ZOE Science & Nutrition - Recap: How much coffee is bad for your health? | Prof. Tim Spector and James Hoffmann

Episode Date: September 10, 2024

Today, we’re discussing the health benefits and potential harms of the world’s most popular drink - Coffee. We drink 2 billion cups of the stuff every day. But how much coffee is bad for your health? Coffee expert James Hoffmann and leading scientist Prof. Tim Spector are here to help us understand. 🥑 Make smarter food choices. Become a member at zoe.com for 10% off with code PODCAST 🌱 Try our new plant based wholefood supplement - Daily30+ *Naturally high in copper which contributes to normal energy yielding metabolism and the normal function of the immune system 📚 Books from our ZOE Scientists: Food For Life by Prof. Tim Spector Every Body Should Know This by Dr Federica Amati Free resources from ZOE: Live Healthier: Top 10 Tips From ZOE Science & Nutrition  Gut Guide - for a healthier microbiome in weeks MenoScale Calculator - learn about your symptoms Have feedback or a topic you'd like us to cover? Let us know here Listen to the full episode here

Hello, and welcome to Zoe Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health. Today we're discussing the health benefits and potential harms of the world's most popular drink, coffee. We drink two billion cups of the stuff every day. But how much coffee is bad for your health? Coffee expert James Hoffman and leading scientist Professor Tim Spector are here to help us understand.

There's a sort of broad guideline of about 300 milligrams per day as your sort of recommended daily limit. Though I have to say my own experience, it is so incredibly personal and that people's response to caffeine particularly is, you know, a broad spectrum. So just because you're below 300 doesn't mean it's the right quantity for you. I sort of want to add that in there. And actually, one of the interesting things about coffee just quickly or caffeine that people don't talk about enough, it's one of the few good legal performance enhancing compounds that are sort of left, though it was temporarily banned by the Olympic Committee for a while. So you couldn't have too much coffee before running a race because it does increase your power output. So caffeine before the gym is a good thing. And I think from my own experience, definitely see the benefits of that. It's only about 1% advantage.

So if you're an elite athlete, 1% is a lot, but for the average weekend gym go. Well, I was just thinking that I always really like a cup of tea just before I go to the gym. And this has always made everybody laugh. And now I finally, I mean, let's be honest, it's because I like a cup of tea a lot. But I'm now going to say it's just about pushing that extra 1%. It's brilliant. I've got my, I've got, I think everyone's got their excuse now for bringing in their super frappuccino into the gym. Though the, I think everyone's got their excuse now for bringing in their super frappuccino into the gym. Though I think the tested quantity was about a 200 milligram dose. So it's quite a lot of caffeine, really. So just to sort of caveat my way out of that one just

quickly. That's fine. And on sleep. So I mean, I would say at a personal level, I definitely find that caffeinated drinks affect sleep. And we know that sleep is really important for health. That's come up in so many of the different studies that we and others have been involved with. So I've definitely sort of felt that there's a ceiling, which for me is probably about sort of three o'clock that I need to cut back. But interestingly, that wasn't true when I was younger. Tim, like what's going on?

Is this true for everybody? They need to stop their caffeine so early in the day. How do we think about figuring out whether you need to stop and at what time? The average levels in epidemiology tell us that things change for most people with age and the ability of breaking down the caffeine so that it's no longer potent and how quickly it comes out of the system. So we know the half-life, which is the time at which it takes to get to half the dose, so you've got half that coffee, is somewhere between five and seven hours. But that means that it could take double that to actually clear the system.

And everyone has a different threshold of how that affects them, but also a different rate at which they break it down, just like alcohol. And so they found that these averages are fine, but men will actually break down coffee quicker than women. So generally females will have less, coffee will have a greater effect on them in terms of their sleep. We also know that cigarette smokers break down caffeine more. So to get that hit, they need to actually double the amount of intake than non-smokers. And a number of medications also influence this as well. So the oral contraceptive pill is another one.

And then on top of that, you've got this enormous, perhaps genetic difference between people that, just like alcohol, confounds the whole problem. So I think everyone just has to do their own experiments and don't believe someone else's story about what works for them or not. They should do their own experiments and try using decaf coffee instead, get someone to switch their coffees around so you don't get the placebo effect and test it out for themselves. And some people really are absolutely fine drinking a cup of coffee just before going to bed.

