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intest (2)What Is Obnoxious Gas?

Obnoxious gas, or flatus, is gas that is not only offensive when passed but also lingers in the air longer than ordinary gas does.

Gas is a natural digestive product within the colon that is composed mainly of hydrogen and carbon dioxide gases. These gases are given off in the necessary bacterial breakdown of undigested fermentable food entering the colon from the small intestine.

Q: What makes gas obnoxious?

A: The production of obnoxious gas depends on the type and quantity of undigested food residue that is passed into the colon from the small intestine, dysfunctional motility instead of normal peristalsis, and dysbiosis. Dysbiosis is the condition of  having unhealthy or insufficient populations of microbes responsible for digesting (fermenting) foodstuffs in the lower gut or colon. 

Gases produced by intestinal microbes may modulate intestinal motor function (muscle movement) in individuals with functional bowel disease. Methane, produced by enteric bacteria in the human gut, is associated with slowed intestinal transit and constipation.1

What Is Obnoxious Gas In Celiac Disease and/or Gluten Sensitivity?


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  1. Jahng J, Jung IS, Choi EJ, Conklin JL, Park H. The effects of methane and hydrogen gases produced by enteric bacteria on ileal motility and colonic transit time. Neurogastroenterol Motil. 2012 Feb;24(2):185-90, e92. doi: 10.1111/j.1365-2982.2011.01819.x. Epub 2011 Nov 20.

    Methane is produced in the colon by intestinal methanogens (microbes) that metabolize hydrogen, one of the end products of normal anaerobic (meaning without oxygen) bacterial fermentation.  Fermentation of the undigested starchy part of carbohydrates produces hydrogen in the intestine, which is the food for methane production by intestinal methanogens.

    Hydrogen and methane are excreted in the flatus and in breath giving the opportunity to indirectly measure their production using breath testing. ((Triantafyllou K, Chang C, Pimentel M. Methanogens, Methane and Gastrointestinal Motility. J Neurogastroenterol Motil. 2014 Jan;20(1):31-40. Epub 2013 Dec 30. []