Why Are Chilli Peppers So Hot (And Could They Be The Key To Weight Loss)?

Dan Chesman

Naked mole-rats: the mammalian wonders of the animal kingdom. They are best known for their near-immunity to cancer, their insanely long lifespan for a mammal so small and for being ridiculously good-looking (see below). In addition to this, they do not feel chronic pain. For many, this would be a dream come true. Sadly, for these perky little critters it also means they are immune to the burn of every masochist’s favourite piquant pockets of firepower: chilli peppers.

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I call this one blue steel – A supermodel naked mole rat posing for the camera.

Image Credit: Wikimedia Commons

However, scientists have found that by infecting naked mole-rats with the herpes virus, the animals could happily enjoy a Friday night vindaloo in much the same way any (slightly insane) human would. So, the herpes virus confers an ability to feel the pain of spicy foods. But before you go running to your doctor post-curry, it’s not herpes itself that causes us to feel the ‘ooh-aah-aah’ of a habanero.

The infection of naked mole rats with the herpes virus caused their cells to begin manufacturing a compound known as ‘substance P’ which mole-rats normally lack. Substance P is a compound is used to convey pain signals between nerve cells, and therefore allows the naked mole-rat to feel the effect of a group of irritant compounds in chillies, the capsaicinoids.

The capsacinoids all have the same basic structure. Though there is some variation between members of the family, they are all long-chain hydrocarbons possessing an amide group (the adjacent oxygen and NH groups) and an aromatic ring (the six-membered ring at the end of the tail). They are insoluble in water because of this, which means pouring of gallon of H2O down your throat after a particularly hot curry will be about as useful as a chocolate teapot.

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Capsaicin (top) and dihydrocapsaicin (bottom) – the two most common capsaicinoids

Image Credit: Dan Chesman’s School of Art

Capsaicinoids cause us pain by binding to mucous membrane receptors in our mouths. Though toxic in large quantities, capsaicinoids are only found in very small amounts in most chilli peppers and do not cause any lasting damage at that concentration. Even the ghost chilli, with a heat intensity of 1.4 million Scoville units (a measurement of capsaicin concentration), is not toxic. It will seriously burn though.

There are recent rumours surfacing around the internet about chilli as a potential aid in weight loss, but is there any truth in this?

A recent article published in the Appetite journal suggests that consuming chilli with meals can reduce energy intake from the meal by up to 74 calories. The research was based on a combined analysis of eight studies with a combination of 191 participants, and found that around 2 milligrams (0.002 grams) of capsaicin would be required with each meal.

In addition to this, another study found that chilli can increase the sensation of fullness after a meal, ultimately leading one to eat less. The same study also found that the hunger arising from the negative energy balance caused by eating less is somewhat negated by consumption of chilli.

In addition, drinking a bottle of chilli sauce will make you sweat pounds; that could help. Unless you’re a herpes-free mole-rat, that is.

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