What does caffeine do to our bodies?

You've downloaded BBC Inside Science first broadcast on the 4th of September 2025. I'm Marnie Chesterton. Hello! Could a few rousing bars of Ravel one day replace your medication? We'll be finding out. We'll also be asking why this week's earthquake in Afghanistan was so deadly, and Science Broadcaster Caroline Steele joins me in the studio for a run through the best of the newest science. Tempt us to stay tuned in Sentence, Caroline. Okay, so I'm going to share how a volcanic eruption is linked to the French Revolution, a new way to detect unwanted solar storms, and why Science says your dog could go vegan. Intriguing. But first, energy drinks have hit the news this week as the government announced it wants to ban sales to under 16 year olds. I'm talking about the fizzy sweet cans of drink that almost a third of children say they have every week. Now, a highly caffeinated adult tends to have headaches and problems sleeping, but do children experience any extra problems? Is there any science to back the ban? Joining me is James Betts, a professor of metabolic physiology at the University of Bath. James, you study caffeine and the effect it has on us, right? Correct. We have done a few trials in this area, yes. Excellent. So caffeine is in tea and coffee, and one time I drew up a fun list of everything I could find that a British newspaper claimed has either cured or caused cancer and coffee was on both of the lists. So can you give me your meta analysis in a word, coffee, good or bad for me? Yeah, I'm not unfortunately going to fall into the trap of calling it good or bad, but I'm completely with you that I can understand it's on both lists. I find it quite interesting. Anytime there's a newspaper report on this, it's fun to just scroll down to the public comments and see people feeling rightly confused because they say, didn't this same newspaper tell us last week not to have coffee and then the next week you should have coffee. They are contradictory, but as a scientist, when you look at the different types of science, I can maybe understand a little of the reason behind some of those different findings. Well, let's unpack that. What is caffeine and why do we drink it? In most cultures, maybe one person in five consumes caffeine every day, but it isn't a nutrient. It's a pharmacological agent or a drug. If I'm doing interviews about other foods, I generally am sitting on the fence and saying, well, one food alone doesn't make or break any particular functional response in the body. Caffeine has very, very potent effects. Tiny amounts can have very clear effects on the body. I guess what it comes down to is whether you want those effects. Some of them you never want and some of them you want sometimes and not others, like the most obvious one is a wake-up call. Is it working by a particular pathway to have those effects? Unlike other nutrients that might target a particular cell in a particular tissue, caffeine is taken up by almost every cell and every tissue in your body, which is why its effects are not just really profound, but really quite wide-ranging. What about children? Because the reasons I've heard for not selling these energy drinks to children include their sugar content and the caffeine content, the fact that some of them are marketed to kids. Is there any science about caffeine that looks at the effects on young people specifically? There is science out there. Even the science in adults is, as we've covered, kind of a bit equivocal. There's less of the basic physiological work in children and I think there's three reasons we don't have evidence there. One is that it's very difficult and maybe unethical to do studies where you would feed high doses of caffeine to youngsters. Secondly is that the kind of invasive measurements you'd need to see those effects we tend not to do in children. And the third one is that some of these effects we're thinking about are necessarily longer term, so if we're wondering about the effects on development or long-term chronic disease, these energy drinks haven't been around in their current form long enough for us to see the outcomes there. So there is science. We don't have clear answers, but I think there's a lot of things that intuitively we know will be the case here. So while we know very high caffeine intake can be a problem for adults, children, one thing that really is going to define many of them is that they are generally smaller than adults. So although we're often talking about this drink having x-many espresso's worth of caffeine in it, we have to remember we could be dealing with an individual here who is half the size, third of the size of an adult. So as a scientist I would be not talking about the number of milligrams of caffeine, but how many milligrams per kilo of person. And we know that children also there's greater focus on developmental issues here as a fully developed adult. Caffeine in a way can't interfere with your development because it already happened. Is the caffeine added to these drinks different? Will my body take it up differently from the caffeine in the cup of tea I had this morning? Yes, so while caffeine in itself is just the same chemical being