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A weekly show where we endeavor to answer one of your big questions. This week, "doxysrox" asks, "Why does Asparagus make your pee smell?"
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Hi, I'm Craig, and if you wanted to watch metal floss on YouTube today, you're in luck. Today I'm going to answer doxysrox's big question: "Why does asparagus make your pee smell?" [forcefully/defensively]: Why does asparagus make your pee smell?  

(00:10) Thank you for your question doxysrox, I'm not sure why you capitalized the word asparagus but I'm going to assume that you're referring to the vegetable, not because you have a friend named asparagus who makes your pee smell, because that sounds like a personal problem. Regardless, this is one of those hard-hitting questions that made me want to be a host in the first place. Let's get started. 

[Intro plays]

 History of the Subject

(00:32) First of all doxysrox, you're in good company. In 1781 Benjamin Franklin wrote a letter to the Royal Academy of Brussels basically telling them to invent a drug that would make bodily functions smell better. In the letter he wrote, "A few Stems of Asparagus eaten, shall give our Urine a disagreeable Odour." That guy really had a wide range of interests.

 The Scientific Explanation

(00:49) Anyway, asparagus has a chemical in it that scientists believe is only found in that vegetable, hence the name "asparagusic acid." During digestion, the acid gets broken down, just like when you eat any protein, your body breaks it down into amino acids, just like how I break it down on the dance floor. And you'll feel like you've dropped acid.

(01:05) Asparagusic acid gets broken down in our bodies into different compounds that contain sulfur. Methanethiol and dimethyl sulfide create a pungent smell and dimethyl sulfoxide and dimethyl sulfone create a sweeter smell. The combination of these, in addition to other sulfur-containing compounds produce the pungent urine smell. They're known as volatile organic compounds because they can evaporate thanks to their low boiling point which means that we can smell it.

 Practical Solutions

(01:27) Amazingly, the digestion process happens so fast that some people notice that their urine starts to smell a mere fifteen minutes after eating asparagus, but there's actually a way to lessen the odor: drink water. Also just, never go to the bathroom. Hold it.

 Differences Between People

(01:38) Now some of you are like "What are you talking about, Craig? My pee doesn't smell after I eat asparagus oh my god oh my god oh my god lol." Well, it turns out that only some people experience the asparagus-pee-smell phenomenon. That's not actually what its called, but, that's what I'm going to call it because I'm an innovator. And it has been studied quite a bit over the past few decades. 

(01:53) There are probably a few things happening here. First, around one quarter of people actually possess the ability to smell compounds in urine. That's right, some of you can't even smell your own urine. Secondly, some people seem to digest asparagus differently altogether. For them, less sulfur-containing compounds are produced, so their urine doesn't smell at all. Well aren't they special. 


(02:11) Thanks for watching Mental Floss on YouTube, made with the help of these lovely people, one quarter of whom know that I smell like urine. If you have a big question, leave it in the comments below. Thanks for watching. See you next week.