How Does Coffee Affect Your Brain?

How Does Coffee Affect Your Brain?


  • Caffeine keeps us alert by blocking the effects of adenosine (which would normally and naturally cause us to get drowsy as the day goes on).
  • A build up of adenosine in the system due to drinking coffee leads to grogginess upon waking and thus a dependency cycle.
  • Caffeine has a half-life of around 6 hours.
  • Thus you can limit the negative affects of caffeine by drinking the same amount of coffee in a smaller window.
  • Try and finish drinking coffee by or swapping to decaf after 2PM.
  • The effects vary greatly based on genetics.
  • Even if you fall asleep easily drinking coffee close to bed time could still be negatively affecting your slow wave sleep.
  • If you do cut back on your caffeine intake it makes it even more pertinent to choose only the most delicious and most sustainable coffee to drink ;)


Adam Marley: (00:01)
Hi, everyone. Welcome back to another tips and tricks with me, Adam. Sorry, it's been a little while between videos. So I apologize for that, but sure enough, we're still doing these. Not fear, if you were afraid that we weren't doing them anymore, we are. In this tips and tricks, we are going to be telling you why caffeine keeps you awake or does it keep you awake? Does it make you more alert? How has it actually doing that? And maybe providing some advice around caffeine and sleep and how soon before bed you should be having coffee and how much coffee you should be having. I want to point out right now, before I forget to, that I am not a doctor. Do not construe any of this as medical advice. This is just one coffee geek talking to you about the research that I've done on caffeine and how it affects you. It's not medical advice. Just want to make that clear.

Adam Marley: (00:52)
So how does coffee make you feel more alert? I feel like this is probably like a lot more common knowledge these days, but just in case it isn't, so caffeine itself, doesn't ... it's a stimulant, but it's not kind of a direct stimulant. Caffeine itself doesn't make you more alert. It doesn't make your brain fire fast or anything like that. What it does is interrupt a normal process in your brain, which does the opposite, which makes you drowsy. So when you're feeling more alert from coffee, you're actually feeling less drowsy as opposed to more alert, if that makes sense. Yeah. Hopefully, that makes sense. It's a key difference.

Adam Marley: (01:32)
What's the key difference for me? The way it does this is let's start with adenosine as opposed to caffeine. So your brain endogenously produces a chemical, a neurotransmitter called adenosine. And it does this throughout the day. The longer you're awake, the more adenosine builds up in your brain. The adenosine latches itself onto neurons, onto nerve endings and it tells your brain to start slowing down, to start getting sleepy. Basically, I think this is what sleep scientists called sleep pressure. And so there's a couple of ways you get sleepy towards the end of the day and this is one of them. It's not the only one, but this is one of them. So you're awake, you're doing things, your sunlight's hitting your skin. You're eating. All of these things contribute to the increase in adenosine. And then that tells your body, "Hey, you've been awake for a certain amount of time. It's time to start getting sleepy and get some rest."

Adam Marley: (02:26)
What caffeine does is caffeine mimics the adenosine in terms of it latches on to the adenosine receptors. It doesn't have the same effect as adenosine however. So what this means is the adenosine just keeps building up in your brain, but it has nowhere to go. And it doesn't signal to your neurons, doesn't tell your brain to start slowing down, because the caffeines there kind of blocking it and the caffeine doesn't tell your brain to slow things down. And so, yeah, that's pretty much it. Obviously, it's a lot more complicated than that.

Adam Marley: (02:55)
But so what's happening is hopefully the first bit makes more sense now. You're not actually getting more alert, you're simply unable to get drowsy the way that your brain wanted you to get drowsy naturally. And this has a few downstream effects that we should probably be cognizant of as coffee drinkers.

Adam Marley: (03:15)
So a few key facts. Caffeine has about the half-life of six hours, and this is very genetically dependent. And we'll get into how that kind of sort of, "Oh, I can have coffee right before bed." We'll get into that.

Adam Marley: (03:29)
This was very genetically dependent, but for the average person is about six hours. So half-life simply means if you have a medium-sized coffee, you've got around 200 mg of caffeine in your system, six hours later, you have about 100 mg of caffeine in your system. If you had four coffees, two hours later, it's the same as if you just had two coffees in terms of how much caffeine is in your system. This is also important for when we're talking about how soon before bed should we have coffee and how much coffee should we have. So those are the things to keep in mind, but again, very genetically dependent.

