in: Health, Health & Fitness, Podcast

• Last updated: July 1, 2023

Podcast #608: How Caffeine Hooks, Hurts, and Helps Us

More than 80% of the world’s population consumes the same psychostimulant every single day. Yet few of us know very much about our favorite daily drug . . .  caffeine.

My guest today will shed some light on humanity’s love affair with this pick-me-up substance. His name is Murray Carpenter and he’s the author of Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks Us. We begin our discussion exploring what caffeine does to our mind and body, before delving into how caffeine consumption developed in different places all around the world and how the way we get our caffeine fix has evolved over the millennia. Murray and I then discuss the popularity of coffee in America and how our grandparents actually drank way more of it than we do today. Murray explains how caffeinated sodas became a stimulating competitor to coffee in the 19th century and how energy drinks became a huge business in the late 20th. Murray and I then discuss how you’re probably ingesting more caffeine than you realize, and what the generally recommended maximum amount to consume per day is. We then get into whether caffeine can enhance athletic performance, and how much you need to take for it to make a difference. We then discuss the overlooked benefits of caffeine, as well as its downsides, and end our conversation with the question of whether caffeine is an addictive substance. 

This episode will get you thinking about your morning joe differently.

If reading this in an email, click the title of the post to listen to the show.

Show Highlights

  • What is caffeine? Is it a drug?
  • What does caffeine do in our body?
  • The origins of caffeine use 
  • The various ways you get caffeine into your system
  • How is it that we’re consuming less coffee than our grandparents’ generation? 
  • The rise of caffeinated soda 
  • How coffee and soda have changed over the decades 
  • The fascinating history of energy drinks 
  • Why is it so hard to figure out exactly how much caffeine you’re consuming?
  • How much caffeine is safe/healthy to consume? 
  • Does caffeine help you in physical endeavors?

Resources/People/Articles Mentioned in Podcast

Book cover of Caffeinated by Murray Carpenter.

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Murray’s website

Murray on Twitter

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Read the Transcript

Brett McKay: Brett McKay here and welcome to another edition of The Art of Manliness podcast. More than 80% of the world’s population consumes the same psychostimulant every single day, yet few of us know very much about our favorite daily drug, caffeine. My guest today will shed some light on humanity’s love affair with this pick-me-up substance, his name is Murray Carpenter and he’s the author of ‘Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks Us.’ We begin our discussion exploring what caffeine does to our mind and body before delving into how caffeine consumption developed in different places all around the world, and how the way we get our caffeine fix has evolved over the millennia. Murray and I then discuss the popularity of coffee in America, and how our grandparents actually drink way more coffee than we do today.

Murray explains how caffeinated sodas became a stimulating competitor to coffee in the 19th century and how energy drinks became a huge business in the late 20th century. Murray and I then discuss how you’re probably ingesting more caffeine than you realize and what the generally recommended maximum amount to consume per day is. We then get into whether caffeine can enhance athletic performance, and how much you need to take for it to make a difference. We then discuss the overlooked benefits of caffeine, as well as its downsides, and we end our conversation with the question of whether caffeine is an addictive substance. This episode will get you thinking about your morning Joe differently after the show’s over. Check out our show notes at

Alright, Murray Carpenter, welcome to the show.

Murray Carpenter: Thanks, thanks for your interest in caffeine.

Brett McKay: So yeah, a couple of years ago, you published a book called ‘Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks Us.’ So, what’s the story behind this book? You were just… You had a caffeine habit and you wanted to explore, “Why do I drink coffee every morning?”

Murray Carpenter: Yeah, that’s the nut of it. I’ve been a caffeine drinker for decades and I’ve been intrigued by it, the idea that most of us do consume caffeine daily and yet we don’t think of it as a drug. And so that was sort of my point of entry is, what is it about this substance that makes us want to consume it, to drink coffee every day?

Brett McKay: So let’s talk about, okay, what is caffeine? So is it a drug?

Murray Carpenter: It is a drug by any standard, yeah. It’s a drug. It’s a simple drug. It’s an alkaloid. It’s a compound that emerged independently in many different plants all over the world. And so, wherever caffeine seems to have evolved, humans seem to have figured out how to put it to use for their own purposes.

Brett McKay: So broadly speaking, ’cause we’ll get in the details of what caffeine does to our minds and bodies, but broadly speaking, what do we know that caffeine does to our physiology and even our minds?

Murray Carpenter: Well, its primary mechanism is very, very simple. There’s a neurotransmitter called adenosine, and in broadest terms, what this does is lets us know that we’re tired. And caffeine looks remarkably like adenosine and is able to sit in the receptors for adenosine and basically nudge them aside and not let adenosine sit there. And it’s like it’s sitting at the bar stool and adenosine has to walk away. And so, it’s this simple trick of pushing adenosine aside that allows caffeine to work the magic we know so well, which is basically to make us feel a little bit more stimulated, a little bit more energetic.

Brett McKay: So that’s interesting. So the caffeine itself isn’t giving us energy, it’s just blocking a neurotransmitter that makes us feel tired, and we don’t feel tired.

