How does caffeine keep us awake? - Hanan Qasim

譯者: Sherl H 審譯者: Thomas Ho

Over 100,000 metric tons of caffeine are consumed

全世界每年消耗了超過

around the world every year.

十萬公噸的咖啡因

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

這相當於十四座艾菲爾鐵塔的重量

其中大部分咖啡因消耗於咖啡和茶

Most of this caffeine is consumed in coffee and tea,

but it's also ingested in some sodas,

但也會被攝取自某些汽水

chocolate,

巧克力

caffeine pills,

咖啡因藥丸

and even beverages labeled decaf.

甚至標示為無咖啡因的飲料

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

咖啡因幫助我們感到警戒 專注、快樂、並充滿活力

even if we haven't had enough sleep.

即使我們沒有睡飽

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

但它也能夠升高我們的血壓 並讓我們感到焦慮

It's the world most widely used drug.

這是世界上使用最廣的藥物

So how does it keep us awake?

所以它如何使我們醒著呢

Caffeine evolved in plants where it serves a few purposes.

咖啡因在植物中演化 扮演著幾個角色

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

高劑量咖啡因

如同在某些物種的 葉子及種子中能找到的

it's toxic to insects.

對昆蟲有毒性

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

但當牠們攝取低劑量時 如同花蜜中能找到的

it can actually help them remember and revisit flowers.

咖啡因實際上可以幫助牠們 記住並重返花朵

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

在人體內，咖啡因作為一種 中樞神經興奮劑

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

它藉由阻斷體內其中一種 誘發睡眠的關鍵分子而使我們醒著

a substance called adenosine.

一種叫做腺苷的物質

Your body needs a constant supply of energy,

你的身體需要穩定的能量供應

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

藉由分解一種叫三磷酸腺核苷 (ATP) 的高能分子而得到

In the process,

在過程中

it liberates adenosine, ATP's chemical backbone.

它釋出腺苷 就是 ATP 的化學結構骨架

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

你腦中的神經元 有為這種分子量身打造的受體

When adenosine docks to these receptors,

當腺苷停泊於受體時

it activates a cascade of biochemical reactions

它會活化一連串的生化反應

that cause neurons to fire more sluggishly

使得神經元較慵懶地放電

and slow the release of important brain-signaling molecules.

並減緩重要大腦傳訊分子的釋放

In other words, you get sleepy.

換句話說，你會感到想睡

Caffeine is what's called an adenosine receptor antagonist.

咖啡因是所謂的腺苷受體拮抗劑

That means it derails this process of slowing your neurons down

意思是咖啡因會藉由阻斷腺苷受體

by blocking adenosine receptors.

來阻止使神經元變遲緩的過程

Caffeine and adenosine have a similar molecular structure,

咖啡因和腺苷有相似的分子結構

close enough that caffeine can wedge into the adenosine receptors,

接近到咖啡因可以卡進腺苷受體中

but not close enough to activate them.

但沒有接近到能夠活化受體

To summarize, adenosine inhibits your neurons.

總結來說，腺苷抑制你的神經元

Caffeine inhibits the inhibitor, so it stimulates you.

咖啡因抑制了抑制劑，所以它刺激你

Caffeine can also boost positive feelings.

咖啡因也能促進正向的感覺

In some neurons, the adenosine receptors

在某些神經元中

腺苷受體與另一種叫 多巴胺的分子之受體連接

are linked to receptors for another molecule called dopamine.

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

多巴胺在腦中的其中一個角色 是提升愉悅感

When adenosine docks in one of these paired receptors,

當腺苷停泊在這些 成對受體中的一個時

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

會使多巴胺較難結合到自己的位置上

interrupting its mood-lifting work.

便干擾了它提升心情的作用

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

但當咖啡因取代腺苷的位置時 它不會有相同的作用

and dopamine can slide in.

並且多巴胺可以滑進來

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

有證據顯示咖啡因 對腺苷和多巴胺受體的作用

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

也可能對於減少某些疾病 有長期的益處

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

像是帕金森氏症、阿茲海默症 和某些類型的癌症

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

咖啡因也能提升身體燃燒脂肪的能力

In fact, some sports organizations think

事實上，有些運動協會認為

that caffeine gives athletes an unfair advantage

咖啡因給予運動員不公平的優勢

and have placed limits on its consumption.

並已對咖啡因的使用設下限制

From 1972 until 2004,

從 1972 年到 2004 年

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

奧運選手的血中咖啡因 必須保持在某特定濃度之下

to compete.

才能比賽

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

當然咖啡因的作用不全是有幫助的

It might make you feel better and more alert,

它可能會讓你感覺較好，並較警覺

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

但它也能升高你的心率和血壓

cause increased urination or diarrhea,

造成多尿或腹瀉

and contribute to insomnia and anxiety.

並引起失眠和焦慮

Plus, the foods and beverages caffeine is found in

此外，含有咖啡因的食物和飲料

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

它們本身對你身體的影響 也必須列入考慮

Your brain can adapt to regular consumption of caffeine.

你的大腦可以適應規律的咖啡因攝取

If your adenosine receptors are perpetually clogged,

如果你的腺苷受體被長期堵塞

your body will manufacture extra ones.

你的身體會額外製造

That way, even with caffeine around,

這樣一來，即使有咖啡因存在

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

腺苷還是能做它傳訊 使大腦省電的工作

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

這就是為什麼你可能會發覺 你需要消耗越來越多的咖啡因

to feel as alert.

以感受到相同的警覺

There are more and more adenosine receptors to block.

有越來越多的腺苷受體需要被阻斷

It's also why if you suddenly quit caffeine,

這也是為什麼 如果你突然戒掉咖啡因

you may experience an unpleasant withdrawal.

你可能會經歷一段不舒服的退癮

With plenty of receptors and no competition,

有著許多受體，並且沒有競爭者

adenosine can work overtime,

腺苷可能加班

causing symptoms like headaches,

造成症狀如頭痛

tiredness,

疲倦

and depressed moods.

和憂鬱的心情

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

但幾天後，多餘的腺苷受體就會消失

your body will readjust,

你的身體會重新調整

and you'll feel just as alert as ever,

然後你會感覺像從前一樣警覺

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

即使沒有注入全世界 最受歡迎的興奮劑