[00:06] Water is virtually everywhere,
[00:08] from soil moisture and ice caps,
[00:11] to the cells inside our own bodies.
[00:14] Depending on factors like location,
[00:16] fat index,
[00:17] age,
[00:18] and sex,
[00:19] the average human is between 55-60% water.
[00:23] At birth, human babies are even wetter.
[00:27] Being 75% water, 
they are swimmingly similar to fish.
[00:32] But their water composition drops to 65%
by their first birthday.
[00:37] So what role does water 
play in our bodies,
[00:40] and how much do we actually need to drink
to stay healthy?
[00:44] The H20 in our bodies works to cushion
and lubricate joints,
[00:48] regulate temperature,
[00:49] and to nourish the brain and spinal cord.
[00:53] Water isn't only in our blood.
[00:56] An adult's brain and heart are almost
three quarters water.
[01:00] That's roughly equivalent to the amount
of moisture in a banana.
[01:04] Lungs are more similar to an apple at 83%.
[01:08] And even seemingly dry human bones
are 31% water.
[01:14] If we are essentially made of water,
[01:16] and surrounded by water,
[01:17] why do we still need to drink so much?
[01:20] Well, each day we lose two to three liters
through our sweat,
[01:24] urine,
[01:25] and bowel movements,
[01:26] and even just from breathing.
[01:28] While these functions 
are essential to our survival,
[01:30] we need to compensate for the fluid loss.
[01:33] Maintaining a balanced water level
is essential to avoid dehydration
[01:37] or over-hydration,
[01:39] both of which can have devastating
effects on overall health.
[01:43] At first detection of low water levels,
[01:45] sensory receptors 
in the brain's hypothalamus
[01:48] signal the release 
of antidiuretic hormone.
[01:51] When it reached the kidneys, 
it creates aquaporins,
[01:54] special channels that enable blood
to absorb and retain more water,
[02:00] leading to concentrated, dark urine.
[02:03] Increased dehydration can cause
notable drops in energy,
[02:06] mood,
[02:07] skin moisture,
[02:08] and blood pressure,
[02:10] as well as signs of cognitive impairment.
[02:13] A dehydrated brain works harder 
to accomplish the same amount
[02:17] as a normal brain,
[02:18] and it even temporarily shrinks
because of its lack of water.
[02:22] Over-hydration, or hyponatremia,
[02:25] is usually caused by overconsumption
of water in a short amount of time.
[02:30] Athletes are often the victims 
of over-hydration
[02:33] because of complications 
in regulating water levels
[02:36] in extreme physical conditions.
[02:39] Whereas the dehydrated brain amps
up the production of antidiuretic hormone,
[02:43] the over-hydrated brain slows,
or even stops, releasing it into the blood.
[02:49] Sodium electrolytes in the body
become diluted,
[02:51] causing cells to swell.
[02:54] In severe cases,
[02:55] the kidneys can't keep up with 
the resulting volumes of dilute urine.
[02:59] Water intoxication then occurs,
[03:01] possibly causing headache,
[03:03] vomiting,
[03:04] and, in rare instances, seizures
or death.
[03:08] But that's a pretty extreme situation.
[03:10] On a normal, day-to-day basis,
[03:12] maintaining a well-hydrated system
is easy to manage
[03:15] for those of us fortunate enough 
to have access to clean drinking water.
[03:19] For a long time, conventional wisdom said
that we should drink eight glasses a day.
[03:23] That estimate has since been fine-tuned.
[03:26] Now, the consensus is that the amount
of water we need to imbibe
[03:30] depends largely on our weight
and environment.
[03:33] The recommended daily intake varies from
between 2.5-3.7 liters of water for men,
[03:39] and about 2-2.7 liters for women,
[03:42] a range that is pushed up 
or down if we are healthy,
[03:46] active,
[03:46] old,
[03:47] or overheating.
[03:49] While water is the healthiest hydrator,
[03:51] other beverages,
[03:52] even those with caffeine 
like coffee or tea,
[03:55] replenish fluids as well.
[03:57] And water within food makes up 
about a fifth of our daily H20 intake.
[04:02] Fruits and vegetables like strawberries,
[04:04] cucumbers,
[04:05] and even broccoli are over 90% water,
[04:08] and can supplement liquid intake while
providing valuable nutrients and fiber.
[04:14] Drinking well might also have various
long-term benefits.
[04:17] Studies have shown that optimal hydration
can lower the chance of stroke,
[04:21] help manage diabetes,
[04:23] and potentially reduce the risk
of certain types of cancer.
[04:27] No matter what, getting the right amount
of liquid makes a world of difference
[04:32] in how you'll feel,
[04:33] think,
[04:34] and function day to day.