A randomised controlled trial conducted in general practice has examined the effectiveness of increasing the dietary content of soluble fibre (psyllium) or insoluble fibre (bran) in patients with irritable bowel syndrome (IBS).

The study involved 275 patients aged 18-65 years randomised to 12 weeks of treatment with 10g psyllium (n=85), 10g bran (n=97), or 10g rice flour (placebo, n=93). The primary end point was adequate symptom relief during at least two weeks in the previous month, analysed after 1, 2, and 3 months of treatment. Secondary end points included symptom severity score, severity of abdominal pain, and quality of life.

The following findings were reported:

• 54 (64%) of the patients on psyllium, 54 (56%) on bran and 56 (60%) in the placebo group completed the three month treatment period.

• The proportion of responders was statistically significantly greater in the psyllium group than in the placebo group during the first month (57% vs 35%; relative risk 1.60, 95% CI, 1.13 to 2.26) and the second month of treatment (59% vs 41%; 1.44, 1.02 to 2.06).

• Bran was more effective than placebo during the third month of treatment only (57% vs 32%; 1.70, 1.12 to 2.57), but this was not statistically significant in the worst case analysis (1.45, 0.97 to 2.16).

• After three months of treatment, symptom severity in the psyllium group was reduced by 90 points, vs. 49 points in the placebo group (p = 0.03) and 58 points in the bran group (p = 0.61 vs placebo).

• No differences were found with respect to quality of life.

• Early dropout from the study was most common in the bran group due to worsening of IBS symptoms.

The researchers conclude that their findings “support the addition of soluble fibre, such as psyllium, but not bran as an effective first treatment approach in the clinical management of patients with IBS.”