title: Frequency of lactose malabsorption among healthy southern and northern Indian populations by genetic analysis and lactose hydrogen breath and tolerance tests.
abstract: BACKGROUND
  Lactose malabsorption (LM), the inability to break down lactose into glucose and galactose, is due to a deficiency in the small intestinal lactase phlorizin hydrolase enzyme. Ethnic and geographic variations of LM are known.
  
  
  OBJECTIVE
  The aim of this study was to compare the frequency of LM in healthy southern and northern Indian populations.
  
  
  METHODS
  A total of 153 healthy volunteers (76 from southern and 77 from northern India) were evaluated for LM by using a lactose tolerance test (LTT), a lactose hydrogen breath test (lactose HBT), and polymerase chain reaction-restriction fragment length polymorphism to identify the lactase gene C/T-13910 polymorphism (confirmed by sequencing).
  
  
  RESULTS
  Volunteers from southern and northern India were comparable in age and sex. The LTT result was abnormal in 88.2% of southern Indians and in 66.2% of northern Indians (P = 0.001). The lactose HBT result was abnormal in 78.9% of southern Indians and in 57.1% of northern Indians (P = 0.003). The CC genotype was present in 86.8% and 67.5% (P = 0.002), the CT genotype was present in 13.2% and 26.0% (P = 0.036), and the TT genotype was present in 0% and 6.5% (P = 0.03) of southern and northern Indians, respectively. The frequency of symptoms after the lactose load (47.4% compared with 15.6%; P < 0.001) and peak concentrations of breath hydrogen (88.5 +/- 71.9 compared with 55.4 +/- 61.9 ppm; P = 0.003), both of which might indicate the degree of lactase deficiency, were higher in southern than in northern Indians.
  
  
  CONCLUSIONS
  The frequency and degree of LM is higher in southern than in northern Indian healthy populations because of genetic differences in these populations.
authors.affiliation: Department of Gastroenterology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India.
authors.forename: Janaki
authors.initials: J
authors.lastname: Babu
authors.forename: Sunil
authors.initials: S
authors.lastname: Kumar
authors.forename: P
authors.initials: P
authors.lastname: Babu
authors.forename: Jaishri H
authors.initials: JH
authors.lastname: Prasad
authors.forename: Uday C
authors.initials: UC
authors.lastname: Ghoshal
mesh_terms: D001786:Blood Glucose / Q000378:metabolism; D001944:Breath Tests; D004247:DNA / Q000097:blood / Q000235:genetics; D017931:DNA Primers; D005215:Fasting; D005838:Genotype; D005843:Geography; D006801:Humans; D006859:Hydrogen / Q000032:analysis; D007194:India / Q000453:epidemiology; D007421:Intestine, Small / Q000201:enzymology; D043183:Irritable Bowel Syndrome / Q000175:diagnosis; D043322:Lactase / Q000378:metabolism; D010694:Lactase-Phlorizin Hydrolase / Q000172:deficiency / Q000235:genetics*; D007785:Lactose / Q000378:metabolism*; D007787:Lactose Intolerance / Q000453:epidemiology* / Q000235:genetics*; D007789:Lactose Tolerance Test / Q000379:methods*; D012150:Polymorphism, Restriction Fragment Length; D012680:Sensitivity and Specificity
chemical_list: D001786:Blood Glucose; D017931:DNA Primers; D006859:Hydrogen; D004247:DNA; D043322:Lactase; D010694:Lactase-Phlorizin Hydrolase; D007785:Lactose