One Good Reason Not to Hold in a Fart: It Could Leak Out of Your Mouth

The next time you hold in a fart for fear of being heard by polite company, just remember this: It could leak out of your mouth instead of your butt. Writing on The Conversation, University of Newcastle nutrition and dietetics professor Clare Collins explains that pent-up gas can pass through your gut wall and get reabsorbed into your circulation. It's then released when you exhale, whether you like it or not.

“Holding on too long means the build up of intestinal gas will eventually escape via an uncontrollable fart,” Collins writes. In this case, the fart comes out of the wrong end. Talk about potty mouth.

A few brave scientists have investigated the phenomenon of flatulence. In one study, 10 healthy volunteers were fed half a can of baked beans in addition to their regular diets and given a rectal catheter to measure their farts over a 24-hour period. Although it was a small sample, the results were still telling. Men and women let loose the same amount of gas, and the average number of “flatus episodes” (a single fart, or series of farts) during that period was eight. Another study of 10 people found that high-fiber diets led to fewer but bigger farts, and a third study found that gases containing sulphur are the culprit of the world’s stinkiest farts. Two judges were tapped to rate the odor intensity of each toot, and we can only hope that they made it out alive.

Scientific literature also seems to support Collins’s advice to “let it go.” A 2010 paper on “Methane and the gastrointestinal tract” says methane, hydrogen sulfide, and other gases that are produced in the intestinal tract are mostly eliminated from the body via the anus or “expelled from the lungs.” Holding it in can lead to belching, flatulence, bloating, and pain. And in some severe cases, pouches can form along the wall of the colon and get infected, causing diverticulitis.

So go ahead and let it rip, just like nature intended—but maybe try to find an empty room first.