What do you think of this fact?
Bitter is your tongue’s alarm bell. Many toxic substances taste bitter, so spitting out bitter stuff is a decent survival strategy. That’s why it’s odd that the same kind of sensor also sits somewhere that never touches food: your lungs.
A discovery by accident
In 2010, a team led by lung specialist Stephen Liggett at the University of Maryland School of Medicine published a study in Nature Medicine. Principal author Deepak Deshpande and colleagues had found working bitter taste receptors on the smooth muscle of the airways, the muscle that tightens and relaxes the tubes you breathe through. According to Medical News Today, they stumbled on them by accident while studying other receptors in lung muscle.
Unlike on your tongue, these receptors aren’t bundled into taste buds. And they don’t send a taste signal to your brain. So your lungs don’t actually taste anything. They react.
The opposite of what everyone expected
The researchers figured that bitter compounds would make the airway muscle tense up and contract, as a kind of warning reaction, Scientific American reports. That would have made sense if bitter means danger. Instead, the muscle relaxed and the airways opened up.
“It turns out that the bitter compounds worked the opposite way from what we thought”, Liggett said, as quoted by Medical News Today. In tests on mice with asthma, bitter substances including quinine, chloroquine and the sweetener saccharin relaxed the airways.
Bonus fact: Bitter sensors also sit on the tiny hairs called cilia that line your airways. A University of Iowa team reported in 2009 that when these receptors detect a bitter compound, the cilia beat faster to sweep it out, without any help from your nerves.
So the bitter sensors in your chest don’t serve dinner, they serve your airways. Your tongue just gets all the credit.