为什么人们喜欢辣味食物——即使吃起来很痛苦？

The first thing to understand about eating spicy food is that it really isn’t a matter of taste. Capsaicin, the active chemical in capsicum plants that are a key ingredient in anything you’d think of as “spicy”, evolved as an irritant to stop mammals from chewing and destroying plant seeds. It acts on the nervous system directly through receptors in the tongue, throat and skin – no taste buds required – and, in theory, tells our bodies that the thing we’ve just ingested is something to get rid of as soon as possible. The obvious question, then, is: why do some of us like the sensation so much?
要理解吃辣的原因，首先要明白这并非关乎口味。辣椒素是辣椒植物中的活性化学物质，它是构成任何我们认为“辣”的食品的关键成分。辣椒素进化成一种刺激性物质，以阻止哺乳动物咀嚼和破坏植物种子。它通过舌头、喉咙和皮肤上的受体直接作用于神经系统——无需味蕾——理论上告诉我们的身体，刚刚摄入的东西需要尽快排出。那么，显而易见的问题就是：为什么有些人如此喜欢这种感觉？

To start to understand that, it’s helpful to know a bit more about what’s going on in the body. “Think of an engineering brief where we have to detect irritants in a system and clear them rapidly,” says Liam Browne, an associate professor at UCL who specialises in the neuroscience of sensory perception and pain. “Capsaicin binds to a receptor in the body called TRPV1, which is found in a specialised class of neurons called nociceptors that usually detect things that are potentially damaging to the body.” When that happens, it’s like a little fire alarm goes off and activates parts of the autonomic nervous system, which regulates various involuntary bodily functions without conscious control. “That’s what leads to all these physiological effects like tearing up, sweating, or your nose running,” says Browne. “It’s your body trying to get rid of the irritant.”
要开始理解这一点，了解身体内部正在发生的事情是有帮助的。“想象一下，我们需要在系统中检测刺激物并迅速清除它们的工程简报，”伦敦大学学院（UCL）的感觉知觉与疼痛神经科学专家、副教授利亚姆·布朗（Liam Browne）说。“辣椒素与体内的 TRPV1 受体结合，这种受体存在于一种称为伤害感受器的特殊神经元类别中，通常用于检测可能对身体造成损害的东西。”当这种情况发生时，就像一个小型火灾警报器响起并激活自主神经系统的一部分，该系统调节各种无意识的身体功能而无需意识控制。“这就是导致所有这些生理效应的原因，比如流泪、出汗或流鼻涕，”布朗说。“这是你的身体试图清除刺激物。”

TRPV1 (pronounced trip-vee-one, if you’re explaining this to someone over a delicious curry) is also activated by other things, like your body’s temperature rising above 42C – the point where heat becomes tissue-damaging – and piperine, the main active component in black pepper, which gives a much more mild response. Other hot (but not exactly spicy) foods activate different receptors – mustard, wasabi and radishes are handled by TRPA1, while TRPM8 is mostly responsible for cold temperatures and menthol. “You can actually find other chemicals that have a far more potent effect than capsaicin on TRPV1,” says Browne. “There’s one plant, Euphorbia resinifera, that’s known as ‘resin spurge’ because of its associations with the idea of purging. It contains resiniferatoxin, a capsaicin-like compound that’s often described as around 1,000 times more potent, and is genuinely dangerous.” Yes, a YouTube creator has tried it.
TRPV1（如果向别人解释这个，可以读作“trip-vee-one”，比如在品尝美味的咖喱时）也会被其他事物激活，比如体温升高到 42 摄氏度以上——这是热量开始造成组织损伤的温度点——以及胡椒中的主要活性成分胡椒碱，它产生的反应要温和得多。其他热（但不一定辣）的食物会激活不同的受体——芥末、山葵和萝卜由 TRPA1 处理，而 TRPM8 主要负责寒冷温度和薄荷醇。“实际上可以找到其他化学物质，它们对 TRPV1 的作用比辣椒素强得多，”布朗说。“有一种植物，Euphorbia resinifera，被称为‘树脂大戟’，因为它与‘排毒’的概念有关。它含有树脂大戟毒素，一种类似辣椒素的化合物，通常被认为强约 1000 倍，而且确实非常危险。”是的，一位 YouTube 创作者尝试过它。

So how are we enjoying any of this? After all, it’s not a recent development. The first evidence of people eating chillies comes from around 7000BC in Mexico and Central America, with similar plants being cultivated roughly 1,000 years later. Peppers weren’t introduced to Europe until about the 16th century, but they’ve boomed in popularity since: the global hot sauce market is projected to be worth $5bn (£3.8bn) by 2030, up from just over $3bn two years ago. Who really likes crying out irritants and quaffing milk that much?
那么我们是如何享受这一切的呢？毕竟，这并非近期的现象。关于人们食用辣椒最早的证据来自公元前 7000 年左右的墨西哥和中美洲，而类似的植物则在大约 1000 年后开始被种植。辣椒直到 16 世纪才传入欧洲，但自那以后便迅速流行起来：据预测，到 2030 年，全球辣酱市场的价值将达到 500 亿美元（380 亿英镑），而两年前这一数字还略超过 300 亿美元。谁会真的喜欢忍受刺激物的眼泪和大量饮用牛奶呢？

