Caffeine: How Much Is Too Much?

Summary

Science Vs – “Caffeine: How Much is Too Much?”

Spotify Studios | Host: Wendy Zuckerman | Airdate: June 18, 2026

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Episode Overview

This episode tackles the world’s favorite stimulant — caffeine. The Science Vs team investigates what caffeine does to our bodies and minds, examines common concerns about sleep, addiction, and scary headlines about energy drink deaths, and asks: How much caffeine is safe, and does it actually have health benefits? Featuring leading researchers, the episode separates science from hype in an engaging, humorous style.

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Key Discussion Points and Insights

1. Why Worry About Caffeine? Hype, Guilty Pleasures & Deadly Headlines

• Caffeine’s prevalence: 85% of Americans consume caffeine daily, including children.
• Ongoing fears: “Your cup of coffee could soon come with a spoonful of cancer warning.” (Wendy Zuckerman, 00:19)
• Scary recent energy drink deaths: High-profile cases of teenagers dying after consuming energy drinks spark lawsuits and media coverage.
• Episode goal: To dig into what caffeine (and energy drinks) really do to us — are we waking up or risking our lives?

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2. What Does Caffeine Do to Your Body and Brain?

The Gut Reaction

• Coffee activates digestion quickly—often sending some folks to the bathroom soon after consumption.
  • “Once the coffee gets to your stomach, it’s basically going to wake up your guts.” (Rose Rimler, 05:42)
  • Notable quote: “Some scientists in the ‘80s got permission to stick probes up people’s buttholes… to see if there’s an actual physical change… after coffee.” (Rose Rimler, 06:10)
• Timestamps:
  • [05:41] What happens when you drink coffee
  • [06:56] Measurable effects in “responders”

Caffeine & The Brain: The Wake-Up Call

• Caffeine crosses the blood-brain barrier, blocking adenosine ("the sleepy molecule"), creating alertness.
  • “You drink your coffee and all of a sudden your whole body, including your brain, gets invaded by these caffeine molecules.” (Astrid Nilig, 08:59)
  • Caffeine doesn’t stimulate directly — it blocks signals that make you sleepy.
• Timestamps:
  • [08:36] Caffeine’s journey to the bloodstream/brain
  • [09:55] Mechanism of action

Performance Boost — Is It Real?

• Caffeine improves alertness, focus, reaction time, and even physical performance; “if you’re facing a lion… you will react faster after caffeine.” (Astrid Nilig, 10:27)
• Real-world studies show caffeine helps fatigued people drive more safely at night ([11:01]) but doesn’t improve their sense of humor ([12:52]).

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3. Caffeine and Sleep: Is It Ruining Your Rest?

• Unique sleep study: Dr. Gregory Marcus randomized 100 coffee drinkers to have or skip caffeine. Sleep, steps, and heart data tracked with Fitbits and monitors.
  • On average, having coffee in the evening = 30 minutes less sleep.
  • Each cup/shot = ~15 minutes less sleep.
  • Genetic differences: Slow caffeine metabolizers lose nearly an hour of sleep; fast metabolizers aren’t affected. “So people who say, ‘Oh yeah, I can have a coffee at night, I go right to sleep,’ may be really telling the truth.” (Gregory Marcus, 17:56)
• Takeaway: The effect of caffeine on sleep is highly individual; blanket online advice is “kind of bollocks.” (Wendy Zuckerman, 18:36)
• Timestamps:
  • [15:03] Describing the coffee/sleep study
  • [16:44] Sleep impacts (30 min less)
  • [17:49] Genetics and sleep

Caffeine & Exercise

• On coffee days, participants walked 1,000 more steps.
• Caffeine boosts exercise performance (e.g., swimmers swam a 1500m race 23 seconds faster).
• Mechanisms: mood and motivation (dopamine), reduced pain perception, and possibly more efficient muscle contraction due to increased calcium release.

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4. Is Caffeine Addictive? What About Withdrawal?

• Withdrawal: About half suffer headaches, some get “flu-like” symptoms, but most symptoms disappear within 2–9 days.
• Addiction vs dependence:
  • Dependence = feeling unwell if you suddenly stop
  • Addiction = using despite harm, unable to quit
  • Science says caffeine isn’t typically considered addictive: “There is no caffeine use disorder in the DSM… not officially in there.” (Rose Rimler, 28:01)
• Tolerance: Most people don’t need to escalate their dose; too much brings on anxiety and jitters, so there’s a “natural cap.”
  • “This window between the good and the bad feelings is pretty short.” (Rose Rimler, 27:04)
• Timestamps:
  • [25:04] Withdrawal symptoms
  • [26:03] Difference between dependence and addiction

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5. Health Risks and Benefits: Is Caffeine Bad for You?

