The role of colonic microbiota in lactose intolerance

Dig Dis Sci. 2004 Jan;49(1):78-83. doi: 10.1023/b:ddas.0000011606.96795.40.


In a previous study we observed a clear difference in lactose intolerance symptoms after a 25-g lactose load in two groups of persons with lactase nonpersistence and similar small intestinal lactase activity. From this observation we hypothesized a colon resistance factor. To identify this factor, the microbial composition of fecal samples of the two lactose intolerant groups (one with mild symptoms, n = 16, and one with diarrhea-predominant symptoms, n = 11) was compared using the fluorescent in situ hybridization technique. Large interindividual differences were found in the numbers of total bacteria and main groups of bacteria (CV: 0.65 and 0.64-0.82 respectively). The bacterial numbers were not significantly different between the two groups. A significant negative correlation, however, was found between the individual symptom scores of the intolerant persons and the numbers of total hybridizable bacteria (r(s) = -0.42, P = 0.03). The results suggest that an increased number of bacteria might contribute--by means of a higher fermentative capacity--to the reduction of lactose intolerance symptoms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Clostridium / genetics
  • Clostridium / isolation & purification
  • Colony Count, Microbial
  • DNA Probes
  • DNA, Bacterial / analysis
  • Eubacterium / genetics
  • Eubacterium / isolation & purification
  • Feces / microbiology
  • Female
  • Humans
  • In Situ Hybridization, Fluorescence
  • Lactose / metabolism
  • Lactose Intolerance / metabolism
  • Lactose Intolerance / microbiology*
  • Lactose Intolerance / pathology
  • Lactose Tolerance Test
  • Male
  • Middle Aged
  • Severity of Illness Index


  • DNA Probes
  • DNA, Bacterial
  • Lactose