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You know that whole thing about drinking eight glasses of water a day? Sorry to have to tell you this, but it's a myth.
你知道“每天要喝八杯水”这个说法吗？很抱歉地告诉你，这一说法是虚构的。
It won't make your skin brighter, it won't make you feel clearheaded, it won't make you feel more energetic. It might, however, make you have to pee a lot.
它不会让你的皮肤更亮，不会让你的头脑更清醒，也不会让你感觉更有活力。相反，它只会让你一天跑几十趟厕所。
Many people don't understand the biology behind their bodies. There's a lot of misinformation out there.
很多人不了解身体背后的生物学，而外界流传出来很多错误的信息。
But the truth is that when you understand how your systems function, you're able to make better decisions.
事实是，当你了解自己的身体系统如何运作时，你就能做出更好的选择。
You're not as prone to fall for hype or pseudoscience. You'll feel empowered to understand what's really going on.
你不会轻易相信炒作或伪科学，你会觉得自己有底气去弄明白到底发生了什么。
One myth that really bugs me is the idea that you need eight glasses of water a day.
有一个非常困扰我的误区，就是“人每天需要喝8杯水”。
Honestly, it's pretty shocking how ingrained it is. You hear it on TV, you see it in articles. But like I said, it's nonsense.
说实在的，这一说法真的根深蒂固。在电视上能听到，在文章里能看到。但是呢，就像我说的，这是无稽之谈。
For the most part, your body will tell you when you need to drink water, because you've got these wonderful, amazing, undervalued things -- kidneys.
在大多数情况下，你的身体会告诉你什么时候需要喝水，因为你有一样美好的、神奇的、被低估了的东西——肾。
Kidneys are the bean-shaped organs located to either side of your spine, right below your ribs.
肾脏是位于脊柱两侧、肋骨正下方的豆状器官，
They're often thought of as a filter or a waste-removal system, but that doesn't do the kidneys justice.
通常被认为是过滤器或废物清除系统，但这样说对肾并不公平。
Your body is an environment where everything, fluid and chemicals, needs to be in a delicate balance.
人的身体是一个环境，所有的液体和化学物质都需要处于微妙的平衡当中。
The kidneys do a lot of the heavy lifting when it comes to this balance.
肾脏在这一平衡中做了很多繁重的工作。
Every day, blood in your body passes through the kidneys.
人体内的血液每天都要通过肾脏。
What you eat, drink, the temperature around you, how much you exercise -- all of this affects what's going on with your body.
你吃什么、喝什么、周围的温度、锻炼几何——所有这些都会影响你的身体。
Your kidneys, along with your nervous system and various hormones, are constantly watching many gauges and making adjustments about fluid, salt and levels of other substances in real time.
你的肾脏，连同你的神经系统和各种激素，都在不断地观察许多仪表，并实时地调整液体、盐和其他物质的水平。
They do this with about one million tiny structures called nephrons.
它们用大约一百万个叫做“肾元”的微小结构来完成这项工作。
These nephrons are kind of like workers on a conveyor belt, actively adding things and taking things away, things like sodium, glucose or sugar, calcium, amino acids and water, to make sure the body maintains homeostasis, or balance.
这些肾元有点像传送带上的工人，积极地添加和带走一些东西，比如钠，葡萄糖或糖，钙，氨基酸和水，以确保身体保持稳态或平衡。
If levels of anything get too high or too low, then that can be harmful.
如果任何物质的含量过高或过低，那都是有害的。
And it is the job of the kidneys to keep the levels of many of these substances in the just-right zone.
肾脏的工作就是将这些物质的水平保持在正确的区域。
Substances that aren't needed leave the kidney and head to the bladder, where you excrete them in the form of urine.
不需要的物质离开肾脏，进入膀胱，在那里以尿液的形式排出。
So where do eight glasses of water a day fit in? They don't.
那么，一天八杯水能起到什么作用呢？没有作用。
Noticed that I did not say that the kidney function is improved with excess water.
注意，我并没有说肾脏功能会随着水分的增加而增强。
Imagine that you're sweating a lot, so you're losing water from your blood.
想象一下你在出着大量的汗，你的水分正在从血液当中流失。
The kidneys know your blood volume is dropping ever so slightly and that your blood is getting ever so slightly saltier.
肾脏知道你的血容量在轻微下降，血液也在轻微变咸。
They compensate by absorbing more water back into the blood, making the urine more concentrated.
之后它们会通过吸收更多的水来补偿血液，使尿液更加浓缩。
If the kidneys sense enough fluid can't be reabsorbed from the urine, you're signaled to drink, meaning you get thirsty.
如果肾脏感觉到无法从尿液中重新吸收足够的液体，你就会收到喝水的信号，也就是说你渴了。
If you don't have fluid available, the thirst message gets stronger and stronger.
如果你没有喝足够的水，口渴的信号就会越来越强。
A person facing real dehydration won't be unsure if they need water. They'll do whatever they need to get it.
一个脱水很严重的人不会意识不到自己需要喝水，他们会不惜一切代价喝到水。
It's one of our most basic instincts that's evolved over a very long time, in environments where clean water wasn't nearly as readily available as it is today.
这是我们在很长一段时间里进化出来的最基本的本能之一，当时的环境并不像现在这样容易获得干净的水。
So thanks to your kidneys, your body is really good at maintaining hydration.
所以多亏了肾脏你的身体才能很好地维持水分。
But if you stop counting eight glasses of water a day, how much should you be drinking?
那么，如果说一天不需要喝八杯水，那应该喝多少呢？
The answer is simple: there is no should. When you feel thirsty, drink some water. You can trust your body.
答案很简单：没有应不应该一说，觉得渴了就喝呗，你要信任自己的身体。
Unless you have kidney stones or are elderly -- sometimes, our messaging systems get a little worn with age -- or your doctor has told you otherwise, constantly monitoring how much water you drink is not really necessary.
除非你有肾结石或上了年纪——有时，我们的信息系统会随着年龄的增长而有些老化——或者你的医生告诉你不是这样，一直监测你喝了多少水其实不是很有必要。
Here's a point that's often missed: every single thing you consume contains water.
有一点经常被忽视：人摄入的每一样东西都含有水分。
Your morning coffee has water, so does your breakfast.
早上的咖啡里有水，早餐也有水。
And that snack -- an apple, an orange, a glass of juice, a granola bar -- just like you, they're made of water too.
而那些零食——苹果、橙子、果汁、一条格兰诺拉麦片棒——就像人一样，它们也是由水组成的。
So as long as you're listening to your body's internal sense of thirst, there's really no need to be counting those eight glasses.
所以只要听从自己身体内部对口渴的感觉，真的没有必要非得喝正好八杯水。