• Past cancer fears (like bladder cancer) have been debunked.
• In pregnancy, high doses best avoided, but moderate consumption is fine (1-2 cups/day).
• Benefits: Coffee drinkers have lower risk of Parkinson’s, depression, type 2 diabetes, heart disease, and may also see reduced cancer risk (e.g., liver, breast).
  • Even heavy drinkers (up to 8 cups/day) may live longer than abstainers. “The science suggests that coffee is not actively harming you.” (Rose Rimler, 30:35)
• Uncertainty about cause: Might be caffeine, might be other compounds (antioxidants, anti-inflammatories) also present in coffee/tea.
• Timestamps:
  • [29:36] Pregnancy and caffeine
  • [29:58] Health benefits summary

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6. Energy Drinks: Why Are They Linked with Young People’s Deaths?

• Caffeine content usually modest: Prime Energy = 200mg caffeine (“two shots of espresso” — [32:55]).
• Overdose threshold ≈1200mg (6 cans of Prime); but deaths reported at much lower doses — mystery!
• Research focus: Dr. Satchin Shah studied the impact of energy drinks on heart rhythm (QT interval).
  • Energy drinks (not regular caffeine) prolonged QT interval 6–10 milliseconds. Drugs have been pulled from the market for this effect.
  • Coffee/caffeine alone didn’t prolong the QT interval.
• What ingredient is to blame?
  • Not clear. Isolated components (caffeine, taurine, glucuronolactone) didn’t have this effect alone or together; only the energy drink “cocktail” did.
  • Vulnerable people (with a long QT heart condition) are at higher risk.
  • “That’s the million dollar question.” (Satchin Shah, 38:56)
• Timestamps:
  • [32:26] Energy drink deaths
  • [33:50] Satchin Shah discusses case reports
  • [36:00] Energy drinks and heart rhythm (QT)

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Memorable Quotes & Moments

• Wendy Zuckerman on caffeine guilt:

  • “You know what? I’m not into meth, but I’m gonna be fine with my caffeine use.” (04:20)

• Astrid Nilig on awkward confessions:

  • “I meet somebody and they ask me what I work, and I say, oh, I work on coffees. And people are very shy all of a sudden and withdrawing a bit and telling me, oh, it’s very bad. I should probably not drink.” (04:48)

• On the coffee/poop connection:

  • “Some scientists in the 80s got permission to stick probes up people’s buttholes.” (06:10, Rose Rimler)

• Humor in science:

  • “There is a scientific test of sense of humor… Panda Mating Fails, Veterinarian Takes Over — that’s headline two, which is funnier?” (12:33, Rose Rimler & Wendy)

• Caffeine and sleep:

  • “Each cup of coffee cost these people about 15 minutes of sleep…” (17:09, Rose Rimler)

• On energy drinks:

  • “The thinking here is that there are some people who could be really vulnerable… the energy drink might extend [their QT interval] even more and that could tip you over into Chihuahua territory.” (37:13, Rose Rimler)

• Summary of health effects:

  • “I walked away feeling pretty reassured about caffeine… people who drink coffee have a lower risk of Parkinson’s, depression, type 2 diabetes, and heart disease.” (29:36, Rose Rimler)

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Actionable Takeaways

• Sleep: Caffeine cuts sleep, but the impact depends on your genetics. Some people really can have coffee late with no effect.
• Addiction: Withdrawal happens, but “addiction” is rare.
• Health: Moderate caffeine (coffee/tea) seems not only safe but potentially beneficial, outside special groups (e.g., pregnant women).
• Energy drinks: Not simply about “too much caffeine”—some ingredient combinations may rarely trigger dangerous heart rhythms in vulnerable people.
• If concerned: Listen to your individual response, not online myths.

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Important Segments & Timestamps

• [05:41-07:31] — Coffee and digestion: why it makes some people need to poop
• [09:55-11:33] — Caffeine’s effect on alertness and a real-world driving study
• [15:03-17:19] — Large sleep study: how caffeine affects sleep and the influence of genetics
• [19:15-20:30] — Caffeine and exercise: more steps, improved athletic performance
• [25:04-28:01] — Caffeine withdrawal and the science of addiction
• [29:36-31:21] — Health risks, benefits, and debunked cancer links
• [32:26-39:28] — Energy drinks, heart risks, and the QT interval mystery

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Conclusion & Recap

• Caffeine’s gut and brain effects are immediate and measurable (and sometimes funny).
• For most people, moderate coffee or tea is safe, can boost alertness and even provide health benefits; effects on sleep really do depend on individual biology.
• Energy drinks pose a rare but real risk for some, and it’s not only the caffeine content that matters.
• The true “danger” of your morning brew? Mostly just going to the bathroom.
• “Listen to your body and not what people online might be telling you about what you should and should not do with caffeine.” (Wendy Zuckerman, 40:04)

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For links to studies, see the episode transcript—this episode contains a remarkable 118 citations!

