A taste for spice
Why would anyone willingly eat something that causes pain? Capsaicin triggers a rush of stress hormones. These will make the skin redden and sweat. It can also make someone feel jittery or energized. Some people enjoy this feeling. But there is another reason why chilies show up on dinner plates the world over. Hot peppers actually make food safer to eat.
When food sits out in warm weather, microbes on the food start to multiply. If people eat food with too many of these germs, they risk getting very sick. The cold temperature inside a refrigerator stops most microbes from growing. That’s why most people today rely on refrigerators to keep their food fresh. But long ago, those appliances weren’t available. Chilies were. Their capsaicin and other chemicals, it turns out, can slow or stop microbial growth. (Garlic, onion and many other cooking spices can, too.)
Before refrigerators, people living in most hot parts of the world developed a taste for spicy foods. Examples include hot Indian curries and fiery Mexican tamales. This preference emerged over time. The people who first added hot peppers to their recipes probably had no idea chilies could make their food safer; they just liked the stuff. But people who ate the spicy food tended to get sick less often. In time, these people would be more likely to raise healthy families. This led to populations of hot-spice lovers. People who came from cold parts of the world tended to stick with blander recipes. They didn’t need those spices to keep their food safe.
Why chilies hurt
The heat of a chili pepper is not actually a taste. That burning feeling comes from the body’s pain response system. Capsaicin inside the pepper activates a protein in people’s cells called TRPV1. This protein’s job is to sense heat. When it does, it alerts the brain. The brain then responds by sending a jolt of pain back to the affected part of the body.
Normally, the body’s pain response helps prevent serious injury. If a person accidentally places fingers on a hot stove, the pain makes him or her yank that hand back quickly. The result: a minor burn, not permanent skin damage.
Biting into a jalapeño pepper has the same effect on the brain as touching a hot stove. “[Peppers] trick our brain into thinking we are being burned,” says Tewksbury, who now leads the Boulder, Colo., office of Future Earth. (The group promotes research to protect Earth's resources). Pepper plants likely evolved their fake-out