, a professor of nutrition at the University of Newcastle in Australia, has recently been making headlines for an article she wrote in The Conversation
in which she claimed that if you hold in a fart too long some of it will eventually come out your mouth:
Trying to hold it in leads to a build up of pressure and major discomfort. A build up of intestinal gas can trigger abdominal distension, with some gas reabsorbed into the circulation and exhaled in your breath. Holding on too long means the build up of intestinal gas will eventually escape via an uncontrollable fart.
To back up this claim she cites a 2010 article in the journal Digestive Diseases and Sciences
, and this article does indeed say this:
Both H2 and CH4 are thought to be produced exclusively by anaerobic fermentation in the gut. These gases can then traverse the intestinal mucosa and be absorbed into the systemic circulation. Once in the circulation, the only known source of clearance of these two gases is via the lungs. One study found that the volume of H2 present in the bowel of ten normal subjects averaged 0.24 ml/min in the fasting state. This rate sharply increased upon instillation of lactulose, to a mean peak rate of 1.6 ml/min. It was found that 14% of total H2 produced was excreted via the lungs and that breath H2 excretion correlated well with total H2 production. Another much more physiological study of hydrogen production and excretion found that overall 58% of H2 is excreted in the breath.
However, it's hydrogen sulfide, H2
S, that makes farts smell, and according to the article, this isn't excreted in your breath: "Once in circulation, H2
S is excreted primarily by the kidneys as free or conjugated sulfate."