Transcript

[Wendy Zuckerman]

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

[Co-host/Interviewer]

drugs in the world.

[Wendy Zuckerman]

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.

[Sponsor/Ad Voice]

My heart was racing. I was super anxious. Something was happening. I was having a panic attack.

[Rose Rimler]

Could it all be a sign, though, of a serious problem? A problem like caffeine addiction?

[Wendy Zuckerman]

And our worries around caffeine have reached new heights when it comes to energy drinks. Just Last year, a 17 year old from Texas died after drinking Alani New.

[Gregory Marcus]

A Texas family is filing a wrongful

[Rose Rimler]

death lawsuit over an energy drink that they claimed killed a teenage girl.

[Wendy Zuckerman]

According to family lawyers, a coroner's report

[Rose Rimler]

shows that she died from an enlarged heart caused by stress and a large

[Wendy Zuckerman]

amount of caffeine from Aulani 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 scary stories from the past several years of people, often younger people, dying soon after drinking energy drinks.

[Rose Rimler]

Davis collapsed in the classroom of his

[Dan Heath]

high school in South Carolina.

[Rose Rimler]

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.

[Wendy Zuckerman]

So today on the show, 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.

[Sponsor/Ad Voice]

My heart was racing.

[Wendy Zuckerman]

But then there's science. Science versus caffeine is coming up just after the break. Now on Acorn tv, there's a killer on the loose. Brooke Shields stars in the new original murder mystery. You're killing me.

[Sponsor/Ad Voice]

You spin some crackpot theory and I find the evidence.

[Wendy Zuckerman]

I solved mysteries for a living.

[Astrid Nilig]

I think I'm good to go.

[Rose Rimler]

Murder has met its match. You cannot be here. This is a police investigation.

[Astrid Nilig]

I've written you. What does that mean?

[Wendy Zuckerman]

He was a big city cop with a small jurisdiction.

[Rose Rimler]

Boomers are so cute and they flirt.

[Wendy Zuckerman]

You're killing me. All new episodes now on Acorn TV.

[Sponsor/Ad Voice]

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[Wendy Zuckerman]

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.

[Rose Rimler]

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. 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?

[Wendy Zuckerman]

Yes. I love. 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 gonna be fine with my caffeine use. You know, I felt guilty about it, and I do wanna know whether I. I need to. So where do we begin?

[Rose Rimler]

Let's start with Astrid Nilig. She's a caffeine researcher, and she says she hears this idea about people feeling guilty about their caffeine intake all the time.

[Astrid Nilig]

I meet somebody and they ask me on what I work, and I say, oh, I work on coffees. And people are very shy all of a sudden and withdrawing a bit and telling me, oh, it's very bad. I should probably not drink.

[Rose Rimler]

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 gonna walk you through what caffeine is doing to your brain and to your body.

[Co-host/Interviewer]

Okay?

[Rose Rimler]

So, Wendy, I asked you to come prepared with your favorite caffeinated beverage that's right. So what did you bring today?

[Wendy Zuckerman]

I have an oat cappuccino.

[Rose Rimler]

Okay. Take a sip.

[Wendy Zuckerman]

Should I do it like ASMR or if I'm.

[Co-host/Interviewer]

I guess if you have misophonia. Just chewed out.

[Rose Rimler]

Okay, so I'm going to tell you what it's doing right now.

[Wendy Zuckerman]

Okay.

[Rose Rimler]

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.

[Astrid Nilig]

So it's really an activator of digestion.

[Rose Rimler]

Is that why? Not to be crude, but sometimes you have to go number two after you drink coffee.

[Astrid Nilig]

Yeah. At least in some especially sensitive individuals. Yeah, it's like that.

[Rose Rimler]

We know this because thankfully some scientists in the 80s got permission to stick probes up people's buttholes.

[Astrid Nilig]

Oh.

[Rose Rimler]

And then give them coffee to see what happens. And the reason they wanted to test it this way is 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 on this 100 person survey said, yeah, actually coffee makes me have to poop. So they got some of these people and some other 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?

[Wendy Zuckerman]

And what did they find in the

[Rose Rimler]

people who said, yes, coffee does this to me. They could actually measure increased rectal activity.

[Wendy Zuckerman]

Oh, so that I'm clenching. I'm clenching. Have you been clenching as you've been reading this research?

