This episode of Science Versus explores whether caffeine is harmful, addressing common fears about addiction, sleep disruption, and energy drink risks. Caffeine, consumed by 85% of Americans, works by blocking adenosine receptors in the brain, reducing sleepiness and enhancing alertness, focus, and reaction time—potentially even saving lives in driving studies. However, its impact on sleep varies genetically: slow metabolizers lose up to an hour of sleep per night, while fast metabolizers lose almost none, debunking blanket advice about cutoff times. Coffee also boosts physical activity, adding about 1,000 steps daily, and improves athletic performance. Caffeine is not considered addictive in the clinical sense; withdrawal symptoms like headaches and fatigue resolve within 2–9 days, and there’s no caffeine use disorder in the DSM. Moreover, coffee and tea consumption are associated with lower risks of Parkinson’s, depression, type 2 diabetes, heart disease, and some cancers, with benefits seen even at high intakes. However, energy drinks pose distinct risks: they prolong the heart’s QT interval, potentially triggering fatal arrhythmias, though the exact culprit remains unknown—caffeine alone doesn’t cause this. While rare, these cases are tragic, and experts suggest choosing coffee or tea over energy drinks for a safer boost. Overall, caffeine appears safe for most people, with benefits outweighing harms, but individual genetics and drink type matter.
Hi, I'm Wendy Zuckerman and you're listening to Science Versus, and this is the show that
pits facts against flat whites.
On today's show, caffeine, should you quit it?
Caffeine is one of the most used drugs in the world.
85% of people in the US drink at least one caffeinated beverage each day, and that includes
kids.
But yet, despite the fact that we are shoving this drink down our pie holes, there have
always been these fears that caffeine is bad for our health.
Your cup of coffee could soon come with a spoonful of cancer warning.
My heart was racing, I was super anxious, something was happening, I was having a panic
attack.
Could it all be a sign, though, of a serious problem?
A problem like caffeine addiction.
And our worries around caffeine have reached new heights when it comes to energy drinks.
Just last year, I was in a coffee shop and I was drinking a cup of coffee.
Just last year, I was drinking a cup of coffee.
Just last year, a 17-year-old from Texas died after drinking Alani New.
A Texas family is filing a wrongful death lawsuit over an energy drink that they claimed
killed a teenage girl.
According to family lawyers, a coroner's report shows that she died from an enlarged heart
caused by stress and a large amount of caffeine from Alani Energy drinks.
The distributor being sued denies the claims, and the company that makes the drink says
it's labeled not recommended for children.
But this is just the latest in a string of news.
But this is just the latest in a string of scary stories from the past several years
of people, often younger people, dying soon after drinking energy drinks.
Davis collapsed in the classroom of his high school in South Carolina.
It wasn't a car crash that took his life.
Instead, it was an energy drink.
She drank two 24-ounce energy drinks in less than 24 hours.
And it took her life.
So today on the show, what is this drug?
What is this drug doing to our brains and our bodies?
Is it ruining our sleep, turning us into caffeine addicts, and potentially even killing us?
When it comes to caffeine, there's a lot of. My heart was racing.
But then, there's science.
Science vs. Caffeine is coming up just after the break.
Welcome back.
Today on the show, we're taking on caffeine and energy drinks
to find out once and for all, how bad is this stuff?
What is it doing in our bodies and our brains?
And we first drank up the science on caffeine a few years ago
when we first put down this episode.
And back then, there was all of this hubbub about the energy drink prime.
And that's what got senior producer Rose Rimler interested in this topic in the first place.
Yeah.
Yeah.
A lot of the talk was about how it's got a crazy amount of caffeine, it's bad for us,
and energy drinks are bad for us, and sort of just this feeling that, like, caffeine is bad for us.
And I don't know about you, but I have caffeine every day when I have my coffee.
So it made me wonder, like, is my caffeine habit something I should take a second look at?
Or is caffeine, like, just all hunky-dory?
Yes.
I love this question because caffeine has been a thing that I have actively said,
you know what, I'm not into meth, but I'm going to be fine with my caffeine use.
You know, I felt guilty about it, and I do want to know whether I need to.
So where do we begin?
Let's start with Astrid Nielig.
She's a caffeine researcher.
And she says she hears this idea about people feeling guilty about their caffeine intake all the time.
I meet somebody, and they ask me on what I work, and you see, I work on coffees.
