Among the many seasonal flavors of winter, peppermint is one of my personal favorites. Whether it’s peppermint-flavored coffee, candy canes, or just the peppermint wafers themselves, there’s something for everyone in peppermint this time of year. While chewing on some peppermint candy, you may notice a cold feeling in your mouth. Peppermint doesn’t actually cause the temperature to decrease in your mouth; it feels cold because of a particular quirk of biology.
The human body transmits sensory information, such as pain, coldness, and touch, through neurons. These neurons are linked to a variety of sensors, with different sensors on the look-out for different sensations. The sensors that respond to cold have a particular reception protein in them: TRPM8.
TRPM8 is an ion channel protein. It regulates the flow of ions across the membranes of sensor cells. When TRPM8 senses cold, it opens and allows Na+ (sodium) and Ca2+ (calcium) ions to flow into the cell. This causes a change in the electric potential of the sensor cell, which triggers neurons to send a message to your brain that is interpreted as a sensation of cold.
The cold feeling produced by mint is caused by a compound called menthol. Menthol is a component of mint and binds to TRPM8 proteins, causing a false signal of coldness. Numbness and coldness go hand in hand and menthol can also numb areas that it’s exposed to. Doctors have tapped into this numbing effect to make soothing menthol creams to lessen muscle and bone aches. Menthol also reduces inflammation and increases blood flow, adding extra benefits to this already useful compound.
Mint and menthol are tricky substances, but add flair to our winter flavors and can help if you slip on the ice and injure yourself as well.
- Kate Dzikiewicz, Paul Griswold Howes Fellow