The scientific chef
Peter Barham on asparagus pee
Why does my wee smell when I've eaten asparagus?
Karen Marriott, Edinburgh
Friday September 23, 2005
"Asparagus pee" has long been the subject of scientific debate. The problem is that if you ask people if their wee has an unpleasant, sulphurous smell after they've eaten asparagus, half say it does and half say it does not.
Scientists used to believe that people digested asparagus differently and divided them into "excretors" and "non-excretors". We now know that it is not whether or not individuals excrete chemicals that makes the urine smell, but whether an individual can smell these chemicals. Scientists still argue whether or not all of us produce the chemicals that make the asparagus pee odour. Most people certainly produce them, but many can't smell them as they lack the necessary sensory cells in their noses.
So if your wee smells after you have eaten asparagus it is because your body deals with asparagusic acid in such a way that it produces smelly chemicals, and you have the ability to smell these.
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· Peter Barham is a physicist at Bristol University. His book, The Science of Cooking, is published by Springer.
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