And people are very. Very shy all of a sudden, and withdrawing a bit, and telling me, oh, it's very bad.
I should probably not drink.
Astrid is an emeritus research director at France's National Institute of Health and Medical Research.
And she has studied caffeine for decades.
So with her help, I'm going to walk you through what caffeine is doing to your brain and to your body.
Okay.
So, Wendy, I asked you to come prepared with your favorite caffeinated drink.
A caffeinated beverage.
That's right.
So what did you bring today?
I have an oat cappuccino.
Okay.
Take a sip.
Should I do it like ASMR?
Or if I'm. I guess if you have misophonia, just chewed out.
Okay.
So I'm going to tell you what it's doing right now.
Okay.
So scientists think that once the coffee gets to your stomach, it's basically going to wake up your guts.
It's going to get your stomach to make more acid.
It's going to get your liver to start making bile.
So it's really an activation.
Fatal of digestion.
Is that why, not to be crude, but sometimes you have to go number two after you drink coffee?
Yeah.
At least in some especially sensitive individuals, yeah, it's like that.
We know this because, thankfully, some scientists in the 80s got permission to stick probes up people's buttholes.
Oh.
And then give them coffee to see what happens.
And the reason they wanted to test it this way is because. Because they had given these people a survey and said, does, do any beverages make you have to poop?
And a third of the people in this 100-person survey said, yeah, actually, coffee makes me have to poop.
So they got some of these people and some other, you know, non-responders into the lab.
And they put this probe up in their upper part of their rectum.
And so what they were looking for was to see, is there an actual physical change in your lower intestine when you've had coffee?
And what did they find?
In the people who said, yes, coffee does this to me, they could actually measure increased rectal activity.
Oh.
So that. I'm clenching.
I'm clenching.
Have you been clenching as you've been reading this research?
No, I'm quite relaxed.
Oh, okay.
As soon as you said increased rectal activity, I was just like. Well, I like kind of, I like thinking about like these sort of peristalsis of your butthole, you know?
Yeah, it's graceful.
How food gets down.
It's something else has to make it come.
Come out.
And that increased.
Right.
In response to coffee for some people.
Interesting.
Okay, I have a very important question.
Yeah.
How quickly, how quickly does this activation happen?
Because. It can happen within minutes.
Oh my God, I feel so validated.
Wow.
Because I, like, I will sometimes just take a few sips of coffee and just like need to do a sh**.
Sorry for the kids.
I'm sorry for the kids out there.
Need to do a big crap.
And I have come to believe that, oh, it's just placebo at this point.
Like, surely it can't be working that quickly.
But it can.
It can.
Like, just so you know, Rose, because this is my first coffee for the day.
Yeah, if you have to, if you have to run off on the way.
No, I don't.
Because I took a couple of sips before our chat.
And I'm all sorted.
Took care of business.
I appreciate that.
That level of planning.
Always come prepared.
That is me.
Okay.
So that's how coffee can affect the gut.
And from there, caffeine starts getting absorbed in your bloodstream.
Okay.
Depends on your body, but this takes about half an hour to an hour to peak.
So caffeine's in your blood.
It gets to the blood-brain barrier, and it just sails right past it.
I talked to Astrid about this.
When I think of coffee entering our brain, I just imagine my brain is a sponge.
That just soaks up the coffee.
Is that kind of right?
Yeah, why not?
Yes, because, you know, you drink your coffee, and all of a sudden,
your whole body, including your brain, gets invaded by these caffeine molecules.
In the brain, it stimulates some neurotransmitters, including dopamine,
and that gives us a bit of a mood boost.
But the big thing that caffeine does in our brain is, of course, that it wakes you up.
Yes.
Yes.
It's claimed to fame.
And this happens because caffeine basically barges into the brain
and, like, elbows out this molecule called adenosine from these special receptors.
Mm-hmm.
And what adenosine is, it's like the sleepy molecule.
So it, like, binds receptors in your brain that basically turn on the feeling of sleepiness.
So caffeine's like, out of my way, I'm coming in, I'm going to bind to those adenosine receptors.
And that means you don't feel as sleepy.
So just—
Just to get, like, real nerdy here,
it's not that caffeine is binding onto these receptors and going,
let's go, brain, get excited.
It's rather the lack of adenosine, the lack of sleepiness that wakes you up.
Yeah, and that's what we like about caffeine, right?
Like, that is the whole point, that it wakes us up.
