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. It won't make your skin brighter, it won't make you feel clearheaded, it won't make you feel more energetic.

你知道每天喝八杯水的事吗？很抱歉告诉你，这只是个虚构的神话。一天八杯水不会提亮你的肤色，不会让你觉得头脑清醒，也不会让你觉得活力四射。

It might, however, make you have to pee a lot. Many people don't understand the biology behind their bodies. There's a lot of misinformation out there. But the truth is that when you understand how your systems function, you're able to make better decisions.

但是，它可能，让你比平时多跑几趟厕所。许多人不了解他们自身的生物机能。外界有很多误导信息。但事实上，当你了解你自身是如何运作的，你就能做出更好的决定。

You're not as prone to fall for hype or pseudoscience. You'll feel empowered to understand what's really going on. One myth that really bugs me is the idea that you need eight glasses of water a day. Honestly, it's pretty shocking how ingrained it is. You hear it on TV, you see it in articles.

不会轻易相信那些假新闻和伪科学。你会觉得自己有权利搞清楚你的身体到底是怎么回事。“一天需要喝八杯水”这个说法真的很困扰我。老实说，这个想法竟然在很多人心中都如此根深蒂固，这相当令人震惊。你能在电视上听到这句话，也能在文章里看到它。

But like I said, it's nonsense. 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. Kidneys are the bean-shaped organs located to either side of your spine, right below your ribs.

但就像我说的，这是胡说八道。大部分情况下,你的身体会告诉你你是否需要喝水，因为你拥有这个奇妙的，惊人的，常常被低估的东西——肾脏。肾脏是位于脊柱两侧的豆状器官，就在你肋骨下面。

They're often thought of as a filter or a waste-removal system, but that doesn't do the kidneys justice. Your body is an environment where everything, fluid and chemicals, needs to be in a delicate balance. The kidneys do a lot of the heavy lifting when it comes to this balance.

他们经常被当作是过滤器或垃圾清除系统，但这对肾脏不公平。在你的身体这个环境中，所有东西，液体和化学物质，都需要保持微妙的平衡。关于这种平衡，肾脏做了很多繁重的工作。

Every day, blood in your body passes through the kidneys. What you eat, drink, the temperature around you, how much you exercise -- all of this affects what's going on with your body. 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.

每天，你身体中的血液都通过肾脏。你吃什么喝什么你周围的温度，你做了多少运动——所有这些都会影响你体内的运作。你的肾脏，神经系统和各种荷尔蒙，不断地观察着你体内的各种数值，并对液体，盐和其他物质的含量进行实时的调整。

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

他们需要和大约一百万个被称作肾单元的微小结构来完成这些。这些肾单元有点像传送带边上的工人，积极地加上一些东西，拿走一些东西，比如钠，葡萄糖，糖，钙，氨基酸和水，以确保身体保持内环境稳定或平衡。

If levels of anything get too high or too low, then that can be harmful. And it is the job of the kidneys to keep the levels of many of these substances in the just-right zone. Substances that aren't needed leave the kidney and head to the bladder, where you excrete them in the form of urine.

如果体内任何东西的含量水平过高或过低，都是有害的。肾脏的工作就是把许多这些物质的水平保持在正确的水平。废物会离开肾脏，进入膀胱，以尿液的形式排出体内。

So where do eight glasses of water a day fit in? They don't. Noticed that I did not say that the kidney function is improved with excess water. Imagine that you're sweating a lot, so you're losing water from your blood. The kidneys know your blood volume is dropping ever so slightly and that your blood is getting ever so slightly saltier.

而一天八杯水起了什么作用呢？没啥作用。注意，我并没有说补水能改善肾功能。想象一下你出了很多汗，水分正在从你的血液中流失。肾脏感觉到你的血容量在轻微下降，你的血液变得越来越咸了。

They compensate by absorbing more water back into the blood, making the urine more concentrated. If the kidneys sense enough fluid can't be reabsorbed from the urine, you're signaled to drink, meaning you get thirsty. If you don't have fluid available, the thirst message gets stronger and stronger.

它们会吸收更多的水到血液中来弥补，使尿液更加浓缩。如果肾脏感觉到不能从尿液中吸收足够的液体，你会收到喝东西的信号，这就意味着你渴了。如果你没有液体可以喝，口渴的信息就会越来越强烈。

A person facing real dehydration won't be unsure if they need water. They'll do whatever they need to get it. 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. So thanks to your kidneys, your body is really good at maintaining hydration.

一个真正面临脱水的人很确定他们需要水。他们会不惜一切代价得到水。这是我们经过很长时间进化而来的本能之一，而我们所经历长期进化的环境并不像现在一样可以轻易的得到干净的水。所以多亏了你的肾脏，你的身体才会很擅长保持水分。

But if you stop counting eight glasses of water a day, how much should you be drinking? The answer is simple: there is no should. When you feel thirsty, drink some water. You can trust your body. Unless you have kidney stones or are elderly -- sometimes, our messaging systems get a little worn with age --

但如果你不照着每天八杯水这样做，那你应该喝多少？答案很简单：其实并没有应该喝多少这种说法。当你感到口渴时，那就喝一些水。你可以相信你的身体。除非你有肾结石或者是老年人——有时，我们的信息系统会随着年龄的增长而磨损——

or your doctor has told you otherwise, constantly monitoring how much water you drink is not really necessary. Here's a point that's often missed: every single thing you consume contains water. Your morning coffee has water, so does your breakfast.

或者你的医生告诉过你，并没必要总是监测你喝了多少水。这里有一点经常被忽略：你吃的每一件东西都含有水。你早上的咖啡里有水，你的早餐也是。

And that snack -- an apple, an orange, a glass of juice,a granola bar -- just like you, they're made of water too. 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.

还有小吃——一个苹果，一个橘子，一杯果汁，一根麦片——就像你一样，它们也是水做的。所以只要你去感受你的身体是否渴了就行，没必要再数那八杯水了。