Background: Respiratory symptoms are over-represented in inflammatory bowel disease. There are similarities between the epidemiology of inflammatory bowel disease and that of respiratory conditions for which an adverse influence of salicylate has been identified. Natural salicylates exist within our diet.
Aims: To determine whether a lower intake of dietary salicylates is associated with less active inflammatory bowel disease and fewer concurrent respiratory symptoms.
Patients and methods: Respiratory status, inflammatory bowel disease activity, quality of life, and dietary habits were established in 73 patients with Crohn's disease and 69 with ulcerative colitis, using a self-administered questionnaire and peak expiratory flow rate readings. Harvey-Bradshaw and Simple Birmingham/Royal Free Colitis indices, an internally validated respiratory score, and estimated weekly dietary salicylate intake, were calculated for each patient.
Results: There was at least one respiratory symptom in 63.4% of patients. The commonest underlying respiratory diagnosis was asthma. Respiratory impairment was similar in ulcerative colitis and Crohn's disease; 56.3% of Crohn's disease patients with an active respiratory diagnosis had other extra-intestinal manifestations. The dietary salicylate intake was independent of respiratory status, but inversely correlated with ulcerative colitis activity (dietary salicylate intake 37.0mg versus 21.4mg for low and higher Simple Birmingham/Royal Free Colitis index, respectively; p<0.02). A similar association was not seen in Crohn's disease.
Conclusions: Respiratory impairment is common in inflammatory bowel disease. Higher intake of dietary salicylates is associated with less active colitis and possibly causally so.