ZOE Science & Nutrition - Is Coffee Healthy?

Episode Date: May 12, 2022

Coffee’s earliest consumption dates back millennia when the tribesmen of Ethiopia used its ground-up berries to help aid concentration during prayer.  Arriving in Europe in the 17th century, Coffee quickly began to replace beer and wine as a favourite breakfast drink.  In the 20th century, coffee was blamed for high blood pressure and heart attacks, and more recently linked to a rising epidemic of poor sleep.  None of this has prevented coffee’s relentless rise. Over 2 billion cups of the stuff are drunk each day.  So, is coffee a guilty treat as many of us suspect? Or is it a health drink feeding your good gut bacteria?  In this episode, Jonathan speaks with James Hoffmann and Tim Spector to find out. They discuss how coffee affects your gut bacteria, your hormones and your heart, whether decaffeinated coffee is healthy, and discover some of coffee’s most surprising side effects – which could come in handy if you find yourself in the jungle. James Hoffmann is a leading coffee expert and author of the World Atlas of Coffee and co-founder & chairman of the Square Mile Coffee Roasters. Tim Spector is a co-founder at ZOE and one of the top 100 most cited scientists in the world. Download our FREE guide — Top 10 Tips to Live Healthier: https://zoe.com/freeguide Timecodes: 00:00 - Intro 00:11 - Topic introduction  01:54 - Quickfire questions 03:30 - What is coffee and why are we willing to spend money on it? 04:51 - Views on coffee 08:07 - Health properties of coffee 10:24 - How is coffee made? 14:32 - Quantities of caffeine in beverages  16:12 - How important is fermentation for coffee flavor? 17:20 - What does the fermentation stage look like? 19:51 - Fiber & coffee 24:00 - Effects of coffee 24:54 - How much is too much coffee? 26:39 - What time is the best to drink coffee? 30:32 - What is decaf and is it safe? 34:03 - Does James drink decaf? 34:44 - Is decaf as healthy as caffeinated coffee? 36:01 - Does coffee quality matter? 37:00 - James' coffee preference 38:15 - Health side effects of coffee 40:25 - Is it healthy to mix coffee with milk? 42:48 - James' opinion on coffee with milk 44:31 - Summary 46:39 - Instagram question: Does coffee dehydrate you?  47:00 - Goodbyes 47:17 - Outro Episode transcripts are available here. Follow James: https://www.instagram.com/jimseven/ Follow Tim: https://twitter.com/timspector Follow ZOE on Instagram: https://www.instagram.com/zoe/ This podcast was produced by Fascinate Productions

Welcome to ZOE Science and Nutrition, where world-leading scientists explain how their research can improve your health. In Ethiopia, coffee berries have been ground up and boiled for thousands of years, where they were used to aid concentration during prayer. They arrived in Europe in the 17th century, and within a few years there were 3,000 coffee houses in England alone. Coffee quickly began to replace beer and wine as a favorite breakfast drink. Early coffee drinkers felt dramatically improved alertness and coordination by swapping their

alcohol for caffeine. Handy when earning a living with your hands. However, it was also met with fear, with some church clergymen calling it the bitter intervention of Satan. In the 20th century, coffee was blamed for high blood pressure and heart attacks. More recently, caffeine in coffee has been linked to a rising epidemic of poor sleep. None of this has prevented coffee's relentless rise. Today, over 2 billion cups of the stuff are drunk each day. So, is coffee a guilty treat, as many of us suspect?

Or is it a health drink, feeding your good gut bacteria? My expert guests are here to set the record straight with the latest scientific evidence. I'm joined by James Hoffman, leading coffee expert and author of The World Atlas of Coffee, and my friend Tim Spector, one of the top 100 most cited scientists and my scientific co-founder at Zoe. In this episode, you'll learn how coffee affects your gut bacteria, your hormones and your heart, whether decaffeinated coffee is healthy, and discover some of coffee's most surprising side effects, which could come in handy if you find yourself in the jungle. James and Tim, thank you for joining me today. Thanks for having me.

It's a pleasure. Why don't we start with a quick fire round of questions, starting with James. Is there a best way to make coffee? No, there's a best way for you, but there's not a sort of best overall way. Does coffee affect your sleep? Yes, it does. Can you drink too much coffee? I mean, there's a lethal dose of caffeine, so about 150 espressos will kill you. So yes, yes, you can drink too much coffee? I mean, there's a lethal dose of caffeine, so about 150 espressos will kill you. So yes, yes, you can drink too much coffee. Okay, I'm guessing that most people don't hit

that level. I would hope not. And finally, James, is coffee addictive? Complicated, but I'm going to say no. Tim? I think it depends how you define addiction. Certainly, if you stop having it, there are side effects. So by some definitions of addiction, it would meet those criteria, but clearly it's not like heroin. Brilliant. And Tim, is coffee a high-fiber food? It is. It's probably the drink you have regularly that contains the most fiber. There's more fiber in it than a glass of orange juice. Are there coffee-loving gut bacteria?

