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

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2021-06-09 ・ TED


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

852,075 views ・ 2021-06-09

TED


Please double-click on the English subtitles below to play the video.

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You know that whole thing about drinking eight glasses of water a day?
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Sorry to have to tell you this, but it's a myth.
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It won't make your skin brighter,
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it won't make you feel clearheaded,
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it won't make you feel more energetic.
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It might, however, make you have to pee a lot.
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(Music)
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[Body Stuff with Dr. Jen Gunter]
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(Music)
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Many people don't understand the biology behind their bodies.
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There's a lot of misinformation out there.
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But the truth is that when you understand how your systems function,
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you're able to make better decisions.
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You're not as prone to fall for hype or pseudoscience.
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You'll feel empowered to understand what's really going on.
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One myth that really bugs me
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is the idea that you need eight glasses of water a day.
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Honestly, it's pretty shocking how ingrained it is.
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You hear it on TV, you see it in articles.
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But like I said, it's nonsense.
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For the most part,
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your body will tell you when you need to drink water,
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because you've got these wonderful, amazing, undervalued things --
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kidneys.
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Kidneys are the bean-shaped organs located to either side of your spine,
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right below your ribs.
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They're often thought of as a filter or a waste-removal system,
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but that doesn't do the kidneys justice.
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Your body is an environment where everything, fluid and chemicals,
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needs to be in a delicate balance.
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The kidneys do a lot of the heavy lifting when it comes to this balance.
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Every day, blood in your body passes through the kidneys.
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What you eat, drink, the temperature around you,
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how much you exercise --
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all of this affects what's going on with your body.
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Your kidneys, along with your nervous system and various hormones,
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are constantly watching many gauges
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and making adjustments about fluid, salt and levels of other substances
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in real time.
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They do this with about one million tiny structures called nephrons.
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These nephrons are kind of like workers on a conveyor belt,
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actively adding things and taking things away,
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things like sodium, glucose or sugar, calcium, amino acids and water,
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to make sure the body maintains homeostasis, or balance.
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If levels of anything get too high or too low,
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then that can be harmful.
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And it is the job of the kidneys
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to keep the levels of many of these substances in the just-right zone.
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Substances that aren't needed leave the kidney
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and head to the bladder,
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where you excrete them in the form of urine.
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So where do eight glasses of water a day fit in?
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They don't.
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Noticed that I did not say
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that the kidney function is improved with excess water.
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Imagine that you're sweating a lot,
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so you're losing water from your blood.
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The kidneys know your blood volume is dropping ever so slightly
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and that your blood is getting ever so slightly saltier.
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They compensate by absorbing more water back into the blood,
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making the urine more concentrated.
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If the kidneys sense enough fluid can't be reabsorbed from the urine,
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you're signaled to drink, meaning you get thirsty.
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If you don't have fluid available,
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the thirst message gets stronger and stronger.
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A person facing real dehydration won't be unsure if they need water.
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They'll do whatever they need to get it.
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It's one of our most basic instincts
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that's evolved over a very long time,
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in environments where clean water
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wasn't nearly as readily available as it is today.
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So thanks to your kidneys,
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your body is really good at maintaining hydration.
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But if you stop counting eight glasses of water a day,
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how much should you be drinking?
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The answer is simple:
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there is no should.
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When you feel thirsty, drink some water.
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You can trust your body.
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Unless you have kidney stones or are elderly --
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sometimes, our messaging systems get a little worn with age --
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or your doctor has told you otherwise,
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constantly monitoring how much water you drink
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is not really necessary.
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Here's a point that's often missed:
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every single thing you consume contains water.
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Your morning coffee has water, so does your breakfast.
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And that snack -- an apple, an orange, a glass of juice, a granola bar --
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just like you, they're made of water too.
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So as long as you're listening to your body's internal sense of thirst,
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there's really no need to be counting those eight glasses.
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