[Rose Rimler]

No, I'm quite relaxed.

[Astrid Nilig]

Oh, okay.

[Co-host/Interviewer]

As soon as you said increased rectal activity, I was just like, well, I

[Rose Rimler]

like kind of, I like thinking about like these sort of peristalsis of your butthole. You know, like disgraceful how food gets down. It's something else has to make it come out. And that increased right. In response to coffee for some people.

[Wendy Zuckerman]

Interesting. Okay, I have a very important question.

[Rose Rimler]

Yeah.

[Wendy Zuckerman]

How quickly, how quickly does this activation happen? Because it can happen within minutes. Oh my God.

[Co-host/Interviewer]

I feel so validated.

[Astrid Nilig]

Wow.

[Wendy Zuckerman]

Because I like, I will sometimes just take a few sips of coffee and just like need to do a. 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.

[Co-host/Interviewer]

But it can.

[Additional Voice (possibly crew member)]

It can.

[Wendy Zuckerman]

Like, just so you know, Rose, because this is my first coffee for the day.

[Co-host/Interviewer]

Yeah.

[Rose Rimler]

If you have to. If you have to run off, I'll know what. No, I don't.

[Wendy Zuckerman]

Cause I took a couple of sips

[Co-host/Interviewer]

before our chat, and I'm all sorted

[Rose Rimler]

and took care of business. I appreciate that level of planning. Always come prepared.

[Wendy Zuckerman]

That is me.

[Rose Rimler]

Okay, so that's how coffee can affect the gut. And from there, caffeine starts getting absorbed in your bloodstream.

[Wendy Zuckerman]

Okay.

[Rose Rimler]

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.

[Astrid Nilig]

Yes.

[Rose Rimler]

I just imagine my brain is a sponge that just soaks up the coffee. Is that. Is that kind of right?

[Astrid Nilig]

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.

[Rose Rimler]

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 claim to fame. And this happens because caffeine basically barges into the brain and like, elbows out this molecule called adenosine from these special receptors. And what adenosine is, it's like the sleepy molecule. So it, like, binds the 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 gonna buy into those adenosine receptors, and that means you don't feel as sleepy.

[Wendy Zuckerman]

So just to get real nerdy here, it's not that caffeine is binding onto these receptors and going, let's go, brain, get excited.

[Co-host/Interviewer]

It's rather the lack of adenosine, the lack of sleepiness that wakes you up.

[Rose Rimler]

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 faster.

[Astrid Nilig]

This has been quite extensively studied. This is clear. So for if I take a stupid example, but please, you. You are facing a lion. If you have been drinking caffeine, you will react faster and you will run away before.

[Rose Rimler]

Could save your life.

[Astrid Nilig]

Yeah. Of course. Absolutely. Could make a difference and save your life.

[Rose Rimler]

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.

[Co-host/Interviewer]

Amazing. And they got away. They got away.

[Rose Rimler]

Some got away, some didn't.

[Wendy Zuckerman]

That's right.

[Co-host/Interviewer]

Those in the placebo group were less likely to get away. We are joking.

[Rose Rimler]

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.

[Co-host/Interviewer]

Oh my God.

[Rose Rimler]

They had a driving instructor in the next seat who could take over control. Things were getting bad.

[Co-host/Interviewer]

Thank goodness.

[Rose Rimler]

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.

[Co-host/Interviewer]

Okay.

[Wendy Zuckerman]

The powers of caffeine.

[Rose Rimler]

Yes.

[Astrid Nilig]

Right.

[Rose Rimler]

And then I found this study that just made me laugh because it's just so such a funny concept. These 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. It takes a hit. So the researchers were wondering, would caffeine give us back our sense of humor or improve that?

[Wendy Zuckerman]

Uh huh.

[Rose Rimler]

And I don't know if you know this, Wendy, but there is a scientific test of sense of humor.

[Co-host/Interviewer]

Oh my gosh.

[Wendy Zuckerman]

That was entirely my next question. What is the joke that scientists ask that? They're like, if you find this funny,

[Co-host/Interviewer]

you have a good sense of humor,

[Rose Rimler]

then you're operating on full cylinders.

[Wendy Zuckerman]

Yes.

[Rose Rimler]

Yeah. So they would show them like two different pictures and ask which picture is funnier or. 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.

[Wendy Zuckerman]

I feel very cocky about my sense of humor.

[Rose Rimler]

Okay, so here's the, here's the example. Which of these two headlines is funnier? Veterinarian investigates Failed Panda mating. It's headline one. Or Panda Mating fails Veterinarian takes over. That's headline two, which is funnier.

[Wendy Zuckerman]

Headline two is funnier because it suggests. I mean, headline one isn't funny at all. Right. But headline two suggests just something really, really disturbing, actually.

