June 06, 2010

Why Eating Asparagus Causes a Smelly Urine... You Know Who You Are!

About 50% of the population experiences a very foul smelling urine after eating asparagus. For those in the know, the odor is compared to rotting cabbage, ammonia, rotten eggs, etc. In fact, the smell is so foul, even the culprit person who is urinating can barely tolerate it himself!

For awhile there was an argument in the scientific community whether this phenomenon was due to a smell disorder or a urine problem...

Hypothesis #1:
EVERYBODY's urine smells... it's just that half the population can't smell it.

Hypothesis #2:
It's not a nose problem... it's a urine problem due to an inability to digest (or resorb) sulfur-containg compounds found within asparagus after breakdown. In fact, this would be the same mechanism that makes a skunk smell.

It ends up that possibly BOTH Hypothesis #1 (study link) and 2 (study link) are correct depending on the individual who is peeing and the individual doing the smelling. In other words, there are some individuals whose urine does smell after eating asparagus AS WELL AS some individuals who may or may not be able to smell this foul odor.

The exact culprit compound is still unclear however. The top contestants are methyl mercaptan, thioesters, and asparagusic acid.

Regardless, there's no harm in eating asparagus at all whether you stink or not... or whether you can smell or not.

Read more about this phenomenon in the Boston Globe here.
Fauquier blog
Fauquier ENT

Dr. Christopher Chang is a private practice otolaryngology, head & neck surgeon specializing in the treatment of problems related to the ear, nose, and throat. Located in Warrenton, VA about 45 minutes west of Washington DC, he also provides inhalant allergy testing/treatment, hearing tests, and dispenses hearing aids.

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