transcript

Speaker 1:
[00:01] Welcome to Feel Better, Live More, Bitesize, your weekly dose of positivity and optimism to get you ready for the weekend. Today's clip is from Episode 404 of the podcast with Dr Tommy Wood. Like myself, Tommy is passionate about empowering individuals to take control of their health by simplifying the wealth of information that exists and giving people practical, realistic recommendations. In this clip, we cut through some of the confusion that exists about caffeine and aim to give some nuanced, practical advice. Caffeine, good or bad for our health?

Speaker 2:
[00:49] Yes, as ever, I think this is going to happen several times. The answer is, it depends. Certainly, if we go back to the epidemiological observational evidence where you ask people how much coffee they drink, and then you look at their health outcomes, it seems like drinking up to three or four, maybe more small cups of coffee. So probably like one or two of my cups of coffee per day is associated with improved health outcomes, and that's liver disease, Alzheimer's disease. There's certainly no signal of harm, so it doesn't seem to be harmful up to those levels, and maybe some benefit. Of course, there's no randomized controlled trials of coffee drinking that show that definitively. But there does seem to be some potential benefit there, and there's lots of polyphenols and other things in, say, coffee, for instance, or tea. So these are the compounds. Often, they're colorful that make up these beans or berries, and it's the same, they're in the same class of compounds that make, like, blueberries blue, but they have, coffee has its own compounds like that, that seem to affect our gut microbiome, they affect our vascular health, and there are randomized controlled trials. Actually, on some of that, they extract those polyphenols out, and they give them to people and look at their cardiovascular function, or the health of their blood vessels, or their cognitive function, and they seem to be beneficial. So, those are the kinds of things that are coming along for the ride with caffeine. But sometimes, when you look at the research, like decaf coffee, for instance, doesn't have some of the benefits, but maybe not all of the benefits of caffeinated coffee. But again, you have to think about, well, what kind of person drinks decaf versus regular coffee? And it's probably the differences in those people that's driving that rather than the caffeine itself. So I think there's definitely a signal that some caffeinated beverages may be associated with improved health outcomes. That's probably because some of the compounds that come along for the ride in those, both tea and coffee separately. But then you have to think about the other side. So what are the things that caffeine can potentially negatively affect? The most obvious one is sleep. And different people have different abilities to metabolize caffeine. So there's a gene that affects how fast you metabolize caffeine. And anybody who's done a genetic test will have probably gotten that on there and know if they're a fast or slow metabolizer. And there's some early evidence that suggests that people who are slow metabolizers that drink a bunch of caffeine may be getting some negative effects of that just because it's hanging around in their system for much longer. But you probably know that a little bit about yourself anyway, or a lot of people do. So I know some people who are very sensitive to caffeine, right? They have any at all and they're awake for 24 hours, they can't sleep. Whereas others, and then again, it becomes, you don't know what's habit versus real, but some people who say, I can drink caffeine late at night and it doesn't affect my sleep at all. We don't really know if that's necessarily true, but it's certainly, there's some good evidence from randomized controlled trials. There's a meta-analysis that came out in the last year or two that looked at caffeine intake and it can affect sleep architecture and how much sleep you're getting.

Speaker 1:
[03:58] Negatively.

Speaker 2:
[03:59] Negatively, yes. So then it's just a case of making sure that you're timing your caffeine relative to your sleep so that doesn't negatively affect your sleep. So for me, I try not to drink caffeine after mid-day because there was this period of time where I was having coffee every night. We're in the lab and everybody's drinking coffee in the late afternoon. This is very, I did my PhD in Norway and it's very normal to have a cup of coffee at four o'clock in the afternoon or something. I couldn't figure out why I couldn't sleep. Then tinkering with caffeine timing, that made a really big difference. But that's going to be very personal from person to person. How much it affects them. The other thing that I think is very interesting about caffeine is how it affects cognitive function. If you're doing very simple tasks or you're very sleep deprived, caffeine does seem to be beneficial. But if you consume a lot of caffeine, it can actually negatively affect your cognitive function, particularly on complex tasks. So it might improve your action time. But if you had to think through some complex task, they do this in the lab with complex executive function. How fast can you interpret this diagram? Or how fast can you reel off these different things? Having a bunch of caffeine in your system can actually make you perform worse. And it's interesting because people think they're performing better, but they're actually performing worse. So caffeine improves your mood, which we know it does, but it doesn't necessarily improve your performance.

