WHY HUMANS TOLERATE SPICE

by Megha – Chillis and bell peppers add a good, spicy edge to our meals. Some people even seek out extreme spices, so much so that there are spicy food eating challenges held across the globe, and loads of videos on YouTube of people reacting to eating them. Surely then, spicy flavors should be a pleasant feeling?

Well, no. A burning sensation starts spreading across the mouth, the sensory system signals “HOT HOT!” to the brain and the eyes and nose start running. Blood vessels dilate and blood rushes in, increasing the temperature that triggers sweating to cool the body down. The lungs alert the diaphragm to hiccup quickly and continuously to eject the fiery invader. In the distance, sirens.

In 2001, a study was conducted by Tewksbury et al. to find out if capsaicin, the element responsible for the heat we sense when consuming these fruits, was produced by chili peppers to fend off mammals and certain other animals. The study employed two varieties of peppers, Capsicum annuum and a similar but non-pungent Capsicum chacoense. Their findings showed that cactus mice and packrats avoided consuming both varieties of the fruit, but curve-billed thrashers scarfed them down. Further, they found that mammals destroy the fruit’s seed when they bite them. But birds, who lack capsaicin receptors, did not crush the seed while eating the fruit, making them effective pollinators.[1]

And yet, about six million years ago, early human hunter-gatherers most likely wrapped their meat in leaves of spice plants and discovered that they liked the flavours that were imparted. And today, we cannot get enough of Taco Bell’s fire sauce.

Why do human beings like spices so much?

An interesting theory, called Darwinian Gastronomy, provides possible answers.

A pattern can be found with spice usage across the globe. Cuisines from tropical countries tend to be spicier compared to those of countries in the north. A study was performed to quantify this difference. In a sample that represented every continent, and 16 of the 19 major linguistic groups, it was found that in 10 countries – Ethiopia, Kenya, Greece, India, Indonesia, Iran, Malaysia, Morocco, Nigeria, and Thailand – every meat-based recipe called for at least one spice, and in Scandinavian countries, only a third of their recipes contained spices.

The flavour enhancing properties of spices do not answer the evolutionary questions of why we like pungent tastes in our dishes, and why certain phytochemicals are tasty to us. Throughout history, microbes carried by food, such as Salmonella, Escherichia and Clostridium, have posed a threat to our health. If spices were to kill or inactivate these microorganisms, their use would reduce foodborne diseases.

Thus, it is only natural that spice usage might be at a maximum in hotter climates, where unrefrigerated foods spoil very quickly. As average temperatures increased among countries, the study found that there were significant increases in the proportion of recipes that used at least one spice, and the numbers of different spices used.

Also, relative usage of individual spices increased. As average temperatures went up, so did the use of onion, garlic, chilis, coriander, anise, cinnamon, nutmeg, turmeric, ginger and lemongrass. All of these are highly inhibitory for bacterial growth. (A couple of negative relationships were found between temperature and frequency of usage for dill and parsley, but these are not antimicrobial.) [2]

So, is spice tolerance genetic? Possibly yes. Some people are born with fewer capsaicin receptors, making them more resilient to the antagonizing sensations that spices whip up. Not much is known about the genetics behind somatosensory perceptions such as pungency. A 2012 study on twins showed that about 18-58% of spice preference is due to genetic effects, but environmental factors also play a role in influencing the pleasantness of spicy foods and pungent tastes. Questionnaire tests conducted on the participants of the experiment expressed their attitudinal and memory-based view on spiciness.[3] This is no wonder considering the huge range of external factors such as social context, physical environment and information that govern a person’s food biases.

This means good news! Spice tolerance can be learnt. Children in tropical countries like India and Mexico are fed sweet, sugary food laced with chili powder to build tolerance. We can effectively desensitize our nerves to the unpleasant effects of capsaicin and other “hot” phytochemicals by repeated exposure and lots of patience. So the next time you sit down with a plate of nachos and salsa, add an extra dash of pepper because maybe…you might just have a chance to beat a record and win the next spicy food eating challenge!

CITATION:

  1. Tewksbury, J. J., & Nabhan, G. P. (2001). Directed deterrence by capsaicin in chillies.
  2. https://www.utsc.utoronto.ca/~burton/foodcourse/spices.html
  3. Törnwall, O., Silventoinen, K., Kaprio, J., & Tuorila, H. (2012). Why do some like it hot? Genetic and environmental contributions to the pleasantness of oral pungency.

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