It's not exactly dinnertime conversation, but it's probably not dinnertime.
Unless you watch Scishow while while you're eating dinner. In which case: I applaud you.
But let's get it out there: we all burp, we all fart.
Sometimes we do these things loudly and oftentimes they smell.
But why do we do these things?
And why do some foods and drinks exacerbate the problem?
[scishow jingle]
Formally referred to as belching and flatulence these two often lampooned bodily functions
actually share a common cause: swallowed air.
Every time you swallow you take in some air. But you can swallow even more air than normal
if you eat or drink too quickly, chew gum, smoke, drink carbonated beverages or even wear loose fitting dentures.
Now the majority of swallowed air comes back up in the form of burps.
As the air builds up in the upper portion of the stomach
it causes streching that eventually triggers the lower esophageal sphincter to relax.
The result is air escaping up the esophagus into the mouth
where the sound and smell of the burp depends on how much coke you just chugged.
Babies in particular are big burpers, especially for their small size.
Mostly because they tend to gulp in too much air while nursing.
And because young digestive systems haven't developed to the point where
the babies can easily burp on their own it's up to Mom and Dad
to pat their backs, help get those gas bubbles out.
But for babies and adults: What about the air that isn't burped out?
Well it passes from the stomach into the small intestine and later the large intestine.
Along the way, as it passes through the gastrointestinal tract
that air mixes with the the products of some good old bacterial fermentation, that's going on in your guts.
That fermentation is the result of carbohydrates, like sugars and starches
that can't be digested by enzymes in the small intestine.
Some foods that include these hard to digest starches
include cabbage, cauliflower, beans and bran.
Which explains why you may feel excessively gassy after that big bowl of chili.
When those undigested carbs reach the colon and the lower intestines bacteria take over.
The by-product is a combination of gases
that include carbon dioxide, hydrogen, methane, even hydrogen sulfide: a stinky one.
That mix of gases plus the air that you've swallowed
is what makes it's way through the large intestine to the anus where it is expelled.
Of course everyone has different amounts of various species of bacteria and yeasts working away in their guts.
But I'm sure you're dying to know, so I'll just tell you:
The average human toot contains roughly 59% nitrogen, 21% hydrogen, 9% CO2, 7% methane and 4% oxygen.
It's that last 1% in the form of hydrogen sulfide and other sulfur compounds
that is the most potent in terms of producing those notorious, unpleasant rotten egg smells.
While some of these chemicals are produced by bacteria in your gut
eating sulfur-rich foods like eggs and onions and beans
doesn't help on the smelly front.
So be sure to trundle out these factoids at your next dinner party.
And thank you for watching this episode of scishow
and an extra sweet smelling thank you to all you Subbable subscribers
for a second I thought I'd said sweat smelling
You don't smell like sweat!
If you'd like to sponsor a graphic with your name on it
or get a scishow poster signed by the whole crew here
whole crew say noise!
[whee from the background] aaaahh
you can go to Subbable.com to get those exclusive items.
You can also find us at facebook and twitter and don't forget to go to youtube.com/scishow and subscribe
so you can continue to get smarter.
[scishow jingle]