Some individuals who eat enough asparagus notice that their urine smells pungent which is similar to rotting cabbage, rotten eggs and ammonia. The scientists are still unsure about which chemicals cause this asparagus urine. Experts think that those with a particular gene are producing a digestive enzyme during ingestion that breaks the asparagus into different chemical compounds and one of which is methyl mercaptan, which is a chemical similar to the defensive smell in a skunk.
Genetics of the person eating the asparagus is the reason that it makes urine smell bad. There is only about forty percent of the people that eat asparagus that have the gene to break it down enough to release the odor in the urine.