title: Prevalence of lactose malabsorption in Mexican children: importance of measuring methane in expired air.
abstract: OBJECTIVE
  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 H₂ and CH₄ 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 (H₂ ≥20 ppm), prevalence of LM was 31%; however, when methane concentration was considered (H₂ + (CH₄ 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.
authors: Laboratory of Gastro-Hepatology Research and Department of Nutrition, Hospital de Pediatría, Centro Médico Nacional, Instituto Mexicano del Seguro Social, México City, Mexico. segundomoran@hotmail.com
authors: Segundo
authors: S
authors: Moran
authors: Aline
authors: A
authors: Mina
authors: Ximena
authors: X
authors: Duque
authors: Salome
authors: S
authors: Anaya
authors: Uritzimar
authors: U
authors: San-Martin
authors: Patricia
authors: P
authors: Yañez
authors: Gustavo
authors: G
authors: Rodriguez-Leal
mesh_terms: D000293:Adolescent; D001944:Breath Tests; D002648:Child; D002675:Child, Preschool; D045853:Exhalation; D005243:Feces / Q000469:parasitology; D005260:Female; D006801:Humans; D006859:Hydrogen / Q000032:analysis; D007787:Lactose Intolerance / Q000175:diagnosis* / Q000453:epidemiology; D008297:Male; D008697:Methane / Q000032:analysis*; D008800:Mexico / Q000453:epidemiology; D015995:Prevalence
chemical_list: D006859:Hydrogen; D008697:Methane