Murray Carpenter: Yeah, yeah, that would be the simplest way to look at it. Yeah.

Brett McKay: Okay. And besides blocking that neurotransmitter, any other effects that it has on our brain chemistry or physiology?

Murray Carpenter: You know, there are some more subtle things. It may enhance a calcium pump that’s in muscles that might subtly enhance your muscle strength. But by and large, the principle mechanism for which it’s known and loved is its effect, its relationship with adenosine.

Brett McKay: Okay. So you talked about how this is, it’s a substance that’s all… It’s natural, it’s found all around the world. Do we know when human beings figured out that if they ate a leaf or drink… Ate a nut, that they would have this boost of energy from caffeine?

Murray Carpenter: We have a pretty good sense that… Well, we know it’s been going on for thousands of years at least. And I visited the place that we have the earliest known, the earliest evidence of human use of caffeine, and that’s in a part of what’s now Mexico in Chiapas. And basically, there were people there who were consuming cacao, who were consuming chocolatey drinks 3,000 years ago. And so, archaeologists have been able to extract or find the caffeine in the residue of these chocolatey drinks 3,000 ago. So we know that back then, people were cultivating cacao, a caffeinated product, and they were consuming it. And so, we know that that was going on 3,000 years ago. Around the same time, it looks like tea culture probably emerged in China. By folklore, the Chinese tea culture might be as old as 5,000 years, but it seems to have been around 3,000 years ago that that started happening. So, those are some of the earliest indications that people were using caffeine.

Brett McKay: So this is interesting, ’cause these are independent discoveries, like multiple discoveries, human beings just… Disparate groups figured this out on their own without an any connection to each other.

Murray Carpenter: That to me is one of the most fascinating things, yeah, because we haven’t even talked about coffee, which was another independent discovery but much later, maybe only as recent as 1,000 years ago that people in Africa and Northern Africa were starting to then chew the coffee bean and eventually started to roast it and develop it into the beverage we know now. But yeah, and additionally, in North America, there were Native Americans who were consuming in tea form, yaupon holly, which is also caffeinated. So, yeah, it is odd, because, yeah, I think it’s hard for us to imagine people sort of wandering around doing amateur ethnobotany, right? Like, “Hey, I wonder if I chew on this, what it’ll do to me.” But yeah, people did it and they figured it out.

Brett McKay: Yeah, people have been looking for… I guess, being a human is tiring, it’s exhausting. So we’ve been looking for something to help us out with that for thousands of years.

Murray Carpenter: Yeah, I think that’s part of it. And I think… And we can talk about this more, but it’s… I think one of the underestimated aspects of caffeine, it’s not just a stimulant, right? We know it for its stimulant effects particularly at higher doses, but at lower doses, it has a much more subtle and yet I think a very significant effect. It just makes you feel good. And so, I think that’s part of the appeal all over the world.

Brett McKay: So let’s talk about different ways we get caffeine. So we’ve talked about three ways already. So in Mexico, they were cacao, so it was chocolate. In China, it was tea. And then in Africa, I think that most people don’t realize is… Here’s another thing I think what I love about this book it really explores like where caffeine comes from. Most people just take it for granted. The coffee bean, it’s originally from Africa, but I think most people think when they think coffee, they think, “Oh, Juan Valdez, South America.” That was a transplant.

Murray Carpenter: It was a transplant, absolutely, yeah. Yeah, originally from Africa, and then spread through the Islamic world and didn’t even probably get into Europe until maybe the 1600s. I mean, it was kind of a slow migration. And then eventually, of course, came over to the US. But, yeah, it’s not native to many of what we consider the coffee-growing regions. Yes, it’s… The plant is native to the African continent and has been transplanted worldwide. And, of course, yeah, some of the coffees that we are most fond of are now grown in South and Central America.

Brett McKay: And let’s talk about coffee consumption ’cause that’s a… That’s, for most of American history, that’s been the primary caffeine delivery substance. So, why did coffee take root in America compared to other cultures? Like even in Europe, tea was the sort of the place where they got their caffeine from. And how has caffine consumption changed throughout American history?

Murray Carpenter: Well, yeah, in terms of how it took root, I don’t know, there have been… There are some good historians who’ve gotten into this, but it’s certainly been an American beverage, perceived as an American beverage for quite some time. There are some people who even think that, at the time of the Boston Tea Party, it was perceived as patriotic to not consume tea but instead to consume coffee. So it’s been… At least for a long time throughout the history of America, it’s been a popular beverage, increasing in popularity through the 1800s and through the early 1900s, and then really peaking around the World War II years. And that’s one of the things that really fascinated me to learn is that people are… I guess, our great grandparents’ generation, that era, they were consuming about twice as much coffee as we do now and that’s… That was a real surprise to me.

Brett McKay: What’s going on there? ‘Cause I mean, there’s like a Starbucks in every corner now, you can go to any convenience store, you get coffee, how is it that we’re consuming less coffee than our great grandparents?

