| But Really, Why on Earth Do We Eat Chiles Anyway? |
A love for herbs, a love for travel – two necessary prerequisites for any would-be herb explorer. New herbs are the lifeline of Richters Herbs, and getting out into the world, preferably the under-developed world, is one way we find new, interesting plants and seeds for our customers.
One year I found myself in Oaxaca City, in Mexico, where I treated myself to the local delights on offer at the market near the zocalo, like fried grasshoppers. Not too bad, actually, except the legs get stuck between the teeth. I criss-crossed the market hunting for interesting items that might be fun to grow back in Canada, especially chiles – lots of different chiles, of different shapes, sizes, and colours. Like any self-respecting plant explorer, I saw gold in them chiles. I saw with my x-ray vision plantable seeds inside every pod, and I excitedly scooped up every available variety that the farmers offered. In my excitement it didn’t occur to me to wonder what the vendors might think about the sight of a gringo stocking up on every type of chile, but they would have been quite right to think “This gringo is loco.”
|Dried chiles, Mercado Teotitlán del Valle, Oaxaca.|
Back in my hotel room, I eagerly set up to remove the seeds from every chile bought, carefully keeping the varieties separate, and spreading the seeds out on labeled sheets of newspaper to dry. It was a tedious job in a hot room, and I kept reminding myself to never, ever wipe the sweat of my brows for fear of getting the hot burning oil of the chiles in my eyes. I remember priding myself for having had some training in Buddhist single-pointed mindfulness meditation, helping me, I thought, to resist the urge to wipe the sweat with my contaminated hands. Halfway through the seed extraction job, I felt the urge to pee. This was one urge that could not be resisted. I was annoyed because I was so excited about the seeds and wanted nothing to interfere with the job of getting them out of the pods. Reluctantly, I put the knife down and quickly slipped into the bathroom to urinate, and just as quickly I was back at the bed that was buried with newspapers covered in seeds – ready to resume work.
But something wasn’t right. Something down ‘there’. A warm tingle erupted into a violent blast of heat. The pain engulfed me, and gasping for air, I could only think of fire extinguishers and amputation. I made it to the shower but copious cold water had little effect. I figured I had two options: drag myself to the hospital, or wait until the pain subsided. Not relishing the humiliation of explaining what happened in broken Spanish, I opted for the latter.
A few years earlier, while completing post-graduate studies in botany, I shared a house with several people. One of my housemates was a woman whose grown son became crippled after hitting his head on concrete in a running accident. After months of hospitalization, Vance moved into the house to be in the care of his mother. We could tell that the injury had had a profound effect on his personality. He had become more jovial, less restrained, and generally unsuspecting of the intentions of others, and his uplifting attitude toward life endeared us all to him.
One day we played a joke on Vance. We sprinkled some chili powder on his slices of a pizza that all of us were about to share. We waited for Vance to blurt out “Spicy!” but there was no reaction at all. Naturally the joke did not go over too well with his mother when she found out. A week later, Vance ordered a pizza for himself and decided to smother his pizza with chili powder. Not just a sprinkling but a thick layer slathered over the pizza with a knife. We were besides ourselves with alarm. Did he know what he was doing? We pleaded with him not to eat the pizza but he would not listen. In shock we watched him eat the entire pizza covered with perhaps a spice jar’s worth of cayenne pepper. But this time the joke was on us – he had almost no reaction to the chili powder. We were in awe of what we had witnessed.
Thinking about the very different reactions to hot peppers, such as mine and Vance’s, prompted me to learn more about hot peppers, why some of us handle them easily, and why the rest of us masochists endure the pain and eat them anyway. The story, as I discovered, has unexpected twists and turns, just like a good mystery.
Of the twenty or so species that belong to the pepper genus Capsicum, five are domesticated. All the hot chiles that humans consume belong to one of these five species. The compounds responsible for the heat are a group of chemical constituents called capsaicinoids. The most important is capsaicin which accounts for more than two-thirds of all the heat activity in hot peppers. Capsaicin is mostly found in the pods, especially in the interior ribs to which the seeds are attached. It is a very interesting chemical: it acts like a key to turn on the pain system. It binds to ion channels in the membranes of neurons and when it does that, the channels open and let calcium into the neuron. The sudden influx of calcium is what triggers a constellation of events that lead to the sensation of pain.
Humans are not the only animals that are sensitive to capsaicin; many other mammals are too. Birds, significantly, are insensitive. In the wild, birds are the primary agents for the dispersal of pepper seeds; when they swallow a pod the seeds pass through the digestive system intact and germinate readily wherever the bird droppings fall. Rodents, on the other hand, are discouraged from eating hot peppers because they feel the pain. That is a darn good thing if you are a pepper plant because rodents have molars and they crush the seeds when they eat peppers, and are of no use for spreading seeds. This selective quid pro quo has important implications for us humans because we share 97.5% of our genome with mice, hence our common sensitivity to capsaicin. Effectively, we have been lumped in with the rodents as enemies of peppers.
