Go to Brilliant.org/SciShow to learn more.

前往Brilliant.org/SciShow瞭解更多。

There's a widespread belief that caffeinated drinks will make you dehydrated because the caffeine itself makes you pee.

人們普遍認為，含咖啡因的飲料會讓你脫水，因為咖啡因本身會讓你撒尿。

But is caffeine really a diuretic?

但咖啡因真的是利尿劑嗎？

Technically, yes. But it's not affecting you as much as you might think.

技術上來說，是的。但它對你的影響沒有你想象的那麼大。

You might find you need to pee after your morning coffee.

你可能會發現你早上喝完咖啡後需要尿尿。

But you may also need to pee after drinking a similar amount of water.

但你可能也需要在喝完同樣數量的水後小便。

Still, is the caffeine making you pee more?

不過，咖啡因是不是讓你尿得更多？

It may seem like this would be easy to figure out.

這看起來似乎很容易弄明白。

You just need to know how much liquid goes in and how much comes out, right?

你只需要知道有多少液體進去，多少液體出來，對吧？

Actually, it's trickier than that.

其實，它比這更棘手。

First of all, people vary a lot in how much liquid they take in, and in how much they pee out.

首先，人在攝取液體的多少，和尿出液體的多少上有很大的差異。

So rather than giving some test subjects coffee and others water, it's best to measure the same people on different days, plus or minus caffeine.

所以，與其給一些測試對象喝咖啡，給另一些測試對象喝水，不如在不同的日子裡測量同一個人，加減咖啡因。

And it may matter when you take a measurement.

而且在你測量的時候可能會很重要。

Kidney output changes with sleep-wake cycles.

腎臟輸出量隨睡眠-覺醒週期變化。

They slow way down overnight, then crank up again during the day.

他們在一夜之間慢了下來，然後在白天又開始了。

So it's probably a good idea to monitor subjects over at least a 24 hour period.

所以，至少在24小時內監測受試者可能是個好主意。

Plus, we don't know exactly how much liquid a person needs in a day, it depends on who they are and what they're doing.

另外，我們不知道一個人一天到底需要多少液體，這取決於他們是誰，在做什麼。

Which makes a difference when you're monitoring them for hydration.

當你監測他們的水合作用時，這就不同了。

How much water we lose can also change, based on things like how much we exercise or the temperature outside.

我們失去的水的多少也會發生變化，根據我們的運動量或外界的溫度等情況。

You can get around some of this by establishing a baseline fluid intake level for each subject, and making sure they do basically the same things on their caffeine and non-caffeine days.

你可以通過為每個受試者建立一個基線的液體攝入量，並確保他們在有咖啡因和無咖啡因的日子裡做基本相同的事情來解決一些問題。

So it's actually quite a challenge to design an experiment that really demonstrates people are gaining or losing water.

所以要設計一個實驗，真正證明人們的水分在增加或減少，其實是一個相當大的挑戰。

That said, researchers over the years have attempted it, just not always successfully.

也就是說，多年來，研究者們一直在嘗試，只是不一定成功。

The idea that caffeine makes you dehydrated dates back at least several decades, possibly to a study from 1928.

咖啡因會讓你脫水的想法至少可以追溯到幾十年前，可能是1928年的一項研究。

This study wasn't ideal, since it included just three subjects, and the only measure was urine output.

這項研究並不理想，因為它只包括三名受試者，而且唯一的衡量標準是尿量。

I don't know about you, but I'm not going to quit drinking caffeine based on ninety-year-old data from three dudes.

我不知道你是怎麼想的，但我不會因為三個花花公子九十年前的數據就戒掉喝咖啡因。

Lucky for all of us, plenty more studies have been done since then, looking at the effects of everything from caffeine pills to energy drinks to coffee.

我們大家都很幸運，從那時起就有很多更多的研究，研究從咖啡因藥丸到能量飲料再到咖啡的一切影響。

When you look at all the data together, some trends emerge.

當你把所有的數據放在一起看，就會發現一些趨勢。

A moderate amount of caffeine, in the neighborhood of 300 to 500 milligrams, does not seem to lead to water loss in most studies.

在大多數研究中，適量的咖啡因，在300到500毫克左右，似乎不會導致水分流失。

That's the equivalent of 2 to 3 cups of barista-brewed coffee, or 6 cups of tea, or more than 2.5 liters of cola.

這相當於2到3杯咖啡師煮的咖啡，或者6杯茶，或者2.5升以上的可樂。

When you go above those amounts, caffeine can have a minor diuretic effect.

當你超過這些量時，咖啡因會有輕微的利尿作用。

But, as even those researchers back in 1928 recognized, if you have caffeine every day, you quickly become resistant to its dehydrating effects.

但是，即使是1928年的那些研究人員也認識到，如果你每天都喝咖啡因，你很快就會對它的脫水作用產生抵抗力。

In one 1997 study, the diuretic effect of even a relatively high dose of caffeine also disappeared when the subjects were exercising.

在1997年的一項研究中，當受試者進行運動時，即使是相對較高劑量的咖啡因的利尿作用也消失了。

This myth has a surprising amount of staying power.

這個神話有著驚人的持久力。

It's everywhere, and even some medical professionals continue to spread outdated guidelines.

到處都是，甚至一些醫學專家還在繼續傳播過時的指南。

But take comfort.

但請放心

The research is clear: drinking a few servings of coffee, tea, or caffeinated soda will not make you dehydrated.

研究很清楚：喝幾份咖啡、茶或含咖啡因的蘇打水不會讓你脫水。

There may be other reasons to stay away from sugary, caffeinated drinks, but hydration isn't one of them.

也許還有其他理由遠離含糖、含咖啡因的飲料，但水合作用不是其中之一。

If you've got a caffeine buzz going from this high-energy episode, and you're wondering what to do next, you could keep your learning streak going with a course on Brilliant.org.

如果你已經從這個高能量的情節中獲得了咖啡因的嗡嗡聲，並且你想知道下一步該做什麼，你可以通過Brilliant.org上的課程來保持你的學習連續性。

Brilliant has courses that can help you hone your math and science skills.

Brilliant的課程可以幫助你磨練你的數學和科學技能。

They're hands-on, interactive, and illustrated to help you pick up even their advanced topics.

它們具有實踐性、互動性和圖文並茂的特點，即使是高級的題目也能幫助你掌握。

With Brilliant, you'll be learning multivariable calculus in no time.

有了Brilliant，你很快就能學會多變量微積分。

And the first 200 people to sign up at Brilliant.org/SciShow will get 20% off an annual Premium subscription to Brilliant.org.

而在Brilliant.org/SciShow上註冊的前200人將獲得Brilliant.org年度高級訂閱的20%折扣。

And supporting them supports us too, so thanks for checking them out.

而支持他們也是支持我們的，所以感謝他們的檢查。