Why does asparugus make your urine smell?

Asparagus contains a sulphurous compound called mercaptan (which is also found in rotten eggs, onions and garlic). When your digestive system breaks down mercaptan, by-products are released that cause the strange smell. The process is so quick that your urine can develop the distinctive smell within 15 to 30 minutes of eating asparagus. Not everyone suffers this effect; your genetic makeup may determine whether your urine has the odour -- or whether you can actually smell it. Only some people appear to have the gene for the enzyme that breaks down mercaptan into its more pungent parts.

Your Comments, Thoughts, Questions, Ideas

majormacher's picture
majormacher says:

Very interesting fact. Just curious as to where you heard or read about it.

posted on Mon, 11/03/2008 - 7:03pm
ARTiFactor's picture
ARTiFactor says:

Click this link to find lots of info about asparagus urine.

posted on Tue, 11/04/2008 - 1:32pm
ARTiFactor's picture
ARTiFactor says:

The exact words in this story are used in several internet pages - the most popular of which is this one at

posted on Tue, 11/04/2008 - 8:56pm
mdr's picture
mdr says:

My wife and I figured this out by ourselves back in the '80s. For a while we couldn't pinpoint why our urine smelled so strong at different times. At first we thought it was from eating steak because -as it turned out - we usually had asparagus when we had steak. We finally narrowed it down to the asparagus. Our hypothesis was confirmed after my wife heard a radio report about the reaction which included the details mentioned in the post of how only some of the population (about 40%) produce the odor and only some people can smell it. This has led to some interesting (yet cautious) dinner conversations while dining with friends and when asparagus is on the menu. Precious10 is right, the reaction time between eating asparagus and one's urine presenting the odd odor is very rapid (sadly, I must admit my wife and I have had races to this effect). For me the odor is metallic and/or chemical in nature, fairly strong, but not offensive. Others have reported it to smell like rotten cabbage. I don't think I'd like that.

posted on Mon, 11/03/2008 - 10:39pm
ARTiFactor's picture
ARTiFactor says:

I had to take classes in urine analysis to get my doctor degree. We had bring urine samples to test. I would eat asparagus so that my sample would get lots of interesting descriptions for "smell".

We would also spin the urine in a centrifuge, then look at what settled out. The urine of one female classmate had lots of lively sperm which were fun to watch.

posted on Tue, 11/04/2008 - 1:22pm
Hunter Jordan's picture
Hunter Jordan says:

Hi, I am in the 4th grade and I am doing my science fair project on, "Does Asparagus make your pee smell?" I am trying to come up with a questionnaire for my test subjects to answer. Like age, gender, medical history, medicines taking. Can you help me with any other questions I might need to ask. Thanks in advance.

posted on Fri, 12/05/2008 - 6:50pm
Anonymous's picture
Anonymous says:


posted on Thu, 10/28/2010 - 6:56pm

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