[Rose Rimler]

And the third headline is Veterinarian Pand. You're right, it is the Second headline. Yes, according to science, that is objectively funnier, which I guess it is.

[Wendy Zuckerman]

Although I'm so proud of them for being a little. A bit naughty.

[Rose Rimler]

Well, it turns out that the caffeine in this case did not help people.

[Co-host/Interviewer]

Yeah, I totally forgot we were talking about caffeine.

[Rose Rimler]

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.

[Wendy Zuckerman]

Yes, I have worried about this, too, and in fact, cut down on caffeine because I've been worried about this.

[Rose Rimler]

So let's meet Gregory Marcus.

[Gregory Marcus]

I'm just going to move my dog.

[Astrid Nilig]

Come on, hon.

[Rose Rimler]

He's a cardiologist and a professor of medicine at ucsf. If you could be any caffeinated product, which caffeinated product would you be?

[Gregory Marcus]

Oh, cappuccino, no doubt.

[Wendy Zuckerman]

I guess he sees himself as serious on the bottom, but, like, a little bit frothy and sweet on the top.

[Rose Rimler]

You know, he didn't refer to himself that way, but based on my conversation with Greg, I would. I would say that's an accurate description of him.

[Gregory Marcus]

Buttercup has been removed for the moment.

[Rose Rimler]

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.

[Wendy Zuckerman]

Ooh, okay.

[Rose Rimler]

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.

[Gregory Marcus]

So it's essentially like a very big band aid. And it goes on the chest to the left of the sternum, essentially.

[Rose Rimler]

And like, interestingly, in the middle of the sticker, there's this big button.

[Gregory Marcus]

We instructed them, just push that button whenever you have a cup of coffee or a caffeinated drink.

[Rose Rimler]

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 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?

[Gregory Marcus]

Yeah, that's a good idea. Interesting idea.

[Co-host/Interviewer]

That's exactly what I was thinking.

[Rose Rimler]

Well, luckily for the people in the study, we didn't design it. They did not get shocked.

[Co-host/Interviewer]

Oh, okay.

[Wendy Zuckerman]

Okay, so I'm going to go out

[Co-host/Interviewer]

on a limb here, Rose, and say that on average, coffee did affect people's sleep.

[Rose Rimler]

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

[Gregory Marcus]

where people were randomly assigned to consume coffee that evening, they on average slept 30 minutes less.

[Rose Rimler]

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.

[Wendy Zuckerman]

Okay, so loosely, for every shot of

[Co-host/Interviewer]

espresso or just like regular coffee, you'll

[Wendy Zuckerman]

get around 15 minutes less sleep a day.

[Co-host/Interviewer]

Uh huh.

[Satchin Shah]

Okay.

[Rose Rimler]

Yes.

[Co-host/Interviewer]

That's not.

[Astrid Nilig]

Oh.

[Rose Rimler]

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 on average.

[Co-host/Interviewer]

Oh, wow.

[Rose Rimler]

And the fast metabolizers lost basically no sleep at all. Huh.

[Gregory Marcus]

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.

[Co-host/Interviewer]

My mum proudly says that she can drink coffee like at dinner time and it will not affect her sleep to

[Wendy Zuckerman]

the point where she will mock me when she wants a coffee at 4pm and I say, too late for me, Mama Zook vindicated once more by a science versus episode.

[Rose Rimler]

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.

[Co-host/Interviewer]

Okay?

[Wendy Zuckerman]

But you know who isn't right is those people.

[Co-host/Interviewer]

Online influences, I don't know, I don't know what we want to call them

[Wendy Zuckerman]

anyway, who have these like definitive statements about how much coffee you're allowed to drink and you need to stop at 10am and only drink two cups or whatever, Whatever that they're saying. Like, actually what the science says is this is very dependent on your genetics. And, and, and those blanket statements are kind of bollocks.

[Rose Rimler]

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.

[Gregory Marcus]

And on days randomly assigned to coffee, participants on average exhibited 1,000 more steps on those days.

[Rose Rimler]

Wow.

[Additional Voice (possibly crew member)]

That's a lot.

[Gregory Marcus]

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.

[Wendy Zuckerman]

Oh, wow. Yeah.

[Rose Rimler]

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.

[Wendy Zuckerman]

Oh, that's cool.

[Rose Rimler]

And it's not just step count. We actually have a lot of data showing that caffeine can help us athlet. 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.

[Wendy Zuckerman]

Cool.

[Rose Rimler]

There's a study that looked at swimmers doing a 1500 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 don't overdo it. Like it's the equivalent of one or two coffees before exercising.