consumed in both forms, there is evidence that the form in which you consume caffeine can be different. So for example if we are then changing focus and thinking of the situations where caffeine is helpful, a lot of athletes for example will consume caffeine because it's well established that it will improve performance in some sports. We do know from that context that you can have a strong coffee but if you're having powdered caffeine might achieve those ends much more effectively. But I would never make that statement without immediately adding afterwards that this brings in a much greater concern for me. If someone's having a coffee you're kind of limited in how much caffeine you're going to provide. You would notice if you consumed 50 coffees in a row. Whereas if someone is then preparing a caffeinated supplement by using powdered caffeine or caffeine tablets, there's unfortunately you may have seen each year reported deaths from people who've overdosed. So again we come back to the point that caffeine isn't a nutrient, it isn't like putting teaspoons of sugar in your coffee. You are talking about milligram amounts here. A tiny pinch of caffeine has a huge physiological effects. Okay, so just sort of reiterating that it is a drug. I realised I haven't asked you whether you thought the ban on caffeinated drinks for under 16s is a good idea. I thought that, is it a good thing? And if I was a manufacturer of the energy drinks, I think it was a bit unfair because they'd be thinking, so they can't buy this drink, but they could buy a coffee in a cafe or make a coffee at home. And it can have just as much caffeine. So it's difficult to defend it on that basis. But I would actually support this because frankly I think that teenagers shouldn't even be having those very large strong coffees. But yeah, I think it's probably a good thing to do. That's a good note to end on. James Betts, thank you very much. Thank you. Afghanistan is a region familiar with earthquakes. Positioned where the India and Eurasia plates meet, it's in an area of very high seismic energy. Still, the magnitude six quake which hit the mountainous Kunar province was deadly. More than 1400 people have died according to the Taliban government and that number is likely to rise. Just why was it so destructive? Dr. Judith Hubbard is an earthquake scientist at Cornell University and earthquake insights and she joins me now. Hello Judith. Hi. Zooming in on that number first, is magnitude six that big? No, magnitude six earthquake is actually pretty small. We see them, you know, regularly once a week or so. But this one has been particularly devastating. We had earlier in the summer a magnitude 8.8 earthquake in Russia. How much stronger was that than this one? Well, I would have to look that up. But typically when you go up one order of magnitude, you have about 30 times as much energy released. So between a six and an eight, that's a factor of about a thousand already. So an 8.8 is much, much bigger than a magnitude six. And this was a shallow quake? What does that mean? Yes, that's right. Earthquakes can happen on faults at depths between zero and about 700 kilometers depth. Typically the closer you are to the earthquake, the more shaking you'll feel. So if the earthquake is very deep, it's naturally quite far away from people. But if it's shallow, if it's within the upper 10 kilometers of the crust, the shaking is coming from a fault very close by. And so you can have very intense shaking close to the epicenter. And tell me a bit more about the plates that formed the place. What's going on under Afghanistan? Afghanistan sits on top of what we call the India Eurasia Collision Zone, which is a very large zone. It doesn't just impact Afghanistan. It continues through the Himalaya to the east. It goes into Bangladesh and Myanmar. Even further east in the west, you can continue it through Iran. It even continues all the way towards the Alps, so that it's not India colliding. It's Arabia. This whole region is an area where there used to be a subduction zone. There was an ocean basin between India and Eurasia. Subduction zones, we see them all around the world. They also can produce very large earthquakes. But the ocean basin subducted away. So now we have two continents that are colliding continents. They can't just sink down into the mantle. They're not dense enough. So you have this very wide zone of collision, where you have these mountains growing between the two tectonic plates. Okay. And I was going to say, subduction zone is where one plate goes under another. Yes, that's right. So this earthquake in Afghanistan, did we know about its fault line? Was it expected? I would say a magnitude 6 earthquake could occur in almost any mountainous part of Afghanistan. There are a lot of faults, but we don't know a whole lot about them. We know there are faults that have formed sometime in the last 50 million years, right? So that's roughly when the continental collision started. It's a long time. There's a lot of time for these faults to develop. We don't know specifically which fault slipped in this earthquake. We have some guesses, but it's not a surprise. Are there tools on the ground or remotely to help understand