What would happen if you didn’t drink water? - Mia Nacamulli

22,280,493 views ・ 2016-03-29

TED-Ed


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

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Water is virtually everywhere,
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from soil moisture and ice caps,
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to the cells inside our own bodies.
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Depending on factors like location,
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fat index,
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age,
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and sex,
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the average human is between 55-60% water.
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At birth, human babies are even wetter.
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Being 75% water, they are swimmingly similar to fish.
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But their water composition drops to 65% by their first birthday.
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So what role does water play in our bodies,
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and how much do we actually need to drink to stay healthy?
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The H20 in our bodies works to cushion and lubricate joints,
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regulate temperature,
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and to nourish the brain and spinal cord.
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Water isn't only in our blood.
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An adult's brain and heart are almost three quarters water.
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That's roughly equivalent to the amount of moisture in a banana.
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Lungs are more similar to an apple at 83%.
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And even seemingly dry human bones are 31% water.
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If we are essentially made of water,
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and surrounded by water,
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why do we still need to drink so much?
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Well, each day we lose two to three liters through our sweat,
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urine,
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and bowel movements,
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and even just from breathing.
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While these functions are essential to our survival,
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we need to compensate for the fluid loss.
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Maintaining a balanced water level is essential to avoid dehydration
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or over-hydration,
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both of which can have devastating effects on overall health.
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At first detection of low water levels,
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sensory receptors in the brain's hypothalamus
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signal the release of antidiuretic hormone.
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When it reached the kidneys, it creates aquaporins,
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special channels that enable blood to absorb and retain more water,
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leading to concentrated, dark urine.
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Increased dehydration can cause notable drops in energy,
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mood,
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skin moisture,
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and blood pressure,
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as well as signs of cognitive impairment.
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A dehydrated brain works harder to accomplish the same amount
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as a normal brain,
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and it even temporarily shrinks because of its lack of water.
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Over-hydration, or hyponatremia,
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is usually caused by overconsumption of water in a short amount of time.
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Athletes are often the victims of over-hydration
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because of complications in regulating water levels
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in extreme physical conditions.
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Whereas the dehydrated brain amps up the production of antidiuretic hormone,
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the over-hydrated brain slows, or even stops, releasing it into the blood.
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Sodium electrolytes in the body become diluted,
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causing cells to swell.
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In severe cases,
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the kidneys can't keep up with the resulting volumes of dilute urine.
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Water intoxication then occurs,
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possibly causing headache,
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vomiting,
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and, in rare instances, seizures or death.
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But that's a pretty extreme situation.
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On a normal, day-to-day basis,
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maintaining a well-hydrated system is easy to manage
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for those of us fortunate enough to have access to clean drinking water.
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For a long time, conventional wisdom said that we should drink eight glasses a day.
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That estimate has since been fine-tuned.
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Now, the consensus is that the amount of water we need to imbibe
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depends largely on our weight and environment.
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The recommended daily intake varies from between 2.5-3.7 liters of water for men,
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and about 2-2.7 liters for women,
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a range that is pushed up or down if we are healthy,
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active,
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old,
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or overheating.
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While water is the healthiest hydrator,
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other beverages,
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even those with caffeine like coffee or tea,
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replenish fluids as well.
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And water within food makes up about a fifth of our daily H20 intake.
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Fruits and vegetables like strawberries,
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cucumbers,
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and even broccoli are over 90% water,
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and can supplement liquid intake while providing valuable nutrients and fiber.
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Drinking well might also have various long-term benefits.
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Studies have shown that optimal hydration can lower the chance of stroke,
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help manage diabetes,
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and potentially reduce the risk of certain types of cancer.
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No matter what, getting the right amount of liquid makes a world of difference
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in how you'll feel,
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think,
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and function day to day.
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