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Is it better to keep a fart or burp in, or let it out?
Peter Gibson
Professor of gastroenterology, Monash University, Melbourne, Australia
Farting in public is generally considered antisocial – worse, if it’s smelly – and is a source of jokes and “cute” phrases such as “cutting the cheese” and “silent but deadly”. Even the word “fart” is considered unacceptable or impolite in some situations, yet there is no other single word that best describes the act.
Everyone has gas in their gut, and most people fart multiple times a day, while many burp. The sources of the gas are what is swallowed normally (we all do it) or in association with fizzy drinks – some makes it through to the large intestine – and what our microbiota (bacteria and other microbes) in the large intestine make by fermenting carbohydrates (like dietary fibre) and protein. Some of the gases are used by the microbiota in the colon, some are absorbed into the bloodstream and are breathed out from the lungs, and some make their way to the outside world via farting or burping.
How much gas an individual has depends on their diet. A high fibre intake will lead to more odourless gas, whereas higher protein intake may be associated with more smelly farts. Their microbiota, their physiology (how fast content moves through the gut for instance) and how much air is swallowed are also factors.
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To hold a fart or a burp in or let it out presents a balance between social acceptability and personal comfort
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The vast majority of these gases are odourless: carbon dioxide, hydrogen, methane and nitrogen (from swallowed air). Some are not. The smelly gases are generally from the fermentation of protein and some other pathways associated with our microbiota. These are all normal. Our noses are exquisitely sensitive to malodorous gases, so farts need only a very small percentage of smelly gases to be detected.
If you suppress the urge to fart, the accumulation of gas in the bowel can cause problems, as shown in experiments where gas was bubbled into the bowel of healthy people and they were told to either fart on the “call” from their abdomen or to suppress the call and not fart. Those who didn’t fart experienced pain and discomfort.
The gas stretches the wall of the bowel, and this stretch sends messages to the brain that will be interpreted as awareness, discomfort or pain. The interpretation depends on the tuning of the bowel (called visceral sensitivity) and the tuning of the brain. For example, people with irritable bowel syndrome have heightened visceral sensitivity (less gas may produce greater awareness or discomfort); a footballer during a match will suppress brain perception, and therefore be less aware of gas during the game.
To hold it in or let it out represents the balance between social acceptability and personal comfort. My opinion is that it is best to get it out in a socially acceptable place. Perhaps we should discourage the “unacceptability” of farting or belching (especially important for children during their impressionable years). No matter, the jokes will surely continue!
Peter Holness
Hertford, UK
Old as I am, one should never become too old to find burps and farts funny. I don’t suffer from funny. I don’t suffer from flatulence myself – I enjoy it! And a flippant question like this in a science magazine deserves answering both flippantly and scientifically. To that end, at the risk of sounding obvious, the answer to this question is: “It depends on the social and medical context.”
As a teenage boy, I remember going around with other young men, drinking fizzy lemonade and sounding like bullfrogs as we competed to produce the longest, loudest burps. But an involuntary, throat-scorching, eggy belch at the wrong moment could easily sabotage a burgeoning romance. It might also indicate a medical condition requiring treatment, such as acid reflux or a stomach infection.
Anyone who has ever eaten a flatulent food item may have experienced discomfort that would be medically inadvisable to endure for too long. As such, the need to excuse oneself to let it out can become irresistible. It’s bad luck if one is in a lift, though!
David Muir
Edinburgh, UK
Better an empty house than a bad tenant.
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