Intestinal absorption in health and disease--sugars

Best Pract Res Clin Gastroenterol. 2003 Dec;17(6):943-56. doi: 10.1016/s1521-6918(03)00107-0.


Carbohydrates are mostly digested to glucose, fructose and galactose before absorption by the small intestine. Absorption across the brush border and basolateral membranes of enterocytes is mediated by sodium-dependent and -independent membrane proteins. Glucose and galactose transport across the brush border occurs by a Na(+)/glucose (galactose) co-transporter (SGLT1), whereas passive fructose transport is mediated by a uniporter (GLUT5). The passive exit of all three sugars out of the cell across the basolateral membrane occurs through two uniporters (GLUT2 and GLUT5). Mutations in SGLT1 cause a major defect in glucose and galactose absorption (glucose-galactose Malabsorption), but mutations in GLUT2 do not appear to disrupt glucose and galactose absorption. Studies on GLUT1 null mice and Fanconi-Bickel patients suggest that there is another exit pathway for glucose and galactose that may involve exocytosis. There are no known defects of fructose absorption.

Publication types

  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Carbohydrate Metabolism*
  • Dietary Carbohydrates / metabolism
  • Fructose / metabolism
  • Galactose / metabolism
  • Glucose / metabolism
  • Glucose Transporter Type 2
  • Glucose Transporter Type 5
  • Humans
  • Infant, Newborn
  • Infant, Newborn, Diseases / metabolism
  • Intestinal Absorption* / physiology
  • Malabsorption Syndromes / metabolism*
  • Microvilli / metabolism
  • Monosaccharide Transport Proteins / deficiency
  • Mutation


  • Dietary Carbohydrates
  • Glucose Transporter Type 2
  • Glucose Transporter Type 5
  • Monosaccharide Transport Proteins
  • Fructose
  • Glucose
  • Galactose