At the end of each week, the participants were brought into the lab and, in a carefully controlled experiment, had an intra-rectal catheter inserted to quantify how gas (in terms of gas volume, pressure and number) moved through the intestine over a couple of hours.
They found the high psyllium-fibre diet led to longer initial retention of gas, but the volume stayed the same, meaning fewer but bigger farts.
Where do the gases come from?
Gas in the intestines comes from different sources. It can be from swallowing air. Or from carbon dioxide produced when stomach acid mixes with bicarbonate in the small intestine. Or gasses can be produced by bacteria that are located in the large intestine.
While these gases are thought to perform specific tasks that impact on health, producing excessive intestinal gas can cause bloating, pain, borborygmus (which means rumbling sounds), belching and lots of farts.
The smelliest farts are due to sulphur containing gases. This was confirmed in a study of 16 healthy adults who were fed pinto beans and lactulose, a non-absorbable carbohydrate that gets fermented in the colon. The odour intensity of flatus samples was evaluated by two judges (pity them).
The good news was that in a follow-up experiment, the researchers identified that a charcoal-lined cushion was able to help quash the smell of the sulphur gases.
Finally, some bad news for jet-setters: pressurised cabins on aeroplanes mean you’re more likely to pass flatus due to the gas volume expanding at the lower cabin pressure, compared to being on the ground. With modern noise-reduction features, your fellow passengers are more likely than they used to be to hear you fart.
What should you do?
The next time you feel a large volume of intestinal gas getting ready to do what it does, try to move to a more convenient location. Whether you make it there or not, the best thing for your digestive health is to just let it go.
For some creative ideas (and a chuckle) on how to hold in a fart, check this Wiki How to do anything.