Why does Asparagus make urine smell?
Asparagus contains odorous compounds called odorants. These are chemicals produced when certain plants or animals produce volatile organic compounds (VOCs). VOCs are chemicals that have been chemically altered to release their aroma into the air. They range from simple aromatic molecules like alcohol and acetone to complex mixtures of hundreds of different chemical components. Some of these compounds are poisonous while others may cause no ill effects at all. However, some VOCs are known to irritate the nose and throat, causing coughing, sneezing, runny noses and even asthma attacks.
The odorants released by various plants and animals vary greatly in concentration, but they tend to fall into one of two categories: terpenes and flavonoids. Terpenes are responsible for most of the smell in flowers, herbs, spices and other plant materials. Flavonoids are responsible for the distinctive flavor of many fruits and vegetables. Both are in the odorant category for VOCs.
For example, some of the components in asparagus are terpenes including terpinolene and methanethiol. These are partially the reason why the stem, stalk, and roots of asparagus plants smell stronger than the green parts. On the other hand, the odorants in bananas are almost entirely made up of esters and aldehydes, with a few ketones mixed in.
The odorants in asparagus don’t pose a risk to human health, but they can make the urine smell quite strong and unappealing. The chemicals may also be mildly toxic if eaten in large enough quantities. You will notice that infants tend to have particularly smelly urine after eating asparagus, this is actually a common problem in babies as their metabolisms are not yet fully developed.
While asparagus may make urine smell stronger and unappealing, it is otherwise no more dangerous than eating any other food. Each of these odorants are either eliminated from the body through the urine or breaking them down during digestion, so there is no long-lasting effect of eating asparagus.
The amount of odorant that builds up in the body over time varies from person to person and depends on diet, health, and genetics. Some people never experience any smelly urine after eating asparagus, while others seem particularly sensitive to the odorants.
If you currently find yourself in the later category, the only way to avoid the smell is by not eating asparagus. This shouldn’t be an issue as there are plenty of other foods to eat and most people enjoy the flavor of asparagus, so it is easy to avoid.