Firstly, some people have different variants of the TRPV1 gene, which change how easily it switches on and turns off after activation (interestingly, the gene is present but insensitive to capsaicin in all birds and one species of tree-shrew, letting them eat spicy seeds with impunity). But the receptors also become less sensitive over time, so it’s entirely possible to develop a relative immunity to moderately spicy foods – or deliberately cultivate one.
首先，有些人 TRPV1 基因存在不同变异，这会改变其在激活后开启和关闭的容易程度（有趣的是，所有鸟类和一种树鼩的基因存在但对其不敏感，让它们可以随意吃辛辣种子）。但受体也会随时间变得不那么敏感，因此完全有可能对中等辛辣食物产生相对免疫力——或者刻意培养这种免疫力。

As for why we like it, that might be because of the sensation it causes. “Research is still ongoing into how human brains learn what is and isn’t safe, including which foods are safe for consumption,” says Browne. “Recent work emphasises prediction, context and controllability. The idea is that when you eat something spicy, you get an initial alarm-like ‘heat’ signal. With repeated exposure the peripheral response desensitises, and the brain learns the cue is safe and under control. That shift in prediction and certainty is a large part of why the experience becomes tolerable – and then rewarding.” The more spice you eat, the theory goes, the less intense the first painful part becomes, and the more relief you get afterwards.
至于我们为什么喜欢它，那可能是因为它引起的感受。布朗说：“关于人类大脑如何学习什么是安全的、什么是不安全的，包括哪些食物适合食用，研究仍在进行中。” “最近的研究强调预测、环境和可控性。其想法是当你吃辣的东西时，你会得到一个最初的类似警报的‘热’信号。随着反复接触，外周反应会变得迟钝，大脑会学习到这个信号是安全的并且处于控制之下。这种预测和确定性的转变是为什么这种体验变得可以忍受——然后是令人愉悦的大部分原因。”理论认为，你吃的辣越多，最初痛苦的部分就越不强烈，之后得到的缓解就越多。

“There’s also the idea of reappraisal, or the fact that through exposure and experience, we reframe the meaning of what the pain represents and that it’s actually safe for us,” says Browne. “That sense of control and mastery matters – on top of the social and cultural component of doing this with your family or friends. It’s the same logic as watching scary films or going on rollercoasters, sometimes called ‘benign masochism’. Importantly, these learning and revaluation mechanisms also tell us something useful about pain more broadly: when a stimulus is mislabelled as threatening, reframing and restoring a sense of control can reduce its impact.” Like other initially unpleasant experiences – think running, cold showers or hot saunas – pushing on through the initial pain also coaxes the body into releasing endorphins, transforming those Korean chicken wings into a mild sort of high.
“此外，还有重新评估的概念，即通过接触和经验，我们重新定义了疼痛所代表的意义，并认为它实际上对我们是安全的，”布朗说。“这种掌控感和掌控力很重要——除了与家人或朋友一起进行这种行为的社会和文化成分之外。这与观看恐怖电影或乘坐过山车是同样的逻辑，有时被称为‘良性自虐’。重要的是，这些学习和重新评估机制也告诉我们一些关于疼痛的普遍性有用信息：当刺激被错误地标记为威胁时，重新定义和恢复掌控感可以减少其影响。”像其他最初令人不快的经历一样——想想跑步、冷水浴或热桑拿——在最初的疼痛中坚持下来也能促使身体释放内啡肽，将那些韩国炸鸡翅膀变成一种温和的快感。

But what do you do if you’ve been invited out for wings and you’re not feeling up to it? The first thing to remember is that capsaicin is fat-soluble and hydrophobic: this means that if you drink water it will stay where it is, while milk will dissolve the capsaicin and then bind to it, ultimately carrying it away.
但如果邀请你出去吃鸡翅而你感觉不舒服怎么办？首先要记住的是，辣椒素是脂溶性的和疏水的：这意味着如果你喝水它将停留在原地，而牛奶会溶解辣椒素然后与之结合，最终将其带走。

Alcohol, in case you’re wondering, can dilute capsaicin, but won’t bind to it – and will only do the job if it’s present in high percentages, meaning that beer is unlikely to help. Yoghurt, if you’ve got a little pot on the side, will do the same job as milk – but there’s an even tastier option. “Mint ice-cream provides the fat and protein to carry capsaicin away but will also trigger your TRPM8 receptors, which signal coolness and can take the edge off TRPV1’s ‘heat pain’,” says Browne.
如果你想知道，酒精可以稀释辣椒素，但不会与之结合——而且只有当其含量很高时才会起作用，这意味着啤酒不太可能有所帮助。如果你旁边有一小罐酸奶，它也会起到和牛奶相同的作用——但有一个更美味的选择。“薄荷冰淇淋提供脂肪和蛋白质来带走辣椒素，但也会触发你的 TRPM8 受体，这些受体传递凉爽的信号，可以减轻 TRPV1 的‘热痛’，”布朗说。

Keep a tub on hand next time you invite people over for a jalfrezi – and remind everyone that it’s a cultural ritual with deep historical resonances.
下次邀请朋友来家吃 jalfrezi 时，准备一个桶，并提醒大家这是一种具有深厚历史渊源的文化仪式。