And it's not just about being awake.
We actually have a lot of evidence that caffeine helps us be more alert, more focused,
and helps us to react to stuff.
This has been quite extensively studied.
This is clear.
So for—if I take a stupid example, but—
Please.
You are facing a lion.
If you have been drinking caffeine, you will react faster, and you will run away before.
Could save your life.
Yeah, could, absolutely.
Could make a difference and save your life.
And scientists have actually tested this.
They gave free coffee?
to people who were visiting the zoo that day,
and then they opened the lion cage.
Amazing. And they got away? They got away?
Some got away, some didn't.
That's right. Those in the placebo group were less likely to get away.
We are joking.
No, there are no lions.
But there is one small study that suggests that caffeine really could save your life.
So this study, researchers had people stay up really late
and then drive a car on the highway in the middle of the night.
This is a real car on a real highway.
Oh, my God.
They had a driving instructor in the next seat who could take over control
if things were getting bad.
My goodness.
So the scientists were counting how many times people veered out of their lane
when they had placebo versus when they had coffee.
And it turns out the coffee made a big difference.
The number of times people veered over the lane went way down after people had coffee.
Okay. The powers of caffeine.
Yes, right.
And then I found this study that just made me laugh
because it's just such a funny concept.
Okay.
So the scientists really wanted to find out if coffee can make us appreciate humor more.
When we are sleep deprived, we kind of lose our sense of humor or it takes a hit.
So the researchers were wondering,
would caffeine give us back our sense of humor or improve that?
Uh-huh.
And I don't know if you know this, Wendy,
but there is a scientific test of sense of humor.
Oh, my gosh.
That was entirely my next question.
What is the joke that scientists ask that they're like,
if you find this funny, you have a good sense of humor?
Then you're operating on full cylinders.
Yes.
Yeah.
So they would show them like two different pictures
and ask which picture is funnier or more podcast appropriate.
They would have them read two different headlines,
fake news headlines, and ask which is funnier.
So here's an example.
I'm curious if you're going to get it right.
I feel very cocky about my sense of humor.
Okay.
So here's the example.
Which of these two headlines is funnier?
Veterinarian investigates,
Failed panda mating.
That's headline one.
Or panda mating fails, veterinarian takes over.
That's headline two.
Which is funnier?
Headline two is funnier because it suggests.
I mean, headline one isn't funny at all, right?
But headline two suggests.
Suggests something really, really disturbing, actually.
And the third headline is veterinarian f***ed panda.
You're right.
It is the second headline.
Yes.
According to science, that is objectively funnier, which I guess it is.
Also, I'm so proud of them for being a little bit naughty.
Well, it turns out that the caffeine in this case did not help people.
Yeah, I totally forgot we were talking about caffeine.
So bottom line, caffeine may not improve your humor,
but we have lots of evidence to show that it's not a myth or a placebo effect.
Like caffeine does help us.
Wake up, stay up, stay alert.
So that brings us to something that people actually worry about with caffeine,
that it's keeping you too awake, that it's messing with your sleep.
Yes, I have worried about this too.
And in fact, cut down on caffeine because I've been worried about this.
So let's meet Gregory Marcus.
I'm just going to move my dog.
Come on.
He's a cardiologist and a professor of medicine at UCSF.
If you could be any caffeinated product, which caffeinated?
What kind of caffeinated product would you be?
Oh, cappuccino, no doubt.
I guess he sees himself as serious on the bottom, but like a little bit frothy and sweet on the top.
You know, he didn't refer to himself that way, but based on my conversation with Greg,
I would say that's an accurate description of him.
Buttercup has been removed for the moment.
So Greg did this like pretty unique study where he got people to either drink coffee or not drink coffee at random.
And then he was able to like precisely measure exactly how that affected their sleep.
Ooh, okay.
So they recruited about 100 coffee drinkers in San Francisco.
They put a bunch of stuff on them.
They wore a Fitbit, which measured how well they slept and their steps.
And they wore a portable heart monitor.
So it's essentially like a very big Band-Aid.
And it goes on the chest to the left of the sternum, essentially.
And like, interestingly,
in the middle of the sticker, there's this big button.
We instructed them, just push that button whenever you have a cup of coffee or a caffeinated drink.
So you have your coffee and you hit your button.
And one way they made sure that people were doing what they were supposed to do,
you know, not drinking coffee if they weren't supposed to that day.