Others can't have it after 10 o'clock in the morning. Yeah, it's amazing. My father-in-law really can have an espresso after dinner and no effect whatsoever. I can tell you for sure that I'm wired and even if I fall asleep, you know, it's going to really affect how I wake up. And I think, Tim, you would definitely say that's cancelling all the health impacts of the coffee if it's damaging your sleep has big knock-on effects. So you need to use this carefully. And I think we need to start thinking about how to give people advice in a personalized manner. You can test your genes for coffee now, if you go to something like 23andMe, which gives you a rough idea of, it doesn't explain most of the variation, it'll just give you a rough idea whether you're particularly sensitive but i think people doing their own experiments is probably the better way forward and um yeah and you can get used to it as well i mean i think as james has hinted at if you did start as a child

probably you build up a pretty good resistance you know to this so that you need higher doses to actually keep your weight. That's the other factor here. Although I'm not saying we should be giving all our kids large expressos before going to school. I was going to say, is that your official advice as a doctor? Well, it might be better than most of the breakfast cereals we're giving them at the moment. So the Italian breakfast might be the solution.

We'll have to see. Sounds like we need to do some studies. I don't think I'm going to be pushing coffee on my children quite yet. So one natural consequence, I guess, is to think about decaffeinated coffee, if you like the taste. We actually had lots of questions about this. Maybe like, what is it to start with? And then a lot of questions about, is it safe? Do you get the same health effects? But maybe start, James, by just helping us to understand what it is. So decaffeination is done to the coffee as a sort of the raw seed stage. So it's done before roasting.

And I think the coffee has to be sort of 99.5% caffeine free at the end of the whole thing. So it's an effective sort of process from that point of view. It's done a number of different ways. And essentially what they're all trying to do is sort of bind the caffeine into a solvent, into a solution without taking other things out of the coffee as well. You can do it with water, and there's a process you'll see called the Swiss water process that sounds very lovely. There's one done with what's called supercritical carbon dioxide. Essentially, if you compress CO2 enough, it becomes a liquid, and you can use that as a solvent. That's a gross simplification, but go with me. And then there are other processes that have lovely names like the sugarcane process, which sounds great. The proper name for that is

the ethyl acetate process, which scares people. So you'll tend to see sugarcane process on the packaging. All of it is completely safe. It's absolutely safe. And done well should have a very limited impact on taste. Decaffeinated coffees are harder to work with as a roaster and they go stale faster. So if you're a decaf lover, you really want to be buying fresh roasted beans and grinding them yourself for the best experience. And you can have truly, truly delicious decaf coffee. And Tim, any view from on your side on decaf? Is it as healthy as caffeinated coffee? There is some indication that it is nearly as healthy. And so most of the studies,

they lack a lot, the big numbers of decaffeinated coffee drinkers. So the confidence intervals are a bit wider, but most of the data, not all, most of the data points to decaf having some health properties as well. So I think this all adds up that if it's well-made coffee that still contains polyphenols that hasn't been killed off in the industrial process of making perhaps the cheapest instant coffees, then there will be some benefits also because the polyphenols are still there and the fiber is still there. And I think that's really a good point. And I was brought up on saying that basically decaf was the devil and it also tasted revolting when I was a teenager. So it put me off for a long time. But in my research, seeing that in blind tastings to coffee snobs, the decaf version could often win, I think, is a real turnaround. So I think we need to change our minds about high-quality decaf.

And we haven't touched on a few other health side effects of coffee. Some people might notice that they go to the toilet more, have a pee more. And there is some evidence that it causes increased sensitivity of the bladder. And you might notice this when you have three coffees in succession, you suddenly go into lots of Zoom calls or meetings and you have to leave the room, which has happened to me. But it's not a diuretic, but it does seem to have, when you have large doses, an effect on the bladder wall that makes you more likely to go to the toilet. So that's something to look out for.

Some people do find it as a useful sort of laxative and helps them, which is generally a good thing if you get the dose right. So there are a number of these health issues which are very personalized and will affect some people and not others. And I think it's just important to realize that they can occur. And again, a sign that you need to maybe titrate the dose if you are going to the toilet every 15 minutes and something's wrong. Though I will say the whole stimulating the bowels thing,

it really threw me for quite a long time because of how rapidly it happens for people. So it's clearly not a kind of traditional sort of digestive reaction, so to speak, because people will experience that within a few minutes of drinking coffee. So clearly there's a sort of hormone release tied to the experience of drinking coffee rather than it's getting all the way down and sort of stimulating your bowels that way. It's a sort of interesting mechanism from that perspective. Does coffee dehydrate you? Quick answer is no. There's no evidence it's a diuretic. So you can keep drinking your coffee and you'll be all right.

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