In every issue of WebMD the Magazine, we ask our experts to answer readers' questions about a wide range of topics. In our July-August 2010 issue, we turned to WebMD's Nutrition Expert, Carolyn O'Neil, MS, RD, to learn just why asparagus makes our urine smell, well, different.
Q: I've noticed that when I eat asparagus, my urine has a funny smell. Is that normal?
A: It's totally normal. In fact, the effect of asparagus on urine odor has been observed for centuries. French novelist Marcel Proust famously wrote in 1913 that asparagus "transforms my chamber-pot into a flask of perfume." And one British men's club is said to have put up a sign reading, "During the asparagus season, members are requested not to relieve themselves in the hat stand."
Depending on which study you read, between 22% and 50% of the population report having pungent pee after eating asparagus. But that doesn't mean only some people's bodies generate that smell. Researchers believe that, during digestion, the vegetable's sulfurous amino acids break down into smelly chemical components in all people. And because those components are "volatile," meaning airborne, the odor wafts upward as the urine leaves the body and can be detected as soon as 15 minutes after you eat this spring delicacy.
But only about one-quarter of the population appears to have the special gene that allows them to smell those compounds. So the issue isn't whether or not your pee is smelly; it's whether you're able to smell it. If you smell a funny fragrance in your urine after you eat asparagus, you're not only normal, you have a good nose.