Transcriber:
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.
It might, however,
make you have to pee a lot.
(Music)
[Body Stuff with Dr. Jen Gunter]
(Music)
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 --
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.
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.