Adam Marley: (04:03)
So the other kind of issues I'm hesitating because it's going to make caffeine sound horrible, but it's not. Caffeine's perfectly fine in moderation and kind of like let's say used correctly, because you are using a stimulant by drinking coffee. You just might not be aware that you are, and it's very socially acceptable and legal, thankfully, because it's delicious.

Adam Marley: (04:25)
So things to keep in mind are that adenosine that we're now blocking from going into the receptors by having coffee, that's still there. It's still floating around. It has nowhere to go. Now, ordinarily, when you're sleeping, that adenosine gets metabolized. It gets reduced down again, so you've got this cycle. And obviously, you got your circadian rhythm and to do with sunlight and melatonin and other things, but you've also got an adenosine cycle where what's going to happen is during the day it will build up. And then at night, by sleeping, you use it all up. And then the next morning, you wake up feeling very refreshed because you don't have very much adenosine in your brain anymore. And then it slowly builds up through the day and then it gets metabolized again overnight.

Adam Marley: (05:05)
Now, your body's going to keep producing it. If you've got caffeine blocking it, your brain tends to keep producing the adenosine to try and combat this. And so you have a lot higher of a peak of it. Notice, you might not be feeling drowsy because the caffeine is blocking it. But it means that during sleep, you don't eat through all of it and you wake up the next morning already feeling a bit groggy.

Adam Marley: (05:26)
What's your solution? Have more coffee. And so you can see why it's this kind of cycle. And anyone who's gone off caffeine for a while will tell you that caffeine doesn't make you feel more awake than usual. It brings you back to baseline to where you would be if you weren't having the caffeine. And there was a lot of truth to that. Obviously, that's anecdotal, but the science corroborates that. There is quite a lot of truth to that. This doesn't mean, don't have coffee. Please don't stop drinking coffee.

Adam Marley: (05:54)
There are a few ways that we can help mitigate this. So let's use that half life to our advantage. For instance, I don't drink less coffee than a lot of people. I'm very cognizant of these things. I don't drink less coffee than a lot of people. In fact, I probably drink a lot more. I'm a coffee roaster. However, I deliberately get all of that caffeine ... I get all of my coffee drunk before midday. Now, it doesn't have to be that early in the day. Again, we're going six hours here, but because I drink so much coffee and the half-life is obviously, it doesn't ... it's not like all the caffeine is gone in that time or halved in that time. I mean, it is, but if you've got a lot more coffee to start with, even half of it is still quite a lot. So in order to be able to get a good rest and feel drowsy when I should feel drowsy and not be too groggy in the morning, then I'll make sure to have all of my coffee drunk before mid day.

Adam Marley: (06:40)
Now, if you're drinking a lot less coffee than me, then 4:00 PM would probably be okay. And then I say for the average person, if you ... and this is an N equals one kind of experiment. If you know that your sleep quality is not fantastic, if your sleep hygiene is not fantastic, then maybe try stopping at 12:00 PM or stopping at 2:00 PM. And if you get to sleep really easily, you have no issues with sleep, then 4:00 PM's probably fine. So you listen to your body and you make those decisions that it depends so much on your genetics and so much on how much coffee you actually drink. So I can't make a specific recommendation. I know for me that if I have coffee after mid day, other than decaf, we'll get into that, but you can also have decaf. But if I have a normal coffee after mid day, then the next morning I wake up a little bit more groggy than I probably should.

Adam Marley: (07:31)
Now, some people will tell you that they can have coffee right before bed, and it won't affect their sleep quality at all. There's a couple of things here. Perhaps that is true. So there's a good chance that genetically they just metabolize coffee a lot faster. Also, if they're a smoker, smokers, nicotine tends to help you metabolize coffee a lot faster. I am not recommending smoking, by the way, because again, not medical advice, but just for a scientific fact, smokers tend to metabolize caffeine a little bit faster. So maybe they're a smoker. Genetically, there is a massive difference in how quickly people metabolize caffeine so maybe they can, but I actually think it's more likely that a lot of the time when people say they can still fall asleep even after having a coffee right before bed with dessert, they can fall asleep. But it doesn't mean that they're getting the same quality sleep.

