Description:
We couldn't live without water. But if we drink too much, it can wreak havoc
on our brain and body. Drinking more water than your kidneys can process
can throw your blood sodium levels out of balance. That's called water intoxication.
And in extreme cases, it can cause brain damage, comas, and even death.
Transcription:
Narrator: What do you think of when you hear the word poison? Arsenic?
Cyanide? How about water? Life couldn't exist without water, but in the right
circumstance, water can be as dangerous as any poison. Your kidneys filter out
excess waste and water from your bloodstream. But they can only process 800
to 1,000 milliliters of water an hour, and if you somehow managed to drink more
than that without throwing up, you could run into trouble. Because you're drinking
faster than your kidneys can process it. So the excess ends up in your cells.
Normally, your cells are surrounded by a carefully balanced solution of sodium
and water, which flows in and out through tiny holes in the cellular membrane.
So it keeps the sodium concentration, both in and out of the cell, balanced.
But when you drink too much water, the sodium solution gets diluted. It's not
salty enough. So some of that excess water rushes into the cell to restore
balance. And that causes it to swell up. Doctors call this water intoxication,
and it's a big problem. Now, most of your cells can handle the swelling to
a degree, since soft, flexible tissue like fat and muscle can stretch. But for
the cells in your brain, it's another story, because your skull isn't stretchy.
It's bone. It's hard, like a rock. So, as your brain swells it builds up pressure
in your head. At first you might experience headaches, confusion, or
drowsiness, but as the pressure increases, you risk brain damage, coma,
and even death. And it could all be over in less than 10 hours. A 64-year-old
woman for example, died the same evening after drinking between 30 to 40
glasses of water. And a group of US Army trainees suffered vomiting and
seizures after downing over two liters per hour after a tough day of training.
But it's marathon runners who need to be especially careful. A study found
that one in six marathon runners develop at least mild water intoxication,
because the race stresses their body, including the kidneys. So they
don't excrete water as efficiently, which can cause water to back up into
the blood more easily. And the problem isn't unique to water. For example,
the same thing can happen if you down too much beer at once.
That's called potomania. The good news is, severe water intoxication is rare,
and is more likely to happen in people who have kidney issues, since they
can't process water properly to begin with. Plus, there is an easy way to
stay safe. The average healthy adult needs somewhere around three to four
liters of water a day. And since this can come from food and other drinks too,
drink when you're thirsty, and then stop.
Questions:
1. What does water intoxication mean?
2. What would happen if the cells in your brain gets too much water?
3. How much water did the old woman drink?