What is the benefit of coarse wheat bran in patients with irritable bowel syndrome?

The effect of open treatment with coarse wheat bran was compared with response to placebo, given in the form of a double blind, cross over drug trial, in patients with irritable bowel syndrome. Both bran and placebo significantly reduced the severity of most of the symptoms. Constipation was the only symptom that improved significantly with bran, but not with placebo, and was the only symptom that predicted a successful outcome with bran. Diarrhoea did not improve with bran. In fact, stools became less formed in patients presenting with this symptom. The incidence of pain and urgency was significantly more frequent on bran compared with placebo. Compared with a baseline period, bran treatment resulted in an acceleration of whole gut transit time (p less than 0.05) increases in daily stool weight (p less than 0.01) and the proportion of unformed stools (p less than 0.01) but no change in stool frequency. Coarse wheat bran was no better than placebo for most symptoms in irritable bowel syndrome, although its efficacy in constipation was confirmed.