Have you ever eaten asparagus and noticed how it changes the way your pee smells? You may have heard about the phenomenon but wonder why it seems to affect some people and not others.
Many researchers agree that the smell of asparagus pee results from the metabolism of a compound found exclusively in asparagus known as asparagusic acid. The compound is broken down into sulfur-containing compounds such as methanethiol, dimethyl sulfide, and dimethyl sulfoxide –which are responsible for the most prominent odor detected in asparagus pee. All of the above components can easily vaporize into a gaseous state at room temperature [1] –which brings them to your nose.
Why can’t some people smell it?
The whole asparagus pee smell issue is a little complicated. Various theories attempt to explain why only some people can detect the odor in their pee after eating asparagus. Some researchers suggest that people who don’t detect the asparagus smell in their pee do not have the ability to produce the scent; others argue that everybody breaks down the asparagusic acid in the asparagus equally, only that some people simply lack the ability to detect the smell.
M Lison and other researchers [2]carried out a study to explore this phenomenon back in 1980 and discovered that actually everyone produces this “asparagus smell” but only a few people were able to smell it. The study also revealed that people who were able to detect the smell could even smell it in the urine of those who could not smell it. This reinforced the idea that the difference in the two groups of people was more as a result of perception than production.
Another study published in the Oxford Journal [3] throws in yet another interesting twist. The study revealed that there still existed some differences even within the groups of subjects who could detect the smell and those who could not. Nevertheless, most scientists generally seem to back the theory that perception is the main reason some people are not able to detect any difference in the smell of their pee after eating asparagus.
Could the variation be genetic?
A DNA-sequencing company (23andMe) carried out an investigation in 2010 to find out if the ability to smell asparagus pee was linked to any genetic component. The study asked subjects if they could detect any odor in their urine after eating asparagus, and investigated the genetic similarities in the two groups. Findings revealed that the ability to detect the asparagus smell was linked to a certain DNA sequence that varied among different people. This means that a single mutation in the genes responsible for smell [4] may be the reason some people are unable to smell asparagus odor in urine.
When all is said and done, it’s important to mention that only about 25% of the population seems to have this unique DNA sequence that allows them to smell asparagus pee. So basically, you do not need to worry about a thing; if you are able to smell the funny scent in your pee after eating asparagus, you’ve got a good nose and can be proud of it.
Featured photo credit: jackmac34 via pixabay.com
