今日內容提要：
關于喝咖啡好不好？喝多少為適量？什么是過量？一直是健康話題的熱點。
這個話題有必要么？很有。
最近玲瑯滿目，層出不窮的咖啡店，再看看咖啡的種類，從簡單的美式到現在越來越盛行的氮氣咖啡，搞的跟啤酒像同父異母的兄弟一樣，確實好喝。
喝多少為宜，喝多少能給你帶來需要的幫助，今天我們分享的就是這個點。
我本人是每天一大杯，很多老外是一天3-4杯，他們好像從來沒在關心睡不睡的著這件事…為什么呢？
喝咖啡不存在“過量”的問題
First the good news.
It's almost impossible to overdose on coffee.
There is a lethal dose of caffeine but it's somewhere around 10 grams and the average cup of joe has around 100 milligrams.
我們先從好的說起。
咖啡幾乎不可能攝取過量。
咖啡因社區(qū)達到一定程度確實會致命，但你得喝到10公克，我們一般喝的咖啡一杯只有100毫公克。
You'd likely have to drink 100 cups in rapid succession to OD.
你大概得喝上100杯才算超量。
But that's not to say there's no such thing as too much.
The FDA recommends no more than four to five cups a day for the average healthy adult.
More than that and you might start to experience some nasty side effects.
不過這并不代表你可以想喝幾杯就幾杯。根據美國食品藥品監(jiān)督局建議，普通健康成年人一天不要超過四到五杯。
為什么我們要喝咖啡？
Most people take in coffee to increase their focus and concentration.
But once you take in too much you start to lose that focus.
People start getting more agitated, irritable.
大部分人喝咖啡是為了提高注意力，專注程度。
一旦喝太多，你反而會降低你的注意力。
人會變得躁動不安，易怒。
That's thanks to the hormone, adrenaline.
When caffeine hits your system it stimulates your adrenal glands which release the hormone into your body, it makes you feel energetic and alert.
這是因為腎上腺素這種荷爾蒙所導致的。當咖啡因開始發(fā)生作用，它會刺激腎上腺素，將荷爾蒙釋放至體內，讓你充滿活力，提高警覺。
喝多了會怎樣？
引起焦慮
But too much can be a bad thing.
Especially if you suffer from anxiety.
But with anxiety you also wanna be careful not to overstimulate or trigger any sort of panic attacks and make anxiety worse, which certainly too much caffeine can do.
但太多就是變成壞事。
特別是你在焦慮的時候。談到焦慮癥狀，要小心不能過度刺激，不能誘發(fā)任何形態(tài)的恐慌感，讓焦慮癥惡化；而太多咖啡絕對會造成這種情況。
心率不齊
Adrenaline from caffeine can also increase your heart rate.
That's why doctors also recommend against drinking coffee if your heart sometimes beats irregularly.
But the risk is really only for bona fide coffee junkies.
咖啡因激起的腎上腺素也可能使心跳加速。這就是為什么如果有什么心跳不規(guī)律的問題，醫(yī)生會建議不要喝咖啡。
然而這樣的風險只針對真正的咖啡上癮者。
According to at least two observational studies you have to drink at least nine cups of coffee a day to put yourself at risk of arrhythmia.
根據研究，你一天得喝超過九杯咖啡才可能讓自己處于心率不齊的風險。
影響睡眠
And finally, there's the question of sleep.
Coffee's enemy.
Caffeine launches a double threat on your slumber.
It blocks the neurochemical adenosine which is what tells your brain that you're tired.
It releases a cocktail of stimulants into your brain: adrenaline, dopamine, and glutamate.
最后還需要說到睡眠問題。
咖啡對睡眠很不利。
咖啡因對你的睡眠會產生雙重威脅。
神經化學方面，咖啡因會抑制腺苷，當你疲累時腺苷會傳訊給大腦。
咖啡因會釋放出混合刺激物給大腦，包含腎上腺素，多巴胺，谷氨酸。
So after donning your sixth cup of coffee, you don't just feel awake but full of energy. It will power you through that 2:30 meeting or the last class of the day.
因此六杯咖啡下肚以后，你不但十分清醒，而且活力滿滿。它能帶你撐過下午兩點半的會議，或者熬過最后一節(jié)課。
It's sort of just stuck in this loop where you're not sleeping because you drink too much coffee. And then you wake up in the morning and you're not well rested and you're drinking more coffee just to stay awake in the day.
你會困在一種循環(huán)：喝太多咖啡因而睡不好。隔天早上起來休息不夠，所以喝更多咖啡來撐過這天。
喝咖啡難道沒有好處么？
Here's the good news.
If you cut yourself off by 2:00 p.m, you typically won't have trouble falling asleep. That's because the half-life of caffeine is around five hours.
And so most of its stimulating effects will wear off well before the lights go out.
好消息來了。只要在下午兩點以后不碰咖啡，你基本上是不會有睡眠問題的。這樣晚上關燈睡覺前，大部分的刺激效果就會消退。
And if you also limit your consumption, well then coffee can actually offer a number of health benefits.
Research shows that it can help with everything from memory, to exercise, to your relationships with your colleagues.
And that's great because for some of us, coffee is just something we'll just never give up.
而且如果你有在注意攝取量的話，事實上咖啡會帶來不少健康益處。研究結果顯示咖啡對你的記憶，運動效果，職場關系都有幫助。這真是太好了，因為對某些人來說，咖啡可是我們永遠不想放棄的東西。
喝咖啡指南
一日不超過4-5杯
下午2點后不喝咖啡
超過9杯會引起心率不齊
對記憶有好處
對運動有幫助
對職場關系好