[Additional Voice (possibly crew member)]

Wow.

[Wendy Zuckerman]

And so why is that happening?

[Rose Rimler]

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.

[Wendy Zuckerman]

Wow.

[Rose Rimler]

So, Wendy, do you still feel guilty about your coffee? Oh, no. Thus far, no.

[Wendy Zuckerman]

But at the same time, we haven't really talked about risks yet.

[Rose Rimler]

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.

[Wendy Zuckerman]

And that's coming up just after this quick coffee break.

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[Rose Rimler]

this episode

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[Wendy Zuckerman]

Welcome back. Today on the show, we are asking, should you quit your caffeine? Should you 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.

[Rose Rimler]

Hey, Wendy. So the next thing I want to dive into is this idea that you can get addicted to caffeine, 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.

[Co-host/Interviewer]

Oh, wow.

[Rose Rimler]

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?

[Additional Voice (possibly crew member)]

Do I?

[Co-host/Interviewer]

Like, if they, if suddenly there was an apocalypse and they couldn't get their coff, how bad would it be?

[Rose Rimler]

All those symptoms, they go away for most people somewhere between two to nine days.

[Wendy Zuckerman]

Okay, so if they can survive for

[Co-host/Interviewer]

nine days, they'll be back to normal.

[Rose Rimler]

Yes. Just hunker down in your bunker. Hunker in your bunker.

[Co-host/Interviewer]

Great.

[Rose Rimler]

And it'll play itself out. Right.

[Satchin Shah]

Okay.

[Rose Rimler]

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, 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.

[Wendy Zuckerman]

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.

[Rose Rimler]

Yeah, we typically don't really see that with caffeine. 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.

[Wendy Zuckerman]

Oh, this is why you get all

[Co-host/Interviewer]

like jittery and like, if you have

[Rose Rimler]

too much caffeine, there's sort of a, 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, he calls it a window between the good and the bad feelings, is pretty short. So you can kind of 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.

[Co-host/Interviewer]

Yes.

[Rose Rimler]

So there's kind of a natural cap for, for most people on how much caffeine we're gonna drink every day.

[Wendy Zuckerman]

Yeah, yeah, yeah, yeah. You know, because recently I did, I was like, it, I'm just gonna drink more coffee. And it did make me feel anxious

[Co-host/Interviewer]

and so I was like, no, no, just go back to, to one or two cups. Like just, yeah, this isn't. Go for a run instead or whatever.

[Rose Rimler]

Yeah, it's not like worth it to most people at a certain point. 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.

[Co-host/Interviewer]

Okay.

[Astrid Nilig]

So.

[Wendy Zuckerman]

So for now we could say science

[Co-host/Interviewer]

says caffeine isn't really that addictive. Is that where we're at?

[Wendy Zuckerman]

I think, I think so.

[Rose Rimler]

I think, yeah, yeah, I think so.

[Wendy Zuckerman]

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.

[Rose Rimler]

I actually might have an answer. In the 90s, there was news that coffee was associated with bladder cancer.

[Wendy Zuckerman]

Oh, really?

[Rose Rimler]

But that has been debunked in more recent years. 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.

[Astrid Nilig]

Uh huh. Okay.

[Rose Rimler]

Plus There's a lot of fears around pregnancy and caffeine.

[Wendy Zuckerman]

Right.

[Rose Rimler]

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. 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.

[Co-host/Interviewer]

Right.

[Rose Rimler]

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.

[Co-host/Interviewer]

Really?

[Rose Rimler]

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?

[Wendy Zuckerman]

Are you kidding me? Are you sick? Like, yeah.

[Rose Rimler]

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 people apparently getting some benefit. Like, 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.

[Gregory Marcus]

Wow.

[Co-host/Interviewer]

Yeah.

[Rose Rimler]

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.

[Wendy Zuckerman]

I mean, are we sure? Are we sure about this?

[Co-host/Interviewer]

Like, why would caffeine. Why would coffee and tea have these benefits?

[Rose Rimler]

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 is. Has antioxidant potential.

[Wendy Zuckerman]

Wow.

[Co-host/Interviewer]

I'm feeling very good about my coffee. I was not expecting this from science, but thank you.

[Rose Rimler]

Anytime.

[Wendy Zuckerman]

So then what? I don't want to.

[Co-host/Interviewer]

I don't want to crap all over this party.

[Wendy Zuckerman]

Is that how that phrase goes?

[Rose Rimler]

Yes.

[Co-host/Interviewer]

Rain on your parade.

[Wendy Zuckerman]

Is that what I.

[Rose Rimler]

That's a very. It's a visceral expression.