Murray Carpenter: I know, it’s really counter-intuitive. And you’re right, yeah, it seems like you can’t throw a rock without hitting a coffee shop or… I guess one way of looking at it is we’re sort of consuming coffee more conspicuously now, we’re making a bigger deal out of it, we’re paying more for it. But in the era that I am talking about, when people were drinking something like 53 gallons of coffee a year per capita, there was probably like just a coffee machine going in the break room. There was a coffee pot or a percolator probably at the time just cranking in your house all the time. People were just sort of habitually, routinely consuming cups of coffee, and eventually what happened is coffee got displaced by other beverages that are more popular.

Brett McKay: And one of those beverages, and you talk about this, the rise of soda pop and caffeinated soda drinks.

Murray Carpenter: Yeah, that’s a huge… I think that would be the one that you would say really… If you look at the the graph of where, of how coffee has declined and how sodas, Coke, et cetera, have grown, that they pretty much… You can see that one is replacing the other. And the lines crossed probably around the early ’70s and that, that’s a big part of it is we’re consuming a lot more Coca-Cola or a lot more soda in general than we did in the late ’40s or early ’50s, and that, in part, displaced coffee drinking. And to be clear, there’s been a… Something of a rebound like over the last 15-20 years during this golden age of coffee that we’re talking about with the Starbucks in every corner. Certainly, I think per capita our coffee consumption has increased somewhat, but still we’re pikers compared to what people were doing in the ’40s and ’50s.

Brett McKay: And imagine the coffee in the ’40s and ’50s wasn’t that great. They weren’t doing like these exotic roasts. It was just like, “Alright, you got Folgers instant coffee, there you go.”

Murray Carpenter: Yeah, and I think to our palates today it probably wouldn’t have been good at all. The coffee beans were probably, and I’ve talked to a few people about this, they’re… You could probably get some really good coffees back then, but part of it has to do with how it was processed. Yeah, if you were getting the big can of Maxwell House or Folgers that… Just a commercial blend, it would be roasted far away from you long before you consumed it, ground, put in a can, and then it may be weeks, months before you even crack the can. And so, yeah, the coffee wouldn’t have… Even if it was a great bean that was being roasted, it’s not gonna taste the same as a good bean that was freshly roasted and that you ground just before you consumed it. And additionally, people were percolating coffee, and some people like percolator coffee. I’ve given it a hard time before and people have rushed to its defense, but it over-extracts. It tends to over-extract the flavors. And so this will be like if you’re using a cone filter and after you’ve put the right amount of coffee through, you think, “Oh, I’m not gonna put any more coffee and I’m just gonna try to get that last bit out of there.” And it kinda has this funky stale flavor. I think that’s part of what percolators did.

Brett McKay: Right. So coffee was the primary source of caffeine for Americans for a long time, but then starting in the late 19th century, coffee began to have a competitor in the form of caffeinated sodas like Coca Cola. What I think is interesting is when soda, caffeinated soda first came out on the scene, the temperance movement for example touted it as a healthier alternative to alcohol and really sung it’s praises, but eventually drinks like Coke and other caffeinated sodas, they came in for some criticism for their caffeine content. And what’s interesting is that coffee, even though it had caffeine, didn’t get the same amount of criticism as caffeinated soda. What was going on there?

Murray Carpenter: Yeah. Well, so Coke went through an interesting evolution. It was first launch as like a patent medicine with wine and a little bit of cocaine. I think it would have been a pretty powerful beverage for most of us. But then eventually it became a temperance beverage. It was actually marketed that way and it was mostly then sugar or sweetness and caffeine. And what happened was in the early 1900s, people were beginning to be concerned about the caffeine in the product and just about the product in general and about the fact that it might be addictive and that it might be marketed to kids. And there was a hard-charging regulator in the Bureau of Chemistry, which was basically the precursor to the FDA. And he basically challenged Coca-Cola in a court case over their use of caffeine and said it was an adulterated substance, that it was marketed to children, that it was addictive. And so that was one of the early regulatory challenges to cocaine… Sorry, not to cocaine, to Coca-Cola and the soda industry.

Brett McKay: And as you highlight in the book, I didn’t know this, but the early Coca-Colas, they had the same amount of caffeine as a modern day Red Bull.

Murray Carpenter: That surprised me too. Yeah, and I was glad there were some good statistics that I could mine to find that. And that all came out of this court case ’cause they were able to detail the constituents of the early Coca-Cola. Yeah, so it had more caffeine. And the way I look at it is Coca-Cola invented the energy drink something like 80 years before Red Bull did. As a result of the court case… And I’ve scoured Coca-Cola’s archives and every other historical account I can find, so I don’t know, I’ve never heard Coca-Cola say that, “This is what we did,” but some time during that court case, it appears that they reduced the caffeine content and that it was probably the further reduced through the 1930s. So that original sort of energy drink Coke that would have been very much akin to a modern Red Bull was pretty much gone by at least the 20s or 30s.

Brett McKay: And something you highlight too is that even then Coca-Cola and some of the other soda manufacturers, they understood, it sounded kind of like some of the tobacco stuff that we saw in the ’80s and ’90s, where the pop makers, they’d say that caffeine was there just for flavor, but they knew that it actually was a stimulant and kind of addicted people, but they didn’t wanna say that because then it would, they’d have to sort of market it as a drug basically.

