Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff, I'm Lauren bog Obam, and I've got another classic episode for you today. In it, our former host Christian Sagar answers a basic yet nonetheless burning question, why do we fart? Hey, brain Stuff? It's Christian Sager. So in the late eighteen hundreds, there was this French guy and his name was Le Peto Man, and he was one of the stars of Mulan Rouge. People would come from far and wide just
to watch this guy fart, Yeah, to watch him fart. Lepetumn, you see, was a professional flat glist, which, as it turns out, is still sort of a thing, and certainly it's a dream job for some. But if you want to move out of the ranks of amateur windbreakers and into those stinking, hallowed halls of the professionally flatulent, you will need to know a thing or two about farts, like what are they, why do they happen? And why do they smell so bad? Well, first things first, everyone farts,
every single person. Yes you two listening to this, you do too. To not fart would be medically fascinating and probably dangerous. On average, most people are passing about one leader of gas a day, spread out over thirteen to wait for it, twenty one incidents. That's twenty one separate times in one day. The composition of a fart varies widely, but usually what we're smelling is something that's mostly nitrogen,
along with oxygen, carbon dioxide, and even methane. This gas itself comes from several sources, the air, you swallow, gas that enters your intestines, from your bloodstream, and so on. But about seventy five of your farts are created in your lower intestine, and unfortunately not by you. See the bacteria living inside you right now. They comprise a microbiome all all of their own. And when we say it's intricate, we mean it's so intricate that David Attenborough could make
a documentary about it. These bacteria form this thriving empire with billions of tiny, separate organisms living inside their host, and that's you. They're living with you in symbiosis. Now, flatulence occurs when food passes through your stomach and small intestine without fully breaking down. So what does this mean. This means that the food hits the large intestine in an undigested state. So For example, let's look at lactose, which is present in dairy products like milk and cheese.
If you're lactose intolerant, then you lack the enzyme that breaks lactose into sugar molecules for the bloodstream. Without this, lactose just breezes through your stomach and small intestine into your large intestine, where it becomes the special of the day for billions of hungary bacteria. Those guys love lactose, and if you're not going to dudge just it, they will.
As they digest this lactose, they emit a number of gases, including methane, hydrogen, carbon dioxide, and hydrogen sulfide, which is responsible for the unpleasant aroma. This process is similar to how yeast produces carbon dioxide to leaven bread. And speaking of food, it's true that some foods do produce more flatulence, primarily because they contain more indigestible carbohydrates. I'm looking at you. Beans, nutrient dense vegetables, and fiber rich foods all have a
reputation for enabling flatulence. That's not necessarily a bad thing. See as scientists learn more about the relationship between diet, health and a person's microbiome. They're discovering that these flatulent foods may encourage the growth of beneficial bacteria in your gut. When they're producing that next embarrassing puff of gas, they're also making molecules to protect your intestinal lining and prevent infections.
So remember, the next time your silent crime accidentally ends up sounding like a stuttering trumpet, your intestinal bacteria are the real culprits. They are the ones actually farting. And look, I want to emphasize this, they are farting inside of you, and then you fart their farts out. Are we clear on that part? Which leads us to the bigger question of the day, who are we farting inside of? Today's episode was written by Ben Bollen and produced by Tyler Clang.
To hear more weird and funny true stories from men, check out his show Ridiculous History, available wherever you get your podcasts, And of course, for more on this and lots of other easily digestible topics, visit our home planet, how Stuff Works dot com.