Prevalence of lactose malabsorption in Mexican children: importance of measuring methane in expired air.

Background and Aims To compare the prevalence of lactose malabsorption (LM) in children by analyzing hydrogen content in expired air vs. the inclusion of methane excretion. Methods A total of 138 children (4–17 years old) attending different boarding schools in Mexico were included in this study. To measure H 2 and CH 4 in expired air, breath samples were collected before administering whole milk (240 mL for 4- to 6-year-old children and 360 mL for 7- to 17-year-old children) and at 60, 120, 180, and 240 min afterward. A coprological examination was also carried out. Results Methane production prevalence was 47.8% (29.7% of the children produced methane and hydrogen, whereas 18.1% produced methane only). When measuring only exhaled hydrogen in expired air (H 2 ≥20 ppm), prevalence of LM was 31%; however, when methane concentration was considered (H 2  + (CH 4 x 2)) ≥18 ppm, prevalence increased significantly to 44%. Among children with LM, 51.6% presented intestinal parasites. Conclusions Methane should be measured in exhaled air to improve diagnosis of LM in populations with a high prevalence of methane production.