They had everyone in the study get this app on their phone that allowed the team to monitor their location.
So the team could see if they've been drinking coffee or not.
They visited coffee shops.
So if they went to a coffee shop on a day they weren't supposed to have caffeine,
that would be highly suspicious.
Would they get like, would there be like a bright, a button goes off in your office?
Like a flashing red light?
Would they get an electric shock?
Yeah, that's a good idea.
Interesting idea.
That's exactly what I was thinking.
Well, luckily for the people in the study, we didn't design it.
They did not get shocked.
Oh, okay.
Okay.
So.
I'm going to, I'm going to go out on a limb here, Rose,
and say that on average, coffee did affect people's sleep.
Yes, but the key question here is how much?
Because there is this idea that coffee just really robs you of your sleep.
Well, in reality, Greg found.
On days where people were randomly assigned to consume coffee,
that evening, they on average slept 30 minutes less.
Duh!
Yeah, so on average, if they were in the coffee,
drinking group, they had half an hour less sleep.
And Greg could even dive into the research and figure out
how much sleep each cup of coffee cost these people.
And it turns out about 15 minutes of sleep.
Okay, so loosely for every shot of espresso or just like regular coffee,
you'll get around 15 minutes less sleep a day.
Uh-huh.
Okay.
Yes, but.
That's not terrible.
That's not.
Oh, oh, oh, but.
There is an important.
Caveat, which is that Greg found this really varied from person to person
based on their genetics.
So on top of all that other stuff,
Greg also took saliva samples from people
and worked out if they had these genes that make them either a fast
or a slow metabolizer of caffeine.
And he found that the slow metabolizers lost closer to an hour of sleep a night.
Oh, wow.
And the fast metabolizers lost basically no sleep at all.
Huh.
So people who say, oh, yeah, I can have a, you know, cup of coffee at night.
I go right to sleep.
They may be really telling the truth.
My mom proudly says that she can drink coffee like at dinner time
and it will not affect her sleep to the point where she will mock me
when she wants a coffee at 4 p.m.
And I say too late for me.
Mama Zook vindicated once more by a Science Versus episode.
Well, it's like you're both right.
She's right that she can have a coffee late at night.
And you're right that you can't.
You're probably both right.
Okay.
But you know who isn't right?
Is those people online, influencers, I don't know what we want to call them.
Anyway, who have these like definitive statements about how much coffee
you're allowed to drink and you need to stop at 10 a.m.
and you can only drink two cups or whatever they're saying.
Like actually what the science says is this is very dependent on your genetics.
And those black people.
Those blanket statements are kind of bollocks.
Yeah.
Okay.
So that's sleep.
But Greg's study looked at something else that people don't necessarily associate
with having a cup of coffee.
And that is exercise.
So on top of measuring sleep, he also measured how many steps they took every day.
And.
On days randomly assigned to coffee, participants on average exhibited a thousand more steps
on those days.
Wow, that's a lot.
It is a lot.
And in fact, there's other evidence that that magnitude of a difference
may be meaningful in the long run in enhancing longevity.
Oh, wow.
Yeah.
For example, one study found that older women who take 5,000 steps a day
live longer than similar women who took 4,000 steps a day.
Oh, that's cool.
And it's not just step count.
We actually have a lot of data showing that caffeine can help us athletically.
So when people have caffeine before they exercise, they tend to go a little harder.
So, like, people will be able to run for longer or, for example, do more squats.
Cool.
There's a study that looked at swimmers doing a 1,500-meter race, so that's almost
a mile.
And it found that having some caffeine beforehand shaved 23 seconds off their time, compared
to a placebo.
And having caffeine before exercise is considered safe as long as you have caffeine before exercise.
long as you don't overdo it. Like the equivalent of one or two coffees before exercising. Wow.
And so why is that happening? Well, you know how caffeine can boost your dopamine.
So that might be like putting us in a better mood so we can work harder. And we also know that
caffeine can kind of turn the dial down on feelings of pain. That's why some painkillers have caffeine
in them. So maybe athletes aren't feeling the burn quite as much. And then finally,
there's some evidence that caffeine can actually increase the amount of calcium.
getting released by your cells, which could make your muscles work better.
So, Wendy, do you still feel guilty about your coffee?
Oh, no.
Thus far, no, but at the same time, we haven't really talked about risks yet.
Good point.