Murray Carpenter: I think that’s the case and I think to their credit, one of the arguments at that time is what would you do next, regulate coffee? And the argument, of course, and it’s a valid argument. Coffee has more caffeine than this beverage, so why would it be fair to regulate Coca-Cola and not coffee. But I think that’s been a question through the years. And every time the regulatory battles heat up again, and this happened in the 1980s, it happened more recently with energy drinks, the question is this, is to what degree does caffeine the drug drive the consumption, the purchase pattern of these products? Of sodas and of energy drinks? And it’s a question that I don’t think has been adequately resolved, even today.

Brett McKay: But you do highlight research where they’ve done studies on that, where they’ll give people like a soda that has caffeine and not caffeine in it. They don’t tell what it was, but people seem to be drawn to the beverage with caffeine in it.

Murray Carpenter: Yeah. And it increases… The term is liking. It increases the liking of the product. There’s another term of reinforcement, so the caffeine reinforces the purchase of the product. So in other words, if you reach for a soda that’s caffeinated, you’re gonna tend to like it and you’ll be more inclined to reach for it next time than for an uncaffeinated product. And I think the social science, again, or the science, the metabolic science, we need more of that and it would be good to see more of that. But I think something that we overlook, is the market has spoken on this. Eight of the top 10 selling sodas are caffeinated. If you want to sell a beverage in America and you want it to be, or all over the world, and you want it to be successful, I think adding caffeine is a pretty sure bet.

Brett McKay: Yeah, it’s hard to find Postum these days you can’t really find that stuff anymore.

Murray Carpenter: Yeah. Or even caffeine free coke. And so, some people do like Sprite and some people like Fanta. But aside from that, the Colas, the Diet Cokes, Mountain Dew, Diet Mountain Dew, all of the top sellers, Dr Pepper, they’re all caffeinated.

Brett McKay: So, soda pop, caffeinated soda beverages, they overtook coffee consumption for the source of caffeine in the ’70s. But caffeinated soda has been overcome by energy drinks. This is something that started in the 90s. Let’s talk about the history ’cause this is really interesting. When did energy drinks start taking off? This idea that there’s a drink that’s just designed for energy? Like coffee and coke, they might have been marketed as a sort of a pick-me-up, but they never said, “This will give you energy.” When did this idea that you have a drink just for energy?

Murray Carpenter: Yeah, I would say the late ’90s for sure, early 2000s this was starting to become a trend. And 2005, from there on I would say Red Bull was really, really starting to take off. And you’re right, it’s a different thing. It’s not just saying, “Oh this is a refreshing beverage,” or, “This is a stimulating beverage.” It’s like, “Here, have this, it’ll give you energy.” It was a brazen, very direct marketing of the caffeine, of the stimulating effect of the drink and it was something new at the time.

Brett McKay: No, I know from my own personal experience, like 2000… About year 2000, I was a senior in high school and I remember that’s when Red Bull came out. I think Red Bull came out in the late ’90s. But I started, before my football games, I would get two Red Bulls; one was to drink before the game and the other was to drink at half-time. And that was like the first time ever I consumed a beverage just for performance. Before I would drink Coke and Mountain Dew because it just tasted good, but here I was, 17 years old, buying a drink so it could enhance my performance.

Murray Carpenter: Wow, you’re an early adopter, really, because a lot of people were not yet consuming energy drinks at the time.

Brett McKay: And what’s interesting about the energy drinks is that in the beginning, they often downplayed the caffeine in their products and instead they promoted the other ingredients like the guarana or the other weird supplements they have in there. Why did they downplay the caffeine?

Murray Carpenter: Yeah, that’s a really important point. I think they downplayed the caffeine because the regulatory framework had been fraught. It had never been resolved very much. FDA basically had considered caffeine generally recognized as safe, that’s one of their terms, when it was used cola-type beverages. So it’s for very specific uses. And I think what Red Bull did was they kinda nudged the door open and they’re like, “Hey, what if we market this highly or more caffeinated beverage and just see what happens?” And it became wildly successful. And then other energy drink manufacturers came in behind it and they’re like, “Well, nobody has stopped Red Bull. The FDA hasn’t done anything. I guess this must be okay.” And then gradually, you have seen this evolution where caffeine was not really talked about. Yeah, it was taurine or whatever, all these other products, when caffeine is really the so-called energy product in any of these… The energy ingredient in any of these drinks. But more recently, you have seen bottlers more brazenly or more openly, I’d say, using the word caffeine on their products.

Brett McKay: And this is sort of… The energy drinks allows you… A lot of people see the weird murky world of food and drug regulation because in the early days, a lot of these energy drinks, they wouldn’t put the caffeine content on the thing itself. And so, they say it’s like there’s a proprietary energy blend and you had no clue how much caffeine you’re getting in your energy shot. And it’s because they were marketing themselves as a supplement, and because they marketed themselves as a supplement, there’s less stringent standards if they had marketed themselves as a beverage drink.

