吃辣，竟是“痛觉”体验！你爽的是舌头，而痛的是全身……
是什么，
让人在冬季凛冽的寒风中
面色潮红、大汗淋漓？
是什么，
让人胃痛、喉咙灼烧、涕泗横流
却停不下来？
当然是
吃！辣！
人生苦短，无辣不欢。
然而，辣，可真是一个“磨人的小妖精”。
吃辣的人感受到的是快乐，
并痛着！
吃辣时，口腔、喉咙、食道、肠胃乃至全身的皮肤共同反应，痛与热伴随着唇舌间的火焰迸发，这种极致的体验，是不是和其他味觉享受，有点不太一样呢？
不一样就对了！
最近，在一则科普中，CD君发现了“辣”的奥秘：辣并非是被人体味蕾感知到的一种味觉体验，而是混合着痛觉与触觉的混合物！
换句话说，吃辣时，辣到的不仅仅是舌头，而是全身！
那么，我们的身体究竟是如何接收“辣”这一讯号的呢？痛并快乐着的嗜辣人士究竟为何无辣不欢？“恐辣”星人又该如何安全地尝试吃辣？
跟着CD君一起探究“辣的奥秘”吧！
吃辣时身体如何反应？
早在1997年，加州大学旧金山分校的药理学家David Julius和他的同事们就探究出了“辣包含痛觉”这一奥秘。
他们在辣椒素的活性成分中发现了一种能够使肾细胞反应的基因，并将其命名为“TRPV1”。这种辣椒素受体使肾细胞活跃，同时还会造成人体的高温反应。
换句话说，当你把辣椒称为“热辣”时，这不仅仅是一个类比——就你的大脑而言，你的嘴真的被烧了。这是一种感觉，而不是气味或味道，它通过处理触觉的神经传递到大脑。像其他触觉感受器一样，TRPV1受体遍布皮肤内层。
In other words, when you call a chili pepper “hot,” that’s not just an analogy—as far as your brain can tell, your mouth really is being burned. That’s a feel, not a smell or taste, and it passes to the brain through nerves that handle the sense of touch. Like other touch receptors, TRPV1 receptors are found all over the inner layer of your skin.
《自然》杂志的姐妹出版物《科学美国人》（Scientific America）曾发布科普问答《为什么吃辣的食物会造成身体的热反应（例如与出汗、灼烧类似的反应）？》（Why is it that eating spicy, "hot" food causes the same physical reactions as does physical heat (burning and sweating, for instance)？）
其中提到：
辛辣食物会激发皮肤中通常对热有反应的受体。这些受体是疼痛纤维，严格意义上被称为多模式伤害感受器。它们可以应对极端温度和强烈的机械刺激，如捏和割伤；它们也会对某些化学影响产生反应。
…spicy foods excite the receptors in the skin that normally respond to heat. Those receptors are pain fibers, technically known as polymodal nociceptors. They respond to temperature extremes and to intense mechanical stimulation, such as pinching and cutting; they also respond to certain chemical influences.
中枢神经系统对感觉系统正在发生的事情做出反应。因此，疼痛和温暖神经纤维的活动模式会触发感觉和热量的物理反应，包括血管舒张、出汗和潮红。
The central nervous system reacts to whatever the sensory system tells it is going on. Therefore, the pattern of activity from pain and warm nerve fibers triggers both the sensations and the physical reactions of heat, including vasodilation, sweating and flushing.
大多数人认为辛辣食物的“灼热”是一种味道。实际上，这两种感官体验是相关的，但是非常明显。他们以同样的方式支配舌头，但是由辣椒素引发的疼痛系统发生在身体的任何地方，人们都可以在任何地方获得热效应。
Most people think of the 'burn' of spicy food as a form of taste. In fact, the two sensory experiences are related but are very distinct. They innervate the tongue the same way, but the pain system that is triggered by capsaicin is everywhere on the body, so one can get thermal effects everywhere.
