Why Asparagus Makes Your Urine Smell Funny

Chemical That Causes It and Why Only Some People Smell It

Everyone's urine smells funny after eating asparagus, but only certain people can smell the odor.
Everyone's urine smells funny after eating asparagus, but only certain people can smell the odor. David Jakle, Getty Images

When you eat asparagus, your urine will smell funny. However, not everyone's noses can detect the odor of asparagus pee. The chemical that produces the effect is called asparagusic acid. Asparagusic acid is not volatile, so if you sniff a spear of aparagus, you won't smell anything noteworthy. However, when your body digests asparagus, aspargusic acid is broken down into simpler compounds, which are volatile, so they transfer from urine into the air, where they make their way to your nose so you can smell them.

These compounds include dimethyl sulfide, dimethyl disulfide, dimethyl sulfone, and dimethyl sulfoxide. The sulfurous compounds or mercaptans are related to the chemicals that make skunk spray and rotten eggs so odious.

Asparagus Doesn't Make Everyone's Pee Stink


While it is believed everyone excretes these compounds in their urine after eating asparagus, somewhere between 22% and 50% of the population lack the chemoreceptors to detect the funky smell. Also, some people may metabolize asparagusic acid in a way that produces lower quantities of the distinctive-smelling molecules.

Whether or not you can smell the distinctive funky odor of asparagus pee depends on your genetics. Inability to smell the chemical results from a single base pair genetic mutation, which is passed on in families. While you might not consider yourself fortunate if you can smell it, the upside is you're more likely able to smell other sulfurous molecules, which might protect you from toxic chemicals.

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Helmenstine, Anne Marie, Ph.D. "Why Asparagus Makes Your Urine Smell Funny." ThoughtCo, Jul. 13, 2016, thoughtco.com/why-asparagus-makes-urine-smell-funny-607376. Helmenstine, Anne Marie, Ph.D. (2016, July 13). Why Asparagus Makes Your Urine Smell Funny. Retrieved from https://www.thoughtco.com/why-asparagus-makes-urine-smell-funny-607376 Helmenstine, Anne Marie, Ph.D. "Why Asparagus Makes Your Urine Smell Funny." ThoughtCo. https://www.thoughtco.com/why-asparagus-makes-urine-smell-funny-607376 (accessed December 11, 2017).