title: Prevalence of lactose intolerance in Chile: a double-blind placebo study.
abstract: OBJECTIVE
  Lactase non-persistence (LNP), or primary hypolactasia, is a genetic condition that mediates lactose malabsorption and can cause lactose intolerance. Here we report the prevalence of lactose intolerance in a double-blind placebo study.
  
  
  METHODS
  The LCT C>T-13910 variant was genotyped by RT-PCR in 121 volunteers and lactose malabsorption was assessed using the hydrogen breath test (HBT) after consuming 25 g of lactose. Lactose intolerance was assessed by scoring symptoms (SS) using a standardized questionnaire following challenge with a lactose solution or saccharose placebo.
  
  
  RESULTS
  The LNP genotype was observed in 57% of the volunteers, among whom 87% were HBT⁺. In the HBT⁺ group the median SS was 9 and in the HBT⁻ group the median SS was 3 (p < 0.001). No difference was observed in the SS when both groups were challenged with the placebo. The most common symptoms included audible bowel sounds, abdominal pain and meteorism. In the ROC curve analysis, an SS ≥ 6 demonstrated 72% sensitivity and 81% specificity for predicting a positive HBT. To estimate prevalence, lactose intolerance was defined as the presence of an SS ≥ 6 points after subtracting the placebo effect and 34% of the study population met this definition.
  
  
  CONCLUSIONS
  The LNP genotype was present in more than half of subjects evaluated and the observed prevalence of lactose intolerance was 34%.
authors.affiliation: Medical Student, School of Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Latorre
authors.forename: Pablo
authors.initials: P
authors.lastname: Besa
authors.forename: Carmen G
authors.initials: CG
authors.lastname: Parodi
authors.forename: Verónica
authors.initials: V
authors.lastname: Ferrer
authors.forename: Lorena
authors.initials: L
authors.lastname: Azocar
authors.forename: Marife
authors.initials: M
authors.lastname: Quirola
authors.forename: Luis
authors.initials: L
authors.lastname: Villarroel
authors.forename: Juan F
authors.initials: JF
authors.lastname: Miquel
authors.forename: Eduardo
authors.initials: E
authors.lastname: Agosin
authors.forename: José
authors.initials: J
authors.lastname: Chianale
mesh_terms: D000293:Adolescent; D000328:Adult; D002677:Chile / Q000453:epidemiology; D004311:Double-Blind Method; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D043322:Lactase / Q000235:genetics; D007785:Lactose / Q000008:administration & dosage; D007787:Lactose Intolerance / Q000453:epidemiology* / Q000208:ethnology / Q000235:genetics; D007789:Lactose Tolerance Test; D008297:Male; D015995:Prevalence; D011446:Prospective Studies; D055815:Young Adult
chemical_list: D043322:Lactase; D007785:Lactose