September 16, 2026 • 12 mins
Our bodies need salt and our bodies need water, so why is drinking saltwater not good for you? Learn what salt does in our bodies and why seawater will actually dehydrate you in today's episode of BrainStuff, based on this article: https://science.howstuffworks.com/science-vs-myth/what-if/what-if-you-drink-saltwater.htm
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Speaker 1 (00:01):
Welcome to BrainStuff, a production of iHeartRadio. Hey BrainStuff, Lauren
Vogelbaum here. Have you ever daydreamed, maybe from a windowless
office or classroom, about being stranded on a deserted island? Well,
if your genie comes around, you might want to pop
(00:22):
in a clause regarding fresh running water. If your paradise
doesn't have a convenient source of fresh water available, those
lapping ocean waves won't be a calming presence for long.
They might start to seem like they're mocking you because
you can't drink any of it. 71% of our planet's
surface is covered with water, yet most of it is
(00:45):
ocean water that we can't consume thanks to salt. Salt
water might not sound as deadly as some of the
other dangers of the wild. After all, our bodies depend
on both water and salt to function. Water is a
solvent and carrier for all kinds of compounds, and salt
is essential for electrochemical reactions that help us metabolize food,
(01:09):
use our muscles, pump our blood, and even think. So
what's the problem? If anything, drinking salt water sounds efficient,
not deadly. Today, let's talk a little about how salt
works in our bodies, and why there is absolutely such
thing as too much. Salt is a compound made up
(01:31):
of two elements, sodium and chlorine. There can be other minerals,
for example, in different kinds of salt, but those are
the two elements we're talking about today. Both sodium and
chlorine are electrolytes. Electrolytes are not what plants crave, but
rather minerals that conduct electricity in our fluids and tissues.
(01:52):
The other main electrolytes are potassium, calcium, and magnesium. Our
kidneys maintain the balance of electrolytes and water in our
bodies by regulating the fluids that we take in and
pass out. If this balance is disturbed, our muscles, nerves,
and organs won't function correctly because our cells won't be
able to generate muscle contractions and nerve impulses. Too little salt,
(02:16):
or hyponatremia, is one of the most common electrolyte disturbances.
You can lose sodium when you sweat or urinate excessively.
experience vomiting or diarrhea, or when you drink a lot
of water without consuming any salt. This is why sports
drinks contain electrolytes. Ultimately, hyponatremia can lead to brain swelling
(02:39):
and death. So consuming some salt is essential for our
physiological well-being and for the french fries to taste good.
But how much dietary salt is too much? science is
actually still figuring out what different levels of salt intake
can do in our bodies. I've said it here before
and I'll say it again, nutrition is complicated. Our bodies
(03:02):
are complicated. It actually tickles me to no end that
I haven't done an episode about how caffeine works yet
because it boggles me, but I found our recent episode
about Geiger counters to be refreshingly straightforward. But let's go
over the basics. The wisdom about salt consumption since at
least the 1970s has been that less is best. The
(03:26):
working hypothesis has been that when you eat too much sodium,
your system has to hold extra water in order to
wash it from your body, and that this extra water
puts stress on your heart by increasing the amount of
fluid it has to pump through your body, and that
this may cause your blood pressure to rise, which is
a risk factor for cardiovascular disease. But we don't know
(03:51):
for sure exactly what all causes high blood pressure. Recent
studies have found that prior recommendations of under 2 grams
of sodium per day for heart health are probably too stringent,
and instead, that anything between 3 grams and 5 grams
of sodium a day is healthy for most people. It
(04:11):
seems like going above or below that is where most
people run into problems. Of course, if you have any
questions or concerns about your personal sodium or salt intake,
you should talk to a medical professional, which I am not. Furthermore,
I don't know your medical situation. But okay, for our
(04:31):
purposes today, suffice it to say that too little or
too much salt wreaks havoc in our bodies. For humans,
the magic number is right around 0.9%. That's the approximate
salinity of human blood, sometimes expressed as 9 grams per liter.
(04:52):
In medicine, fluids that have the same salinity as blood
are referred to as isotonic. Salt water is a hypertonic fluid,
or one that contains more salt than human blood. Ocean
salt water has a salinity of 3.5%, or 35 grams
per liter. That's very nearly four times saltier than human blood.
(05:14):
Consuming too much salt is called hypernatremia, as opposed to hyponatremia.
