title: Intestinal carbohydrate absorption and permeability at high altitude (5,730 m).
abstract: To investigate the effects of high altitude on intestinal function, the absorption and permeation of nonmetabolizable carbohydrates were measured in 14 volunteers (median age 21 yr, range 19-37 yr) at sea level in Oxford, UK; at 1,050 m in Nepal; at 5,570 m after 5 days at > 5,500 m; and at 5,730 m after 11 days at > 5,500 m. Body weight decreased 5.7 +/- 1.19 kg from sea level to 5,570 m (P < 0.001 by paired t test) despite 72-h dietary records showing no change in energy intake. Absorption of carbohydrates by mediated transport was measured by urinary xylose and 3-O-methyl-D-glucose excretion. Xylose excretion (%oral dose) decreased from 31.4 +/- 4.5% to 20.7 +/- 4.5% (P < 0.001) and 3-O-methyl-D-glucose excretion decreased from 39.7 +/- 6.1 to 33.7 +/- 7.0% (P = 0.003) from sea level to 5,730 m. Monosaccharide permeation measured by L-rhamnose excretion decreased from 11.3 +/- 2.5 to 6.2 +/- 2.0% (P = 0.001). Intestinal permeability, a measure of barrier function (ratio of lactulose to L-rhamnose), increased from 0.036 +/- 0.014 at sea level to 0.084 +/- 0.042 at 1,050 m (P = 0.006), possibly due to infective enteropathy after arrival in Nepal, but reverted to normal (0.045 +/- 0.013; P = 0.062) at 5,730 m. Absorption of all carbohydrates returned to normal after return to the UK. This study showed that a decrease in mediated (D-xylose or 3-O-methyl-D-glucose) and diffusional (L-rhamnose) monosaccharide absorption occurs at high altitude but that intestinal permeability at 5,730 m is unchanged.
authors.affiliation: Department of Service Industries, Bournemouth University, United Kingdom.
authors.forename: A J
authors.initials: AJ
authors.lastname: Dinmore
authors.forename: J S
authors.initials: JS
authors.lastname: Edwards
authors.forename: I S
authors.initials: IS
authors.lastname: Menzies
authors.forename: S P
authors.initials: SP
authors.lastname: Travis
mesh_terms: D019325:3-O-Methylglucose; D000328:Adult; D000531:Altitude; D004040:Dietary Carbohydrates / Q000493:pharmacokinetics*; D004435:Eating / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology*; D007792:Lactulose / Q000652:urine; D008297:Male; D008757:Methylglucosides / Q000493:pharmacokinetics; D010539:Permeability; D012210:Rhamnose / Q000652:urine; D012885:Skinfold Thickness; D015431:Weight Loss / Q000502:physiology; D014994:Xylose / Q000493:pharmacokinetics
chemical_list: D004040:Dietary Carbohydrates; D008757:Methylglucosides; D019325:3-O-Methylglucose; D007792:Lactulose; D014994:Xylose; D012210:Rhamnose