Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterised by abdominal pain, bloating and alteration in bowel frequency. The diagnosis is based upon symptom duration of at least 12 consecutive weeks of the preceding 12 months; these include abdominal pain or discomfort that is relieved with defecation and/or has an onset associated with a change in frequency of stool and/or in its form (appearance). Point prevalence of IBS in the developed world has been estimated to be approximately 10.5 per cent (6.6 per cent of men and 14 per cent of women) (Wilson et al. 2004). There is signiﬁ cant morbidity associated with IBS; quality of life is reduced and mental component scores have been found to be worse than in patients with a stroke or heart failure (Wilson et al. 2004).