Some of the body’s TRPV1 receptors are part of the trigeminal nerve, a branched nerve structure that stretches through the face, responsible for sensory regulation and some motor functions like chewing.
But that chili-spice sensation isn’t the result of an actual burn inside your mouth. It’s a sort of chemical trickery caused by the capsaicin. “In the arms race between plants and animals—in animals wanting to eat plants and plants not wanting to be eaten—the chili pepper evolved a chemical that fits into that molecular receptor [TRPV1] and lowers the activation energy from 43 [degrees] Celsius to about 34 [degrees] Celsius,” Hayes says. In other words, whereas the TRPV1 receptors would normally read a mouth temperature of 43 degrees as a burn, they are suddenly reading a lower number—one lower then your actual mouth temperature—as harmful. Suddenly it feels as if something is literally burning inside your mouth. “Human body temperature is 37, mouth temperature about 35, so now all the sudden you’re activating this nerve that is sending a signal to the brain that says, ‘Ow, I’m on fire.’” This is why we describe chill spice as hot or fiery. But is it possible to increase one's tolerance to the effects of capsaicin?
“Absolutely,” Hayes says. “Anecdotally we absolutely know it’s true. It’s not, ‘If you didn’t start eating it at five, you’ll never learn to love it.’”
“It’s the ‘mere exposure’ effect,” adds Nadia Byrnes (pronounced, fittingly, “burns”), a post-doctoral fellow at the University of California, Davis, in the department of viticulture and enology. “Basically, if you don’t like something, the more you eat of it, the more you’ll like it.” Sounds simple enough. If you have a low tolerance to spicy food but make an effort to eat it more and more, Byrnes explains, you will eventually start to desensitize your nerves to the pain so that you will need to consume higher levels of capsaicin to reach that original intensity of burn.
But there have only been a handful of human case studies on capsaicin consumption, and the exact biological mechanisms behind individual tolerance levels and preferences remain fuzzy.
The psychological mechanisms, though, are a bit clearer. A recent study published in the journal Physiology and Behavior announced intriguing results. Researchers from the University of Grenoble-Alpes in France invited 114 men aged 18 to 44 into a testing lab for a meal of mashed potatoes and hot sauce. Researchers noted a positive correlation between the levels of testosterone in a subject and the amount of hot sauce he chose to apply to his potatoes: Those with higher levels drizzled on more of the spicy condiment. Those men also shared tendencies towards social dominance, aggression, and risk-taking behaviors, the researchers found.
But that doesn’t necessarily mean women would be less likely than men to order the Hell Scorcher Wings at the local pub. “In men and women, there may be divergent mechanisms leading to the intake of spicy foods,” Byrnes and Hayes wrote in a paper on gender differences and individual preferences towards spicy food. “Specifically, men may respond more to extrinsic factors, while women may respond more to intrinsic factors.” They found that men would typically choose to up the Scoville count of their meal (Scoville being the unit used to measure capsaicin concentration), because they enjoyed the praise from onlookers. Women tended to do so simply because they enjoyed the heat-pain sensation.