what happened here? Yes. So the first information you get about an earthquake is the seismic waves. In this case, I think one of the closest seismometers is in Kabul, which is not that close to this earthquake. So it was a little bit uncertain initially when the earthquake happened exactly where it happened. But within the couple of days after the earthquake, there was a satellite flyover that uses radar so it can see through the clouds. And that helped us see which parts of the earth went up and down, which gives us a better pinpoint on where the fault was that slipped. But it's still a little bit ambiguous. The satellite data can't see below the ground. We can't quite tell which fault it was yet, but we have a pretty good sense of where it was. Dr. Judith Hubbard, thank you so much for coming on to Inside Science and telling us more about the earthquake. Thank you. Just a reminder that you're listening to BBC Inside Science, your home for all the breaking science news. Next, could you replace some of the medicines we take with something as simple as a song? Welcome to the subject of the third of our shortlist for the annual Royal Society Trivedi Book Prize. The author is Professor Dan Leviton, cognitive psychologist, neuroscientist, musician and author of four books. First, before we hear from him, let's hear what the judging panel thought of his latest. Hello, my name is Roma Agrawal. I'm an author and an engineer. And the book that I'll be talking about today is Music as Medicine by Daniel Leviton. So this book is a really interesting coming together of science and music. And what Daniel is looking at is how music can actually rewire and reshape the brain in a way that may be used in therapeutic settings. And I'm really excited to see how that develops alongside the more traditional roots of medicine. I found this such an engaging and easy read because it's got an amazing mix of personal anecdotes of Daniel's own musicianship and the instruments he plays alongside the neuroscience. And so I learned so much about both topics about music, about medicine, but also how music and neuroscience are so incredibly well linked. So that was the review from the judging panel. Dan Leviton came into the studio earlier to talk to me about his book, Music as Medicine. Music has sometimes subtle, sometimes profound effects on our body and mind. It can lead us to deep emotions, tears of joy, tears of sorrow. It can evoke memories. And it can coordinate physical movement better than any other art form. People don't wiggle to artworks, paintings, and sculpture usually, but music gets the pudendum going. The subtitle of your book is How Can We Harness Its Therapeutic Power? So I'd like to talk about some specific examples. We'll start with one that people may know about, which is stuttering. A lot of Star Wars fans may be aware that James Earl Jones was a stutterer, but not when he was acting, right? Right. So stuttering is a timing disorder. In order to create smooth and continuous speech, your brain has to work out a very complex series of movements of the tongue, the jaw, and the lips and the airways. And they have to be timed precisely or you end up trying to talk and your mouth is closed or your tongue moving, or something like that. What James Earl Jones, and for that matter Elvis Presley, who is a stutterer, figured out is that if they have a rhythm, either an external rhythm in a song or an internal rhythm in their head, the rhythmic parts of the brain can stand in and fix the broken parts of the brain that cause the stuttering. So James Earl Jones would learn his lines rhythmically. And of course, with music, you don't notice it because the music is effectively stimulating circuits in the brain that entrain to the timing, lock in to the timing. And that gives the brain all it needs to know about how to coordinate the movements of the articulatory system. Okay, so you can coordinate the movements if you've got a rhythm in your mouth, but let's move to a disease of movement of the body Parkinson's. So Parkinson's is a degenerative disease, and it affects primarily a region of the brain called the basal ganglia, which helped to coordinate smooth and continuous voluntary movement, like walking or even getting food from the plate to the mouth. And as in the case with stuttering, what people with Parkinson's lack is the internal timing circuits, the internal clock as it were, telling the brain when to affect particular movements. So if we play music that has a steady beat that's at about the pace of a person's normal walking speed, entire populations of millions of neurons automatically entrain to that they synchronized to it. And so that allows somebody with Parkinson's listening to music after a few seconds of it, their brains lock in and then they can start walking again. So Ravel's Balero would be a version of a piece of music that would work well with this. Depends on a person's walking speed and the tempo that the conductor used, but yeah if it's going... Is it just useful for Parkinson's patients for helping them, you know, coordinate movement? Well it's more than that because music stimulates the production of dopamine in the brain and Parkinson's among other things