The first thing to understand about eating spicy food is that it really isn’t a matter of taste. Capsaicin, the active chemical in capsicum plants that are a key ingredient in anything you’d think of as “spicy”, evolved as an irritant to stop mammals from chewing and destroying plant seeds. It acts on the nervous system directly through receptors in the tongue, throat and skin – no taste buds required – and, in theory, tells our bodies that the thing we’ve just ingested is something to get rid of as soon as possible. The obvious question, then, is: why do some of us like the sensation so much?
To start to understand that, it’s helpful to know a bit more about what’s going on in the body. “Think of an engineering brief where we have to detect irritants in a system and clear them rapidly,” says Liam Browne, an associate professor at UCL who specialises in the neuroscience of sensory perception and pain. “Capsaicin binds to a receptor in the body called TRPV1, which is found in a specialised class of neurons called nociceptors that usually detect things that are potentially damaging to the body.” When that happens, it’s like a little fire alarm goes off and activates parts of the autonomic nervous system, which regulates various involuntary bodily functions without conscious control. “That’s what leads to all these physiological effects like tearing up, sweating, or your nose running,” says Browne. “It’s your body trying to get rid of the irritant.”