Speaker 1:
[05:31] Yeah, it's so interesting. There's quite a few things to pick up on there. First of all, genetic testing. I like the theory behind the genetic testing of fast metabolizers and slow metabolizers. But what I've seen with certain people and experienced myself, I think I am a fast metabolizer genetically, but I'm exquisitely sensitive. So I'm like, wait a minute, the genes are saying this, but I can be, I've got to be very careful with my caffeine intake, both in terms of dose and timing. For many years, I won't touch caffeine after 12 o'clock midday, unless there's some, you know, I'm tired and I'm driving, right? Or I really need to get through knowing there may be a consequence that evening as well, but for whatever reason, I need to get through something. So that was the first thing to comment on.

Speaker 2:
[06:23] And I'll just quickly respond to that by saying that whenever you think about any part of a biological system, it's not just one thing that's important, right? So your caffeine metabolism should tell you on average how fast you'll clear it, but caffeine attaches to a receptor. So it's an adenosine receptor antagonist. So there's going to be polymorphisms in the receptors. There's going to be differences in how you then respond to that, to caffeine binding to that receptor and what happens in the cell. And that's going to be different from person to person as well. So yeah, you're right, just that one thing isn't going to be enough to tell you exactly how you're going to respond to caffeine.

Speaker 1:
[07:01] Yeah. And I think also something I'm quite passionate about, whether it be alcohol or caffeine, is I've noticed with patients and myself that the kind of stress load in your life also can play a role here. For example, I remember when I did use a drink, not to excess, but if I'd have a glass of red wine or a beer in midweek, let's say after work, sometimes I wouldn't sleep so well. And you'd feel it the next day, maybe one or two units of alcohol, but the same amount when I was on holiday, I wouldn't feel a thing. Now it could be different alcohol, but it was kind of similar. And I really thought about this, I thought, well, my stress load is right down. I feel I've got a lot of headroom psychologically and mentally as well. And I think, I really think about this idea that I don't think we can completely separate biology and psychology. Like, I do feel there's something about that. So if you're really, really stressed and you're using caffeine to get you through, I don't know. I really sort of believe there'll be a different impact if you're very relaxed in drinking it.

Speaker 2:
[08:07] Yeah. And caffeine partly activates the sympathetic nervous system, which the stress fight or flight side of your nervous system. So if you're adding, if you're pouring that on top of a whole bunch of other psychological stress, of course, there's the potential for greater negative effects. Like the context is important as well. Absolutely.

Speaker 1:
[08:26] Did you ever see the study, I think it was in 2011 from the University of Bristol where they looked at caffeine drinkers and they tried to really answer the question from recollection, does caffeine really enhance performance and enhance our cognition? And the conclusion of that study was, if you are a habitual caffeine drinker, then yes, consuming your caffeine in the morning does raise your mood and cognition, but only to the level of where non-caffeinated drinkers are all the time. And I find that really interesting because it kind of makes sense to me that for a lot of us, that would be the case if we, because in the past I have quit and I haven't had it for a few months, and I'm like, I feel great all the time. Even I don't need a morning cup of tea or coffee, but I do enjoy it. So, what is your perspective on that? And then how does that fit alongside the fact that athletes, for example, or I know you're working for me, The One, for example, so I don't know if you encourage your drivers to maybe have caffeine or not.

