That Neuroscience Guy - The Neuroscience of Consuming Caffeine

Episode Date: March 27, 2022

Most of us start our day with a cup of coffee or any other caffeinated beverage. But why do we all feel like we need it? And is it actually hurting our brain more than it's helping? In today's episode of That Neuroscience Guy, we discuss the neuroscience behind how caffeine benefits and impairs our brain. 

Hi, my name is Olaf Kregolsen, and I'm a neuroscientist at the University of Victoria. And in my spare time, I'm that neuroscience guy. Welcome to the podcast. Caffeine is the most widely consumed central nervous system stimulant that exists in the world today. It is estimated that between 60 to 70% of North Americans start their day with a morning cup of coffee. Now, I have to admit, I'm not an expert here. I've never had a sip of coffee in my life. But like everyone, I do tend to ingest caffeine sometimes in other manners. I used to have a really bad problem with Diet Pepsi, where shortly after breakfast, I'd be into the Diet Pepsi to try to boost my arousal

levels. Luckily, I've broken that habit. But what is the impact of caffeine on the brain? On today's podcast, the neuroscience of caffeine. There is no doubt that caffeine impacts the central nervous system. In other words, your brain. Now, caffeine is a naturally occurring substance that's found in the coffee bean, the tea leaf, the koala nut, the cocoa bean. And what these things do is they contain methylxanthines, which are alkaloids that can be found in high concentrations, therefore, in things like tea, coffee, and chocolate.

And it's these methylxanthines that impact the brain. Now, what is the impact of these things on the brain? Well caffeine increases energy metabolism throughout the brain and at the same time it decreases cerebral blood flow and this creates a relative hypoperfusion, an inadequate blood supply to the brain. Now don't panic, this doesn't appear to have any serious consequences because the relative imbalance is really quite small. But caffeine also targets neurotransmitters, the chemicals that the brain uses to communicate. Now, one of the neurotransmitters that caffeine targets is dopamine. Now, if you remember, dopamine is tied to neural learning systems and is associated with pleasure.

And that's why caffeine might evoke positive feelings or emotions when it's confused. In other words, the love of coffee, for instance. Caffeine targets another neurotransmitter, noradrenaline, and that underlies a range of brain responses, including the fight or flight response. And this is why caffeine might make some people feel anxious. Now, the third neurotransmitter that's impacted is serotonin. And the release of serotonin in the brain basically increases our levels of arousal and alertness. And that's something that's quite commonly associated with caffeine consumption. So in sum, these three neurotransmitters that are released, dopamine, noradrenaline, and serotonin, they lead to

you possibly feeling feelings of pleasure, feeling a little bit anxious or ready to go, and then serotonin in terms of general levels of alertness and arousal. So that's one of the big sort of results people see with caffeine consumption is this increased feeling of arousal and decreased fatigue. Now, what is the actual impact on the brain? What systems are impacted? So there's a wide range of evidence, and the results just aren't that consistent. For instance, in terms of perceptual processing, our ability to process information, some studies show that caffeine enhances perceptual processing, and other studies show that it doesn't. You know, this is true with learning and memory systems as well.

You know, some studies show that caffeine enhances learning and memory, and other studies don't. And in fact, in some recent research, a group of researchers were looking at brain imaging data, and they found that the striatum, a region of the brain really tied to human learning and specifically reinforcement learning, isn't as activated when people are consuming caffeine or have consumed caffeine. And caffeine, of course, impacts the motor system.

Those are the jitters you might feel when you get a high level of caffeine in the body. In fact, a classic take-home study you can try is to thread a needle before and after consuming caffeine and see how it goes. Now, one of the big things with caffeine consumption is the benefit window. So what is the time course of caffeine activation in the brain? And again, the results aren't that consistent, but I'll tell you about a study from my own laboratory. Essentially what we did is we measured brainwave data on people when they were consuming caffeine or had consumed caffeine. So we were basically doing a simple test of brain function, measuring EEG data or brainwaves, in other words.

And what we found is that there was a small increase in brain function following the consumption of caffeine. But that benefit only lasted for up to an hour. So the way that study worked, you know, yes, it's having a positive impact of the brain, but the benefit window was only one hour. Other researchers have had the same sort of similar findings, which is how long does caffeine actually keep you alert and aroused? And again, the data doesn't, it's not consistent, but I can tell you that my own data shows it may be up to an hour. Now, you might take this as a sign that you need to consume more caffeine.

In other words, a cup of coffee an hour. But you don't want to do that. That would have a massive negative physiological response to it. For example, the post-caffeine crash that people experience in higher levels of anxiety. So the brain data is clear. You can drink too much coffee or consume caffeine, and it will have a negative impact if you do. But you're most likely safe if you keep it to one or two cups a day.

And of course, the timing of caffeine in terms of when in the day it's consumed is also crucial. For example, it's really pretty clear that caffeine consumption after about noon has an impact on sleep behavior. And of course, if you don't sleep, you're going to have a lot of trouble in terms of learning and memory. Now, this is even more the case when we have very high-level caffeine products, such as energy drinks, where the extreme levels of caffeine do lead to arousal issues. All right. So you're definitely more aroused, but they disrupt a whole bunch of brain systems and including sleep, learning,

memory, the motor system and the perceptual system. So again, these extremely high caffeine content substances are really not that good for you. But I want to emphasize one or two cups of coffee a day and you're probably perfectly fine. So just in sum, what is caffeine doing? Well, caffeine, if you remember, does have to create this relative imbalance in terms of cerebral blood flow. But it seems that that isn't really that big of a deal. And caffeine also impacts neurotransmitters. And if you remember, we talked about dopamine, which might lead to feelings of pleasure and happiness, and noradrenaline, which underlies

responses like the flight or flight response, and also could be why caffeine makes some people anxious. And the last one, serotonin, which is the one that directly leads to the feelings of arousal and the decreased feelings of fatigue that you get following caffeine consumption. All right, that's all I've got for today's episode. A bit of a short one, but we're back on Wednesday with another neuroscience bite and another episode next Sunday, of course. Please follow me on Twitter. It's a great place to send me questions and to get updates about cool new neuroscience trends and hear about the research from my lab. And feel free to tweet me, send me some messages, let me know what you want to hear about on the podcast. Our website is up, thatneuroscienceguy.com. It's got links to my blog, our Etsy store where

you can get some TNG merch, and Patreon where you can support the podcast. Remember, just a dollar a month isn't that much. It would make a massive help because we're trying to pay some grad students and try to get some new equipment. My name is Olaf Kregolsen, and I am That Neuroscience Guy. Thank you so much for listening, and we'll see you on Wednesday.