So next we're going to talk about is caffeine addictive and what's going on with the scary
stories we hear about people dying after drinking energy drinks.
And that's coming up just after this quick coffee break.
Welcome back.
Today on the show, we are asking, should you quit your caffeine?
Should you just spit out your coffee, spill your tea on the floor?
Say goodbye to your energy drinks?
Rose Rimler, senior producer at Science Versus, is telling us all about it.
Hey, Rose.
Hey, Wendy.
So the next thing I want to dive into is this idea that you can get addicted to caffeine.
Mm-hmm.
You know, and I think a lot of that comes from this, like, terrible withdrawal that
some people have when they stop it.
Now, caffeine withdrawal is a real thing.
And people who quit coffee all of a sudden can totally feel sick.
Like, about half of them will get a headache.
This could be because caffeine restricts blood flow to the brain.
And when we go off it, the blood whooshes back in.
Oh, wow.
Some people even feel like they have the flu and they feel, like, really tired and crappy.
So send them help.
So pray for them.
Do I need to pray for them?
Do I?
Like, if suddenly there was an apocalypse and they couldn't get their coffee, how bad
would it be?
All those symptoms, they go away for most people somewhere between two to nine days.
Okay.
So if they can survive for nine days, they'll be back to normal.
Yes.
Just hunker down.
In your bunker.
Hunker in your bunker.
Great.
And it'll play itself out.
Right.
Okay.
But back to this addiction thing.
So, you know, you might reasonably call yourself dependent on caffeine if you feel sick without it.
But that's not the same thing as addiction.
With addiction, what experts point to is that you are using a substance even though it's
bad for you.
It has negative consequences on your life.
Maybe you even, like, really want to quit and you can't.
And I think right now, the general idea among scientists is that this is not a problem for
most people.
They don't really see any evidence of this, like, negatively affecting people.
Right.
For most people.
And then what about tolerance?
Like, this idea that you need to have more and more caffeine to have the same effect.
Yeah.
We typically don't really see that with caffeine.
Really?
And one reason is probably that at a high dose, caffeine starts to activate this other type
of adenosine receptor in our brain that causes anxiety.
Oh, this is why you get all, like, jittery and like, oh, if you have too much caffeine.
There's sort of a threshold you can cross from all the feeling, like, alert and energetic
and kind of good to, oh, now I feel anxious and jittery and weird.
And one researcher I spoke to said that for caffeine specifically, this window, this,
he calls it a window between the good and the bad feelings, is pretty short.
So you can kind of easily.
You can easily tip yourself over when you've had more caffeine into that anxious feeling.
And if you're starting to feel that way, you know, many people would probably put down
their third venti frappuccino of the day, you know, at that point.
So there's kind of a natural cap for most people on how much caffeine we're going to
drink every day.
Yeah.
Yeah, yeah, yeah.
You know, because recently I did, I was like, fuck it, I'm just going to drink more coffee.
And it did make me feel anxious.
And so I was like, no, no, no, just go back to one or two cups.
Like, just, yeah, this isn't, go for a run instead or whatever.
Yeah, it's not like worth it to most people.
Yeah.
At a certain point.
And, you know, this can be different if you're mixing caffeine with other drugs.
That's more dangerous.
But bottom line, caffeine is not considered a drug of abuse.
There is no caffeine use disorder in the DSM, you know, the big manual for psychiatric disorders.
It's been proposed, but right now it's not officially in there.
Okay, so, so for now we could say science says caffeine isn't really that addictive.
Is that where we're at?
I think, I think so.
I think, yeah.
Yeah, I think so.
So thus far, all right, it doesn't, it's really not seeming like caffeine is that bad.
And I'm trying to think why I thought caffeine was bad for you.
I actually might have an answer.
In the 90s, there was news that coffee was a bad thing.
It was associated with bladder cancer.
Oh, really?
But that has been debunked in more recent years.
Oh, okay.
Turns out it was not a real association.
But even if you don't remember that stuff about bladder cancer, I think that sort of
percolated, so to speak, in the culture.
And we haven't quite gotten over it.
Uh-huh.
Okay.
Plus, there's a lot of fears around pregnancy and caffeine.
Right.
And that is something to think about because we know that caffeine can cross the placenta
and get to the fetus.
And so,
Drinking a lot of caffeine when you're pregnant isn't recommended.
Uh-huh.
But, you know, health guidelines from around the world, they say you can have one or two
cups of coffee a day if you're pregnant.
