Science behind farts and why some smell way worse than others

Difficulty: Challenger (Level 2)

Why do some farts smell and some don’t?

When you digest food, your intestines produce gas as part of the process of breaking it down.

Gases like carbon dioxide, nitrogen, hydrogen and methane don’t smell at all. That is why sometimes, you can fart without anyone noticing.

But there is one gas found in some farts that is really, really smelly. It’s called hydrogen sulphide. It is nicknamed “rotten egg gas” because that is exactly what it smells like.

This is why sometimes you can let out a small fart, but everyone has to hold their nose. These smelly farts contain more hydrogen sulphide.

Your gut produces more hydrogen sulphide when you eat foods with a lot of sulphur.

These include vegetables such as broccoli, Brussels sprouts, cauliflower, cabbage, kale, turnips and Asian greens.

Meat has a lot of sulphur. If you eat a big piece of meat, your body can have trouble digesting it all at once.

As you digest food, it moves from your stomach into the large intestine or colon (see graphic). Once the foods with sulphur get there, bugs in your gut break them down and produce the hydrogen sulphide gas.

If a lot of it builds up and gets released in a fart, it will be very, very smelly.