Murray Carpenter: Yeah, you’re absolutely right. And FDA did issue some guidance on that, basically saying that if something’s consumed like a beverage, then it should be marketed as a beverage. If it’s a 12-ounce energy drink and it’s in the cooler next to the sodas, is that really a supplement or is it essentially a more caffeinated soda? And I think FDA came down on the side of the latter. So yeah, that was one big change. And you are seeing increasingly… I would say you’re seeing improved caffeine labeling. It still leaves a lot to be desired. You still virtually need a magnifying glass in some cases to see how much caffeine is in a product, but at least if you’re looking for it, you can usually find it it.

One of the things that’s really interesting is during the Super Bowl this year, Coca-Cola launched a new, in the US, they’ve launched it elsewhere earlier, a new drink called Coca-Cola Energy. I mean very distinctly it’s an energy drink and it’s got the Coca-Cola brand on it. So this is something that they hadn’t really done before. They had purchased a share in Monster and they had a distribution deal. So Coca-Cola was still sort of keeping the energy drink thing at arm’s length, but now they’ve got this Coca-Cola Energy and on the can it says, “Guarana, B vitamins, caffeine,” right in the front. So it’s an example of how Coca-Cola has tiptoed around to embracing energy and notably, this has pretty much the same caffeine concentration as their 1909 beverage, although now it’s coming in a 12-ounce can. So it has, I don’t know, 118 milligrams. It’s almost the exact shape of a can and caffeine content of a Red Bull, but…

Brett McKay: It all went full circle.

Murray Carpenter: It all went full circle. Yeah, that’s my point. And I think to your point about people, bottlers not using the term caffeine, I think they’re coming around to it and I think Coca-Cola understands the value now of touting caffeine.

Brett McKay: Alright, so let’s talk about figuring out how much caffeine you consume on a daily basis. I remember a couple of years ago, I sat down to think how much caffeine I consume on a daily basis and I was like gobsmacked. I was actually… I was consuming more than I thought I was. So why is it so hard for people to know how much caffeine they’re consuming on a daily basis?

Murray Carpenter: This is something that I became endlessly fascinated with. It’s very difficult. It’s very difficult for a couple of reasons: One, because we consume caffeine often in many different products throughout the day. So many of us drink coffee in the morning. What I came to realize, a lot of people… A very common pattern is to have coffee in the morning and then an energy drink or soda either at mid-morning or mid-afternoon or with lunch. And so yeah, there’s a number of different ways that you can get your caffeine. Another challenge is that, particularly with coffee, the caffeine content can vary widely. So some people like to say, “How much coffee do you drink?” And people say, “I drink a cup a day.” Well, that’s an absolutely worthless metric. A cup could be a five-ounce weak cup that could have 80 milligrams of coffee or it could be a 16-ounce cup from Starbucks that might have 325 milligrams of coffee. So there’s just a tremendous variation. And then on top of this, I think we don’t really think of caffeine in terms of milligrams. We don’t really… If someone says, “How much caffeine do you consume?” You say, “Well, I drink a soda or I drink a cup of coffee,” but you don’t say, “Well, I drink 200-300 milligrams.”

But I think you really kinda do have to total up the milligrams, as you probably did when you were trying to understand your own caffeine consumption, in order to get a handle on how much you’re consuming.

Brett McKay: And do we have any, like a rough idea, the average amount or caffeine people are consuming on a daily basis?

Murray Carpenter: I’d have to say average for coffee drinkers, they’re probably in the range of 250-300 milligrams. That would be my guess. And most people in the US are consuming coffee regularly. So coffee remains… And this is a weird thing to understand. Coffee remains our primary source of caffeine. We’re consuming more caffeine from coffee than from any other beverage, but by ounces, by actually drinks daily, we’re consuming more soda pop. But the soda, it has less caffeine. So by volume, we’re consuming more soft drinks, but by caffeine, we’re still getting most of our caffeine from coffee.

Brett McKay: Gotcha. And what’s the recommended amount from health experts on like what is okay caffeine consumption for an average person?

Murray Carpenter: And here too, this is an area that’s kind of soft, but most people suggest not going above 400 milligrams. And this is gonna vary a lot from person to person because some people are just much more caffeine-sensitive than others. But 400 milligram seems to be sort of a level that most people are saying, “Yeah, up to 400 milligrams, you’re okay. Beyond that, maybe back off.”

Brett McKay: Well, that’s an interesting point. Some people… There’s a genetic component to caffeine. Some people process caffeine a lot faster than other people. So they could drink a cup of coffee, and right before bed, and then go right to sleep, it wouldn’t affect them. And another person does the same thing, they would be up all night.

Murray Carpenter: You’re absolutely right. Yeah, it’s highly variable and certainly seems to be genetic, which is to say… I know a family of people, and they’re all this way, that they’ll drink a pot of coffee with dinner and then just trundle off to bed. But yeah, some people metabolize caffeine quickly, some people metabolize it slowly, and some people are really on the low end of… Are really quite sensitive to caffeine. And this is something that I kinda didn’t… I don’t know, I think I discounted it until I did the research for the book. But even what might be like a very small amount, the trace amount that’s left in a cup of decaf, maybe 12 milligrams of caffeine, that could be enough for someone who’s very caffeine-sensitive to really make them feel uncomfortable, that they would really get a boost out of that. So yeah, our individual reactions to caffeine varies dramatically.