Right.
You know, overall, just putting aside pregnancy, I walked away feeling pretty reassured about
caffeine because here's something that I thought was, like, really kind of great.
So, it turns out that people who drink coffee have a lower risk of Parkinson's disease,
depression, type 2 diabetes.
And heart disease.
Really?
And although we once thought coffee was carcinogenic, more recent studies have found that it actually
might reduce your risk of some cancers.
What?
Like liver and breast cancer.
Are you kidding me?
Are you serious?
Like, yeah.
And even drinking coffee is associated with being less likely to die earlier.
So, the biggest benefits are seen in people who drink two to three cups a day.
But even at higher amounts, we still have people apparently getting some benefit.
Like, once they're drinking coffee, they're less likely to die.
One study looked at people drinking as much as eight cups of coffee a day and found they
still lived a little longer than people who didn't drink any coffee.
Wow.
Yeah.
I mean, there aren't that many people that drink eight cups of coffee a day.
So, that's kind of a smaller sample size.
But I think that point stands that the science suggests that coffee is not actively harming
you.
And caffeinated tea also seems to be good for us.
I mean, are we sure?
Are we sure about this?
Like, why would caffeine, why would coffee and tea have these benefits?
Nobody totally knows.
It could have something to do with the exercise boosts you get from caffeine.
Because like we said earlier, like walking more steps a day.
But also, it could be that it's not really about the caffeine.
It's about the other stuff that's in the plant.
So, the coffee bean, the tea leaf.
There's a lot of stuff in there that's really good for us and is anti-inflammatory and has
antioxidant potential.
Wow.
I'm feeling very good about my coffees.
I was not expecting this from Simon.
But thank you.
Anytime.
So then, what, I don't want to, I don't want to crap all over this party.
Is that how that phrase goes?
Yes.
Rain on your parade?
Yes, yes.
Is that what?
That's a very, it's a visceral expression.
You see, I don't know if I have a good sense of humor or I just laugh so much at myself.
because he's actually been in touch with the parents of kids who have died.
after drinking energy drinks.
Yeah, we've had emails from other countries,
one where somebody's like,
I have kept the drink that my kid drank
from the time when they drank it
just in case it helps future scientists.
I'm happy to give you that drink.
Oh, that's heartbreaking.
Yes.
So Sachin, who's a professor of pharmacy
at the University of the Pacific in California,
he wanted to know why would anyone die
after drinking a couple of energy drinks?
Yeah, yeah.
So to get to the bottom of it,
he did this study where he got people
to drink a couple of energy drinks
and then looked at what their heart was doing.
Because typically what we see in these cases
is that someone's heart stops beating
shortly after drinking energy drinks.
So he got these volunteers to come into the lab.
He hooked them up to an EKG.
Many people see this on TV shows
when they have somebody in the hospital,
they're connected to this screen,
they're lying in the hospital,
they show this squiggly line.
Yes, yes.
That's looking at your heart rhythm.
Beep, beep, beep.
Yes.
Just to avoid us putting the sound effect in.
Always thinking ahead.
Okay, so they've drunk the energy drinks.
And then he monitored them.
And one hour, two hours, four hours,
six hours, and 24 hours.
And he was looking at this particular part
of our heart's rhythm that's called the QT interval,
which is basically looking at
how long it takes your ventricles to contract
after every beat.
And if this takes longer than normal,
it can throw your heart into something
that's called fibrillation,
which is like instead of going squeeze, squeeze, squeeze,
your heart starts quivering like a nervous chihuahua.
And the problem with that is that
your heart isn't actually pumping out any blood
and you can die.
Oh, man.
Okay, so did the energy drinks
muck up the QT interval?
So, yeah.
So, you know, what was interesting
is in that first study,
we found that energy drinks
were prolonging the QT interval by 10 milliseconds.
A follow-up study he did found this again,
that the energy drinks extended the QT interval
by, this time, six milliseconds.
And Sachin points out that several drugs
have been pulled from the market
for prolonging the QT interval by six milliseconds.
Mmm, wow.
Okay, so if I were to drink the equivalent
caffeine,
caffeine from what he gave them,
but in coffee,
would my QT interval be extended like that?
No.
Studies have also looked at this for caffeine or for coffee
and they don't find the same thing.
And actually in Sachin's study,
in one of his studies,
they included a caffeinated control
and it didn't do the same thing to people's hearts.
