The incidence of adult type hypolactasia in patients with irritable bowel syndrome.

Introduction: The incidence of lactose intolerance in irritable bowel syndrome (IBS) varies in the literature (27-72%). Primary adult lactase deficiency (adult type hypolactasia) is the most common type of primary enzyme deficiency. Complaints related to lactose intolerance may overlap with the symptoms of IBS.

Aim: To assess the prevalence of primary hypolactasia in patients with IBS.

Material and methods: The study included 56 patients with IBS diagnosed based on the Rome III criteria and 23 healthy people. All study participants completed a questionnaire on IBS symptoms and lactose intolerance, and they underwent a hydrogen breath test (HBT) with lactose. In the group of patients with positive results of HBT, the polymorphism C/T -13910 and G/A -22018 in the promoter of the LCT gene encoding lactase was determined.

Results: Lactase deficiency was diagnosed in HBT in 34 (60.7%) patients with IBS and in the control group - in 10 (43.5%). Primary adult type hypolactasia was confirmed in 78.9% (n = 30; 79.3% in the study group; 77.8% in the control group). There were no statistically significant differences in the occurrence of LCT gene polymorphisms in particular IBS subtypes. Adult type hypolactasia was significantly more common in patients with severe than moderate and mild enzyme deficiency in HBT (p < 0.05).

Conclusions: The incidence of lactase deficiency in IBS patients is not different from that found in healthy subjects. Nevertheless, irrespective of the IBS subtype, lactose intolerance may pose additional issues in patients with IBS and requires the targeted treatment.