In 1913, Marcel Proust wrote that asparagus "transforms my chamber-pot into a flask of perfume." It's almost certainly not the first time that someone linked their odd-smelling urine to asparagus, yet it remains a topic which still baffles scientists today. So I did some digging to find out everything you need to know about asparagus and why (we think) it changes the odour of your pee.

The down-low on asparagus

asparagus, vegetable
Angela Pizzimenti

Asparagus is a spring vegetable that looks a like a stalk with purple-y feathers at the top. It's absolutely jam packed with nutritious benefits and tastes delicious when cooked in pretty much every single way you can imagine. 

Why asparagus causes an odour in your urine

asparagus, vegetable
Kathleen Lee

Research shows that asparagus contains a unique chemical called "asparagusic acid" which is the culprit when it comes to that weird odour. It's a simple sulphur-containing 5-membered heterocyclic compound, which sounds like gobbledegook but means that you get enhanced chemical reactivity when you eat asparagus. Unfortunately, little more is known except that there are nearly 30 resulting compounds from the vegetable and one of these is suspected to cause the odour.

Why can't I smell the difference?

vegetable, asparagus
Kristine Mahan

Firstly, not everyone smells a change! There's no set science as to why — research appears to be inconclusive, but some fairly popular theories still exist. It's been hypothesised that some people are simply unable to produce the odour after an asparagus feast. This is likely to be due to genetics, or simply that their body breaks down the vegetable differently. Other theories suggest that certain people are unable to detect the change in smell because they don't have the gene that enables them to do this. It's estimated that between 20-40% of the population fall into this category, but precise figures are uncertain.

Whether you notice your pee smelling weird or not after eating asparagus, it's nothing to worry about. Asparagus is delicious whether or not you produce / detect the change in odour!