But if capsaicin is important for seed dispersal, why are some peppers not hot at all? Even in the wild one can find peppers that are hot and others that are not. You might think that the hot ones are found in hot, dry areas while the mild ones are found in wet, cooler areas, but you’d be wrong. In Bolivia, the hot forms of the wild Capsicum chacoense are found in the cooler, wetter areas and the mild forms are found in the drier areas; a pattern that is repeated in Mexico and elsewhere where wild peppers grow. So what gives?
It turns out that, in the case of Capsicum chacoense, in cooler, wetter areas there is a bug that pokes holes in the pods in order to suck out the juice. The birds don’t mind the holes in the pods and still do their job of scooping up the pods and dropping seeds here and there. But the holes are bad for the pepper plants because fungi enter and destroy the seeds, rendering the whole exercise of making seeds a waste of time. Having loads of capsaicin stored all around the seeds is pure genius because of capsaicin’s other important property: it’s a powerful antifungal agent that protects seeds from invading fungi. But in hot, dry areas bugs and fungi aren’t as much of a problem, so wild peppers there don’t need to be as hot.
|Bird pepper, Capsicum chacoense|
But then you may ask, why don’t all peppers just produce loads of capsaicin just to be safe? The answer is that capsaicin is expensive insurance. It requires lots of nitrogen to manufacture, a key nutrient that is not in great abundance in soils where peppers grow. If capsaicin is not needed for the protection of the seeds then why bother wasting a valuable resource that could be used for other purposes? Plants that produce little or no capsaicin are in fact more drought resistant, which of course is of greater priority for pepper plants in dry areas.
Over the past few decades, capsaicin research has been, quite literally, ‘hot.’ Thousands of research papers have been published, much of which is focused on pain research. Capsaicin is a valuable tool for understanding the pain signaling systems of the body. Remember those ion channels that I mentioned earlier? Those channels in the membranes of neurons also open up in response to excessive heat and to applied pressure such as pinpricks. So capsaicin can be used to mimic the effects of real pain caused by heat and by pressure. This first step of the pain signal, starting from the ion channels, is why we so easily conflate the type of pain we are experiencing. When we eat hot chiles we experience the ‘pain’ as ‘heat’. Our brains interpret (or misinterpret) the signal as ‘heat’ because the signal travels more or less along a common path. In pain research, capsaicin is used to turn on the ion channels like switches in order to study the pain mechanisms and to help in the search for new painkilling medicines.
|Capsaicin binds to ion channels which opens them and allows calcium ions to flow inside cells such as nerve cells or neurons. An increase in calcium inside neurons leads to a sensation of pain.|
But as anyone who has felt the wrath of hot peppers knows, there is a lot more to the ‘pain’ of capsaicin than just the simple hijacking of the pain signaling system. We also sweat, often copiously; and we get flushed; and our skin temperature rises. But surprisingly, for the first hour or so after ingesting chiles our bodies actually cool down. Hard to believe, but this was proven in experiments in which both the skin temperature and the temperature in the colon were measured simultaneously. In the first hour, the skin temperature jumps while the internal temperature drops. What happens is that the blood vessels dilate, allowing body heat to escape to the skin where it can dissipate more easily. The dilation effect brings blood closer to the skin surface, hence the flushed skin. And the rise in skin temperature initiates the flow of sweat. Both the flushed skin and the sweating cool the body, so after about an hour there is a net loss of body heat.
But soon after ingestion of capsaicin, a completely separate response mechanism kicks in, slowly increasing the rate of metabolism and creating new body heat. Over a period of twenty-four hours or so this new heat builds up slowly, bringing the body’s temperature back to more or less where it was before ingestion. So, as always with anything involving herbs and the human body, nothing is simple.
Paradoxically, capsaicin not only causes pain but is also used as a painkiller. It is used in topical creams and patches for peripheral neuropathy, postherpetic neuralgia, osteoarthritis, and other chronic pain conditions. In both Canada and the United States, a number of prescription and over-the-counter products containing capsaicin are available in pharmacies. But how in the world does a pain-inducing product become a painkiller, you might ask. To answer this question, we need to understand the phenomenon of desensitization. As the use of a compound is repeated, its effect is diminished over time. In the case of capsaicin, there are two forms of desensitization. One is a short term desensitization that follows from the fact that the calcium signal can only be switched on so many times before it becomes unresponsive. If all the pain switches (i.e. the ion channels) are already thrown, adding more capsaicin, or applying more pressure, or turning up the heat more, won’t cause more pain. This is graphically illustrated in a video on the Internet showing a man eating 40 of the world’s hottest pepper, the Carolina Reaper, 300-800 times hotter than a Jalapeño pepper. The man sweats profusely and suffers terribly; yet he ultimately finishes eating the peppers. As Ed Currie, breeder of the Carolina Reaper, claims in another video, the experience of taking a bite is “amazing,” “incredible,” and “pleasurable” once the peak heat passes. Presumably, all the pain switches that could be turned on are done so by the Reaper and there is not much more pain that can be experienced.
| Pain products made with capsaicin|
The second desensitization effect is a longer term one. This is the one that painkilling patches made with capsaicin rely on. When either a low dose of capsaicin is repeatedly applied or a high dose is applied once, a long-lasting insensitivity to pain results. This happens because repeated or strong stimulation with capsaicin causes the degeneration of sensory nerve fibres, and the painkilling effect lasts for months. People who grow up with hot peppers in their daily diet no doubt also become desensitized, probably in the same way that pain patches work – by destroying sensory nerves. But even where chiles are part of the daily diet, infants are not born with a tolerance to chiles. Mexican parents, for example, are known to give children packets of sugar spiked with chili powder to build up tolerance.
