Science Focus (issue 24)

You must have experienced the aftermath of a bowl of spicy ramen, a dollop of wasabi, a bite of chili pepper. Your tongue feels like it’s on fire; your eyes start watering, and you begin to sweat through your clothes. No other sensation would come close to the overwhelming sensory experience that comes with spiciness. Here is an interesting fact: Spiciness is not a taste, but rather a sensation of pain. Then, why does spiciness intrigue humans so much that we would prepare food “so tasty it hurts”? Chili peppers contain an alkaloid compound known as capsaicin, which can trigger the burning sensation of spiciness. As we chew, capsaicin molecules are released and spread across our tongue. However, they bypass the taste pores and bind to pain receptors instead [1]. Originally functioning as a detector to alert the brain of high temperatures (>43 °C [2]), these pain receptors, by the name of TRPV1, can also be activated by capsaicin. As a cation channel by nature, TRPV1 receptors will open when activated, so cations can diffuse into the nociceptive (pain-sensing) neurons [3]. The increase in electric potential, known as depolarization, will trigger the neuron to fire and send a signal to the brain. Our brain will then interpret the signal and think that our tongue is in contact with a burning hot substance, giving us the false impression that our mouth is on fire. If spiciness truly is a sensation of pain, why will we have the urge to go back for one last bite? Here’s where our body’s self-regulatory mechanism Understand Spiciness: A Pain but Not a Taste 辣……其實是一種痛? By Roshni Printer