Everyone is familiar with the symptoms of eating spicy foods: sweating, runny nose, burning sensations, heartburn, digestive issues, and so on. However, what causes these symptoms and how to counteract them is less straightforward.
The chemical structure of capsaicin
Image from Science and Food
What allows spicy foods to have an effect on us is a chemical called capsaicin (C18H27NO3) which is found in chili peppers. A 2001 study led by Professor Josh Tewksbury aimed to discover why chili peppers began producing this chemical in the first place. The team, who led feeding trials in Arizona, found that capsaicin prevented rodents from eating the peppers while it did nothing to discourage birds. Birds, unlike humans and rodents, lack the taste receptors for capsaicin. The team determined that this could be an effective adaptation, due to the fact that mammals grind chili seeds with their molars, preventing them from germinating. On the other hand, birds do not grind the seeds and are able to disperse them far and wide (1).
Capsaicin works by binding to TRPV1 receptors on the surface of our taste buds and elsewhere. The main purpose of TRPV1 receptor cells is not to detect spicy foods, but foods that are literally hot. Yet, TRPV1 receptors also react to the presence of capsaicin. They open, allowing ions to flow through them. As a result, the sensation is transmitted through the trigeminal nerve, causing the brain to release a sensation of warmth to the mouth.
A visual of the Scoville heat index
The Scoville heat index is an imprecise method of comparing the heat of chilli peppers. It is measured by adding sugar water to a set amount of pepper extract until the heat is unable to be tasted. Because these cells are intended to react to hot foods, the central nervous system is confused by the presence of capsaicin. It reacts as if you are in danger and takes measures to get rid of the perceived threat (2).
For one, the brain believes that the body is overheating and attempts to cool it down by sweating. It also causes increased circulation, a runny nose, and watery eyes. Another result, and one that causes many people to enjoy spicy foods, is that the body releases dopamine and endorphins, natural painkillers, creating a feeling of euphoria (3).
Eating spicy foods can have many health benefits. A group of researchers at the University of Wyoming conducted a study in 2015 in which they found capsaicin could serve as a diet-based supplement. The team conducted studies with mice and found that dietary capsaicin helped to prevent obesity in all mice except for those who genetically lacked TRPV1 receptors. In the future, the team hopes to develop a natural dietary supplement using capsaicin (4).