title: Ability of the normal human small intestine to absorb fructose: evaluation by breath testing.
abstract: OBJECTIVE
  Fructose consumption is increasing, and its malabsorption causes common gastrointestinal symptoms. Because its absorption capacity is poorly understood, there is no standard method of assessing fructose absorption. We performed a dose-response study of fructose absorption in healthy subjects to develop a breath test to distinguish normal from abnormal fructose absorption capacity.
  
  
  METHODS
  In a double-blind study, 20 healthy subjects received 10% solutions of 15, 25, and 50 g of fructose and 33% solution of 50-g fructose on 4 separate days at weekly intervals. Breath samples were assessed for hydrogen (H2) and methane (CH4) during a period of 5 hours, and symptoms were recorded.
  
  
  RESULTS
  No subject tested positive with 15 g. Two (10%) tested positive with 25 g fructose but were asymptomatic. Sixteen (80%) tested positive with 50 g (10% solution), and 11 (55%) had symptoms. Breath H2 was elevated in 13 (65%), CH4 in 1 (5%), and both in 2 (10%). Twelve (60%) tested positive with 50 g (33% solution), and 9 (45%) experienced symptoms. The area under the curve for H2 and CH4 was higher (P < .01) with 50 g compared with lower doses. There were no gender differences.
  
  
  CONCLUSIONS
  Healthy subjects have the capacity to absorb up to 25 g fructose, whereas many exhibit malabsorption and intolerance with 50 g fructose. Hence, we recommend 25 g as the dose for testing subjects with suspected fructose malabsorption. Breath samples measured for H2 and CH4 concentration at 30-minute intervals and for 3 hours will detect most subjects with fructose malabsorption.
authors.affiliation: Department of Internal Medicine and Clinical Research Center, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242-1009, USA. satish-rao@uiowa.edu
authors.forename: Satish S C
authors.initials: SS
authors.lastname: Rao
authors.forename: Ashok
authors.initials: A
authors.lastname: Attaluri
authors.forename: Leslie
authors.initials: L
authors.lastname: Anderson
authors.forename: Phyllis
authors.initials: P
authors.lastname: Stumbo
mesh_terms: D000328:Adult; D000368:Aged; D000388:Air / Q000032:analysis; D001944:Breath Tests / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D005632:Fructose / Q000008:administration & dosage / Q000493:pharmacokinetics*; D006801:Humans; D006859:Hydrogen / Q000032:analysis; D007408:Intestinal Absorption / Q000502:physiology*; D007421:Intestine, Small / Q000378:metabolism*; D008286:Malabsorption Syndromes / Q000175:diagnosis / Q000378:metabolism; D008297:Male; D008697:Methane / Q000032:analysis; D008875:Middle Aged; D011379:Prognosis; D012016:Reference Values; D013549:Sweetening Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D013549:Sweetening Agents; D005632:Fructose; D006859:Hydrogen; D008697:Methane