Why are chilli peppers so hot?

THAT'S THE WHY:I used to work with someone whose mouth must have been lined with asbestos. If our lab went out for curry, he could happily wolf down the spiciest foods with ease while the rest of us turned a shade of beetroot and blew steam out of our ears even from dishes that didn't register quite so high on the Richter scale.

Chilli pepper is one of the hotter spicy ingredients, and it sears the mouths of most mortals because it contains a chemical called capsicain.

This activates a heat receptor called TRPV1, which sends signals screaming along your nerves to your brain.

But why would a chilli do such a thing? Research suggests that capsaicinoid chemicals could offer a mechanism to protect the plant.

For example, a 2008 study looked at genetic variations that affect pungency in the chilli species Capsicum chacoense in Bolivia. It found that higher levels of capsaicinoids seemed to protect the wild plant from attack by a Fusarium fungus.

And it’s possible that such anti-microbial properties may have influenced humans to use the tolerably spicy versions to protect themselves.

“Before the advent of refrigeration, microbial contamination of food was a common cause of illness and death in many cultures, and the consumption of chillies with food may have reduced the risk of microbial infection, providing an adaptive reason to eat pungent food,” write the researchers in the Proceedings of the National Academy of Sciences.