Does your pee stink after eating asparagus?

After eating asparagus, some people's urine has a very distinct, stinky smell.

Asparagus contains a compound called mercaptan. The smelly pee is a result of this compound being broken down in your digestive system. However, not everyone has the gene for the enzyme that breaks down mercaptan. One British study found that 46% of British people tested produced odour after eating asparagus.

Another study of a random sample of 115 people showed that 40% had stinky pee after eating asparagus and they determined that it's inherited through an autosomal dominant inheritance pattern. Interestingly, another study found that all the subjects broke down mercaptan, but their ability to smell it in the urine differed. Those who were able to smell the odour in their own urine could smell it in the urine of anyone who had eaten asparagus irrespective of whether or not that person could smell it. The authors suggested that the ability to smell the stinky urine is also genetically determined.

So are we all stinkers, but only some of us smellers? Not exactly. People, like myself (too much information?!), don't break down mercaptan (so are non-stinkers) but can smell it in other people's urine. Conversely, some people who break down the compound (stinkers) were unable to detect the smell in urine others had identified as outright putrid.

Don't worry, even if your urine smells after eating asparagus, it's not a bad thing and definitely not a reason why you should avoid asparagus. Asparagus is great source of folic acid, thiamin, vitamin B6, fibre and one of the richest sources of rutin, a compound that strengthens capillary walls.

So... are you a stinker?

Sources:
Leyner M, Goldberg B. Why do men have nipples? NY: Three Rivers Press. 2005.
http://student.bmj.com/back_issues/0800/education/277.html
http://www.scq.ubc.ca/asparagus-stinky-pee-and-scientific-curiosity/
http://www.asparagus.org/maab/nutrition.html