About one-third of the world's population eats chili peppers every day. For thousands of years, people have endured the stinging and burning sensation of chili peppers while tirelessly incorporating them into their diets. Why do people like spicy food so much? Scientists in different fields have given possible revelations from different aspects, but it is also impossible to fully understand the reasons why humans have such a preference for chili peppers. Consuming those super spicy peppers may cause serious physical discomfort, so eat it in your capacity.
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In the hot summer, it's a good time to eat spicy food. However, in some places, people are not happy with spicy food, and in other places, the whole country has done its best to ban spicy food. Recently, the Danish Food Authority asked South Korea's Samyang Foods to recall three of its turkey noodles that are known for being super spicy because the chili content is "too high, which may cause acute poisoning to consumers." ”[1]
Similarly, Germany also banned the sale of a Devil's Pepper Potato Chips after a 14-year-old student died of food poisoning within hours of eating it. [2]
In this way, chili peppers fulfill the old saying: "Your honey is arsenic." What is the scientific rationale behind such a divisive assessment?
Nobel laureate deciphers the mechanism of spicy stimulation
When the chili pepper is ingested, it will first produce a stinging sensation in the mouth, followed by a burning sensation, as if a raging fire is burning in the mouth. And this real pain and illusory heat sensation is the "director's play" of the capsaicin in chili peppers and our capsaicin-specific receptor - vanillin receptor type 1 (TRPV1). In addition, it is the study of capsaicin receptors that made American neuroscientist David Julius one of the 2021 Nobel Laureates in Physiology or Medicine [3].
Back in the late '90s, David Julius led a team at the University of California, San Francisco, to analyze how capsaicin evokes the sensations we feel when we come into contact. Through various experimental methods, he finally succeeded in identifying and cloning TRPV1, showing the basis of the body's perception of spicy at the molecular level: TRPV1 is an ion channel activated by pain and heat (nociceptive heat at ≥ 42°C), which specifically recognizes afferent neurons of nociceptive stimuli and is widely distributed in multiple tissues and organs of the body. When the mouth comes into contact with capsaicin, TRPV1 is immediately activated, generating electrical signals that are transmitted along nociceptive afferent neurons to the brain, which uniformly interprets these signals as "painful" stimuli. Scientifically, spicy sensation is defined as "pain" [4-5].
In addition to pain, how does capsaicin make us feel hot? The heat generated by eating chili peppers or chili peppers is not the result of physical heating, but rather the feeling of heat that we feel more sensitive to when we are spicy. When TRPV1 is activated by capsaicin, the threshold for temperature perception is also lowered, and even a body temperature of less than 42°C induces TRPV1 to send a nociceptive heat signal to the brain, causing the brain to have an abnormal perception of "heat". Therefore, under the dual stimulation of capsaicin and temperature, the excitability of sensory neurons expressing TRPV1 receptors was also enhanced. Taken together, our feelings are amplified by the "abnormal", and our mouths are like "breathing fire".
David Julius used capsaicin to identify TRPV1, an ion channel activated by painful heat. Source: nobelprize.org
Next, our body also responds to the stimulus, which is still associated with the TRPV1 receptor. TRPV1 is a non-selective cation channel expressed in both neural and non-neural tissues, and its activation leads to the influx of large amounts of calcium ions, increasing the concentration of calcium ions in non-neural tissues, and mediating the release of a variety of neuropeptides, such as substance P (SP) and calcitonin gene-related peptide (CGRP). The former can trigger vasodilation, increase vascular permeability, lead to edema, and also stimulate mast cells to release inflammatory mediators, inducing leukocytes to release proteases and reactive oxygen species. CGRP, on the other hand, relaxes the arteries and regulates blood flow to the skin, triggering neurogenic inflammation. [6-7] As a result, our organism induces an inflammatory response out of "self-defense", and begins to sweat, runny nose, flush, swelling, etc.
