title: Methane and the gastrointestinal tract.
abstract: BACKGROUND
  Several gases are produced through enteric fermentation in the intestinal tract. Carbon dioxide, hydrogen, hydrogen sulfide, and methane are thought to be the most common of these. Recent evidence suggests that methane may not be inert. In this review article, we summarize the findings with methane.
  
  
  METHODS
  This is a review article discussing the various component gases in the gastrointestinal tract and their relevance to health and disease. Specific attention was paid to understanding methane.
  
  
  RESULTS
  The majority of these gases are eliminated via flatus or absorbed into systemic circulation and expelled from the lungs. Excessive gas evacuation or retention causes gastrointestinal functional symptoms such as belching, flatulence, bloating, and pain. Between 30 and 62% of healthy subjects produce methane. Methane is produced exclusively through anaerobic fermentation of both endogenous and exogenous carbohydrates by enteric microflora in humans. Methane is not utilized by humans, and analysis of respiratory methane can serve as an indirect measure of methane production. Recent literature suggests that gases such as hydrogen sulfide and methane may have active effects on gut function. In the case of hydrogen sulfide, evidence demonstrates that this gaseous product may be produced by human eukaryotic cells. However, in the case of methane, there is increasing evidence that this gas has both physical and biological effects on gut function. It is now often associated with functional constipation and may have an active role here.
  
  
  CONCLUSIONS
  This review of the literature discusses the significance of enteric flora, the biogenesis of methane, and its clinical associations. Furthermore, we examine the evidence for an active role of methane in gastrointestinal motility and the potential applications to future therapeutics.
authors.affiliation: Division of Gastroenterology, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.
authors.forename: Ara B
authors.initials: AB
authors.lastname: Sahakian
authors.forename: Sam-Ryong
authors.initials: SR
authors.lastname: Jee
authors.forename: Mark
authors.initials: M
authors.lastname: Pimentel
mesh_terms: D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology*; D041981:Gastrointestinal Tract / Q000187:drug effects / Q000382:microbiology* / Q000502:physiology*; D006801:Humans; D008697:Methane / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D008697:Methane