So if energy drinks are doing this,
why aren't heaps of people,
like getting heart attacks
and dying after drinking energy drinks?
I mean, millions of people must be guzzling this stuff
and only a handful have died or so?
Yeah, I mean, it's not like anyone in Sachin's study
had to be rushed to the hospital.
Right, right.
But the thinking here is that there are some people
who could be really vulnerable to this.
Like people who have heartbeats
that already have kind of a long QT interval
and then the energy drink might extend it even more.
And that could tip you over into,
wow, what territory.
Right, right.
One study actually found this.
It gave energy drinks to people
with a heart condition like that
and found that the drinks extended their QT interval
in such a way it was actually dangerous.
Uh-huh.
So then, so then can we go back to that point?
Like if it wasn't the caffeine,
if it's not the caffeine doing this,
then what is it in energy drinks that's causing this?
Yeah, I mean, in Sachin's study,
they tested a couple different brands.
They both had caffeine, taurine, which is an amino acid,
and a supplement called glucuronolactone,
which is found in a lot of energy drinks, like Red Bull.
So this is the ingredients.
This is how we get wings.
Is that right?
This is the wing recipe, yes.
Okay.
So all this stuff together seemed to extend the QT interval.
But then I found this one study
that tried to really get to the bottom
of which ingredient is the bad guy here.
So they basically deconstructed a Red Bull
and had people drink a few of the components one at a time
while they were hooked up to an EKG, just like Sachin.
And after drinking the Red Bull,
volunteers had a prolonged QT interval.
But none of the individual components did this.
What?
Neither did the combination of caffeine and taurine together.
So I asked Sachin about this.
What do you think is in these energy drinks that causes these changes?
That's the million-dollar question.
Science!
You know, I was having coffee with my brother the other day,
and he said there is always a point in a Science vs. episode
where the scientist says,
yeah, we don't really know what's going on.
And I guess this is that point.
Yeah, we've arrived at that point in the episode.
And of course, it's also really hard to say what's going on
when this is probably very, very rare, you know.
People drink energy drinks all the time,
and very few people land in the hospital.
Okay, so here is what I think I have learned from this episode, Rose Rimla.
Tell me how I did.
Let's hear it.
And if I pass the test, I have a good sense of humor.
Is that what we learned?
Yeah.
Yes.
Case closed.
Caffeine truly does make me poo very quickly.
It can affect your sleep, but very much dependent on genetics.
So dare I say, listen to your body.
And not what people online might be telling you
about what you should and should not do with caffeine.
And meanwhile, it might reduce your risk of depression
if you're drinking coffee and tea.
What did you say?
Cancer, Parkinson's.
Diabetes.
Diabetes and energy drinks.
There is something weird about them.
So if you are looking for a boost,
it's safer to go with tea or coffee.
How'd I do?
A plus, people.
I'm not surprised.
And you, as a prize, I sent a case of Prime to your house.
So don't drink it all at once.
Excellent.
Cheers, Rose.
Cheers.
But before you go, Rose.
Rose.
Rose.
I'm here.
I'm still here.
Okay.
Okay.
How many citations are in this week's episode?
This episode was the first time I've ever opened so many tabs that my browser stopped
displaying.
Like, I reached the limit of how many tabs I can have open.
That is so many tabs.
It's like getting to the end of your Instagram feed.
You're like, oh, no.
But what is in the script is that we have 118 citations.
118.
Okay.
Yes.
And if people want to see these citations, find out where we got all of our info from,
where should they go?
They can click the link in the show notes that will send them to the transcript.
Excellent.
And I guess while people are scrolling through Instagram and hitting the end, if you have
hit the end of your Instagram, you could just come over to Science Versus.
Was that a segue of like picking up social media accounts?
Thanks.
We are at science underscore VS.
I'm on TikTok at Wendy Zuckerman.
And we will see you next week.
Thanks, Rose.
Thanks, Wendy.
This episode was produced by Rose Rimler with help from me, Wendy Zuckerman, as well as Nick Delrose, Joel Werner and Michelle Dan.
We're edited by Blythe Terrell.
Fact-checking by Sarah Baum.
Mix and sound design by Bumi Hidaka.
Music written by Bobby Lord, Bumi Hidaka, Emma Munger and Peter Lennon.
