title: Review article: lactose intolerance in clinical practice--myths and realities.
abstract: BACKGROUND
  Approximately 70% of the world population has hypolactasia, which often remains undiagnosed and has the potential to cause some morbidity. However, not everyone has lactose intolerance, as several nutritional and genetic factors influence tolerance.
  
  
  OBJECTIVE
  To review current clinical practice and identify published literature on the management of lactose intolerance.
  
  
  METHODS
  PubMed was searched using the terms lactose, lactase and diet to find original research and reviews. Relevant articles and clinical experience provided the basis for this review.
  
  
  RESULTS
  Lactose is found only in mammalian milk and is hydrolysed by lactase in the small intestine. The lactase gene has recently been identified. 'Wild-type' is characterized by lactase nonpersistence, often leading to lactose intolerance. Two genetic polymorphisms responsible for persistence have been identified, with their distribution concentrated in north Europeans. Symptoms of lactose intolerance include abdominal pain, bloating, flatulence and diarrhoea. Diagnosis is most commonly by the lactose hydrogen breath test. However, most people with hypolactasia, if given appropriate advice, can tolerate some lactose-containing foods without symptoms.
  
  
  CONCLUSIONS
  In clinical practice, some people with lactose intolerance can consume milk and dairy foods without developing symptoms, whereas others will need lactose restriction.
authors.affiliation: Department of Gastroenterology, Guy's and St Thomas' NHS Foundation Trust, London, UK. miranda.lomer@kcl.ac.uk
authors.forename: M C E
authors.initials: MC
authors.lastname: Lomer
authors.forename: G C
authors.initials: GC
authors.lastname: Parkes
authors.forename: J D
authors.initials: JD
authors.lastname: Sanderson
mesh_terms: D000328:Adult; D000818:Animals; D001944:Breath Tests; D002648:Child; D003611:Dairy Products / Q000009:adverse effects; D005260:Female; D014644:Genetic Variation; D006801:Humans; D007231:Infant, Newborn; D007421:Intestine, Small / Q000378:metabolism / Q000382:microbiology; D043183:Irritable Bowel Syndrome / Q000209:etiology; D043322:Lactase / Q000235:genetics / Q000378:metabolism; D007787:Lactose Intolerance / Q000175:diagnosis / Q000178:diet therapy / Q000235:genetics; D011247:Pregnancy
chemical_list: D043322:Lactase