When we experience hypernatremia, we excrete the excess salt in
our urine to keep our bodily fluids balanced. But drinking
extremely hypertonic fluids, like seawater, throws the body's coping mechanism
(05:34):
into disarray. Let's talk about diffusion and osmosis. Okay, have
you ever been minding your own business on an elevator
when some aggressively perfumed human stepped on? What happened? The
scent didn't stay with the person. It wafted all over
the elevator so that everyone could smell it. That's diffusion
(05:57):
in action. This net transport of matter from a region
of high concentration to a region of lower concentration is
happening all the time. Of course, human bodies aren't filled
with open air like an elevator. We're largely filled with fluids,
and that's how various compounds get around inside of us.
(06:18):
Human cells have biological membranes, which can prevent salt from
freely wafting into our cells. Although our bodies can normalize
sodium and chloride concentrations to an extent, dealing with extremely
high concentrations of salt in the blood is challenging. That's
because a cell's membrane is semi-permeable, meaning that sodium, chloride,
(06:42):
and other substances might not be able to easily diffuse
into and out of the cell, but water can. When
the salt concentration is higher on the outside of our
cells than on the inside, water will move from the
inside of our cells to the outside to correct the imbalance.
the attempt to equalize the concentrations of matter on both
(07:04):
sides of a semipermeable membrane is called osmosis. Now, when
we talk about drinking seawater, I'm not talking about the
half a mouthful or even the accidental gulp that you
might get while swimming at the beach. That's incidental and
basically fine. But if you drank seawater, the results of
(07:26):
osmosis would be disastrous. Remember that the salinity of seawater
is almost four times that of our bodily fluids. If
gone unchecked, the net transfer of water from the inside
of your cells to the outside would cause your cells
to shrink considerably, and shrinkage is generally not good. Unless
(07:47):
you drank a lot of fresh water as well, the
body's regulatory mechanism in this situation is potentially fatal. With seawater,
the change in sodium concentration outside of our cells is
the main culprit. In order to regain an isotonic state,
which is a must for cell survival, the body will
attempt to get rid of the excess sodium from its
(08:09):
extracellular fluids. So it produces urine for you to eliminate. However,
human kidneys can only produce urine that's slightly less salty
than saltwater. So, in order to remove the extreme amount
of sodium taken in by drinking salt water, we would
(08:29):
urinate more water than we actually drank in the first place.
And so, dehydration would set in. In other words, even
if you're guzzling seawater, you're actually incurring a net loss
of liquid, leading to depleted body fluids, muscle cramps, dry mouth, and, yes,
(08:50):
more thirst. The body tries to compensate for fluid loss
by increasing the heart rate and constricting the blood vessels
to maintain blood pressure and flow to vital organs. So
you're also likely to feel nausea, weakness, and even delirium.
As you become more dehydrated, however, this coping mechanism fails.
(09:11):
If you still don't drink any water to reverse the
effects of excess sodium, the brain and other organs won't
receive enough blood, leading to coma, organ failure, and eventually death. Again,
consuming small amounts of salt water won't kill you. The
take-home message here is clear, though. Salt and water are
(09:31):
best consumed separately, and any significant salt intake should be
accompanied by plenty of fresh water. But okay, side quest.
How is it that marine life doesn't shrivel up and
die from all the salinity around them? Those clever creatures
deal with ocean salinity in two ways. some of them
(09:54):
are able to exist as osmotic conformers. Beings like marine
plants and invertebrates have no mechanism to control osmosis, so
their cells are the same salinity as their environment. That
means that saltwater intake doesn't disrupt their physiological equilibrium. In contrast,
some creatures are osmotic regulators. Most marine fish, reptiles, birds,
(10:19):
and mammals can control their internal salinity in some way.
Lots of seabirds and mammals have much more efficient kidneys
than ours that can output more salt. Or, for example,
take salmon, which are anadromous, meaning that they're born in
freshwater lakes and streams, then migrate out to saltwater environs
(10:39):
for most of their lives. These fish can handle both
of these conditions with a gradual transition, thanks to an
enzyme in animal cells called an NKA pump that works
to move sodium in and out of cells. We have
these pumps, too, in our nerve cells, for example, but
salmon and other fish have a lot of them in
(11:01):
their gills, in cells called chloride cells. In freshwater fish,
like young salmon, NKA pumps work to pump sodium into
the fish's system. Freshwater fish also have super active kidneys
that produce low-sodium urine pretty much constantly. But when a
(11:21):
salmon migrates to saltwater, the chloride cells change, and the
NKA pumps basically reverse and start pumping excess sodium and
chloride out of the fish's system. This allows the fish,
unlike you, to take in saltwater without dehydrating. Today's episode
(11:43):
is based on the article, What If You Drink Salt Water,
on HowStuffWorks.com, written by Vicki M. Jujo. BrainStuff is a
production of iHeart Podcasts in partnership with HowStuffWorks.com and is
produced by Tyler Klang. For more shows from iHeart Podcasts,
visit the iHeartRadio app, Apple Podcasts, or wherever you listen
to your favorite shows.
