Caffeine is a chemical compound that stimulates the central nervous system.

咖啡因是一種刺激中樞神經系統的化合物。

It accomplishes this by attaching itself to adenosine receptors in the brain.

它是透過附著在大腦的腺苷受體上來達成目的。

In doing so, it blocks adenosine molecules, which are responsible for slowing down the central nervous system before we sleep.

如此一來，它會擋下睡前能夠使中樞神經系統放鬆的腺苷分子。

The result?

那麼結果呢？

Adenosine cannot regulate and neurons start firing.

腺苷無法作用，而神經開始高速運轉。

This results in a person's reduced fatigue and increased alertness and cognitive performance.

這會降低一個人的疲勞程度，並提高警覺性和認知表現。

Side effects: many seek by consuming caffeine.

副作用是許多人會依賴咖啡因。

Caffeine occurs naturally in coffee beans, tea leaves, cacao beans and some tree nuts.

咖啡因的主要來源有咖啡豆、茶葉、可可豆以及一些堅果。

People have been consuming it for centuries.

人類攝取咖啡因已有好幾個世紀。

But daily consumption took off sporadically at different times in different places around the world.

但是日常使用分別在世界各地的不同時間、不同地點展開。

Coffee became popular in the 15th and 16 centuries.

咖啡在 15、16 世紀開始流行。

But Cacao was used among early Mesoamerican civilizations hundreds of years earlier.

但是可可早在數百年前就已在中美洲文明被廣泛使用。

Tea became popular by the 14th century in China during the Ming dynasty, but didn't catch on in Britain until almost 400 years later.

茶約在 14 世紀開始在中國明朝流行起來，而英國一直到 400 年後才趕上這股潮流。

Today, caffeine can be found nearly everywhere and more and more caffeine-infused products are hitting the shelves every day.

現在咖啡因幾乎隨處可見，市面上的含咖啡因的商品也不斷推陳出新。

In the United States, nearly 90% of the population has at least one caffeinated beverage every day.

在美國將近九成的人口，每天至少會攝取一份含咖啡因的飲品。

Up to 400 milligrams of caffeine per day or about four cups of coffee is considered safe for an adult.

一個成人平均一天可攝取的咖啡因安全值是 400 毫克以下或是四杯咖啡。

Too much caffeine for any one person can cause side effects, such as migraines, insomnia, nervousness and muscle tremors.

過多的咖啡因會給任何人帶來副作用，例如偏頭痛、失眠、焦慮以及肌肉顫抖。

One tablespoon of pure caffeine equivalent to drinking 75 cups of coffee at once can have lethal consequences.

一湯匙的純咖啡因等同於 75 杯咖啡，足以帶來致命的效果。

Due to this risk of caffeine overdoses, in 2018, the United States Food and Drug Administration banned the bulk sale of products containing pure or highly concentrated caffeine.

由於咖啡因的過量使用，2018 年美國食品藥品監督管理局下令，禁止販售含有純咖啡因或高度濃縮咖啡因的商品。

While caffeine may provide great benefits, such as increased focus, alertness and energy, it comes with considerable risks just like any other substance.

儘管咖啡因可以帶來很多好處，像是提高專注力、警覺度和精力，但就像其他任何物質一樣，它同時也會帶來相當的風險。