Increased prevalence of lactose malabsorption in Crohn's disease patients at low risk for lactose malabsorption based on ethnic origin.

Objectives: The aim of this study was to compare the prevalence of lactose malabsorption (LM) in various subgroups of inflammatory bowel disease patients with controls matched for age, sex, and ethnic origin.

Methods: In 260 patients with IBD [121 Crohn's disease (CD) and 139 ulcerative colitis (UC)] and 158 controls at low and moderate risk for LM the prevalence of lactose malabsorption was determined by H2 breath testing.

Results: A control group at low ethnic risk had a prevalence of LM of 29.2% compared with 40.0% in CD (p < 0.025) and 13.3% of ulcerative colitis patients (p < 0.025). No significant differences were observed in comparable groups at moderate risk for LM. Irrespective of ethnic origin, 68.1% of patients with CD limited to the terminal ileum were lactose malabsorbers compared with 43.5% of patients with Crohn's colitis (p < 0.05). Additional analysis according to anatomical location indicated that Crohn's disease of the proximal small bowel (duodenum, jejunum), terminal ileum, terminal ileum plus colon, and colon alone were associated with a prevalence of LM of 100, 68.1, 54.5, and 43.5% respectively.

Conclusions: In patients at low ethnic risk there is a statistically significant increase in the prevalence of LM in CD patients and a decreased prevalence in ulcerative colitis compared with controls.