Welcome to BrainStuff, a production of iHeartRadio. Hey BrainStuff, Lauren
Vogelbaum here. Have you ever daydreamed, maybe from a windowless
office or classroom, about being stranded on a deserted island? Well,
if your genie comes around, you might want to pop
(00:22):
in a clause regarding fresh running water. If your paradise
doesn't have a convenient source of fresh water available, those
lapping ocean waves won't be a calming presence for long.
They might start to seem like they're mocking you because
you can't drink any of it. 71% of our planet's
surface is covered with water, yet most of it is
(00:45):
ocean water that we can't consume thanks to salt. Salt
water might not sound as deadly as some of the
other dangers of the wild. After all, our bodies depend
on both water and salt to function. Water is a
solvent and carrier for all kinds of compounds, and salt
is essential for electrochemical reactions that help us metabolize food,
(01:09):
use our muscles, pump our blood, and even think. So
what's the problem? If anything, drinking salt water sounds efficient,
not deadly. Today, let's talk a little about how salt
works in our bodies, and why there is absolutely such
thing as too much. Salt is a compound made up
(01:31):
of two elements, sodium and chlorine. There can be other minerals,
for example, in different kinds of salt, but those are
the two elements we're talking about today. Both sodium and
chlorine are electrolytes. Electrolytes are not what plants crave, but
rather minerals that conduct electricity in our fluids and tissues.
(01:52):
The other main electrolytes are potassium, calcium, and magnesium. Our
kidneys maintain the balance of electrolytes and water in our
bodies by regulating the fluids that we take in and
pass out. If this balance is disturbed, our muscles, nerves,
and organs won't function correctly because our cells won't be
able to generate muscle contractions and nerve impulses. Too little salt,
(02:16):
or hyponatremia, is one of the most common electrolyte disturbances.
You can lose sodium when you sweat or urinate excessively.
experience vomiting or diarrhea, or when you drink a lot
of water without consuming any salt. This is why sports
drinks contain electrolytes. Ultimately, hyponatremia can lead to brain swelling
(02:39):
and death. So consuming some salt is essential for our
physiological well-being and for the french fries to taste good.
But how much dietary salt is too much? science is
actually still figuring out what different levels of salt intake
can do in our bodies. I've said it here before
and I'll say it again, nutrition is complicated. Our bodies
(03:02):
are complicated. It actually tickles me to no end that
I haven't done an episode about how caffeine works yet
because it boggles me, but I found our recent episode
about Geiger counters to be refreshingly straightforward. But let's go
over the basics. The wisdom about salt consumption since at
least the 1970s has been that less is best. The
(03:26):
working hypothesis has been that when you eat too much sodium,
your system has to hold extra water in order to
wash it from your body, and that this extra water
puts stress on your heart by increasing the amount of
fluid it has to pump through your body, and that
this may cause your blood pressure to rise, which is
a risk factor for cardiovascular disease. But we don't know
(03:51):
for sure exactly what all causes high blood pressure. Recent
studies have found that prior recommendations of under 2 grams
of sodium per day for heart health are probably too stringent,
and instead, that anything between 3 grams and 5 grams
of sodium a day is healthy for most people. It
(04:11):
seems like going above or below that is where most
people run into problems. Of course, if you have any
questions or concerns about your personal sodium or salt intake,
you should talk to a medical professional, which I am not. Furthermore,
I don't know your medical situation. But okay, for our
(04:31):
purposes today, suffice it to say that too little or
too much salt wreaks havoc in our bodies. For humans,
the magic number is right around 0.9%. That's the approximate
salinity of human blood, sometimes expressed as 9 grams per liter.
(04:52):
In medicine, fluids that have the same salinity as blood
are referred to as isotonic. Salt water is a hypertonic fluid,
or one that contains more salt than human blood. Ocean
salt water has a salinity of 3.5%, or 35 grams
per liter. That's very nearly four times saltier than human blood.
(05:14):
Consuming too much salt is called hypernatremia, as opposed to hyponatremia.
When we experience hypernatremia, we excrete the excess salt in
our urine to keep our bodily fluids balanced. But drinking
extremely hypertonic fluids, like seawater, throws the body's coping mechanism
(05:34):
into disarray. Let's talk about diffusion and osmosis. Okay, have
you ever been minding your own business on an elevator
when some aggressively perfumed human stepped on? What happened? The
scent didn't stay with the person. It wafted all over
the elevator so that everyone could smell it. That's diffusion
(05:57):
in action. This net transport of matter from a region
of high concentration to a region of lower concentration is
happening all the time. Of course, human bodies aren't filled
with open air like an elevator. We're largely filled with fluids,
and that's how various compounds get around inside of us.