[Co-host/Interviewer]

You see, I don't know If I have a good sense of humor, I just laugh so much at my own jokes.

[Rose Rimler]

I know a test you can take.

[Astrid Nilig]

Great.

[Co-host/Interviewer]

Okay, but, but, but, but, but what

[Wendy Zuckerman]

does this all mean about the energy drinks issue?

[Co-host/Interviewer]

Because to change the tune, to get quite serious, there are these stories about

[Wendy Zuckerman]

energy drinks killing people. So what does this mean?

[Rose Rimler]

Which is the opposite of what I just told you about coffee, right?

[Co-host/Interviewer]

Yeah.

[Rose Rimler]

Well, a lot of times what people say is the problem is that energy drinks are dangerous because they are packed way too full of caffeine.

[Wendy Zuckerman]

Right, right.

[Rose Rimler]

But the funny thing is when you look at the labels, many of them really don't have that much caffeine in them.

[Wendy Zuckerman]

Oh, how much caffeine is in your average energy drink?

[Rose Rimler]

Well, okay, so like Chuck Schumer said that prime energy had an eye popping amount of caffeine. So I looked up the label of prime. It contains 200 milligrams of caffeine.

[Co-host/Interviewer]

What? 200? What, like two shots of espresso? That's it?

[Wendy Zuckerman]

That's it, yeah.

[Rose Rimler]

Two. Two or three, depending on how you make them. I love that you were like.

[Co-host/Interviewer]

So I went deep undercover.

[Wendy Zuckerman]

I bought a Prime and I turned

[Co-host/Interviewer]

it around and I looked at the

[Rose Rimler]

label and of course you can overdose on caffeine. The toxic effects are thought to start at 1200 milligrams, which is about six cans of Prime. And there are case reports of people drinking a bunch of energy drinks and being hospitalized. But here's where things get mysterious. There are reports of people, often younger people, dying after drinking less than that, which suggests this isn't just about caffeine. And Professor Satchin Shah saw reports like that in the news and thought, hey,

[Satchin Shah]

there's something going on here.

[Rose Rimler]

You know, it was actually a little bit sad at points talking to Satchin because he's actually been in touch with the parents of kids who have died after drinking energy drinks.

[Satchin Shah]

Yeah, we've had emails from other countries. One where somebody's like, I have kept the drink that my, 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.

[Co-host/Interviewer]

Oh, that's heartbreaking.

[Rose Rimler]

Yes. So Satchin, 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.

[Satchin Shah]

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 and they show this squiggly line, right, that's looking at your heart rhythm.

[Rose Rimler]

Beep, beep, beep. Yes.

[Wendy Zuckerman]

Just to avoid us putting the sound effect in.

[Rose Rimler]

Always thinking ahead.

[Wendy Zuckerman]

Okay, so they've drunk the energy drinks

[Rose Rimler]

and then he monitored them and 1

[Satchin Shah]

hour, 2 hours, 4 hours, 6 hours and 24 hours.

[Rose Rimler]

And he was looking at this particular part of our heart's rhythm that's called the QT interval, which is, it's 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.

[Co-host/Interviewer]

Oh, man.

[Wendy Zuckerman]

Okay, so did the energy drinks muck up the QT interval?

[Satchin Shah]

So, 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.

[Rose Rimler]

A follow up study he did found this again, that the energy drinks extended the QT interval by this time, 6 milliseconds. And Satchin points out that several drugs have been pulled from the market for prolonging the qt interval by 6 milliseconds.

[Wendy Zuckerman]

Mm, wow. Okay, so if I were to drink the equivalent caffeine from what he gave them, but in coffee, would my QT interval be extended like that?

[Astrid Nilig]

No.

[Rose Rimler]

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.

[Wendy Zuckerman]

So if energy drinks are doing this, why aren't heaps of people 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.

[Rose Rimler]

Yeah, I mean, it's not like anyone in Sachin's study had to be rushed to the hospital.

[Wendy Zuckerman]

Right.

[Rose Rimler]

You know, but the thinking here is that there are some people who could be really vulnerable to this. Like people who have heartbeats that are 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 Chihuahua territory.

[Co-host/Interviewer]

Right, right.

[Rose Rimler]

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.

[Wendy Zuckerman]

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. That's causing this?

[Rose Rimler]

Yeah, I mean, in Satchin 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.

[Wendy Zuckerman]

So this is the ingredients. This is how we get wings. Is that right?

[Rose Rimler]

This is the wing recipe, yes.

[Co-host/Interviewer]

Okay.

[Rose Rimler]

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 Satchin. And after drinking, the Red Bull volunteers had a prolonged QT interval. But none of the individual components did this.

[Wendy Zuckerman]

What?

