The hypothesis underlying this study is that failure to recognise the role of lactose intolerance among patients with ulcerative colitis has led to inappropriate dietary advice and treatment with drugs that contain lactose as a filler. These failures exacerbate symptoms and lead to the unnecessary use of immune suppressant drugs.

There is disagreement amongst researchers regarding the amount of lactose needed to cause symptoms in those who are lactose intolerance. The general consensus is that the amount of lactose in a glass of milk (12 grams) is enough to cause mild symptoms in most patients who are lactose intolerant (1). However, there have been a number of studies and case studies that argue that much lower amounts can cause symptoms (2, 3, 4, 5). This could be as little as 0.02 grams (6).

Ulcerative colitis is a chronic relapsing inflammatory disease of the colon and rectum, characterised by recurrent episodes of abdominal pain and profuse diarrhoea. The prevalence of lactose intolerance in patients with ulcerative colitis is not greater than in the general population, but there is no evidence as to whether these patients are more sensitive to lactose.

This study will identify the threshold at which symptoms of lactose intolerance develop in those who have both lactose intolerance and ulcerative colitis, to provide appropriate advice and treatment in the management of patients with these conditions.