Why Does Asparagus Make Your Pee Smell Funny?

Perfectly roasted asparagus is a thing of beauty, but after eating your share of this green vegetable, you might notice that your urine has a special new smell. You're not alone — about 40 percent of people agree that folate-rich asparagus makes their pee smell funny, and it's most likely due to the sulphuric compound asparagusic acid (via NPR). This makes asparagus just one of the many foods that do weird things to your body.

When your body metabolizes asparagusic acid after eating asparagus, it is broken down into several different volatile sulfuric compounds, sometimes as quickly as 15-30 minutes after eating. This volatility is what enables the stinky molecules to travel through the air from your urine and to your nose, while asparagusic acid pre-digestion just gives asparagus a grassy smell (via Smithsonian Magazine).   

Almost stranger than the fact that asparagus can make your pee smell funny is that it's not the case with everyone. Only about 40 percent of people can smell the strange scent asparagus imparts on their urine, and though the science isn't 100 percent clear yet, it's believed that this has to do with perception. Studies seem to show that pretty much everyone has the same volatile sulphuric compounds in their urine after eating asparagus, but that some people have a harmless genetic mutation that means their olfactory receptors don't pick up on the smell. 

Those of us who do get to breathe in that signature scent aren't alone. Benjamin Franklin, Marcel Proust, and John Arbuthnot all wrote of the asparagus urine phenomenon, and Franklin was even trying to convince scientists of his time to come up with a drug that could make all of our bodily waste not just odorless, but pleasant to smell. We're still working on it, but in the meantime, maybe just hold your nose the next time you use the bathroom after eating asparagus.