Asked by: Jamie Todd, Kent
The active ingredient in chilli peppers is capsaicin, one of several related compounds called capsaicinoids that bind to vanilloid receptors inside the mouth and on the tongue. These receptors detect heat and send a signal to the brain about temperature. So it is an accident of nature that capsaicin activates them, tricking the brain into responding to spicy food as though it were hot.
You might think we ought to avoid such foods rather than enjoy them but they may serve many functions. Capsaicinoids are known to increase energy and reduce appetite; they also increase salivation, making it easier to eat bland food such as plain rice. Another theory is that the pain of hot chillies is a kind of benign masochism. The ‘heat’ reduces other pain by inducing the release of endorphins, which are the body’s natural painkillers, and gives a sense of wellbeing.