Spicy food: painful and happy
Since eating spicy food makes us feel pain and anger, why are human beings so desperate? The use of chili peppers has been documented as far back as 7000 BC in Mesoamerica [8], and the article published in Science [9] reveals that it was not until 6000 years ago that humans began to grow and eat domesticated chili peppers from the Bahamas to the Andes, and even in some areas, chili peppers were cultivated before pottery appeared. In the 15th century, during the Age of Discovery, Columbus and other early explorers brought chili peppers from the Americas back to the Old European Continent, and then spread them around the world through sea routes and the overland Silk Road. Today, chili peppers have become an important part of the diet of many countries around the world, including West Africa, East Africa, India, Southeast Asia, parts of China, South Korea, and many more [10].
For thousands of years, people have endured the burning pain of chili peppers while tirelessly incorporating them into their diets. Paul Rozin, a psychologist at the University of Pennsylvania in the United States, pointed out that about one-third of the world's population eats chili peppers every day. Why? To put it simply: just like it.
So far, most scientists still can't fully understand why humans have such a preference for chili peppers. Scientists in different fields have come up with possible explanations from different aspects [11].
Biologists have an evolutionary explanation for why the consumption of chili peppers has become a cultural preference in some regions. Jennifer Billing and Paul W. Sherman of Cornell University analyzed more than 4,000 recipes in 36 countries around the world and found that there is a certain relationship between the regional average temperature and the proportion of spicy food in the diet [12]: the higher the average temperature in a region, the higher the proportion of spicy ingredients used in local cuisine, because hot weather tends to allow food to quickly breed a large number of microorganisms, and spicy substances have a bactericidal effect and ensure food safety. People in cold regions also prefer to eat spicy, which may be related to the physiological effect of eating spicy food to produce a sense of heat and bring about an increase in body temperature. A 2007 study published in Bioscience, Biotechnology and Biochemistry [13] pointed out that the intake of capsaicin will increase the temperature of the body core and body surface, which can play a certain role in keeping out the cold.
In addition, genes also appear to play a role in spicy eating. A 2012 paper published in Physiology & Behavior [14] took Finnish twins as subjects, first asked them to rate their preference for spicy food, and then analyzed the influence of genetic factors and environmental factors on spicy food preference through quantitative genetic models, and found that people who did not like to eat spicy food scored higher for spicy food, but rated the pleasure it produced lower, and the level of explanation for this preference by genetic factors ranged from 18% to 58%. The rest is due to environmental factors, suggesting that there may also be a genetic predisposition to the preference for spicy food.
The theory of "benign masochism" in psychology also provides a reasonable explanation to help understand people's motivations for actively eating spicy food. Healthy self-abuse refers to the fact that individuals enjoy negative experiences that are misinterpreted as threats by the body or brain, and once the individual realizes that there is no real danger, the difference in cognitive and physiological responses produces a pleasant sense of excitement. Therefore, human beings like to eat spicy food is an active behavior of seeking negative experiences. Rozin led a team to conduct research that validated eight types of benign masochistic experiences [15], among which spicy food was a burning experience. The individual's spicy food sends a "false alarm" to the body that it is threatened, causing the body to make a series of defensive responses, but at the same time, the individual realizes that the danger does not exist, and the sin of eating spicy food becomes a stimulus and enjoyment. Moreover, the study also suggested that when individuals eat just slightly less spicy than they can tolerate, the most pleasant spicy experience may be produced, but further validation is still needed.
How many levels of spiciness can you tolerate?
People who love spicy food are often quite confident in their ability to withstand spiciness. So, how do you quantify this ability? The Scoville Scale provides a detailed reference measure.
In 1912, the American pharmacist Wilbur Scoville devised a subjective evaluation method called the Scoville Organoleptic Test to measure the amount of capsaicin in different pepper varieties. He used his last name as a unit of capsaicin content, called the "Scoville Spiciness Unit", abbreviated as SHU. However, his experimental method mainly relied on the subject's personal subjective feelings, and later generations developed a more objective "high-performance liquid chromatography" method to measure it, but the unit of capsaicin content SHU was retained and is still used today [16].