Genetic differences in the sensitivity to capsaicin have been reported but there is not a lot known yet. Korean scientists have studied an individual who was completely insensitive to capsaicin. This person had less than half a normal person’s ion channels in his or her buccal mucosa, the lining of the cheeks and lips inside the mouth opposite the teeth. Because desensitization by capsaicin occurs in the nerve fibres further down the signaling pathway, and not on the ion channels at the start of the pathway, we know that this individual could not have lost all sensitivity by exposure to capsaicin. The scientists found several mutations in the DNA code for the ion channels and presumably these affected the receptor site for capsaicin, making it impossible for capsaicin to bind to the channels and turn them on. This is one of the few published reports showing genetic differences in the sensitivity to capsaicin.
There is also a report of genetic differences among female redheads that unsurprisingly elicited comment from a few wags. Compared to blond and dark-haired females, redheads were found to develop less sensitivity to pain after the application of a low dose capsaicin cream. Unlike high doses or repeated low doses, a single low dose makes people temporarily more, not less, sensitive to capsaicin, and this hypersensitivity effect was found to be less prominent in redheads. What exactly is the significance of this finding, I am not sure, but it does seem to suggest that genetic differences among human groups and races could be important and may warrant further study.
What about Vance? Is he a genetic oddity, born with an insensitivity to capsaicin? Or did he acquire an insensitivity to it? Or was it something else? Actually, he was not as completely insensitive to the chili powder as I made him out to be. I fabricated a little there. He did get a little flushed and a little sweaty; but he did not experience pain. There was no involuntary pinched look or grimace as the effect of the capsaicin in the chili powder enveloped him. My guess is that his brain injury occurred in an area of the brain responsible for processing pain, such as the insular cortex. This area is also involved with the emotions, and we saw that his accident caused changes in his range of emotional expression. So, just maybe, Vance’s ability to tolerate the effects of capsaicin and feel no pain reflected the possibility that his brain was now processing pain differently. But who knows?
So why do we eat this stuff? When did gastronomic pain become a good thing? An idea has emerged that humans – uniquely humans among mammals – seek out and enjoy hot peppers as a consequence of some trickery in the processing of pain in the brain. A mental sleight of hand dubbed “hedonic reversal” or “benign masochism” has been suggested to explain how we derive pleasure from the pain of chiles. Paul Rozin, professor of psychology at the University of Pennsylvania, has been studying the idea since the 1970s. He says that humans are able to dissociate the pain signal from the threat of danger, and can enjoy the thrill of danger without feeling the risk, in the same way that humans love the thrill of a roller coaster ride without worry of injury. Other mammals probably don’t have the brain power to do this kind of mental calisthenics. For rats, any experience of pain means an immediate risk of danger, 100 per cent of the time, and nothing is going to change that. In an experiment, Rozin found that he was not able to condition rats to love chiles even when the rats were given the stark choice of food laced with chiles and food laced with a chemical that made them sick. Rats preferred the food that sickened them come hell or high water.
But despite a growing acceptance of Rozin’s theory, it still does not quite rest well with me. I am not sure that “benign masochism” fully explains a love for chiles that goes back at least 9,500 years when the earliest use of chile peppers is known to have occurred. We know that chiles are a rich source of vitamins B and C, potassium and iron, so nutrition could have played a role. We know that chiles lower blood pressure and habitual use kills pain, so medicinal benefits could have played a role. And we know that capsaicin has antifungal properties that may have had a role in preserving food and may have helped decontaminate unhealthy food, or helped the body to resist the effects of eating unhealthy food. Rozin dismisses all these reasons for explaining our love for chiles.
In the comments section of an online Scientific American article on chiles, a devoted fan of the Bhut Jolokia pepper, a pepper not quite as hot as the Carolina Reaper but pretty darn close, summed up his take on Rozin’s theory by suggesting a simpler, slimmed down alternative. He says eating very hot chiles everyday makes him feel good. “If I’m feeling lethargic before eating a very hot chile, I feel revitalized. It’s a similar reward as when you lift weights (I do this too). Both make you feel good after enduring a little pain.” It doesn’t seem to me that this “revitalized” state is a mere figment derived from mental trickery, of relishing the relief of the cessation of pain, as Rozin would believe. To me, the Jolokia lover is referring to an actual physiological change in his metabolic state, one that overcomes lethargy. We know that there is an immediate inner cooling effect for about an hour after eating hot chiles, and maybe it is this simple change of state that has more to do with why he feels “revitalized” afterwards. Who knows?
|Bhut Jolokia, from India, is one of the world’s hottest chile peppers.|
But I do know one thing: I am not loco enough to eat a Bhut Jolokia to find out.