Adam Marley: (08:20)
What researchers have found is that if you have a lot of caffeine in your system, then you might, if you're so tired, if the sleep pressure is so strong and you're so sleep deprived, you might fall asleep normally. You might be able to fall asleep as soon as your head hits the pillow. But in testing with these people, what they found is that they still have mental impairment the next day. And they still were quite groggy. Groggy is like a kind of catch all term, but they don't feel as refreshed as they otherwise could. And that's because even though caffeine might make it harder for you to fall asleep, even if you can fall asleep, it can also disrupt your slow wave sleep, which is the part of our sleep cycle, which helps us feel really refreshed the next day.

Adam Marley: (09:02)
Obviously, all parts of your sleep cycle are important. That includes everyone focuses on REM sleep, but slow wave also really important. See it, I'd say even if you're the kind of person that goes, "I can ... my head hits the pillow." Be honest with yourself. Are you groggy in the morning? Because honestly for me, this isn't a bragging moment, but for me, I can forget that I haven't had coffee. I have coffee because of the ritual in the morning, I have coffee because of the ritual. I have coffee because it's part of my job and I have coffee because it's delicious and I want to drink it. But there's been days where I just haven't had any coffee because I've been traveling, I haven't been at work.

Adam Marley: (09:35)
I haven't had any delicious coffee accessible and I go the whole day and I'm like, "Oh, wait a minute. I didn't have any coffee." And I didn't feel the need to have it, anyway. If you feel the need to have coffee, then I'm not saying drink less coffee, although if you drink a lot, you might want to think about having some of that as decaf. What I'm saying is potentially drink all of your coffees ... finish drinking it sooner in the day so your body can metabolize it.

Adam Marley: (09:58)
Other tips would be ... and so yeah, be honest with yourself. I fall asleep straight away, even with having an espresso with dessert. Be honest with yourself. Are you groggy in the morning? Do you feel like having a coffee when you wake up? Maybe your slow wave is being affected. So drink the coffee sooner in the day. If you want to drink coffee with dessert or later in the day, have a decaf. We're really proud of our decaf. We put a lot of effort into it. The producers, the importers, exporters, everyone in supply chain for that decaf coffees put a lot of effort into it. We're not the kind of roasters that I roll my eyes at death before decaf and that kind of thing. If you're drinking decaf, then you just want the flavor experience and not the drug. So I feel like we should be putting more effort into the flavor of decaf and not decrying it and not being disparaging towards it. So we take our calf quite seriously. And so you haven't tried it, try it. It's perfect for having with your espresso with dessert.

Adam Marley: (10:51)
And the other thing is if you're going to be drinking less coffee, if you genuinely are drinking too much coffee, then perhaps you should be making, let's say, curating your coffee decisions. If you have to drink less coffee or let's phrase it a different way to say this, only so much coffee you can drink, then it makes it even more crucial to make sure that that coffee is delicious, sourced responsibly and it's actually doing good for people. That's my little ... not to be too preachy, but yeah, if we're going to be drinking a little bit less coffee, then perhaps we should be a little bit more discerning about the coffee that we do drink.

Adam Marley: (11:27)
Yeah. Please feel free to throw anything, any personal experiences into the comments. I think that'll help a lot of people. There might be some people watching this going, "Oh, I don't want to drink less coffee. I don't want to drink ... I want to have my afternoon pick me up." So maybe if you've got any positive experiences with constraining your caffeine into an earlier window or swapping to decaf in the afternoons, please throw them into the comments to encourage those who are struggling to make that change over. You'll probably find an improvement in your sleep quality. And we want everyone to keep drinking coffee and have coffee be a positive influence in their life in all aspects, including their sleep.

Adam Marley: (12:03)
So thanks very much for watching. Hopefully, that answer any questions you may have had about coffee, alertness, sleep. And yeah, if you've got any more questions, then throw them in the comments and we'll get to them. I'm sure. Thanks guys. We'll catch you soon. Bye.