[Rose Rimler]

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?

[Satchin Shah]

That's the million dollar question.

[Wendy Zuckerman]

Science. You know, I was having coffee with

[Co-host/Interviewer]

my brother the other day and he

[Wendy Zuckerman]

said there is always a point in

[Co-host/Interviewer]

a science versus episode where the scientist says, eh, we don't really know what's going on. And I guess this is that point.

[Rose Rimler]

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.

[Wendy Zuckerman]

Okay, so here is what I think I have learned from this episode. Rose Rimbler. Tell me how I did.

[Rose Rimler]

Let's hear it.

[Wendy Zuckerman]

And if I pass the test, I have a good sense of humor. Is that what we learn?

[Co-host/Interviewer]

Yeah.

[Rose Rimler]

Yes. Case closed.

[Co-host/Interviewer]

Caffeine truly does make me poo very quickly. Nice. 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.

[Wendy Zuckerman]

And meanwhile, it might reduce your risk of depression if you're drinking coffee and tea.

[Co-host/Interviewer]

What'd you say? Cancer, Parkinson's, Diabetes.

[Wendy Zuckerman]

Diabetes. And energy drinks. There is something weird about them. So if you are looking for a

[Co-host/Interviewer]

boost, it's safer to go with tea or coffee. How'd I do?

[Rose Rimler]

A plus, people. I'm not surprised. And you as surprise. I sent a case of prime to your house. So.

[Co-host/Interviewer]

Great.

[Rose Rimler]

So don't drink it all at once.

[Co-host/Interviewer]

Excellent.

[Wendy Zuckerman]

Cheers, Rose.

[Rose Rimler]

Cheers.

[Wendy Zuckerman]

But before you go.

[Rose Rimler]

Rose, Rose, Rose. I'm here.

[Additional Voice (possibly crew member)]

I'm still here.

[Co-host/Interviewer]

Okay.

[Rose Rimler]

Okay.

[Wendy Zuckerman]

How many citations are in this week's episode?

[Rose Rimler]

This episode was the first time I've ever opened so many tabs that my browser stopped displaying them. Like, I reached the limit of how many tabs I got to have open.

[Co-host/Interviewer]

Got it. So many tabs.

[Rose Rimler]

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.

[Co-host/Interviewer]

118. Okay. Yes.

[Wendy Zuckerman]

And if people want to see these

[Co-host/Interviewer]

citations, find out where we got all of our info from. Where should they go?

[Rose Rimler]

They can click the link in the show notes that will send them to the transcript.

[Wendy Zuckerman]

Excellent. And I guess while people are scrolling through Instagram and hitting the end, if

[Co-host/Interviewer]

you have hit the end of your Instagram, you could just come over to Science Versus.

[Wendy Zuckerman]

What do you think?

[Co-host/Interviewer]

Was that a segue of, like, picking

[Rose Rimler]

up some media accounts?

[Co-host/Interviewer]

Thanks. Yeah, we are sciencevs.

[Wendy Zuckerman]

I'm on TikTok, Wendy Zuckerman and we will see you next week. Thanks, Rose.

[Rose Rimler]

Thanks, Wendy.

[Wendy Zuckerman]

This episode was produced by Rose Rimler with help from me, Wendy Zuckerman as well as Nick Delrose, Joel Werner and Michelle Dang were edited by Blythe Terrell. Fact checking by Sarah Baum. Mix and sound design by Bumi Hidaka. Music written by Bobby Lord, Bhumi 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 Ferre, Professor Andreas Hynes, Professor Christine Curran, Dr. Erica Loftfield, Dr. Felix Oberhofer, Dr. Alan Wayne Jones, and Dr. Dr. Vijay Yadav. Extra special thanks to Jason Vitlassill 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. Back to you next time.

[Rose Rimler]

Now it's not all fun stuff like rectal probes.

[Co-host/Interviewer]

Name of your sex tape. It's not all fun and rectal probes.

[Rose Rimler]

No, the sex tape is called all fun and rectal probes.

[Co-host/Interviewer]

Right.

[Rose Rimler]

We can't only talk about rectal probes in this episode. We also, unfortunately, have to talk about some unpleasant stuff.

[Dan Heath]

I'm Dan Heath on what it's like to be. I interview people about their jobs. Here's a married couple that drives a long haul truck together.

[Astrid Nilig]

We backed up and they loaded fresh dead rats.

[Dan Heath]

I mean, how many rats would you guess were back there?

[Rose Rimler]

There were 32,000 pounds of them.

[Dan Heath]

32,000 pounds of frozen dead rats. Find out what it's like to be a long haul trucker, a couples therapist or an FBI agent. All on the podcast. What it's like to be.