(06:18):
Human cells have biological membranes, which can prevent salt from
freely wafting into our cells. Although our bodies can normalize
sodium and chloride concentrations to an extent, dealing with extremely
high concentrations of salt in the blood is challenging. That's
because a cell's membrane is semi-permeable, meaning that sodium, chloride,
(06:42):
and other substances might not be able to easily diffuse
into and out of the cell, but water can. When
the salt concentration is higher on the outside of our
cells than on the inside, water will move from the
inside of our cells to the outside to correct the imbalance.
the attempt to equalize the concentrations of matter on both
(07:04):
sides of a semipermeable membrane is called osmosis. Now, when
we talk about drinking seawater, I'm not talking about the
half a mouthful or even the accidental gulp that you
might get while swimming at the beach. That's incidental and
basically fine. But if you drank seawater, the results of
(07:26):
osmosis would be disastrous. Remember that the salinity of seawater
is almost four times that of our bodily fluids. If
gone unchecked, the net transfer of water from the inside
of your cells to the outside would cause your cells
to shrink considerably, and shrinkage is generally not good. Unless
(07:47):
you drank a lot of fresh water as well, the
body's regulatory mechanism in this situation is potentially fatal. With seawater,
the change in sodium concentration outside of our cells is
the main culprit. In order to regain an isotonic state,
which is a must for cell survival, the body will
attempt to get rid of the excess sodium from its
(08:09):
extracellular fluids. So it produces urine for you to eliminate. However,
human kidneys can only produce urine that's slightly less salty
than saltwater. So, in order to remove the extreme amount
of sodium taken in by drinking salt water, we would
(08:29):
urinate more water than we actually drank in the first place.
And so, dehydration would set in. In other words, even
if you're guzzling seawater, you're actually incurring a net loss
of liquid, leading to depleted body fluids, muscle cramps, dry mouth, and, yes,
(08:50):
more thirst. The body tries to compensate for fluid loss
by increasing the heart rate and constricting the blood vessels
to maintain blood pressure and flow to vital organs. So
you're also likely to feel nausea, weakness, and even delirium.
As you become more dehydrated, however, this coping mechanism fails.
(09:11):
If you still don't drink any water to reverse the
effects of excess sodium, the brain and other organs won't
receive enough blood, leading to coma, organ failure, and eventually death. Again,
consuming small amounts of salt water won't kill you. The
take-home message here is clear, though. Salt and water are
(09:31):
best consumed separately, and any significant salt intake should be
accompanied by plenty of fresh water. But okay, side quest.
How is it that marine life doesn't shrivel up and
die from all the salinity around them? Those clever creatures
deal with ocean salinity in two ways. some of them
(09:54):
are able to exist as osmotic conformers. Beings like marine
plants and invertebrates have no mechanism to control osmosis, so
their cells are the same salinity as their environment. That
means that saltwater intake doesn't disrupt their physiological equilibrium. In contrast,
some creatures are osmotic regulators. Most marine fish, reptiles, birds,
(10:19):
and mammals can control their internal salinity in some way.
Lots of seabirds and mammals have much more efficient kidneys
than ours that can output more salt. Or, for example,
take salmon, which are anadromous, meaning that they're born in
freshwater lakes and streams, then migrate out to saltwater environs
(10:39):
for most of their lives. These fish can handle both
of these conditions with a gradual transition, thanks to an
enzyme in animal cells called an NKA pump that works
to move sodium in and out of cells. We have
these pumps, too, in our nerve cells, for example, but
salmon and other fish have a lot of them in
(11:01):
their gills, in cells called chloride cells. In freshwater fish,
like young salmon, NKA pumps work to pump sodium into
the fish's system. Freshwater fish also have super active kidneys
that produce low-sodium urine pretty much constantly. But when a
(11:21):
salmon migrates to saltwater, the chloride cells change, and the
NKA pumps basically reverse and start pumping excess sodium and
chloride out of the fish's system. This allows the fish,
unlike you, to take in saltwater without dehydrating. Today's episode
(11:43):
is based on the article, What If You Drink Salt Water,
on HowStuffWorks.com, written by Vicki M. Jujo. BrainStuff is a
production of iHeart Podcasts in partnership with HowStuffWorks.com and is
produced by Tyler Klang. For more shows from iHeart Podcasts,
visit the iHeartRadio app, Apple Podcasts, or wherever you listen
to your favorite shows.
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