How does caffeine keep us awake? - Hanan Qasim

Translator: Vanessa Leung Reviewer: 潘 可儿

Over 100,000 metric tons of caffeine are consumed

全世界每年消費

around the world every year.

超過 100,000 公噸嘅咖啡因

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

等同於 14 座埃菲爾鐵塔嘅重量

Most of this caffeine is consumed in coffee and tea,

大部分係咖啡同茶裏面嘅咖啡因

but it's also ingested in some sodas,

仲有一部分係喺蘇打水

chocolate,

朱古力

caffeine pills,

咖啡因藥丸

and even beverages labeled decaf.

甚至喺一啲標為冇咖啡因嘅飲料

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

即使喺我哋唔夠瞓嘅時候

even if we haven't had enough sleep.

咖啡因可以令我哋清醒，集中注意力 更加開心同有活力

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

但都會令我哋嘅血壓上升，產生焦慮感

It's the world most widely used drug.

咖啡因係世界上使用最廣泛嘅藥物

So how does it keep us awake?

咁佢係點樣令我地保持清醒呢？

Caffeine evolved in plants where it serves a few purposes.

咖啡因喺唔同植物中有唔同嘅功效

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

喺一啲植物嘅葉同種子中

it's toxic to insects.

含有對昆蟲有毒嘅高劑量咖啡因

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

但係一啲花蜜中嘅低劑量咖啡因

it can actually help them remember and revisit flowers.

可以幫助昆蟲記住花朵同重新採蜜

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

咖啡因喺人體內 可作為中樞神經系統嘅興奮劑

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

佢通過阻斷重要嘅睡眠誘導分子 腺苷

a substance called adenosine.

嚟令我哋保持清醒

Your body needs a constant supply of energy,

我哋身體通過分解高能分子 ATP

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

嚟獲得持續嘅能量補給

In the process,

喺呢個過程當中

it liberates adenosine, ATP's chemical backbone.

身體釋放 ATP 嘅化學骨架︰腺苷

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

大腦中嘅神經元有腺苷嘅特定受體

When adenosine docks to these receptors,

當腺苷同受體結合

it activates a cascade of biochemical reactions

會激活一系列嘅化學反應

that cause neurons to fire more sluggishly

令到神經元嘅反應緩慢

and slow the release of important brain-signaling molecules.

同時令腦信號分子嘅釋放變得遲緩

In other words, you get sleepy.

簡單來講，你會瞌眼瞓

Caffeine is what's called an adenosine receptor antagonist.

咖啡因亦被叫作腺苷受體嘅對抗者

That means it derails this process of slowing your neurons down

即係佢可以通過阻斷腺苷受體

by blocking adenosine receptors.

嚟令到神經元反應遲鈍

Caffeine and adenosine have a similar molecular structure,

咖啡因同腺苷有相似嘅分子結構

close enough that caffeine can wedge into the adenosine receptors,

相似到咖啡因亦可以楔入腺苷嘅受體

but not close enough to activate them.

但並不足以激活受體

To summarize, adenosine inhibits your neurons.

總之，腺苷可以抑制神經元嘅活動

Caffeine inhibits the inhibitor, so it stimulates you.

而咖啡因可以抑制抑製劑嘅效用 令你變得更精神

Caffeine can also boost positive feelings.

咖啡因亦可以令人產生積極嘅感覺

In some neurons, the adenosine receptors

喺一啲神經元

are linked to receptors for another molecule called dopamine.

腺苷受體係同多巴胺受體相連嘅

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

多巴胺嘅一個作用 係令到大腦產生愉快嘅感覺

When adenosine docks in one of these paired receptors,

而腺苷楔入多巴胺受體

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

會令到多巴胺難以楔入

interrupting its mood-lifting work.

打斷咗佢提升情緒嘅功能

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

但係當咖啡因楔入腺苷受體嗰時 就冇咁樣嘅反應

and dopamine can slide in.

多巴胺仍可以楔入受體

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

有證據證明 咖啡因對腺苷同多巴胺受體嘅作用

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

會產生長期嘅效益 降低一啲疾病嘅風險

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

譬如帕金遜病、阿茲海默病同癌症等

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

咖啡因都可以加快身體燃燒脂肪嘅速度

In fact, some sports organizations think

事實上，一啲運動機構認為

that caffeine gives athletes an unfair advantage

運動員攝取咖啡因會獲得唔公平嘅優勢

and have placed limits on its consumption.

因此對咖啡因嘅攝入設置咗限制標準

From 1972 until 2004,

從 1972 年到 2004 年

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

奧運會運動員嘅血咖啡因濃度 必須要低於特定標準

to compete.

先至可以參加比賽

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

當然，唔係所有咖啡因作用都係有益嘅

It might make you feel better and more alert,

佢可以令你感到愉快同有精神

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

但都可以令你嘅心跳加快，血壓上升

cause increased urination or diarrhea,

急尿或腹瀉

and contribute to insomnia and anxiety.

甚至係失眠同焦慮

Plus, the foods and beverages caffeine is found in

另外，含有咖啡因嘅食物

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

對你身體嘅影響都不容忽視

Your brain can adapt to regular consumption of caffeine.

你個大腦可以適應經常性嘅咖啡因攝取

If your adenosine receptors are perpetually clogged,

如果你體內嘅腺苷受體被阻斷

your body will manufacture extra ones.

你個身體會自己再整多個新嘅

That way, even with caffeine around,

所以，即使攝入咖啡因

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

腺苷仍然可以正常通知大腦要休息

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

咁就係點解你會發現

你需要更多嘅咖啡因嚟保持清醒

to feel as alert.

There are more and more adenosine receptors to block.

因為有越來越多嘅受體需要被阻斷

It's also why if you suddenly quit caffeine,

亦係點解

如果你突然間停止服用咖啡因

you may experience an unpleasant withdrawal.

會感到不適同產生退隱嘅症狀

With plenty of receptors and no competition,

當體內存在過多嘅腺苷受體

adenosine can work overtime,

腺苷就會長時間超時做嘢

causing symptoms like headaches,

從而引起似係頭痛

tiredness,

疲倦

and depressed moods.

同鬱悶等嘅病徵

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

但一段時間之後

過量嘅腺苷受體就會消失

your body will readjust,

身體會去重新調整

and you'll feel just as alert as ever,

就算無攝入 呢種全世界最受歡迎嘅興奮劑

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

你都會覺得一樣嘅清醒