Why Does Asparagus Make My Pee Smell

This story may seem a bit off topic for craft spirits but, let’s think about it for a minute. Tasting whiskey is as much art as it is science as it stimulates all the senses. We taste whiskey with our eyes as we look at the color, we taste whiskey with our nose, a chemical sense, as we sniff the aromas and we taste whiskey with our tongues as the liquid passes through our mouths. All these senses combined can bring back pleasant memories of tastes, smells and places we’ve visited in our past. As odd as it sounds, the post-Thanksgiving smell of stinky urine can do the same thing by bringing back memories of Turkey days gone by, friends, family and visiting Grandma’s house.

What’s the Chemical Make Up of Asparagus that Makes Urine Smell?

There is still no definitive verdict as to the manner in which these compounds are formed, it has been suggested that they all form from Asparagusic Acid.

Gas chromatography-mass spectrometry was used to analyse the ‘headspace’ of urine produced after consumption of asparagus. The headspace is the gas space immediately above the liquid surface, which is occupied by light, volatile compounds in the liquid, and analysis of this is useful in identifying odour-causing compounds. The analysis of the post-asparagus urine showed the presence of several compounds that were not present, or present in negligible amounts, in normal urine. The primary compounds present, in quantities a thousand times greater than in normal urine, were methanethiol and dimethyl sulfide. The compounds dimethyl sulfoxide and dimethyl sulfone were also present and it was suggested that they modify the aroma to give it a ‘sweet’ edge. (Hmm, not so sure I agree with the ‘sweet edge’ description?)

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Asparagusic Acid is, unsurprisingly considering the name, a chemical found exclusively in asparagus, and absent in other related vegetables. This has made it an obvious candidate for being the origin of the peculiar effect that asparagus has on urine. It has been suggested by recent studies that it could be metabolised in the body to produce the volatile compounds found in the urine after consuming the vegetable.

Just like some whiskey drinkers are Super Tasters that can taste and define every component in a whiskey there are people that have a super sense of the Asparagusic acid in urine and others, about 16% that can’t detect the smelly urine at all.

The Chemistry of Asparagus

Click the Why Does Your Pee Smell Infographic image to see it full size.

If your into this topic and would like to learn more about food trivia and science, you can check out this book, Why Does Asparagus Make Your Pee Smell?: Fascinating Food Trivia Explained with Science.

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