简单来说，吃辣时，我们的味蕾被激活，口腔中可以与辣椒素结合的受体蛋白质开始与辣椒素结合，刺激痛觉和热觉神经，受到自己的神经将信号传递给大脑，于是大脑经过分析，就得出了“灼痛”的感觉。
为何嗜辣如命？
“辣椒虐我千万遍，我待吃辣如初恋。”可是，为什么要如此“折磨”自己呢？
英国《卫报》对此的解释是：追求“燃烧的感觉”。
根据宾夕法尼亚大学的心理学家Paul Rozin的说法，世界上大约三分之一的人每天都吃辣椒。为什么？ 因为他们“喜欢这种灼烧的感觉”。Rozin在今年的心理科学协会会议期间举办的胃肠心理学研讨会上指出，人类是我们所知道的唯一一种专门追寻负面事件的物种。
According to psychologist Paul Rozin of the University of Pennsylvania, about a third of the people around the world eat hot peppers every single day. Why? Because they "love the burn". At a symposium on gastro-psychology during this year's Association for Psychological Science convention, Rozin pointed out that humans are the only species – we know about – that specifically seek out what would otherwise be considered negative events.
这种对于负面感官刺激的追求被科学家称之为“享乐逆转”（hedonic reversal）或“良性受虐机制”（benign masochism）。科学研究表明，似乎只有人类能从消极的感觉本身中获取快乐。
也许我们追寻吃辣的痛苦经历，同时又有意识地告诉自己吃辣没有真正的危险。
Perhaps we seek out the painful experience of snacking on chillies while consciously maintaining awareness that there is no real danger to ourselves.
文章还将辣椒与其他有刺激性的事物，如过山车、恐怖电影，进行了对比。
毕竟，人们似乎喜欢——并积极地寻找——许多其他不受欢迎但又表面上安全的感觉：过山车或跳伞提供的坠落感，看恐怖片时的恐惧和焦虑感，跳入冰冷的水中时身体上的痛苦经历，甚至是看到煽情画面的悲伤。
After all, people seem to enjoy – and actively seek out – many other sensations that are otherwise undesirable but are ostensibly safe: the sensation of falling provided by rollercoasters or skydiving, the feelings of fear and anxiety while watching horror movies, the physical pain experienced upon jumping into icy water, or even the feelings of sadness that come while watching a tear-jerker.
也许正是这种认知不匹配本身就能带来刺激：就像一次又一次地进入过山车或者将《人皮客栈》的碟片推入DVD播放机一样，辣椒素的燃烧似乎只会带来威胁。
Perhaps it is this cognitive mismatch itself that provides the thrill: like strapping into a rollercoaster or popping Hostel into your DVD player over and over again, the burn of capsaicin only seems to be threatening.
总之，辣椒素在舌尖的燃烧似乎只是一种威胁，而不会带来危险。而恰恰人们“享受”着这种“安全”的“威胁”。
吃辣是否有益？
事实上，吃辣好处多多。
最让人难以抗拒的一项，就是减肥。
英国《太阳报》揭示了吃辣瘦身的原理：当身体处于“产热”（thermogenesis）状态时，卡路里会被燃烧用来生产热能，于是我们就会变瘦。吃辣，可以引导“产热”状态的发生，从而帮助人燃烧脂肪。
注册营养师Helen Bond对此进行了进一步解释：
当辣椒素被包含在饮食中时，每天额外燃烧50卡路里。
When capsaicin was included in the diet, an extra 50 calories were burned each day.
其他小型研究显示，其他香料，如芥末和生姜，可能有助于燃烧卡路里或增加饱腹感，导致我们少吃。
Other small studies show other spices such as mustard and ginger, may help burn calories or improve satiety (feelings of fullness) so we eat less.
美国Push Doctor网站还提出过一种未经证实的理论（乍一看好像很有道理的样子）：辣的食物无法一次性吃太多，所以能让人变瘦。
此外，吃辣还可以让人长寿。
北京大学、哈佛大学和牛津大学研究人员在2015年进行了一项研究。通过观察了50万中国成年人的工作餐饮食，研究人员发现每周至少吃辣一次的人在接下来的七年中死亡的可能性降低了10％。而那些每周吃辣三到七天的人的死亡风险降低了14％。
尽管该研究团队声明说，基于这项研究的观察性质，不可根据研究结果进行因果推断，但来自剑桥大学的Nita Forouhi仍表示，吃辣的潜在益处毋庸置疑：
潜在的益处包括抗氧化，抗炎和抗癌特性。 科学家们还注意到了辣椒对肠道微生物群和抗肥胖效果的贡献。
These included anti-oxidant, anti-inflammatory and anti-cancer properties. Scientists had also noted the benefits for gut microbiota and anti-obesity effects from chilli.
