At LAST science explains why asparagus makes your pee smell funny

Just because most people are used to the volatile aroma their pee gives off after eating asparagus, that doesn’t mean they embrace it or understand it. For so many unsuspecting asparagus-loving humans, the stench of asparagus pee hits them hard in the nose every time. It’s not that people forget the’ve eaten asparagus, it’s that they forget it’s going to turn their urine into something horrendous.

Well, we’ve finally learned why this pee tragedy happens to so many of us (but not all of us). LiveScience rounded up some solid aspartic pee information that we think everyone needs and deserves to know.

Danielle Reed, associate director of the Monell Chemical Senses Center in Philadelphia and an author on a 2011 study in the journal Chemical Senses on how people produce and smell aspartic pee, did the due diligence of explaining just exactly what her pee smells like after eating asparagus.

“To me, my urine after I eat asparagus smells like vegetable soup, maybe even a cabbage soup.”

That’s a super gentle, but accurate way of describing the odor.

In 2010, researchers identified a single variation in the DNA code associated with a person’s unfortunate ability to smell asparagus pee.

“Everyone has his or her own sensory world when it comes to the sense of smell,” Marcia Levin Pelchat, a neuroscientist at the nonprofit independent Monell Chemical Senses Center told LiveScience. “We suspected that individual differences in ability to detect this aroma after eating asparagus might be related to genetic differences in olfactory receptors. And that is something that is being studied very intensively in order to help us better understand how the system codes for different smells.”

The asparagus smell is believed to stem from asparagusic acid metabolizing into other sulfur-containing compounds — like methanethiol, the most prominent odor identified in asparagus pee.

“We think that some of the proteins and amino acids in asparagus are metabolized differently by different people, and so people have a different sulfur volatile profile,” Reed said.

But not everyone’s pee smells bad after eating asparagus, and not everyone can even smell it.

“Not everyone can smell the urinary byproducts of asparagus; those who can smell them assume everyone else can too, and those who can’t smell them think those who can are crazy,” Sirius Radio’s Dr. Steve wrote in Men’s Fitness.

People’s ability to smell their own aspartic pee depends on the both their sense of smell and their ability to produce the odor. So if someone can’t smell asparagus pee, it could be because they just fail to smell it or because they don’t produce it.

So before you think people are absolutely crazy for not smelling what you smell, remember that it’s very possible that their noses just can’t smell asparagus pee. Lucky them.