If you sip a mint leaf, you may notice that it makes your mouth feel cool. That’s because mint, like chili peppers, is a biochemical success story.
The magic of evolution lies in the special molecules these plants produce like capsaicin in chili peppers and menthol in mints. Scientists think that the ancestors of plants may have started producing chemicals to deter predators.
Scientists have just found out why when we eat mint, we feel cool in the mouth.
“Plants can evolve compounds to use as a defense mechanism and through natural selection,” said Paul Wise, a fellow at the Monell Chemical Sensing Center in Philadelphia.
Going back to the question of why mint makes us feel “cool” when put in our mouths is that menthol actually tricks our bodies into feeling cold.
Both menthol and capsaicin affect the human system of sensory receptors that monitor things like touch, temperature, and pain. Called the somatosensory system , this complex network of neurons is distinct from the systems responsible for taste and smell.
“There are nerve cells under the skin that can sense different sensations, like heat and cold,” says Seok-Yong Lee, an associate professor of biochemistry at Duke University.
These neurons monitor the environment using a series of specialized proteins embedded in the cell membrane. Proteins control tiny tunnels called ion channels that can allow matter to pass through cell membranes. The ion channels are closed until the receptor protein detects the stimulus it seeks.
“Once sensing the chemical or heat, the proteins turn on and allow the ions to permeate the cell membrane. New ions from the outside world trigger a small electrical signal, called an action potential, and the cell neurons will be transmitted to the brain,” Seok-Yong Lee emphasized.
The action potential is like a telegram saying “some cold receptors on the tongue have been activated”. The brain will logically interpret that ” the tongue is cold,” but that’s not always the case.
Most receptor proteins are designed to open their ion channels when they detect a specific stimulus.
The reason peppermint makes your mouth feel cool is because the menthol molecules also cause the receptors to open their ion channels and send an action potential to the brain, which automatically interprets the small electrical impulse as “cold tongue” .