Have you noticed after eating asparagus your urine smells funny?
It’s totally normal. In fact, the effect of asparagus on urine odor has been observed for centuries.
Even Benjamin Franklin took note, stating in a 1781 letter to the Royal Academy of Brussels that “A few Stems of Asparagus eaten, shall give our Urine a disagreeable Odour” (he was trying to convince the academy to “To discover some Drug…that shall render the natural Discharges of Wind from our Bodies, not only inoffensive, but agreeable as Perfumes”—a goal that, alas, modern science has still not achieved).
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.