In the table below, for example, bell peppers do not contain capsaicin at all, so their Scoville index is 0; Jalapeños range from 2,500 SHU to 10,000 SHU, and the highest Scoville index is also the hottest pepper in the world today, the X pepper, with a spiciness of more than 2.69 million SHU. However, this pepper is an artificially cultivated variety, cultivated by Ed Currie, the creator of the world's hottest Carolina Reaper pepper and an American pepper breeder, after 10 years of cultivation, Currie made the pepper hybrid gradually show the desired characteristics, and then after more than ten generations of cultivation to stabilize the characteristics, and finally produced the strongest spiciness [17]. However, consuming these super spicy chili peppers may cause serious physical discomfort, so please eat it in your capacity.
Global pepper spiciness rankings measured by Scoville spiciness units, source: wikipedia.com
If you are not familiar with SHU's numerical measurement of spiciness, then the mainland, as a major spicy country and a large producer of chili peppers, also has traditional spiciness classifications: "slightly spicy, medium spicy, high spicy, very spicy" and so on. The slightly spicy taste is manifested by an extremely slight irritation on the tongue and mouth, which most people can bear. When the spiciness is raised to medium, the tongue and mouth can already feel a certain stinging and burning sensation, such is the taste of the home-cooked tiger skin green pepper. Eating spicy chili peppers will cause significant burning sensation on the tongue and mouth, and people who are not good at eating spicy peppers may have begun to sweat, runny nose, sneezing, and even spicy tears. Extremely spicy chili peppers, such as Yunnan's shabu-shabu pepper, are hardly eaten directly because the irritation is too much for most people to tolerate [18].
The above spiciness grades are mainly based on personal subjective feelings, and lack a certain degree of uniformity and precision. In 2006, the College of Food Science and Technology of Hunan Agricultural University was commissioned by the National Standards Committee to formulate a national standard for the spiciness of chili peppers and chili products, and since then, various localities and enterprises have also begun to define the spiciness more precisely. In 2014, the Department of Food Science of Sichuan Tourism University and the Key Laboratory of Culinary Science of Sichuan Provincial Colleges and Universities classified 123 Sichuan dishes into four grades: mildly spicy, moderately spicy, spicy, and extra-spicy, based on the Scoville index, the content of capsaicin substances in food, and the traditional concept of spiciness[19].
The top 20 spicy Sichuan dishes in the study, source: https://www.spkx.net.cn/
In 2020, a joint enterprise team from the Institute of Urban Agriculture of the Chinese Academy of Agricultural Sciences published a paper in the International Journal of Food Properties on the use of Li Spicy Unit (LSU) to measure the pungency of chili condiments such as hot pot base [20]. The team divided the hotpot spiciness into six grades based on "degree": slightly spicy (9°~ 29°), low spicy (30°~ 39°), medium spicy (40°~ 49°), high spicy (50°~ 59°), extra spicy (60°~ 69°), and hot (≥ 70°) [21], helping consumers more intuitively choose spicy foods that suit their tastes and affordability.
Scientific anti-spicy strategy
Given that everyone has a different tolerance for spicy, if we unfortunately overestimate ourselves, our tongue is so hot that the burning sensation is unbearable, how can we effectively relieve spicy [22]?
The first effective method is to disrupt the binding of capsaicin to the TRPV1 receptor. Since capsaicin only dissolves in oil and alcohol, and does not dissolve in water, drinking water will not relieve spiciness, but will spread capsaicin to the entire mouth and even the throat, adding spiciness. Therefore, taking a sip of milk or other dairy products can help relieve spiciness, rather than drinking water. Dairy products contain not only oils and fats, but also casein, which is a non-polar molecule that binds to capsaicin, which is also a non-polar molecule, dissolving it and eliminating the burning sensation. Therefore, such as full-fat ice milk, full-fat yogurt or ice cream, etc., are all "masters" of spicy relief.
In addition, starchy foods can also play a certain relieving role, such as rice, bread, potatoes, etc. Although starch cannot dissolve capsaicin, it can act like a sponge to absorb capsaicin, shorten the duration of the spicy taste, and eliminate the pungency. So if you don't have milk, you might as well take a few more bites of rice if it's accidentally spicy.