Special thanks to all of the researchers that we spoke to for this episode, including Dr. Brian Saunders, Dr. Sergi Foray, Professor Andreas Heinz, Professor Christine Curran, Dr. Erica Loftfield, Dr. Felix Oberhofer, Dr. Alan Wayne-Jones,
and Dr. Vijay Yadav.
Extra special thanks to Jason Vittler-Sill and the Zuckerman family.
Science Versus is a Spotify Studios original.
You can listen to us for free on Spotify or wherever you get your podcasts.
We are everywhere that podcasts are.
I guess we're in a lot of places.
If you are listening on Spotify, follow us and tap the bell icon so you can receive notifications whenever we put out a new episode.
And if you like us wherever you are listening, please give us a five-star review.
I'm Wendy Zuckerman.
Talk to you next time.
pleasant stuff.
Podcast Summary
Key Points:
Caffeine is widely consumed, with 85% of Americans using it daily, but fears about its health effects persist, especially regarding energy drinks.
Caffeine works by blocking adenosine receptors in the brain, reducing sleepiness, boosting alertness, focus, and reaction time, and can even improve athletic performance and humor appreciation (though not proven for humor).
Effects on sleep vary by genetics
Caffeine is not considered truly addictive; withdrawal symptoms (headaches, fatigue) last 2–9 days, but there’s no caffeine use disorder in the DSM, and tolerance is limited by anxiety at high doses.
Coffee and tea are linked to lower risks of Parkinson’s, depression, type 2 diabetes, heart disease, and some cancers, with benefits seen up to 8 cups daily, likely due to antioxidants and lifestyle factors.
Energy drinks, unlike coffee, can prolong the QT interval in the heart, potentially causing dangerous arrhythmias, but the specific ingredient responsible is unknown, and risks are rare.
For pregnant people, one to two cups of coffee daily is considered safe, but high intake is discouraged.
Summary:
This episode of Science Versus explores whether caffeine is harmful, addressing common fears about addiction, sleep disruption, and energy drink risks. Caffeine, consumed by 85% of Americans, works by blocking adenosine receptors in the brain, reducing sleepiness and enhancing alertness, focus, and reaction time—potentially even saving lives in driving studies. However, its impact on sleep varies genetically: slow metabolizers lose up to an hour of sleep per night, while fast metabolizers lose almost none, debunking blanket advice about cutoff times.
Coffee also boosts physical activity, adding about 1,000 steps daily, and improves athletic performance. Caffeine is not considered addictive in the clinical sense; withdrawal symptoms like headaches and fatigue resolve within 2–9 days, and there’s no caffeine use disorder in the DSM. Moreover, coffee and tea consumption are associated with lower risks of Parkinson’s, depression, type 2 diabetes, heart disease, and some cancers, with benefits seen even at high intakes.
However, energy drinks pose distinct risks: they prolong the heart’s QT interval, potentially triggering fatal arrhythmias, though the exact culprit remains unknown—caffeine alone doesn’t cause this. While rare, these cases are tragic, and experts suggest choosing coffee or tea over energy drinks for a safer boost. Overall, caffeine appears safe for most people, with benefits outweighing harms, but individual genetics and drink type matter.
FAQs
Caffeine blocks adenosine, a molecule that makes you feel sleepy, from binding to receptors in the brain. This prevents the feeling of sleepiness, which is why you feel more alert.
On average, people sleep about 30 minutes less on days they drink coffee, with each cup costing roughly 15 minutes of sleep. However, this varies greatly by genetics—slow metabolizers can lose up to an hour, while fast metabolizers lose almost none.
Caffeine can cause physical dependence, with withdrawal symptoms like headaches lasting 2-9 days, but it's not considered a drug of abuse. Experts don't see it as addictive for most people because it rarely leads to negative consequences or an inability to quit.
Yes, caffeine can boost athletic performance. Studies show it helps people run longer, do more squats, and even shave 23 seconds off a 1,500-meter swim, likely due to increased dopamine, reduced pain perception, and improved muscle function.
Yes, drinking coffee or tea is linked to a lower risk of Parkinson's disease, depression, type 2 diabetes, heart disease, and some cancers. Benefits are strongest at 2-3 cups a day, with even 8 cups a day still associated with living longer.
Energy drinks can prolong the heart's QT interval, which can lead to dangerous heart rhythms, while coffee doesn't have this effect. The exact ingredient causing this is unknown, as caffeine alone or with taurine doesn't replicate the effect.
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