The “Asparagus Effect” is Not Universal

July 10, 2011 at 12:00 pm 5 comments

By Kyle Kurpinski

Have you ever noticed a peculiar odor from your urine after eating asparagus? If so, you’re not alone. The “asparagus effect” has been documented since at least the 1700’s and was scientifically analyzed as early as 1891 when a chemist named Marceli Nencki attributed the smell to the chemical “methanethiol.” Most people would probably be satisfied with this explanation and move on, but science leaves no stone unturned; we now know that the distinct aroma is actually due to an intricate combination of sulfur-containing compounds (including methanethiol) formed during the breakdown of asparagusic acid.

So, mystery solved, right? Not quite.

Ask around, and you will find that only a portion of the population actually experiences the asparagus effect. A few early studies in the 1980’s reported that not everyone could smell the asparagus-induced odor, but those who could smelled it in all available samples, suggesting that everyone produces the aroma after eating asparagus, but only a portion of the population has the ability to detect it; a characteristic that was subsequently linked to a specific mutation in a group of olfactory genes. However, a more recent study in 2010 reported that a small percentage of people may not produce the odor at all, likely due to differences in the way they metabolize asparagusic acid.

In short, if you don’t notice the odor in your pee after an asparagus-heavy meal, you either have a unique, asparagus-proof metabolism or you simply lack the smell receptors to perceive your own stinkiness. If you do experience the asparagus effect, keep in mind that the odor-inducing precursor compounds are more prevalent in younger plants, so the smell will be less pronounced if you eat asparagus that is a little more mature. The effect is also extremely rapid – producing smelly pee in as little as 15-30 min after ingesting – so plan ahead if you’re thinking about eating asparagus on a hot date.

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Source: Wikipedia, Monell Center, The Guardian, The Discovery Channel, British Medical Journal

Image: Jonathan Moreau (cc)

Entry filed under: Food and Drink, Health and Beauty. Tags: , , , , , , , .

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5 Comments Add your own

  • 1. David Cain  |  July 10, 2011 at 5:39 pm

    I thought I was the only one! My pee also becomes almost fluorescent from asparagus. It was so colorful it was alarming, until I heard that asparagus has a profound and immediate effect on urine. The only other thing that does that is Rock Star energy drink.

    • 2. Kyle  |  July 11, 2011 at 12:45 am

      I’m a generally curious person, but I think I’m better off not knowing the biochemistry of Rock Star energy drinks.

      • 3. David Cain  |  July 13, 2011 at 6:20 am

        It definitely has something radioactive in it

  • 4. jwerner  |  July 14, 2011 at 12:19 am

    Because I might…pee near my hot date?

    • 5. Kyle  |  July 14, 2011 at 12:36 am

      It’s a crazy world we live in…


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