We all know that asparagus is delicious. However, we seasoned asparagus lovers also know of its extremely unusual side effect: It makes your pee smell pretty terrible. There are not a lot of foods that remind you of their presence shortly after you’ve eaten them (looking at you, beans), but asparagus just so happens to be one of them. That’s because asparagus contains a compound called asparagusic acid (no, I’m not making that up), which contains sulfur, and partially accounts for the intense smell.
No need to worry, either — asparagusic acid is non-toxic, so your kidneys aren’t processing anything harmful, as was historically suggested. Instead, asparagusic acid creates byproducts as it’s broken down in your body. These chemical byproducts contain sulfur and are highly volatile, meaning that when you pee them out, they evaporate quickly. This is why you get hit with that unmistakable scent right away.
But it gets murkier. Scientists still haven’t quite cracked the code on asparagus pee. They’re not sure if it’s one particular compound that’s stinky or if it’s sort of a magic combination that includes methanethiol (methyl mercaptan) — a common strong odorant that’s been discovered in urine post-asparagus consumption. The weird thing is, though, that despite overwhelming scientific evidence that the odor exists, not everyone can smell asparagus pee.
Some people simply can’t smell asparagus pee
If you’ve been left wondering about this mysterious “asparagus pee” phenomenon that you’ve never experienced yourself, that’s because not everyone can pick up on the gnarly scent. A 2016 Harvard study found that over 800 genes are responsible for your ability to identify stinky asparagus pee, and 60% out of the 6,900 pee smellers polled during the experiment (yes, subjects smelled their own pee) could not detect the scent. Those who couldn’t sniff out the odor had genetic mutations in chromosome 1, which is where some of your olfactory receptor genes live.
I’m one of the people who can smell it, and I’m now wondering if I’m going to be in the next Marvel movie after having identified this superpower. (This all reminds me of how some people are genetically predisposed to dislike the taste of cilantro like renowned celebrity chef Julia Child famously did.) I guess the next time you notice the smell after you’ve eaten asparagus, just consider yourself one of the chosen ones. Plus, now you know that something called “asparagusic acid” is really a thing, which is always fun.
