title: Prevalence and presentation of lactose intolerance and effects on dairy product intake in healthy subjects and patients with irritable bowel syndrome.
abstract: OBJECTIVE
  The effects of lactase deficiency on digestive symptoms and diet in patients with irritable bowel syndrome (IBS) have not been well defined. We assessed lactose absorption and tolerance and the intake of dairy products in healthy volunteers (controls) and patients with diarrhea-predominant IBS (D-IBS).
  
  
  METHODS
  Sixty patients diagnosed with D-IBS at the Sir Run Run Shaw Hospital, Hangzhou, China and 60 controls were given hydrogen breath tests to detect malabsorption and intolerance after administration of 10, 20, and 40 g lactose in random order 7-14 days apart; participants and researchers were blinded to the dose. We assessed associations between the results and self-reported lactose intolerance (LI).
  
  
  RESULTS
  Malabsorption of 40 g lactose was observed in 93% of controls and 92% of patients with D-IBS. Fewer controls than patients with D-IBS were intolerant to 10 g lactose (3% vs 18%; odds ratio [OR], 6.51; 95% confidence interval [CI], 1.38-30.8; P = .008), 20 g lactose (22% vs 47%; OR, 3.16; 95% CI, 1.43-7.02; P = .004), and 40 g lactose (68% vs 85%; OR, 2.63; 95% CI, 1.08-6.42; P = .03). H(2) excretion was associated with symptom score (P = .001). Patients with D-IBS self-reported LI more frequently than controls (63% vs 22%; OR, 6.25; 95% CI, 2.78-14.0; P < .001) and ate fewer dairy products (P = .040). However, self-reported LI did not correlate with results from hydrogen breath tests.
  
  
  CONCLUSIONS
  The risk of LI is related to the dose of lactose ingested and intestinal gas production and is increased in patients with D-IBS. Self-reported LI, but not objective results from hydrogen breath tests, was associated with avoidance of dairy products.
authors.affiliation: Department of Gastroenterology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, PR China.
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Yang
authors.forename: Yanyong
authors.initials: Y
authors.lastname: Deng
authors.forename: Hua
authors.initials: H
authors.lastname: Chu
authors.forename: Yanqun
authors.initials: Y
authors.lastname: Cong
authors.forename: Jianmin
authors.initials: J
authors.lastname: Zhao
authors.forename: Daniel
authors.initials: D
authors.lastname: Pohl
authors.forename: Benjamin
authors.initials: B
authors.lastname: Misselwitz
authors.forename: Michael
authors.initials: M
authors.lastname: Fried
authors.forename: Ning
authors.initials: N
authors.lastname: Dai
authors.forename: Mark
authors.initials: M
authors.lastname: Fox
mesh_terms: D000328:Adult; D001944:Breath Tests; D002681:China; D003611:Dairy Products; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000150:complications*; D007787:Lactose Intolerance / Q000150:complications / Q000453:epidemiology* / Q000473:pathology*; D008297:Male; D008875:Middle Aged