How does caffeine keep us awake? - Hanan Qasim

翻译人员: xiao gu 校对人员: fuyu you

Over 100,000 metric tons of caffeine are consumed

全世界每年会消耗

around the world every year.

10万多吨咖啡因。

That's equivalent to the weight of 14 Eiffel Towers.

相当于14个埃菲尔铁塔的重量。

Most of this caffeine is consumed in coffee and tea,

大部分的咖啡因存在于咖啡和茶中。

but it's also ingested in some sodas,

但也存在于碳酸饮料，

chocolate,

巧克力，

caffeine pills,

咖啡因片剂，

甚至标注了无咖啡因的饮料中。

and even beverages labeled decaf.

Caffeine helps us feel alert, focused, happy, and energetic,

咖啡因帮助我们保持清醒， 专注，快乐和充满能量，

even if we haven't had enough sleep.

甚至在我们睡眠不足时也如此。

But it can also raise our blood pressure, and make us feel anxious.

但它也能使血压升高，产生焦虑。

It's the world most widely used drug.

咖啡因是世界上最广泛使用的药物。

So how does it keep us awake?

那么它是如何使我们保持清醒呢？

Caffeine evolved in plants where it serves a few purposes.

咖啡因从植物中的物质进化而来。

In high doses, as it's found in the leaves and seeds of certain species,

咖啡因在某些植物叶片 和种子中含量很高，

it's toxic to insects.

能够使昆虫中毒。

But when they consume it in lower doses, as it's found in nectar,

但当昆虫只从花蜜中 摄取低剂量的蜂蜜时，

it can actually help them remember and revisit flowers.

有助于昆虫记住并偏好这类花朵。

In the human body, caffeine acts as a stimulant for the central nervous system.

在人体中，咖啡因是 中枢神经系统的兴奋剂，

It keeps us awake by blocking one of the body's key sleep-inducing molecules,

通过抑制人体睡眠诱导因子， 一种叫腺苷的物质

a substance called adenosine.

使我们保持清醒。

Your body needs a constant supply of energy,

身体需要通过分解一种叫ATP的高能分子

which it gets by breaking down a high-energy molecule called ATP.

来得到持续的能量供应。

In the process,

在这个过程中

it liberates adenosine, ATP's chemical backbone.

将释放ATP的化学主链，腺苷。

Neurons in your brain have receptors perfectly tailored to this molecule.

大脑中的神经元就存在 腺苷分子的高特异性受体。

When adenosine docks to these receptors,

当腺苷与这些受体结合，

it activates a cascade of biochemical reactions

将激活一系列生化反应，

that cause neurons to fire more sluggishly

促使神经元活动减弱，

and slow the release of important brain-signaling molecules.

从而减缓脑部重要信号分子的释放。

In other words, you get sleepy.

就是说，你犯困了。

Caffeine is what's called an adenosine receptor antagonist.

咖啡因是腺苷受体拮抗剂，

That means it derails this process of slowing your neurons down

能够通过结合腺苷受体

by blocking adenosine receptors.

阻断使神经元反应变慢的过程。

Caffeine and adenosine have a similar molecular structure,

咖啡因和腺苷有类似的分子结构，

close enough that caffeine can wedge into the adenosine receptors,

咖啡因能正好嵌入腺苷受体，

but not close enough to activate them.

但不会激活它们。

To summarize, adenosine inhibits your neurons.

总之，腺苷抑制了神经元，

Caffeine inhibits the inhibitor, so it stimulates you.

咖啡因则抑制了这种抑制剂， 所以能刺激你保持清醒。

Caffeine can also boost positive feelings.

咖啡因也能促进积极的感受。

In some neurons, the adenosine receptors

在某些神经元中，

are linked to receptors for another molecule called dopamine.

腺苷受体和多巴胺受体连接在一起。

One of dopamine's roles in the brain is to promote feelings of pleasure.

多巴胺可以让人感到快乐。

When adenosine docks in one of these paired receptors,

当腺苷结合自身受体后，

that can make it harder for dopamine to fit in its own spot,

便能够阻碍多巴胺嵌入受体位点，

interrupting its mood-lifting work.

打断其改善心情的作用。

But when caffeine takes adenosine's place, it doesn't have the same effect,

当咖啡因代替了腺苷的位置

and dopamine can slide in.

多巴胺就能正常与受体结合。

There's evidence that caffeine's effects on adenosine and dopamine receptors

有证据表明，咖啡因 作用于腺苷和多巴胺时

can have long-term benefits, too, reducing the risk of diseases

也会产生长期的积极作用，

like Parkinson's, Alzheimer's, and some types of cancer.

比如降低如帕金森，阿尔兹海默症 和一些癌症的患病风险。

Caffeine can also ramp up the body's ability to burn fat.

咖啡因也能促进身体燃烧脂肪。

In fact, some sports organizations think

实际上，运动组织认为

that caffeine gives athletes an unfair advantage

咖啡因会让运动员更加兴奋，

and have placed limits on its consumption.

因此会限制运动员的咖啡因摄入量。

From 1972 until 2004,

从1972到2004年，

Olympic athletes had to stay below a certain blood-caffeine concentration

奥委会规定赛时 运动员的血液咖啡因含量

必须保持低水平。

to compete.

Of course, not all of caffeine's effects are so helpful.

当然，咖啡因也不是只有好处。

It might make you feel better and more alert,

它可能让你感觉良好，保持惊醒，

but it can also raise your heart rate and blood pressure,

同时也会让你心跳加速，血压升高，

cause increased urination or diarrhea,

导致尿量增多和腹泻，

and contribute to insomnia and anxiety.

产生失眠和焦虑。

Plus, the foods and beverages caffeine is found in

此外，也要考虑食物和饮料中咖啡因

have their own impacts on your body that have to be taken into account.

对身体的影响。

Your brain can adapt to regular consumption of caffeine.

大脑能接受一定的咖啡因摄入量，

If your adenosine receptors are perpetually clogged,

如果你的腺苷受体不断被占用，

your body will manufacture extra ones.

身体就会额外产生新的腺苷受体。

That way, even with caffeine around,

这就意味着，即使摄入了咖啡因，

adenosine can still do its job of signaling the brain to power down.

新生成的腺苷任依然能让大脑反应变慢。

That's why you may find you need to consume more and more caffeine

这就是为什么你要消耗 越来越多的咖啡因

to feel as alert.

来保持清醒。

There are more and more adenosine receptors to block.

因为身体会产生越来越多的腺苷。

It's also why if you suddenly quit caffeine,

这就是为什么你突然停止摄入咖啡因，

you may experience an unpleasant withdrawal.

愉快的感觉就会消失。

With plenty of receptors and no competition,

大量腺苷受体没有了竞争者，

adenosine can work overtime,

腺苷就会过度发挥作用，

causing symptoms like headaches,

导致头疼，

tiredness,

疲惫

and depressed moods.

情绪低落。

But in a few days, the extra adenosine receptors will disappear,

不过几天后，过量的腺苷受体就会消失，

your body will readjust,

你的身体恢复了，

and you'll feel just as alert as ever,

你会像以前一样清醒，

even without an infusion of the world's most popular stimulant.

即使没有这个世界上最流行的兴奋剂。