A couple of years ago I was out to lunch in Bangkok at a cafeteria-style restaurant with communal tables. I had ordered one of my favorite dishes, larb moo, minced pork with peppers and spices. A few bites in I started to feel the heat. About a minute later my mouth was in full emergency mode. Bright red and with sweat pouring from my forehead, I began chugging down one bottled water after another. My Thai tablemates watched in obvious amusement. Several were also eating the larb moo, yet clearly weren’t feeling the heat to the degree that I was. Why?
“We know that when you eat spicy food over and over again, it does actually start to burn less,” says John Hayes, director of the Sensory Evaluation Center, a research facility at Pennsylvania State University that studies the relationships between food and the senses. “The reason that I might use a lot more Sriracha than you is because I could be desensitized and actually perceive less burn from it.”
How we register the effects of capsaicin, the active chemical in chilis responsible for that burning sensation, is regulated by a pain receptor known as TRPV1. TRPV1 receptors, found not only in the mouth but all over the body along the central and peripheral nervous system, regulate heat exposure and body temperature, says Hayes. “This is why when you chop chilies, and then rub your eyes—or use the bathroom—without washing your hands, you are in for a world of hurt,” Hayes warns.
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.
But it is hard to say if these findings would apply to people everywhere. Issues of gender are tied deeply into cultural and sociological configurations that differ widely across social groups and cultures. Could a guy in Thailand expect high-fives from his pals after going extra-spicy on his larb moo? “When you have a culture where all the food is spicy, I suspect you probably wash out any relationship between spicy food intake and personality because of learned associations and cultural norms and all those sort of things, but until we actually test that, we won’t know,” Hayes says.
Still, it seems that with a little repetition, anyone can learn to enjoy the burn. I would recommend bringing milk, though.