Why do we pass gas? - Purna Kashyap

Flatulence, or passing gas,
is a normal daily phenomenon.

Most individuals, yes,
that includes you,

will make anywhere
from 500-1500 milliliters of gas

and can pass gas ten to twenty
times a day.

But where does this bodily gas come from?

A small proportion may come from
ingesting air during sleep, or at other times,

but the majority of gas is produced by
bacteria in our intestines

as they digest parts of food which we cannot.

Our intestine is home to
trillions of bacteria

living in a symbiotic relationship with us.

We provide them with a safe place
to stay and food to eat.

In exchange, they help us
extract energy from our food,

make vitamins for us, like vitamin B and K,
boost our immune system,

and play an important role in
gastrointestinal barrier function,

motility and the development of
various organ systems.

Clearly, it's in our best interest
to keep these bacteria happy.

Gut bacteria get their nutrition
primarily from undigested food,

such as carbohydrates and proteins,
which come to the large intestine.

They ferment this undigested food
to produce a wide range of compounds,

such as short-chain fatty acids
and, of course, gases.

Hydrogen and carbon dioxide
are the most common gaseous products

of bacterial fermentation,
and are odorless.

Some people also produce methane due to
specific microbes present in their gut.

But methane is actually odorless, too.

Well then, what stinks?

The foul smell is usually due to
volatile sulfur compounds,

such as hydrogen sulfide and
methanethiol, or methyl mercaptan.

These gases, however, constitute
less than 1% of volume,

and are often seen with ingestion
of amino acids containing sulfur,

which may explain the foul smell of gas
from certain high protein diets.

Increased passage of gas is commonly
noticed after eating foods

with high amounts of
indigestible carbohydrates,

like beans, lentils, dairy products,
onions, garlic, leeks, radishes,

potatoes, oats, wheat, cauliflower,
broccoli, cabbage, and brussel sprouts.

Humans lack the enzymes,

so the bacteria able to ferment
complex carbohydrates take over,

and this naturally leads to more
gas than usual.

But if you feel uncomfortable,
bloated or visibly distended,

this may indicate impaired movement
of gas along the gastrointestinal track.

It's important not to just
blame certain foods

for gas and bloating and then avoid them.

You don't want to starve the bacteria
that digest these complex carbohydrates,

or they'll have to start eating the sugars
in the mucus lining of your intestines.

Your personal gas will vary
based on what you eat,

and what bacteria are in your gut.

For example, from the same starting sugar,

the bacteria clostridium produces
carbon dioxide, butyrate and hydrogen,

while propionibacterium can produce
carbon dioxide, propionate and acetate.

At the same time, methanogens
can use hydrogen and carbon dioxide

produced by other bacteria
to generate methane,

which can reduce the total volume of gas
by using up hydrogen and carbon dioxide.

So there's a complex web among
intestinal bacteria

allowing them to flourish by either
directly consuming undigested food,

or using what other bacteria produce.

This interaction largely determines
the amount and type of gas produced,

so gas production is a sign
that your gut bacteria are at work.

But in some instances, people may
develop abnormal increased flatulence.

A common example is lactose intolerance.

Most individuals have the enzyme for
breaking down lactose,

a sugar present in milk and
milk-derived products.

But some people either lack it entirely,
or have a reduced amount,

such as after a gastrointestinal infection,

so they're unable to digest
lactose products and may experience cramping,

along with increased flatulence
due to bacterial fermentation.

But remember, most gas is produced

as a natural result of bacterial
fermentation in the intestine,

and indicates healthy
functioning of the gut.

The amount and type can vary based on your
diet and the bacteria in your intestine.

Exercise social courtesy while passing gas,
and do try to forgive your bacteria.

They're only trying to be helpful.