of coarse wheat bran on specific bowel function parameters and symptoms in patients with irritable bowel syndrome (IBS). A longitudinal, prospective, randomised, placebo-controlled trial was undertaken. The duration of treatment was eight to 12 weeks and this consisted of 10-20g/day of coarse wheat bran or a low fibre placebo taken in addition to the normal diet. Twenty-eight outpatients fulfilling the Rome criteria for constipation-predominant IBS were recruited to the trial (14 in the treatment group; 14 in the placebo group). Twelve people completed the trial in the treatment group and ten in the placebo group.

The main outcome measures included changes in symptoms recorded in a diary, changes in objective measurements of bowel function and subjective overall feelings of improvement. The bran group significantly increased their non-starch polysaccharide (NSP) intake over that of the placebo group (p<0.05). Mean stool wet weight increased significantly more in the bran group than in the placebo group (p<0.05), but other bowel function measurements and all recorded symptoms were not different. Many patients reported changes in bowel habit that were not reflected in the objective measurements. The addition of coarse wheat bran to the diet increased NSP ingestion and stool wet weight in this group of IBS patients, but no evidence was obtained that such treatment was of benefit to these patients, other than a placebo effect on symptoms.


During the 1970s and early 1980s patients with irritable bowel syndrome (IBS) were often advised to increase the fibre content of their diet in an attempt to reduce gastrointestinal symptoms,1 even though trials failed to show any significant benefits. However, the methods used in many of these studies have been criticised.2 It is recognised that there are subsets of the IBS condition3 and because of the wide spectrum of symptoms reported, it is unlikely that one single treatment will benefit all of them. Nevertheless, dietary manipulation with fibre remains the most commonly recommended first step in the management of IBS.4

Constipation in IBS is reported to be relieved by a high fibre diet5 but constipation is a subjective term and can be used to describe infrequent defaecation, the passing of small, formed motions, straining to defaecate, unproductive calls to stool or unsatisfying defaecation.6 Increased dietary fibre is generally recommended for simple constipation, although its effectiveness is thought to be mixed in patients with constipation-predominant IBS.7

In this study we evaluated the effect of increasing non-starch polysaccharide (NSP) intake in IBS patients reporting constipation-predominant symptoms, using a longitudinal, prospective, placebo-controlled trial. Particular attention was paid to measuring changes in individual symptoms throughout the study period and to measuring, objectively, changes in bowel function and dietary intake.



Patients aged 18-70 years were recruited from hospital gastroenterology out-patient clinics in south-east London. All patients diagnosed with IBS (negative investigations, symptoms of the Rome criteria8 and who had no other bowel disorder or serious illness) were interviewed. Patients were included if stool frequency was reported to be less than once per day or was of variable frequency. However, as frequency of defaecation may not be related to transit time,9 patients were also included if stools were passed once or twice a day and were reported to be 'hard', 'pellety' or 'variable' in form, or if straining to defaecate was common. Patients reporting loose or watery stools, or who reported defaecating more than twice a day, were excluded. Patients were also excluded if, in the preceding six months, they had been pregnant or had undergone major surgery, or were following any therapeutic diet or taking medication known to affect bowel function. …

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