What makes chili so hot

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. 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.

The heat of a chili pepper is not actually a taste. 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. 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. People, mice and other mammals feel the burn when they eat peppers. Birds do not. Why would peppers develop a way to keep mammals away but attract birds?

Mammals have teeth that smash seeds, destroying them. Birds swallow pepper seeds whole. Later, when birds poop, the intact seeds land in a new place. That lets the plant spread. Those with pepper allergies or stomach conditions do need to stay away from chilies. But most people can safely eat hot peppers. Capsaicin does not actually damage the body in the same way that a hot stovetop will — at least not in small amounts. In fact, the chemical can be used as a medicine to help relieve pain.

It may seem bizarre that what causes pain might also make pain go away. The human body is good at repairing itself, however. Eventually, the pain will fix this pain system and can once again send pain alerts to the brain. However, if the TRPV1 protein is activated often, the pain system may not get a chance to repair itself in time. The person will only feel discomfort or burning at first. Then he or she will experience relief from other types of pain. She, too, says he must be mistaken.

There's no ulupica here. The other four people in our group linger at the vehicle. We're wet. Biting flies leave red welts on our necks and arms. Noelle Machnicki, a University of Washington graduate student, has a plane to catch. Tewksbury marches down the road, hops over a strand of barbed wire, and lumbers up a slope through a tangle of moist weeds. The others make halfhearted efforts to scan the area around the truck, while I follow Tewksbury up the hill.

As he enters the forest, marble-size red globes catch his eye: C. Tewksbury bites into a fruit. He walks over to another plant. It, too, is sweet. Soon he has tasted fruits from eight plants and not one is spicy. This could well be an entirely mild wild chili population—the first ever—he muses, then erupts into a frenzy of free association, cooking up evolutionary trees for the strange chilies. Suddenly, a monkey in the canopy above us leaps from one branch to the next, and rainwater cascades onto our heads.

Tewksbury watches the animal's acrobatics before performing some of his own: a vine snags his ankle and he tumbles face first into a chili bush, another C. Dazed, he plucks a fruit and bites into it. He spits it out and grimaces—this one is hot. He couldn't be happier. People have been spicing up their food with chilies for at least 8, years. At first they used wild chilies, likely adding them to potatoes, grain and corn, says Linda Perry, an archaeobotanist at Smithsonian's National Museum of Natural History.

She has found traces of chilies on ancient milling stones and cooking pots from the Bahamas to southern Peru. Based on her studies of potsherds from different archaeological sites, she concludes that people in the Americas began cultivating chilies more than 6, years ago.

Just why they did is a matter of scholarly debate. Perry believes it was a question of taste. And some scholars point to medical uses. Ancient Mayans incorporated chilies into medicinal preparations for treating infected wounds, gastrointestinal problems and earaches. Laboratory studies have shown that chili pepper extracts inhibit a number of microbial pathogens, and capsaicin has been used in a local anesthetic. Whatever the benefits, chilies spread around the world with astonishing speed, thanks in part to Christopher Columbus.

In , the explorer encountered some plants cultivated by the Arawak Indians in Hispaniola. Convinced he had landed in India, he referred to them as "pepper," an unrelated spice native to the subcontinent.

The Portuguese got acquainted with chilies at their trading post in Pernambuco, Brazil, and carried them, with tobacco and cotton, to Africa. Within 50 years of Columbus' voyages, Pernambuco chilies were being cultivated in India, Japan and China. Chilies made it to the American Colonies with the English in In the United States, where chilies were once an exotic spice, consumption increased by 38 percent between and The rise reflects both the influx of immigrants from countries where spicy food is common and more adventurous eating among the general population.

According to the U. Department of Agriculture, the average American now consumes 5. When people call chilies "hot," they're not just speaking metaphorically. Capsaicin stimulates the neural sensors in the tongue and skin that also detect rising temperatures. As far as these neurons and the brain are concerned, your mouth is on fire. Similarly, mint stimulates a type of neural receptor sensitive to cool temperatures.

With enough heat, adrenaline flows and the heart pumps faster. This reaction, according to some physiologists, is part of what makes peppers so enticing. The scale that scientists use to describe a chili's heat was developed in by Wilbur Scoville, a chemist at Parke-Davis pharmaceutical company in Detroit. He would dilute a pepper extract in sugar water until the heat was no longer detectable by a panel of trained tasters; that threshold is its Scoville rating. Last year, the naga jolokia, which is cultivated in India, rated a whopping one million SHUs.

What's remarkable is that this variation can occur within a single species. The cayenne pepper, C. The Rev. Ignaz Pfefferkorn had developed a liking for chiltepins there in the s. Pfefferkorn whose name means "peppercorn" in German called them "hell-fire in my mouth.

That's when Tewksbury started wondering why chilies were hot. Chilies, like other fruits, lure birds and other animals to eat them and disperse their seeds. Even with these results, a tantalizing question remained. To answer that, Josh Tewksbury ventured to the heart of chili evolution, in Southeastern Bolivia. Bolivia is not an easy country to do field work in. Nonetheless, the team set about finding wild populations of Capsicum chacoense , and discovered a story with far more characters than they were expecting.

Neither the presence of rodents nor birds seemed to influence how many plants in a local population were spicy. The first critter that did correlate with chili spice was a small insect in a related group called the Hemiptera[4]. These bugs use a proboscis, or needle-like tongue, to puncture the fruit and drink the peppery juice see Photo.

Capsaicin probably deters insects much like it deters rodents. The scientists found that within a population of plants, the average number of puncture marks on the fruits correlated with the proportion of plants that made spice. As the number of insect foraging holes increased, so did the amount of mold on the seeds. But just as early American natives discovered, the scientists saw that these fungi are sensitive to capsaicin. Spicy plants exhibited much less fungal damage on their seeds than non-spicy plants.

By placing the fungi on Petri dishes with varying amounts of capsaicin, they found that greater amounts of capsaicin resulted in less fungal growth. Across Bolivia, chili populations that are wetter, with more insects, and where fungi are more prevalent contain a larger proportion of spicy plants than drier places with fewer insects, where fungi do not grow as readily. Weather, insects, and mold all influence just how spicy Capsicum chacoense can be.

Figure 1. An insect, Acroleucus coxalis , uses its proboscis, a specialized tongue, to suck juice from a wild chili pepper, Capsicum chacoense. The team had done much to explain why chilies evolved to make capsaicin, but why some plants made no spice was still a mystery.

To answer that, they delved into the physiology that governs spice production. The molecule is relatively large and contains lots of precious nitrogen, which is critical for building proteins and DNA.

Furthermore, as a byproduct of making capsaicin, the leaves of spicy plants have more stomata. Non-spicy plants have an advantage over spicy plants during drought, producing more seeds, and thus more progeny, than their spicy brethren. When plants receive enough water, the advantage disappears and the spicy and non-spicy chilies make an equal number of seeds again.

For wild chilies, the dueling selective pressures of fungal pathogens and drought result in a polymorphism, a case where some chilies are spicy and some are not at all.