Brett McKay: So the part of the book that I thought was really interesting, you talk about different groups of people researching and exploring how caffeine can be used to enhance performance. You talk about the military, the military is basically putting caffeine in everything, surprising stuff, like even food they’re putting caffeine in. But the thing that I’d like to focus on is sports, ’cause I think that’s where most people, if they’re athletic in any way, they think… It’s sort of natural now. It’s like, “Well, if I need a boost, I have a little bit of caffeine before I do my workout to kinda give me that extra pep.” What does the research say about caffeine and how it enhances athletic performance?

Murray Carpenter: Well, it backs up that perception you’re talking about, the idea that, “Yeah, if I wanna do well, or as you would have in high school during football, if I wanna do well, I might do a little better caffeinated.” And it looks like the optimal dose for most people would be like three to six milligrams of caffeine per kilo of body weight. And this could be a fair amount for a bigger person, maybe 300 milligrams of caffeine or, say, a couple of strong 12-ounce cups of coffee, if that’s the way you wanted to take it before your athletic event. I think the more notable thing about this is that for most athletic events, and most of the research has been on endurance events, but say if you were gonna run an hour race, the caffeine versus a placebo would probably improve your time between 1%-3% in that race and that’s… I mean, that’s obviously a winning margin in many athletic events. And that’s why you’re seeing so many athletic-specific products, gels and beverages and things for people to consume while they’re doing triathlons or et cetera.

Brett McKay: I was surprised at the amount of like caffeine you need, the dosage for caffeine ’cause I think the example you gave in your book was an 80-kilo athlete, which is about 176 pounds. So if you wanna take six milligrams per kilogram, that would be 480 milligrams of caffeine, which is like double what the average… And that’s like at one time, like you can consume that once and then do your thing. I mean, if you weigh 200 pounds, that’s gonna be insane, like how much caffeine you gotta back to get that effect.

Murray Carpenter: That is. And that’s the high end, but you’re still gonna get a good effect I think in the three to five milligram per kilo range. But yeah, that is to say, yeah, that would be a huge amount. And here… The researchers I spoke with talked about this. You have to weigh the benefits and possibly the cost. If you’re actually getting stressed and anxious or having some like GI, like stomach upset from the caffeine you’re consuming, obviously that’s too much and that gonna… It’s gonna eliminate any benefit you might have gotten from the caffeine. But the short answer is, yeah, some caffeine in probably a moderate dose will improve, for most people, their athletic performance.

Brett McKay: And so what’s the regulations of caffeine? So if it enhances your performance, most drugs that enhance performance in athletics, I’m talking about the Olympics stuff, football, like those are banned or they’re restricted somehow. Why hasn’t caffeine… Why hasn’t that been regulated in sports?

Murray Carpenter: And this is too is, to me, quite fascinating. The reason is that the same dosage, the same therapeutic dosage that would give you an athletic advantage is very much in the range of the average American’s daily consumption. So if you consider that, it’s basically saying, “Okay, most people are consuming caffeine daily, maybe 300 milligrams, but for an athletic event, you can’t do that.” And so I think unlike testosterone or any other sort of whatever you might use to dope with, I think caffeine is really quite in a category by itself that makes this regulation fraught.

Brett McKay: Yeah, and as you said earlier, it’s gonna affect people differently. So someone might boost their performance a lot, and someone could take that same amount of caffeine and not have any performance enhancement.

Murray Carpenter: That’s true, yeah. And so it’s gonna vary. And I think most professional or high-end amateur athletes have figured out their caffeine strategy. And I think this has changed an awful lot over the last 30 years. I used to race bikes in the ’80s and people had a sense that if you had like a short strong cup of coffee at some point, that that might help you in a race, or people would say, “Oh, I drink Coke or I drink Mountain Dew.” But I think people are much, much more… Have a much more finely tuned sense of both what caffeine does, when it does help them, and how best to consume it during a race than even that recently.

Brett McKay: Yeah, I loved how you talked to some of these high-performance athletes and how they would… They were very systematic about their caffeine. They’d have something before and then along the race, they’d have a gel that they would throw back and get that. So they had it timed perfectly on when they were gonna do this.

Murray Carpenter: Yeah, I think so. And I think it makes sense. I mean because these are the same people who are very conscientious about everything that they’re eating on race day and in the days prior, so why not caffeine? And I think a lot of people find that unseemly, because there is at least, I don’t know, sort of a moral distinction between, yeah, maybe they’re consuming the same amount of caffeine you and I would be if we were at a coffee shop, but they’re doing it specifically to enhance their performance. And that does sort of… It’s an ethical challenge, but I think for most people, they’re kind of okay with that.

Brett McKay: Alright, so for basic weekend warrior athletes, if you’re doing a 5K or 15K… And I’ve also seen research that caffeine can help with weightlifting too. Strength training, it actually increases performance there. You’re looking at about three milligrams per kilogram of body weight and the high-end would be like eight or six kilograms.

