title: The prevalence of lactase deficiency and lactose intolerance in Chinese children of different ages.
abstract: OBJECTIVE
  To determine lactose metabolism and lactase activity in Chinese children of different ages, prevalence of lactase deficiency (LD), and lactose intolerance (LI).
  
  
  METHODS
  All 1168 healthy subjects between 3 and 13 years were recruited from schools in four large cities in China. They were screened by a 25 g lactose tolerance test. Some subjects were challenged with 50 g milk powder on different days. Both indicators, the expiratory H2 concentration and intolerance symptoms, were analyzed.
  
  
  RESULTS
  LD occurred in 38.5% of children in the 3-5 year age group, and 87% of the 7-8 year and 11-13 year old groups. The age of occurrence for LD may be at 7-8 years among Chinese children. The prevalence of LI among Chinese children was 12.2% at age 3-5 years, 33.1% at age 7-8 years, and 30.5% at age 11-13 years, respectively.
  
  
  CONCLUSIONS
  The results demonstrate that LD is very common in Chinese children from these four cities. LD and LI have a dose dependent response: lactose absorption and symptoms are based on lactase activity. The relationship between breast feeding history (or the history of cow milk intake) and lactase activity among Chinese children has not been established.
authors.affiliation: Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medicine, Beijing 100050, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Yang
authors.forename: M
authors.initials: M
authors.lastname: He
authors.forename: H
authors.initials: H
authors.lastname: Cui
authors.forename: L
authors.initials: L
authors.lastname: Bian
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000818:Animals; D001944:Breath Tests; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D006801:Humans; D006859:Hydrogen / Q000032:analysis; D043322:Lactase; D007785:Lactose / Q000008:administration & dosage; D007787:Lactose Intolerance / Q000201:enzymology* / Q000453:epidemiology; D007789:Lactose Tolerance Test; D008892:Milk / Q000009:adverse effects; D015995:Prevalence; D001616:beta-Galactosidase / Q000172:deficiency*
chemical_list: D006859:Hydrogen; D043322:Lactase; D001616:beta-Galactosidase; D007785:Lactose