"The Effect of Drinking Water on Adrenal Hormones"
Drink a few cups of water, and within three minutes
the level of the adrenal gland hormone, noradrenaline,
in your bloodstream can shoot up 60%.
Have people drink two cups of water with electrodes stuck
in their legs, and within 20 minutes you can document about a 40% increase
in bursts of fight-or-flight nerve activity. Chug two or three cups of water
and blood flow squeezes down in your calves and arms,
clamping down nearly in half, as arteries to your limbs and skin
constrict to divert blood to your core. That's why, for example, drinking water
can be such a safe, simple, effective way to prevent yourself from fainting—
known medically as syncope. Fainting is the sudden, brief loss
of consciousness caused by diminished blood flow to your brain.
About 1 in 5 people experience this at least once, and about 1 in 10
may have repeated episodes, causing millions of emergency room visits
and hospitalizations every year.
Though fainting can be caused by heart problems, it is most often triggered
by prolonged standing—because blood pools in your legs—
or strong emotions, which can cause your blood pressure to bottom out.
About 1 in 25 people have what's called blood-injury-injection phobia,
where getting a needle stick, for example, can cause you to faint.
More than 150,000 people experience fainting or near-fainting spells
each year when they donate blood.
All you have to do to help prevent yourself from getting woozy though
is just chug two cups of water 5 minutes before getting stuck.
The secret isn't bolstering your overall blood volume. I mean, drinking
2 cups of water—even a whole quart— and your blood volume doesn't change
more than like 1 or 2%. It's due rather to the shift in the distribution of blood
toward your center, caused by
the noradrenaline-induced peripheral artery constriction.
Water drinking stimulates as much noradrenaline release
as drinking a couple of cups of coffee or smoking a couple
unfiltered cigarettes. If the simple act of drinking water
causes such a profound fight-or-flight reaction,
why doesn't it cause our heart to pound and shoot our blood pressure
through the roof? It's like the diving reflex I talked about in the last video.
When we drink water, our body simultaneously sends signals
to our heart to slow it down, to still your beating heart.
You can try it at home.
Measure your heart rate before and after drinking two cups of water.
Within 10 minutes your heart rate should slow by about four beats per minute,
and by 15 minutes you should be down six or seven beats.
One of the ways scientists figured this out is by studying
heart transplant patients.
When you move a heart from one person to another, you have to sever
all the attached nerves. Amazingly, some of the nerves grow back.
But still, give healed heart transplant patients two glasses of water
and their blood pressure goes up as much as 29 points.
The body is unable to sufficiently quell the effect
of that burst of noradrenaline.
Some people have a condition known as autonomic failure,
in which blood pressure regulation nerves don't work properly,
and their pressures can dangerously skyrocket over 100 points
after chugging two cups of water. That's how powerful an effect
the simple act of drinking a glass of water can be.
And the only reason it doesn't happen to all of us is that we
have an even more powerful counter- response to keep our heart in check.
It reminds me of the poor woman who had a stroke after taking
the ice bucket challenge due to an insufficient diving reflex
to tamp down all that extra noradrenaline release.
The remarkable water effect can be useful for people suffering from
milder forms of autonomic failure such as orthostatic hypotension,
which is when people get dizzy standing up suddenly.
Drinking some water before getting out of bed in the morning can be a big help.
But what about that metabolic boost? With so much more noradrenaline
being released, with your adrenal gland hormones in overdrive, might drinking
a few glasses of water cause you to burn more body fat?
Could tap water be like a safe form of ephedra:
all the weight loss with a nice slowing of your heart rate instead?
Researchers decided to put it to the test, which we'll explore next.