Murray Carpenter: Yeah, I would say six. You probably wouldn’t wanna go beyond six. But yeah, something like that. And you would wanna consume it in a way that it wasn’t gonna… That it wasn’t gonna interfere with your performance in any other way. I mean, obviously you’re not gonna stand there at the beginning of a 10K and have a big cup of Starbucks probably. But maybe an hour before, to have a strong cup of coffee would probably be quite helpful.

Brett McKay: Alright, so we know that caffeine helps us not feel tired. It also just makes us feel good generally, after you have some. Were there some surprising benefits of caffeine you came across as you researched this book?

Murray Carpenter: There are, there’s some unusual ones. And I mentioned some of these with trepidation because you need… I think in all cases, we need more research. There are some associations with a reduced risk of suicide. There’s a suggestion that people who consume more caffeine have a lower incidence of basal cell skin cancers. Certainly, caffeinated coffee is associated with a lower risk of diabetes and may be associated with a decreased incidence of Parkinson’s disease. And I mean, coffee itself, there’s been more research recently, coffee drinking, caffeinated coffee drinking is actually associated now with reduced risk of mortality. People who consume caffeinated coffee have a decreased risk of dying at any particular later age. Even that’s not quite right. [chuckle]

Brett McKay: Right, yeah, I know. So you’re not trying to say that, “Oh, if drink coffee you’re… Lesser chance of dying.”

Murray Carpenter: No.

Brett McKay: It decreases… Yeah.

Murray Carpenter: But epidemiological studies show a decreased risk of mortality associated with people who are drinking caffeinated coffee. And there we have to be careful, ’cause we don’t know if it’s the caffeine or another constituent in the coffee. And it may likely or it may very probably be another constituent in the coffee. It might be polyphenols, et cetera, et cetera. But I think all of these health benefits or associations with consuming caffeinated coffee should go a long way towards easing people’s worries if they think they’re drinking too much.

Brett McKay: Yeah, I think drinking full sugar Monsters, that’ll probably give you diabetes and decrease… It’s not the… Like the caffeine would be overwritten by the sugar consumption.

Murray Carpenter: Yeah, you’re absolutely right. And that’s sort of the other end of the scale, you… There seems to be no health risk associated with consuming caffeinated coffee or tea, and there might even be some health benefits, but we know there’s cut and dried health risks with consuming full sugar sodas and energy drinks.

Brett McKay: Well, let’s talk about the downsides of caffeine. We’re talking, okay, it can help with athletic performance, it gives you a boost when you’re feeling kind of sluggish. What are the downsides of caffeine?

Murray Carpenter: Well, the two best known ones, and I think most people are familiar with this, is it can disrupt your sleep and I guess a slightly lesser known one is that it can increase anxiety. So you know the sleep thing, I mean I think a lot… We talked about this before, a lot of people… There are some people who can consume caffeine and just sleep like babies. But for… A lot of people suffer from insomnia and they consume caffeine daily. And there’s certainly some subset of that group that would find that if they stopped or reduced their caffeine consumption, they would sleep better.

Brett McKay: Yeah, ’cause the caffeine, like the half-life of caffeine is like four to five hours. So it stays in your system for at least five hours or something like that.

Murray Carpenter: Yeah, it’s gonna be in your system for quite some time. And for people who are more sensitive, I mean this is really surprising, but even if their sleep is not acutely disrupted, they may be sleeping lighter at night. And so this isn’t gonna be for everyone, but this is one of the surprising things that I’ve found in talking to people is, I’d say, “Do you consume caffeine daily?” “Yeah.” “Do you sleep well?” “No, I suffer from insomnia.” “Have you ever tried reducing or eliminating caffeine?” “Well, no.” And I think it’s almost like saying, “Well, I’d rather be a caffeine consumer and an insomniac.” But it’s not gonna help everybody to reduce their caffeine consumption, but I think if you really do suffer from… If you really would like to sleep better, it’s worth experimenting with reducing your caffeine consumption.

Brett McKay: Alright. So sleep, insomnia, one of the big downsides. What’s the other big downside? Increased anxiety, anger? What do you think?

Murray Carpenter: I think, increased anxiety is a big one and little discussed. Again, if you sort of look at the overlap of people who experience anxiety, either clinical or sub-clinical, and the people who consume caffeine, just because most of us consume caffeine, there’s a lot of overlap. And I certainly talked to a couple of people in my reporting and later when the book came out, who had been anxious, had suffered from anxiety, but had never had anyone suggest that they reduce caffeine, and did reduce caffeine and found that they felt better. So, again, it probably wouldn’t help everyone and it’s not a cure-all to quit caffeine, but I would say, if you’re someone who suffers from anxiety and you consume caffeine regularly, it would be worth just experimenting, just trying to see what your symptoms are like if you decrease caffeine or eliminate it entirely.

Brett McKay: Is there any research on what caffeine does with our thinking? I mean, I know I sort of intuitively, when I’ve got a big project, I gotta do some hard thinking, I think, “Well, I gotta have a little bit of caffeine to help me focus.” Is there anything to that sort of natural inclination that I have?

