You either are aware of, or not aware of the fact that many people experience quite malodorous urine when they eat asparagus. For those who have never experienced it, it is definitely a real phenomenon, albeit a rather unpleasant and even possibly unsettling one if you do not know the cause of the stinky pee. One of the causes of this unpleasant phenomeon is the excretion of a sulphurous metabolite called mercapten.

Bizarrely, mercapten can be begin to be excreted within minutes of ingesting asparagus (no source, just the author's N=1 anecdotal life experiences). It seems that everyone actually produces the compounds, but that only about a lucky 10% of us, including me, are able to smell the sulfurous aromatic asparagus metabolites ⁽²⁾.

If You Can't Smell Asparagus Pee

If you are of the 90% of the population unable to smell the odor, rest assured that you are still a producer of mercapten. However, you are fortunate enough to have the genetic SNP called rs4481887, ⁽¹⁾ that prevents you from detecting asparagus metabolites.

Too bad we are not all so lucky. Although those of us that do smell it can look forward to losing this ability as we age. That's one of the best advantages of getting older that I've heard about.

Sources
(1) Excretion and Perception of a Characteristic Odor in Urine after Asparagus Ingestion: a Psychophysical and Genetic Study
(2) A polymorphism of the ability to smell urinary metabolites of asparagus

Images were taken by me