is a dopamine deficiency disease. And I write in the book about Bobby McFerrin, a longtime friend of mine, who was diagnosed with Parkinson's while I was writing the book. And there's a very moving story in which he explains that performing has actually been a kind of therapy for him. Without the correct dopamine production and uptake in the brain, Parkinson's patients are left not just with difficulty moving but unmotivated to do things that would normally give them pleasure. Dopamine's part of the motivation circuit, the drive that gets you out of bed in the morning. And in McFerrin's case, he found that performing actually gave him the juice, the energy he needed through the dopaminergic system. I think that's fascinating. Is there a particular type of music that he discovered was helpful for him? Well, it was such an interesting question. And a Bobby McFerrin concert is unlike any other in that it's entirely improvised. So he's finding refuge in the music that just occurs to him in the moment. There is no particular music that's more healthful. There's no one genre that's better than another. You can't say that classical is better than hip hop or that hip hop is better than heavy metal or worse than country. It's all what you like. It's very personal. So given that your book is chock full of all of the different ways in which music can help reduce blood pressure, help with diabetes management, Parkinson's, Alzheimer's, reducing pain, increasing resilience, I'm just wondering where the research is when it comes to using music as medicine instead of pharmaceuticals. So let's go back to Parkinson's for a moment. There is no effective medicine that will help get a Parkinson's patient walking again. Music is that medicine. Let's talk about a surgical suite where you're about to go into surgery. The anesthesiologist is going to knock you out. And before doing so, typically they'll give you a pill to relax you. And medication is more expensive at a hospital setting than it is if you know if you just went to the corner pharmacist and filled a prescription. So here in the U.S., that volume might be $3. In a U.S. hospital, that same volume is $750. Where I'm going with this is that we've seen a number of studies that show that if you play people music before they enter an operation, calming, relaxing music. Music, they find calming and relaxing. You get better results during and post-surgery than you would with the pill at a fraction of the cost. Wow. So an economic case for having more music in our life. Yeah. Another case, Marnie, is intractable depression, drug-resistant depression. Antidepressants just notoriously don't work well. So we've got people with depression. And I don't mean just feeling blue once in a while. I mean clinical depression. You can't work, you can't get out of bed. And the medicine does nothing. But music as an adjunct to talk therapy and medication really seems to put it over the hump. So do you see a future where music is just a core part of our healthcare? I sure hope so. And I hope if anybody in the legislature is listening to this, they will consider introducing a bill to incorporate more music into NHS because it's a big cost saver and it's proven now to be effective. That was Professor Dan Leviton. Dancing with me in the studio is Caroline Steele. Caroline, we're going to march through the best of this week's science. What's caught your eye this week? So scientists have found a new way to predict solar storms. Okay, what is a solar storm? So the earth is constantly getting bombarded by charged particles from the sun. But luckily we have a magnetic field which shields us and protects us. But sometimes the sun releases more particles than normal during a coronal mass ejection. And then our magnetic field can become overwhelmed and these charged particles basically rain down on the surface of the earth causing a solar storm which can interfere with electronics. It can be sort of a small interference or if it's a big solar storm it can be a big problem. So for example in 1989 a large solar storm left millions of people in Quebec without electricity for nine hours. So a pretty big deal. Okay, that's bad if you want to charge your phone. But it's clearly more important for things like, I don't know, running the trains and hospitals, aviation. Yeah, exactly. And we've not had a solar storm of that size since 1989. And obviously we rely on electricity so much more now. So it would be really useful if we could be warned in advance. Exactly. And so at the moment we've got satellites and telescopes sort of watching for coronal mass ejections which could lead to solar storms. But we only have about an hour of warning before it hits, which isn't super useful. But Emma Davies at the Austrian Space Weather Office has found a way to give us a heads up earlier using ESA's Solar Orbiter, which is a spacecraft that's currently orbiting the sun. It's up there to sort of learn more about the sun, not specifically to do with solar storms. But on the 17th and 23rd of March the Solar Orbiter was passing between Earth and the sun when coronal mass ejections happened. And it was able to detect these ejections, predict the strength of the storms and give us a heads up