Omeprazole induces altered bile acid metabolism

Gut. 1998 Feb;42(2):266-71. doi: 10.1136/gut.42.2.266.


Background: It has been reported that the acidity of gastric contents could be an important factor in regulating jejunal flora.

Aims: To investigate the effects of omeprazole induced changes in gastric pH on jejunal flora and bile acid metabolism.

Methods: Twenty one patients with gastric ulcer and 19 healthy volunteers were studied. Deconjugation of bile acids was detected using a bile acid breath test. Jejunal fluid was aspirated using a double lumen tube with a rubber cover on the tip and deconjugation was examined using thin layer chromatography. Fat malabsorption was detected by a triolein breath test.

Results: In the bile acid breath test, expired breath samples from all patients and healthy volunteers showed significantly greater 14CO2 specific activity after omeprazole treatment (20 mg/day) than before treatment. Bacterial overgrowth was found in the jejunal fluid and gastric juice of both ulcer patients and healthy volunteers after omeprazole treatment. The following species were identified: Escherichia coli, Candida albicans, enterococcus, Lactobacillus bifidus, Bacteroides vulgatus, B uniformis, Eubacterium lentum, Eu parvum, and Corynebacterium granulosum. All of these species, except E coli and C albicans, deconjugate bile acids. There was a significant correlation between 14CO2 activity and gastric pH, both before and after omeprazole treatment in both groups. The triolein breath test revealed impaired fat absorption in both groups after omeprazole treatment.

Conclusions: Both patients with gastric ulcer and healthy volunteers exhibited increased deconjugation of bile acids caused by bacterial overgrowth in the jejunum and fat malabsorption after omeprazole treatment. The bacterial over-growth consisted of both anaerobes and aerobes with deconjugation ability and was probably associated with an omeprazole induced shift to neutral pH in the gastric juice.

MeSH terms

  • Adult
  • Aged
  • Anti-Ulcer Agents / adverse effects*
  • Anti-Ulcer Agents / therapeutic use
  • Bile Acids and Salts / metabolism*
  • Breath Tests
  • Dietary Fats / metabolism
  • Gastric Mucosa / metabolism
  • Humans
  • Hydrogen-Ion Concentration
  • Jejunum / metabolism
  • Jejunum / microbiology*
  • Malabsorption Syndromes / chemically induced
  • Male
  • Middle Aged
  • Omeprazole / adverse effects*
  • Omeprazole / therapeutic use
  • Stomach / microbiology
  • Stomach Ulcer / drug therapy
  • Stomach Ulcer / metabolism*
  • Stomach Ulcer / microbiology


  • Anti-Ulcer Agents
  • Bile Acids and Salts
  • Dietary Fats
  • Omeprazole