Why do some people crave spice, while others run from it? In the Sichuan episode of Parts Unknown, Bourdain gleefully tortured chef Eric Ripert with the region’s famously hot and mood-altering cuisine. Are Ripert’s tastes more refined than Bourdain’s, or is there something more going on? It’s a topic worthy of investigation, and there’s only one person to call.

To anyone who fancies themself a student or lover of food, Harold McGee is a giant in the field. The author of On Food and Cooking is known for his ability to break down the elements of taste and use science to help us understand why we like what we like and how it got that way—without ever diminishing our pleasure. McGee was kind enough to chat with me about spice, Sichuan peppercorns, and why the hell my entire head sweats when I eat spicy food.

Kaylee Hammonds: What the heck is “sanshool”?

Harold McGee: That’s the active ingredient in Sichuan peppercorns. It’s a chemical relative of capsaicin in red peppers and piperine in black pepper and gingerol in ginger. These are all members of a chemical family that plants in very different families appear to produce primarily to deter animals from eating them. That’s one of the curious ironies of our love of spices that are irritating and painful to eat. They have those qualities because they’re intended to discourage us from eating them, but in fact they have the opposite effect, at least in humans.

Hammonds: So the tingling sensation I get when I slam a bowl of mapo tofu is triggered by these contrary little compounds?

McGee: Yes. The Sichuan pepper is different from capsaicin and red pepper in that it doesn’t really burn you in that way, right? It gives you this weird sensation of tingling and numbing and buzzing. It’s a different kind of effect, but all these compounds have the effects they do because they bind to receptors that we have on our tongues that are meant to detect various things—like chemicals that might be irritating or toxic—but also qualities like heat and cold. In the case of capsaicin, the hot-pepper compound, we talk about it as being hot, as food having heat. That actually turns out to be pretty accurate. Capsaicin triggers receptors and screws with them. The temperature in our mouth has not changed, but our mouth registers the temperature as being higher than it is.

Hammonds: So what about the famous buzz you catch when you eat Sichuan food?

McGee: Sanshool does sort of the same thing but in the other direction. It doesn’t just affect the temperature sensors; it affects other sensors, too. That gives us this general confused input from the tongue. It’s buzzing and numbing and cooling and confusing. In Sichuan food, when you combine hot peppers with Sichuan peppercorns, with ginger, and with black pepper, you’re really giving your mouth a workout.

Hammonds: Why do some people talk about spicy food like it’s a drug? Is there anything to that?

McGee: We don’t know that much about the pharmacological effects of these ingredients in the human body, but it kind of makes sense. These things produce very strong sensations, very strong feelings. Feelings are things that the body is meant to register, to pay attention to. It’s two stages. If you eat something that’s really spicy, first you’re feeling pain and heat and buzzing and very strong sensations in general. Your body is responding to that by producing chemicals to counterbalance that, to kind of tamp that down.

Then, after the sensations that you have in the mouth fade, you’re left with a kind of afterglow [from] the kind of anaesthetics that your body produced to help you get through that. So that’s one theory—though it’s not proven—it’s one theory as to what’s going on and why people become, if not addicted, then why they fall in love with foods like that. The foods produce very strong effects on the body, which the body then responds to with its own chemicals. That whole experience is a very powerful one.

Hammonds: Are we genetically predisposed toward spicy food? A friend of mine has always claimed I like spice because I’m Asian, which doesn’t quite make sense.

McGee: Well, the general feeling among the scientists who study food preferences is that they’re by and large nurture rather than nature. Some people are definitely born being more sensitive to the sensations produced by food, whether it’s taste or smell or heat. You might have more receptors than other people, so yes, you can sort of genetically and biologically be more sensitive to those sensations. But your reaction—whether you’re pleased by them or overwhelmed by them—that has a lot to do with how you’re brought up and what you’re used to and your associations of particular sensations.

(Photo by Patrick Hannaway/Patrick McMullan via Getty Images)
(Photo by Patrick Hannaway/Patrick McMullan via Getty Images)

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Hammonds: So my head sweats when I eat hot food because capsaicin is a trickster that makes my nerves think I’m actually overheated?

McGee: That’s basically it. One of the things that capsaicin does is trigger heat receptors. Your body thinks it’s hotter than it is, and as a consequence of that it does a variety of other things. It boosts metabolism, it increases circulation to get rid of that extra heat; so because of that metabolism boost, your temperature can sometimes actually go up. In any case, your body is thinking that it’s a lot hotter all of the sudden, so it responds by trying to cool itself down and that’s where the perspiration comes from.

Hammonds: I’ve read that the cuisine of Sichuan is spiced the way it is due to the humid, hot climate. Is there any science to back that up? Why this food, at this place, in this climate?

McGee: As far as I know, there’s no convincing explanation for why particular groups of people prefer particular kinds of spices. There are lots of just-so stories—people coming up with a theory like the one you just described—but the actual evidence for that really isn’t there. It’s possible and an interesting idea, but it’s speculation.

Hammonds: And now a question for everyone who’s ever been told to drink a glass of milk after they’ve eaten hot peppers. Once you’ve eaten something spicy, is there anything you can do to mitigate that feeling?

McGee: No. By the time you’re feeling the pain or the buzzing, the chemicals that cause those sensations are already inside your cells. Rinsing your mouth with something doesn’t really do a whole lot; it does kind of slow down the onslaught because the stuff that’s inside your cells is not going to be replaced as quickly. It’s not going to stop the pain or the buzzing right away. The best thing you can do [in the case of capsaicin] is to put something cold in your mouth to counteract that heating effect. That will do about as much as anything.”