seven and 15 hours respectively before the storms hit Earth. Okay, so it can relay the message faster than the storm itself? Yes, because it's using light to communicate, whereas the storm is made up of charged particles which move slower. So you said seven and 15 hours warning. Yeah. Is that enough? Well, it could give us time to maybe do things like unplug stuff, which can protect things from solar storms, charge stuff, because if we're going to be without electricity for a long period of time, bring in backup generators. So I mean, we're not going to be able to get rid of all the risks associated with the solar storm. But I think with more than an hour's warning, it could help some places prepare a bit better. Okay, now we've covered earthquakes, we've just heard about violent space weather, moving on to volcanoes and how they've shaped history. Yes, so recent research suggests that a volcanic eruption could be linked to the French Revolution. What? It sounds like the start of a weird riddle, but it's genuinely great science. So published in the Journal of Global and Planetary Change, scientists at the University of Toulouse in France studied 140 rebellions or revolutions from 1250 to 1860, and they compared these rebellions to records of solar activity, records of volcanic eruptions, and records of the price of bread. And the reason why they were interested in volcanic eruptions, what's that got to do with rebellions? No, I'm drawing some links here. Because volcanic eruptions have a cooling effect. They give off loads of sulfur dioxide, which goes into the atmosphere and ultimately ends up reflecting the sun and cooling the earth. Solar activity obviously affects the temperature of the earth as well. And the scientists found that when temperatures fell, whether that's because of a volcanic eruption or fewer sunspots, there was an increase in the number of rebellions per year. And the team found the strongest correlation when comparing the number of rebellions to the price of bread. So steep increases in bread price led to a steep increase in the number of rebellions. So basically, we've got a sort of sequence of events here. This is correlation, we can't say it's causation, but we've got temperatures dropping, harvests being more likely to fail, prices rising, fan-ins looming, and people being more likely to rebel. That makes sense. So how can you pin the French Revolution on it? So one of the most extreme periods of upheaval followed the Iceland's Larky volcano in 1783. After that eruption, there was a peak of 1.4 rebellions per year, and that includes the French Revolution. That is fascinating. It's such an unexpected link. It's actually not the first time I heard this idea of linking the French Revolution to volcanic eruptions, but this is the first quantitative piece of research I've come across. And it also makes me wonder how could climate change today be interacting with our political behaviours? Which is probably something for PM, which is coming after us. But before that, you mentioned making our dogs vegan. Yes. So we're seeing a lot more vegan humans, and the pet food industry is sort of following suit, and there's a lot more vegan dog foods available on the market. So scientists at the University of Nottingham analysed 25 different commercial dog foods, some meat, some vegan, and they found that none of them met all the official nutritional guidelines for dogs, despite all being labelled as nutritionally complete. So generally kind of concerning. Most, including five out of six of the vegan foods, didn't have enough iodine, but that could be easily fixed by adding some seaweed. And vitamins in general were sufficient across the board, except for vitamin B, which came up short in plant-based foods. Okay. So seaweed and marmite for your dog? Basically. And scientists have gone on to basically call to manufacturers to make up for the deficiencies, not just in vegan food, but in the meat food as well. And they say that a nutritionally complete vegan dog food is entirely possible, and could be a great way of reducing our carbon footprint. Just to say, for cat owners? Sadly, cats do need to eat meat. So dogs are omnivores, like us humans. So humans can get a nutritionally complete diet without eating meat. Dogs can do the same, but cats, carnivores, they do need to eat meat, which is a shame, because I have a cat and I'd love to feed him broccoli. Alas. Alas. Well, thank you very much, Caroline. That's me out for a month. Victoria Gill is presenting next. But if you want to know more about the science that will help you crack the perfect barbecue, we are recording a special in front of a live audience at the Abergavenny Food Festival on the 20th of September. So do join me then. Until next time, bye from Caroline Steele. Bye-bye. And goodbye from me. You've been listening to BBC Inside Science with me, Marnie Chesterton. The producers were Dan Welsh, Jonathan Blackwell, Tim Dodd, Lucy Davis and Claire Salisbury. Technical production was by Rhys Morris and Emma Hart. The show was made in Cardiff by BBC Wales and West. To discover more fascinating science contents, head to bbc.co.uk, search for BBC Inside Science and follow the links to the open university.