Methane CH₄ (breath gas)

CH₄ production by methanogenic archaea in the large intestine. Methane is associated with slower gut transit and constipation; because methane producers are archaea rather than bacteria, the term IMO is now used instead of methane SIBO. How the CH₄ value is to be read is set out in your findings report.

How methane is produced in the gut

Methane is not produced by bacteria but by archaea, a separate group of microorganisms; in the human gut it is mainly Methanobrevibacter smithii. These archaea combine hydrogen released by fermenting bacteria with carbon dioxide to form methane. Four molecules of hydrogen and one molecule of carbon dioxide become one molecule of methane – the gas volume decreases, and the fermenting bacteria can keep working because their hydrogen is removed. Because archaea are not bacteria, an increase in methane-producing microbes is now called IMO (intestinal methanogen overgrowth) rather than methane SIBO.

Low CH₄ – what happens in the gut?

Many people carry few or no methane-producing archaea in their gut. The hydrogen from fermentation is then removed by other routes – exhaled, used by acetogenic or sulphate-reducing bacteria or released as intestinal gas. No disadvantage from low methane alone is known.

High CH₄ – what happens in the gut?

Methane acts on the gut muscles: in studies it slowed the onward movement of the gut contents and increased non-propulsive, rhythmic contractions. The stool stays in the gut longer, loses more water and becomes harder. The slower transit gives the microbes more time for fermentation and the archaea more hydrogen – a cycle that can sustain itself. Methane producers can also multiply in the small intestine.