Speaker 2:
[09:32] So, that's a very well cited study, the one that you mentioned. I think that's probably right, is that a lot of that first caffeine boost is just making up the caffeine deficiency that you've generated because you're so habituated to it, that takes you up to sort of like your normal baseline. And then you can wean yourself off within a couple of weeks and that effect goes away. I think the Formula One driver is very different from driver to driver, but something that I've noticed over the years actually fits very well with what I was saying earlier. So, there are multiple components to performing well in that environment. But if you think about the beginning of a Formula One race, there are two things you want to do. You want to get off the line as fast as you can and you want to navigate the first corner while 19 other cars are trying to do the same thing. So, caffeine, and this is based on the work of Yerkes and Dodson, which looks at your arousal level and your performance of tasks. And there's this classic arousal curve, which basically says that the more aroused you are, the better you perform up to a point where greater arousal is basically more anxiety and more stress and then your performance goes down. And every sport has its own sweet spot for arousal. So, if you're a sprinter in the blocks, your optimal arousal level is very different from a snooker player, right, or an archer, even in the Olympics, right? So, that's why they banned beta blockers, which sort of calm down your nervous system in those sports where you want to be like very calm, like archery, say, or some kind of shooting or snooker.

Speaker 1:
[11:21] I think they used to in the 80s, they drink whilst playing snooker.

Speaker 2:
[11:25] Yeah, because it would calm them down, exactly. For that reason, so they were adjusting their arousal curve. But something like caffeine will improve your performance in a simple cognitive task or a simple task. Particularly, the thing that they measure is reaction time. It's often called a psychomotor vigilance task. So if you want to get off the line fast in a Formula 1 car, caffeine is great. But what happens is that you can get to a point where your caffeine dose is so high, it will then affect your ability to navigate the first corner, which is a much more complex cognitive task because you're trying to figure out the direction you're going plus where all the other cars are. And so you can caffeinate, you want to caffeinate yourself to the point and not all drivers use caffeine. This is like some find some benefit from small doses at the right time. But you want to improve your reaction time off the line, but you don't want to negatively affect your ability to then navigate the first few corners of the race. So there's a really fine line in terms of that arousal curve. And I've seen that in action in Formula 1 drivers, so I think it's really interesting.

Speaker 1:
[12:32] Yeah, absolutely fascinating. Even that idea that different sports have got different times where you want to peak. And I guess then taking it back to a non-sportsman, well, we've all got different things in our lives that are important to us and different times in the day when we want to peak, right? So, again, what's the right dose for you? What's the right time for it? Which I guess comes with experimentation. And I guess what you're saying, and I would agree with Tommy, is that there's pros and cons. And if, for example, you really enjoy your caffeine and it has no seemingly negative effects on your mood, your anxiety levels or your sleep, and even if you accept that drinking it might just bring you back up to the level that if you didn't drink it, but you get so much enjoyment out of it, I love a good cup of black coffee in the morning for sure, then it's probably worth it.

Speaker 2:
[13:30] Yeah.

Speaker 1:
[13:31] But if you enjoy it and love it, and it's giving you palpitations and anxiety, and it's trashing your sleep, and you're moody and reactive with the people around you, you might want to rethink about your relationship with it basically. So it's not black or white.

Speaker 2:
[13:46] If it's not negatively affecting you, you're still performing well, you feel good. Great.

Speaker 1:
[13:50] Yeah. And the whole point of this conversation, Tommy, and I think for me, you're the perfect person to have this conversation with is there's too much of, in my view at least, is it good or bad?

Speaker 2:
[14:02] Yeah.

Speaker 1:
[14:04] You know, you can't really answer that question. We need to figure out what works for us. Hope you enjoyed that bite-sized clip. Do spread the love by sharing this episode with your friends and family. If you want more, why not go back and listen to the original full conversation with my guest. If you enjoyed this episode, I think you will really enjoy my bite-sized Friday email. It's called The Friday Five. And each week, I share things that I do not share on social media. It contains five short doses of positivity, articles or books that I'm reading, quotes that I'm thinking about, exciting research I've come across and so much more. I really think you're going to love it. The goal is for it to be a small, yet powerful dose of feel good to get you ready for the weekend. You can sign up for it free of charge at drchatterjee.com/friday5. Hope you have a wonderful weekend. Make sure you have pressed subscribe and I'll be back next week with my long form conversational Wednesday and the latest episode of ByteScience next Friday.