Why Does Asparagus Make My Urine Stink?

Isn’t it funny how eating asparagus can sometimes make your pee smell bad? What’s funnier is this doesn’t happen to everyone. Why does asparagus make urine stink? Why isn’t it the same for everyone? Is it even the asparagus that make urine acquire that unpleasant scent?

If you think it’s just you, you’re wrong. A lot of people noticed this effect of eating asparagus to their urine, like Benjamin Franklin. He said: A few stems of asparagus eaten shall give our urine a disagreeable odour; and a pill of turpentine no bigger than a pea shall bestow upon it the pleasing smell of violets.

The first attempt in identifying the exact reason for this was made in 1891 by M. Necki. He found that asparagus has a compound named methanethiol which the body metabolizes into a gas that smells awful. In fact, this compound is something similar to that of skunk secretions. The same is found in blood, garlic, feces, eggs and cheese, people with bad breath and flatulent odors.

Another study was made in 1975. It was conducted by Robert H. White who was working that time for the Chemistry Department at the University of California. He found that it was not methanethiol that makes urine smell bad—it was caused by several S-methyl thioesters namely S-methyl thioacrylate and S-methyl 3-(methylthio)thiopropionate.

Sounds funny and hard to read, but simply put, they are the culprits in making your urine stink whenever you eat asparagus. The smell usually manifests itself about an hour after eating a few spears.

But even this is open to question. The disagreement isn’t contained on which specific ingredient makes urine stink but also why not all people are affected by it. Some people claim the smell of their urine doesn’t change after eating asparagus while some do. Others say they can smell the stink, while some are incapable of distinguishing the scent.

Whether it’s methanethiol, S-methyl thioesters or asparagines, asparagus will always be viewed as a veggie that can affect the way your urine smells.