Murray Carpenter: Yeah, well, I think the better research has been on the things that are easier to quantify like reaction time and word associations. But yeah, I think most of us feel intuitively that caffeine can sort of make the wheels of your brain spin a little faster. And before we move on from health risks, it’s worth noting that the other group that should pay attention to this is people who are either pregnant or wanting to become pregnant and who are advised to reduce their caffeine consumption, a lot of people say to 200 milligrams or below daily. And this is because of an association between higher amounts of caffeine and the possibility of miscarriage and of babies that are lower weight at birth. So if you’re hoping to become pregnant or if you are pregnant, it’s worth moderating your caffeine consumption at least.

Brett McKay: So a lot of people you talk about… You just mentioned someone has a hard time sleeping, you say, “Hey, why don’t you give up your coffee and see what that does?” People are like, “Oh, no, I can’t do that.” So there’s this idea that either caffeine it’s a habit or it’s an addiction, what does the research say about that?

Murray Carpenter: I think, and I hate to say this, ’cause it’s really, it feels like being a kill joy, but I think you have to consider it an addictive substance. I think one of my sources put it best, I think he characterized it as mildly addictive. And I think that’s the best way to look at it because it does have the hallmarks of an addictive substance. People feel good when they consume caffeine, they feel lousy when they don’t consume caffeine. Your tolerance increases to it somewhat as you consume it. And then, for many of us, if you stop abruptly consuming caffeine, then you’re gonna have withdrawal symptoms. So yeah, I think it’s hard not to say it’s addictive. I think part of the reason people hate that term for this is because it’s clearly not an addiction with all of the sort of socially negative components of, say, opiate addiction, but in terms of the addictive pattern, I think it’s all there with caffeine.

Brett McKay: What are the withdrawal symptoms whenever you decide to quit caffeine cold turkey?

Murray Carpenter: The best known one is a headache, a caffeine headache, and that often will come on the second day or maybe even late on the first day of a cold turkey withdrawal, but sort of unpleasantness, edginess, and even muscle aches and pains, flu-like muscle aches and pains. But I think the best known one is the classic sort of caffeine headache.

Brett McKay: What’s interesting there, what’s causing that, it’s because when you consume caffeine it restricts blood flow to your brain, and then once you stop, things relax a bit and you’re just having this gush of blood go to your brain and that just, it hurts when that happens.

Murray Carpenter: Yeah, and this is part of the reason that a lot of Excedrin and Anacin headache compounds combine caffeine with analgesics. And additionally, there are some well-known prescription migraine medications that also include caffeine.

Brett McKay: And I’m curious, how did your caffeine consumption change after you researched and wrote this book?

Murray Carpenter: Not dramatically, but I will say, I use caffeine more strategically. I think I have a greater awareness of its sort of more subtle effects. So while I never was someone who consumed caffeine late into the evening, I think I cut off a little bit earlier now and just, I would say, I generally moderated my consumption. I still consume a lot of caffeine in the form of coffee, probably 300-350 milligrams a day. So that would be like 24 ounces of good strong coffee. But I would say I probably use it a little more strategically now.

Brett McKay: So, yeah, maybe it’s the advice to take away there, you don’t have to necessarily quit caffeine, but be smart about it.

Murray Carpenter: Yeah, I’d say be smart about it, be aware of your caffeine consumption and be aware, yeah, it’s a drug. And because it is a drug and it is affecting you in multiple ways, it just makes sense to pay attention to it.

Brett McKay: Well, Murray, this has been a great conversation. Where can people go to learn more about the book and your work?

Murray Carpenter: Well, I’ve got a website, just and the book is available on pretty much from your local bookstore or anywhere else. And I have another book coming out in a year, which is specific to Coca-Cola and health, so you can look for that as well.

Brett McKay: Fantastic. Well, Murray Carpenter, thanks for your time. It’s been a pleasure.

Murray Carpenter: Thank you, I really appreciate your interest.

Brett McKay: My guest today was Murray Carpenter. He’s the author of the book, ‘Caffeinated’. It’s available on and bookstores everywhere. You can also find out more information about his work at his website, Also check out our show notes at where you can find links to resources where we delve deeper into this topic.

Well, that wraps up another edition of The AOM podcast. Check out our website, where you can find our podcast archives as well as thousands of articles that we’ve written over the years about pretty much anything you can think of. And if you’d like to enjoy ad-free episodes of the AOM podcast, you can do so on Stitcher Premium. Head over to, sign up, use code MANLINESS at checkout to get a free month trial. Once you’re signed up, download the Stitcher app on Android or iOS and you can start enjoying ad-free episodes of the AOM podcast. And if you haven’t done so already, I’d appreciate you to take one minute to give us a review on Apple Podcast or Stitcher, whatever podcast platform you use. And if you’ve done that already, thank you, please consider sharing the show with a friend or family member who you think could get something out of it. As always, thank you for the continued support. Until next time, this is Brett McKay, reminding you not only to listen to AOM podcast, but put what you’ve heard into action.


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