Fever till you sizzle,
What a lovely way to burn
— Peggy Lee, ‘Fever’
Many of the things we think of as taste aren’t actually ‘tastes’; the tongue, unfortunately, is a pretty basic and blunt instrument. Our nose, on the other hand… it doesn’t have the range of a dog’s nose, but once something is in our mouths, the olfactory system can detect a whole spectrum of tangs and twangs, hues and hints and aromas.
One of Singapore’s favourite flavours, though, is neither tasted nor smelled; it’s felt. It’s funny how, living in a country that’s searing hot all the time, we like having a fire lit in our mouths; but chilli is something we cannot get enough of.
Many of you may know that capsaicin is the chemical responsible for spiciness. But… well… why capsaicin?
It’s nice being an animal, because animals are mobile. Want to eat something? You can hunt it. Want to not be eaten? You can run away and hide somewhere. Being a plant, and therefore unable to move, restricts your options a bit more. Not being able to run from predators means two things:
- You need chemicals to defend yourself.
- You need to use some other force to disperse your children, ie. seeds.
Capsaicin evolved as a means to achieve the second goal. To disperse its seeds, it has a powerful ally – hungry birds. Attracted to the bright red fruits, they will tear the ripe fruits open and eat everything inside, including the light, yellowish, waxy seeds. Once that’s done, they’ll fly somewhere else and poop all the seeds out at the next convenient stop. Bam, new spot for chillies to grow. It’s the perfect delivery vehicle, or it was, until mammals came along.
The problem with mammals is that we have teeth, especially grinding molars. The protective coating around chilli seeds allows them to go through a bird without any problem. But when a mammal eats a chilli, the coating gets ground away by the teeth, and the seed gets digested, which means it dies – which ruins the whole point of having bright, attractive fruits to start with.
Clearly, this creates a space for evolutionary advantage. If there are somehow chillies which birds don’t mind eating, but mammals don’t like, they will survive and prosper. And if there’s something in the chillies that irritates mammals, well, that’s what will give you that advantage.
And this is where capsaicin comes in.
How does capsaicin work? Well, the mouth is a major point of entry into the body, so think about it like a customs checkpoint – with all the cameras, heat sensors, radar scanners and K9 units. A country wants to keep the drugs and contraband out. Similarly, the mouth has a whole array of sensors to ensure nothing poisonous, or sharp, or of a harmful temperature will enter.
And it’s the heat sensors that capsaicin works on. A sort of nerve receptor called TRPV1 serves the purpose of detecting dangerously high temperatures, sending alarm signals to the brain in the form of heat and scalding pain. So basically, it’s like a fire alarm, looking for things like boiling hot soup and telling your brain to quickly spit it all out before your mouth gets damaged.
Capsaicin works by binding to the TRPV1 receptor, triggering it to keep sending its signals to the brain. In other words, capsaicin basically runs around your mouth, setting off all the fire alarms. Even when there’s nothing actually hot in your mouth; your brain receives the signals, which are interpreted as the burn and slight pain of spiciness.
A little like this.
Spiciness is a fake fire alarm in your mouth, in other words. You feel the searing and burning as if it’s real, and your body does its fire drill, sweating and flushing and asking for water to dissipate that heat – except the heat isn’t there! Basically, if capsaicin was a person, he would be fined $5,000 on the MRT for pressing the emergency button.
Birds also have a TRPV1 receptor in their mouths, but the catch is, capsaicin doesn’t work on bird receptors. It’s a different design of fire alarm, and the prankster can’t set it off. Therefore, while rats and grazing animals get a painful fake fire in their mouths, birds just eat the chillies. That’s exactly what the plant wants. Everybody wins.
Now that we know how capsaicin works, though, the real mystery remains – which is why so many humans enjoy spiciness so much. Remember, chillies made capsaicin in order to deter us. They do not want us to eat them, so they made something that messes with our nerves and makes us all uncomfortable and sweaty. And yet we love it so much we now grow vast amounts of chillies just to eat all their fruits and ruin their reproductive plans.
What makes this even odder is how universal it is for us to love spice. Chillies, after all, are a New World plant; Eurasia never had them until after 1492, and in many cases only after the 1600s. And yet they quickly caught on, in all sorts of places, among all sorts of people. Indians and Thais love the burn, as do Malays and Chinese and Koreans. We say we’re addicted to it, even though – unlike some other chemicals, like nicotine – capsaicin is not actually addictive.
We still aren’t sure why this is, but the most prevalent theory right now is that it’s the fakeness of the spicy burn that we like. In other words, like a demented building manager, the brain knows the fire alarm is fake – but it loves doing the fire drill anyway. After all, if we knew something was actually very hot, like a glowing coal, we would never willingly eat it. But once a child has eaten chilli, and realised she wasn’t actually going to die of a burning mouth, it seems she would then enjoy the illusion. This article from the Guardian gives a bit more context.
Whatever the reason, though, capsaicin is such a reliable and versatile thing that humans have used it in just about everything. No doubt the long weekend will be a chance to indulge in many of the culinary wonders that are enlivened by chilli. Enjoy the burn, readers, and happy National Day to all!