Slow-release L-cysteine capsule prevents gastric mucosa exposure to carcinogenic acetaldehyde: results of a randomised single-blinded, cross-over study of Helicobacter-associated atrophic gastritis

Scand J Gastroenterol. 2017 Feb;52(2):230-237. doi: 10.1080/00365521.2016.1249403. Epub 2016 Nov 3.


Introduction: Helicobacter-induced atrophic gastritis with a hypochlorhydric milieu is a risk factor for gastric cancer. Microbes colonising acid-free stomach oxidise ethanol to acetaldehyde, a recognised group 1 carcinogen.

Objective: To assess gastric production of acetaldehyde and its inert condensation product, non-toxic 2-methyl-1,3-thiazolidine-4-carboxylic acid (MTCA), after alcohol intake under treatment with slow-release L-cysteine or placebo.

Methods: Seven patients with biopsy-confirmed atrophic gastritis, low serum pepsinogen and high gastrin-17 were studied in a cross-over single-blinded design. On separate days, patients randomly received 200 mg slow-release L-cysteine or placebo with intragastric instillation of 15% (0.3 g/kg) ethanol. After intake, gastric concentrations of ethanol, acetaldehyde, L-cysteine and MTCA were analysed.

Results: Administration of L-cysteine increased MTCA (p < .0004) and decreased gastric acetaldehyde concentrations by 68% (p < .0001). The peak L-cysteine level was 7552 ± 2687 μmol/L at 40 min and peak MTCA level 196 ± 98 μmol/L at 80 min after intake. Gastric L-cysteine and MTCA concentrations were maintained for 3 h. The AUC for MTCA was 11-fold higher than acetaldehyde, indicating gastric first-pass metabolism of ethanol. With placebo, acetaldehyde remained elevated also at low ethanol concentrations representing 'non-alcoholic' beverages and food items.

Conclusions: After gastric ethanol instillation, slow-release L-cysteine eliminates acetaldehyde to form inactive MTCA, which remains in gastric juice for up to 3 h. High acetaldehyde levels indicate a marked gastric first-pass metabolism of ethanol resulting in gastric accumulation of carcinogenic acetaldehyde. Local exposure of the gastric mucosa to acetaldehyde can be mitigated by slow-release L-cysteine capsules.

Keywords: Alcohol; carcinogenesis; ethanol; prophylaxis; stomach.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Acetaldehyde / analysis*
  • Adult
  • Carbolines / analysis
  • Carbolines / metabolism*
  • Carcinogenesis / drug effects
  • Cross-Over Studies
  • Cysteine / administration & dosage*
  • Delayed-Action Preparations / administration & dosage
  • Ethanol / administration & dosage*
  • Female
  • Gastric Juice / microbiology
  • Gastric Mucosa / metabolism
  • Gastrins / blood
  • Gastritis, Atrophic / metabolism*
  • Gastritis, Atrophic / microbiology
  • Helicobacter / isolation & purification
  • Humans
  • Male
  • Middle Aged
  • Single-Blind Method
  • Stomach Neoplasms / metabolism
  • Sweden


  • Carbolines
  • Delayed-Action Preparations
  • Gastrins
  • Ethanol
  • 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid
  • gastrin 17
  • Acetaldehyde
  • Cysteine