据称，吃辣可改善血液循环，扩张动脉，降低血压并降低患血栓的风险。 在马里兰大学医学中心进行的研究也表明，姜和姜黄等香料可以降低胆固醇。
Spices have been claimed to improve circulation, widen arteries, lower blood pressure and decrease the risk of blood clots. Research carried out at the University of Maryland Medical Center also indicates that spices such as ginger and turmeric could decrease cholesterol.
如何安全吃辣？
那么，对于不能吃辣星人而言，怎样才能安全地尝试辣椒呢？
费城莫奈尔化学感觉中心(Monell Chemical Senses Center)的嗅觉研究员帕梅拉•道尔顿（Pamela Dalton）为初尝辣椒者提供了几个小贴士：
道尔顿建议，给你已经喜欢的菜加点辣椒。吃一大口。如果感到疼痛，等上两到五分钟，让你嘴里的受体不再那么敏感后，再咬一口。不要太心急，把乳制品放在手边，以防万一；牛奶中的分子可以吸引和溶解辣椒素。把食物放在喉咙后部，而不是唇边。喉咙后部的粘膜不那么敏感。
Add the spice to a dish you already like,” Dalton says. "Take a mouthful. If it hurts, wait two and a half to five minutes for the receptors in your mouth to desensitize before taking another bite. Don’t overdo it, and keep a dairy product nearby in case you do; molecules in milk attract and dissolve capsaicin. Put the food toward the back of your throat, where people tend to find the mucous membrane less sensitive. Don’t get it on your lips.
练习这种良性受虐：通过不断地让你的神经接触辛辣，让你的大脑相信这些是你想要的体验，而不是威胁。道尔顿说:“我们往往喜欢反复经历的事情。”心理学家称这种现象为“纯粹接触效应”。
Practice a benign masochism: By repeatedly exposing your nerves to spices, you reassure your brain that these are desired encounters, not threats. “We tend to like things that we experience over and over,” Dalton says. Psychologists call this phenomenon “the mere-exposure effect.”
“如果你每周至少吃一次辛辣食物，几个月内你就会发现自己的耐受性增强了。”吃辣新手可以从一种较温和的化合物开始，这种化合物的作用时间较短，存在于肉桂、姜、黑胡椒、薄荷或芥末中，它会逐渐积累成辣椒中炽热的辣椒素。
If you eat spicy food at least once a week, you’ll notice an increased tolerance within a few months. True novices might want to begin with one of the gentler chemical compounds, whose effects are shorter-lived, found in cinnamon, ginger, black pepper, mint or wasabi and build up to the fiery capsaicin in chiles. If you need more incentive to start down this path, consider that studies suggest that capsaicinoids have anticancer, anti-inflammatory and antioxidant properties. They also aid in digestion and reduce cholesterol levels.
不要把吃辣看作一个痛苦的过程。
“It’s helpful to think of spiciness as something other than painful.”
如果你需要更多的动力开始尝试辣椒，多想想辣椒素具有抗癌、抗炎和抗氧化的特性。它们还有助于消化和降低胆固醇。
If you need more incentive to start down this path, consider that studies suggest that capsaicinoids have anticancer, anti-inflammatory and antioxidant properties. They also aid in digestion and reduce cholesterol levels.
放轻松，让这种植物化合物扩宽你的味蕾，以一种新的方式体验食物。“你必须愿意放弃控制权。”道尔顿说，“相信你的嘴明年不会这样烧了。”
Relax and let the plant compounds expand your ability to experience food in a new way. “You have to be willing to give up control,” Dalton says. “Trust that your mouth is not going to burn for the next year.
今天，你吃辣了吗？
来源：卫报、太阳报、科学美国人、Push Doctor、中国科普网、搜狐
编辑：胡雨濛
实习生：朱晨、李芸