Why you don't need 8 glasses of water a day | Body Stuff with Dr. Jen Gunter | TED

Transcriber:

You know that whole thing about drinking eight glasses of water a day?

譯者: Zoe Walmsley 審譯者: Helen Chang

聽過每人每天該喝八杯水嗎？

Sorry to have to tell you this, but it's a myth.

很抱歉，我必須說那是錯誤的觀念。

It won't make your skin brighter,

這麼做不會讓皮膚白皙，

it won't make you feel clearheaded,

也不會讓頭腦清晰，

it won't make you feel more energetic.

更不會讓你更有活力。

It might, however, make you have to pee a lot.

比較可能的是讓你一直跑廁所。

(Music)

（音樂聲）

[Body Stuff with Dr. Jen Gunter]

《認識你的身體—珍·岡特醫師》

(Music)

（音樂聲）

Many people don't understand the biology behind their bodies.

許多人不清楚身體的運作方式。

There's a lot of misinformation out there.

加上錯誤的訊息俯拾皆是。

But the truth is that when you understand how your systems function,

事實上，一旦你了解身體如何運作，

you're able to make better decisions.

你就會比較清楚應該怎麼做。

You're not as prone to fall for hype or pseudoscience.

不會輕易被炒作的偽科學蒙騙，

You'll feel empowered to understand what's really going on.

也能清楚看出真相。

One myth that really bugs me

有個讓我很煩的迷思是

is the idea that you need eight glasses of water a day.

每人每天需要喝八杯水。

Honestly, it's pretty shocking how ingrained it is.

這個觀念根深蒂固得嚇人。

You hear it on TV, you see it in articles.

充斥於電視及報導中。

But like I said, it's nonsense.

可是就如同我所說的， 這是沒有根據的。

For the most part,

大體上而言，

your body will tell you when you need to drink water,

你的身體會告訴你何時應該喝水，

because you've got these wonderful, amazing, undervalued things --

尤其是人體有一個很棒、很神奇， 卻被低估的器官──

kidneys.

腎臟。

Kidneys are the bean-shaped organs located to either side of your spine,

腎臟是位於脊椎兩邊， 豆子形狀的器官，

right below your ribs.

就在肋骨的正下方。

They're often thought of as a filter or a waste-removal system,

通常被視為過濾或排泄 代謝廢物的系統，

but that doesn't do the kidneys justice.

但腎臟的功能遠不止於此。

Your body is an environment where everything, fluid and chemicals,

人體中所有的液體及各種物質

needs to be in a delicate balance.

都必須處於一個很精準的平衡點。

The kidneys do a lot of the heavy lifting when it comes to this balance.

腎臟必須執行許多繁重任務 才能達到那個平衡點。

Every day, blood in your body passes through the kidneys.

每天我們體內的血液流經腎臟。

What you eat, drink, the temperature around you,

你的飲食、環境的氣溫、

how much you exercise --

運動量等等的，

all of this affects what's going on with your body.

在在都影響著身體的運作。

Your kidneys, along with your nervous system and various hormones,

腎臟，連同神經系統及各種激素，

are constantly watching many gauges

隨時都在密切觀察、量測

and making adjustments about fluid, salt and levels of other substances

體內的液體、鹽分及其他物質，

in real time.

做出即時的調整。

They do this with about one million tiny structures called nephrons.

這一切是藉由上百萬個 微小的腎元去進行。

These nephrons are kind of like workers on a conveyor belt,

腎元有點像是輸送帶上的工人，

actively adding things and taking things away,

積極地增加或拿走

things like sodium, glucose or sugar, calcium, amino acids and water,

鈉、血糖、鈣、氨基酸及水等等的，

to make sure the body maintains homeostasis, or balance.

確保身體維持一個穩定的狀態。

If levels of anything get too high or too low,

任何一項過多或太少，

then that can be harmful.

都可能對人體造成傷害。

And it is the job of the kidneys

腎臟的功能

to keep the levels of many of these substances in the just-right zone.

就是將所有這些物質 維持在一個恰當的標準內。

Substances that aren't needed leave the kidney

身體不需要的物質就離開腎臟

and head to the bladder,

進入膀胱，

where you excrete them in the form of urine.

以尿液的形式排出體外。

So where do eight glasses of water a day fit in?

所以這跟喝八杯水有何關聯？

They don't.

其實沒有關聯。

Noticed that I did not say

你有注意到我並沒說

that the kidney function is improved with excess water.

水喝愈多腎臟的運作會愈好。

Imagine that you're sweating a lot,

想想看，當你大量流汗時，

so you're losing water from your blood.

血液中的水分也在流失。

The kidneys know your blood volume is dropping ever so slightly

一旦腎臟偵測到血液量下降， 即使只降低一點點，

and that your blood is getting ever so slightly saltier.

血液中的鹽分也會微微上升，

They compensate by absorbing more water back into the blood,

腎臟就提取水分排回血液中去調節，

making the urine more concentrated.

因此造成尿液的濃度上升。

If the kidneys sense enough fluid can't be reabsorbed from the urine,

可是如果腎臟無法 從尿液中提取足夠的水分，

you're signaled to drink, meaning you get thirsty.

你的身體就發出口渴的信號， 提醒你去喝水。

If you don't have fluid available,

如果所需的水分沒有補充，

the thirst message gets stronger and stronger.

口渴的信號就會愈來愈強。

A person facing real dehydration won't be unsure if they need water.

脫水的人會很明確知道需要喝水。

They'll do whatever they need to get it.

也會不顧一切地找水喝。

It's one of our most basic instincts

這是人類最原始的本能之一，

that's evolved over a very long time,

花了很長的時間進化演變而來，

in environments where clean water

因為遠古的環境要有乾淨水源的機會

wasn't nearly as readily available as it is today.

遠不能與今日相比。

So thanks to your kidneys,

還好有腎臟，

your body is really good at maintaining hydration.

幫我們的身體保持水合狀態。

But if you stop counting eight glasses of water a day,

如果不去計算每天八杯水，

how much should you be drinking?

究竟應該喝多少呢？

The answer is simple:

答案很簡單：

there is no should.

也與「應該」無關。

When you feel thirsty, drink some water.

覺得口渴了就喝點水。

You can trust your body.

信任你的身體。

Unless you have kidney stones or are elderly --

除非你有腎結石還是年紀很大了……

sometimes, our messaging systems get a little worn with age --

有時人體的訊號會隨著年紀變弱……

or your doctor has told you otherwise,

還是聽從醫生囑咐也行，

constantly monitoring how much water you drink

無時無刻計算自己喝多少水

is not really necessary.

真的不是那麼必要。

Here's a point that's often missed:

還有一點常常被忽略的：

every single thing you consume contains water.

我們吃的每樣東西都含有水分。

Your morning coffee has water, so does your breakfast.

早晨的咖啡中有水，早餐也是。

And that snack -- an apple, an orange, a glass of juice, a granola bar --

還有點心之類的：蘋果、柳橙、 果汁、燕麥棒等等，

just like you, they're made of water too.

跟人一樣，它們也都含有水分。

So as long as you're listening to your body's internal sense of thirst,

只要你傾聽身體發出的口渴信號，

there's really no need to be counting those eight glasses.

真的沒必要去算是否喝滿八杯水。