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J Gastrointestin Liver Dis. 2012 Jun;21(2):157-63.

Reassessment of the role of methane production between irritable bowel syndrome and functional constipation.

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Gastroenterology Unit, Department of Internal Medicine, University of Genoa, Genoa, Italy.



Modifications of intestinal gas due to changes in microbiota may produce different symptoms. Our aim was to assess whether different patterns of hydrogen (H₂) and methane (CH₄) excretion were related to some intestinal disturbances.


Six hundred and twenty-nine consecutive patients underwent a 50 g-glucose breath test (GBT) on account of intestinal symptoms, which were evaluated by means of a questionnaire. "H₂-producers" and "CH₄-producers" were defined as with the presence of H₂ peak >12 ppm more than the basal sample and mean CH₄ excretion of 2 ppm, respectively. Forty healthy subjects were studied as controls.


A small intestinal bacterial overgrowth was found in 45 cases (7.2%) and was associated with older age (p=0.0122). Methane production occurred in 32.3% of the study population. Methane excretion was strictly related to chronic constipation (p<0.001). Median CH₄ excretion was higher in constipated patients compared with patients with normal daily stools (p=0.0406) and even more with patients complaining of diarrhea (p=0.0011). Different criteria for defining "methane-producers" provided similar results. Mean methane excretion of "methane producers" was 30.3 ppm in functional constipation and 21.5 ppm in constipation-irritable bowel syndrome (C-IBS) (p=0.0458).


Methane excretion is clearly associated with alterations in intestinal motility, particularly favouring those with constipation. Mean methane excretion was higher in subjects suffering from functional constipation than C-IBS. Mean methane excretion ≥ 2 ppm appears to be an appropriate term to define "methane-producers".

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