The second method is to interfere with the brain's perception of spiciness, such as sucrose. On the one hand, the stimulation of spicy and sweet tastes acts on different receptor cells in the mouth, which, when activated, interact with each other and interfere with the brain's perception of spiciness alone. On the other hand, the brain releases analgesic substances when stimulated by a sweet taste, relieving the stinging sensation caused by the spicy taste.
The third method is to use acidic substances to neutralize alkaline capsaicin, such as lemons, sour plums, sweet oranges, etc., which can relieve the pungency.
In addition, a 2018 article published in the journal Physiology and Behavior presented an interesting finding [23]: complete obstruction of nasal airflow can reduce capsaicin perception levels by 50%, because when the nostrils are closed, the temperature of the tongue surface decreases, and cooling reduces the likelihood of activating TRPV1. Maybe in the future, when you choke on spicy, you can also try to pinch your nostrils and use physical methods to relieve spicy?
South Korea's Samyang Turkey Noodles was once selected as the most satisfactory Korean instant noodle brand among Chinese consumers in the 2021 Korean Brand Awards, but now it was unexpectedly banned in Denmark. After all, not everyone can accept instant noodles with a spicy content of more than 4,400 SHU due to health concerns, especially for children with more sensitive taste and digestive systems and frail adults, who will face a higher risk of adverse reactions including nausea, vomiting, gastrointestinal side effects, etc. Therefore, spicy can add vitality to life, but at the same time, be careful not to burden your health.
Resources
[1] http://m.ce.cn/gj/gd/202406/17/t20240617_39039091.shtml
[2] https://c.m.163.com/news/a/J4J91L7U05527UO2.html
[3] https://www.nobelprize.org/prizes/medicine/2021/press-release/
[4] https://www.nature.com/articles/39807
[5] https://neu-reality.com/2021/10/2021nobel/
[6] https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2019.01087/full
[7] https://neu-reality.com/2021/10/2021nobel/
[8] https://www.nytimes.com/2010/09/21/science/21peppers.html?auth=login-google1tap&login=google1tap
[9] https://www.science.org/doi/10.1126/science.1136914
[10] https://www.scientificamerican.com/blog/thoughtful-animal/on-capsaicin-why-do-we-eat-love-hot-peppers/
[11] https://journal.psych.ac.cn/xlkxjz/article/2018/1671-3710/1671-3710-26-9-1651.shtml
[12] https://www.journals.uchicago.edu/doi/10.1086/420058
[13] https://journal.psych.ac.cn/xlkxjz/article/2018/1671-3710/1671-3710-26-9-1651.shtml
[14] https://www.sciencedirect.com/science/article/abs/pii/S0031938412003095?via%3Dihub
[15] https://www.cambridge.org/core/journals/judgment-and-decision-making/article/glad-to-be-sad-and-other-examples-of-benign-masochism/48C0EC2F04412F3CB6EBC18B5E539BE8
[16] https://en.wikipedia.org/wiki/Scoville_scale
[17] https://en.wikipedia.org/wiki/Pepper_X
[18] http://www.ddcpc.cn/detail/d_shehui/11515115741094.html
[19] https://www.spkx.net.cn/fileup/HTML/20150429.shtml#:~:text=%E6%A0%B9%E6%8D%AE%E8%BE%A3%E5%BA%A6%E7%9A%84%E5%BC%BA,%E8%BE%A3%E6%A4%92%E7%B4%A0%E7%B1%BB%E7%89%A9%E8%B4%A8%E5%90%AB%E9%87%8F
[20] https://www.tandfonline.com/doi/full/10.1080/10942912.2019.1711116
[21] https://iua.caas.cn/xkqk/xk/232276.htm
[22] https://helloyishi.com.tw/healthy-eating/other-healthy-eating-tips/get-rid-of-spicy-mouth/
[23] https://www.sciencedirect.com/science/article/abs/pii/S0031938418302270?via%3Dihub
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