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The Science of Spicy

Spicy foods. Not spicy enough is a bit disappointing. Too much spice and you can’t taste anything through the pain. But what causes that pain?


At my old job, the design team and the code monkeys went to the South Bank market every Friday for lunch. In this market there were so many stalls selling all kinds of food, and everything was so delicious! My favourite stall, however, was the Korean Burrito stall, where they had salad boxes, rice boxes and burritos with the choice of three meats: pork, beef or spicy chicken. And after someone highly recommended the chicken, I went for the chicken thinking “It can’t be that spicy”. Boy, was I wrong!

It was so spicy, but at the same time, so delicious that, call me crazy but, I got it again the next time I went. And yes, it was still really spicy, but it still tasted gorgeous!

But getting back to the point of this post, having all this spicy food made me wonder why does spicy food set your mouth on fire, even if it isn’t physically hot? And why is it sometimes painfully spicy? Well, as always, I did some research.

Warning, the following science is Chemistry, which I stopped studying at school about 10 years ago, so forgive if there are mistakes!

Capsaicin is a colourless odourless substance that is in the flesh of chilli peppers. This capsaicin binds to TRPV1 receptors, which is a pain receptor on your tongue and around your mouth that detects hot or acidic foods that could cause damage to any tissues. When these receptors are stimulated, it tells the brain and your brain then tells the body to get whatever is in your mouth the heck out of there!

Now, unfortunately, capsaicin fit into the TRPV1 receptors perfectly so when eating something spicy, the capsaicin binds to the receptors which then tell our brain telling us that we are eating something that we probably shouldn’t be. The capsaicin is then perceived as pain, causing our bodies to want to do anything to get it out of our system and this is apparently why we cry, sweat and grab anything cold and liquid to cool down the burning sensation in our mouths. It’s our brain doing what it thinks will get the painful substance out of our bodies.

But here is a really helpful hint: DO NOT DRINK WATER! Why not? Let me tell you why not!

Capsaicin has a long Hydrocarbon tail, meaning it’s a “nonpolar molecule”, which basically means it’s unbalanced and can bind with other molecules easily. The thing with nonpolar molecules is that they dissolve in other nonpolar substances, because the two molecules bind together. The problem with drinking water is that water is a polar (balanced) substance, which means all it ends up doing is spreading the capsaicin that hasn’t bonded to a receptor around your mouth to the receptors that haven’t been in contact with the capsaicin yet, meaning more pain for the poor diner eating spicy foods.

But milk is another nonpolar substance and contains a molecule called Casein, which attracts capsaicin molecules, so milk will pull the capsaicin molecules off your TRPV1 receptors and dissolve them, reducing the pain in your mouth.

However, if you do suffer through the pain for long enough, there is an upside. You know that hardcore friend that can eat really spicy foods (we all have at least one!) when some people (like myself) break out in a sweat when they eat anything spicier than a Tikka Masala? This is because they are used to it! They have eaten so much spicy foods that their TRPV1 receptors have grown a resistance to capsaicin. How ‘cool’ is that?


So, that is why food is spicy and sometimes painful!

If it’s possible to dedicate blog posts to people, this one goes out to all the people at SDG who made every day of work fun and introduced me to that awesome market and a wealth of different foods to try!

Published inScience


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