There are indeed. And Zoe's discovered some of them. Yes. And you can tell a coffee lover just from looking at their poo. Which is a messy way to figure out whether someone likes coffee. Yeah, you could ask them. Yeah. And last question, which we'll go back into in more detail, but is coffee healthy? For most people, it is a healthy drink for those that tolerate it well. Yes. Excellent. And we'll come back and talk, I'm sure, a lot more about that. So why don't we start before that, James, with you just telling us what is coffee? And I guess also, why are we willing to spend, you know, $5 or £ pounds on a single cup of it. Okay. Hi, I want to take a

quick break here and tell you about something new we've created, a free guide that will kickstart your journey to better gut health. Now, if you're a regular listener of this podcast, you're no doubt already aware of how important the gut microbiome is. It's responsible for so much from digestion to immune support and even our mental well-being. As we've heard many times on this show, and as our members know through using Zoe, we feed our gut microbiome through the variety of foods that we eat. And in return, our microbes give us this wealth of health benefits. So how can you nurture your gut in the best way? Which food swaps can you try to nourish those good bacteria?

What does a high-fiber shopping list look like? Our free gut health guide shares it all. Emails and actionable tips that are designed to put you in control of your gut health. To get yours for free, simply go to zoe.com slash gut guide. So coffee is ultimately the seed of a tropical fruit grows on a shrub between the Tropic of Cancer and Tropic of Capricorn around the world. At some point, we worked out that if we take this seed and ultimately roast it, smash it to little pieces and steep it in water, the resulting beverage is quite stimulating. And that was the sort of early beginnings of coffee. It's obviously evolved a great deal, especially in the last 10 or 20 years.

And so part of it is it has caffeine in it, and we like that. And I think we quickly grow to enjoy the taste, even though caffeine shouldn't be delicious. It's an insect repellent. Ultimately, that's its purpose in the plant. It's not supposed to encourage consumption, quite the opposite, but humans have a funny habit of enjoying the things we're not supposed to. And so recently, coffee's become much more specialized, less commoditized, and we've discovered that where you grow coffee, the variety of coffee that you grow, the way that you roast it, the way that you brew it, has an impact on flavor, and we can make it really very delicious and interesting. And I think it's become a sort of small luxury and delight in people's

lives day to day. This sort of necessary stimulation that they might have wanted in the morning, a little injection of caffeine has become an entertaining, enjoyable, tasty thing. And I think we're willing to spend money on that. Brilliant. And so I guess alongside this pleasure, there's been a lot of discussion back and forth, I think, about whether coffee is good for you or bad for you. Why don't we start to dig into that and both what we think now, but maybe a bit like what I think some of us grew up with stories about how coffee was bad for us. What's the view today? I was brought up through medical school as a junior doctor to really warn people off coffee, that it was bad for you. It was a stimulant that overexcited your heart

and that was probably a cause of heart disease and heart failure, heart attacks, and particular abnormal rhythms of the heart. It was also linked to cancer and other things in the 1980s. I even wrote a paper on it myself saying that coffee caused cancer of the pancreas, which was very good for my career, but was total rubbish in retrospect, as much of epidemiology. Yeah. So it's only really, I think the last five years that the evidence has really

accumulated so much that it's incontrovertible that the studies are showing that coffee drinkers have less heart disease than non-coffee drinkers. And there's certainly no excess in cancers or mortality to suggest there was any real bad effects. Now, I think there's always a caveat to this. And there are some people who are very sensitive to caffeine who might get a pulse that goes faster and they get some real effects of the caffeine. But it generally doesn't kill them or cause them any permanent damage. And they just know to avoid the drink. And that's why these long-term studies have shown that not only is it safe, but it actually has

protective properties on the heart. And do we have any idea what's going on? Like why it might be, in fact, good for us rather than bad for us? We've got some idea. Obviously, there are many chemicals in coffee that aren't just caffeine. And I think this is one of the revelations of what we're discovering about foods is that we're fixated on one of hundreds of chemicals and think that define coffee just by that one chemical when in fact there's hundreds of others. And we think that we've discussed fiber

and people who do have three or five cups of coffee a day are getting considerable amounts of fiber, which will be of benefit. But it's probably other chemicals within the coffee that have beneficial effects on the heart via our gut microbes. And these are the chemicals called polyphenols. So these are the natural defense chemicals in most plants, but particularly ones that have those bitter tastes and dark colors and is typically expressed in coffee. And so high concentrations of these polyphenols are really like rocket fuel for your gut microbes and make them produce these beneficial chemicals that we think have these amazing protective effects on

the rest of the body, particularly our heart. We don't yet understand exactly how that happens. So this is still a working hypothesis. And James, any amazing experiences about the health properties of coffee as you've been traveling around the world? That's a good question. You know, I think it's interesting the way that different cultures have embraced coffee. I think, you know, discovering that they were giving coffee to school kids aged eight in Brazil was sort of shocking to me at one point, because we have this sort of like, oh, no, it's a grown up thing. It's an adult thing. It's not that good for you. And I think other countries are like, no, it's as someone immersed in coffee, you just see a lot of claims on both sides. And I think it's often bewildering even for someone inside the industry to understand exactly what's going on and what's good, what's bad, antioxidants, all of those kinds of things that you see around there. And it's a conversation that I'm often hesitant to get drawn into because

there is so much misinformation around it. I should just add as a caveat that the health data show that if you have it's healthy between about one and five cups of coffee a day as soon as you get to six or more you seem to lose that benefit and we don't really understand why that is but there might be a nice dose you know a sort of safe threshold where the benefits outweigh any risks. But like anything that has chemicals or mild addictive properties, there might be a sweet spot that works for most people. And of course, we're probably going to talk about this more. There's quite a bit of personalization here. The same cup of coffee is going to have a lot of very different effect on different people. Averages can be deceptive. That's what epidemiology does. It takes a very broad average.

But I think we need to advise people down the individual level. Well, I was just going to say, thinking about that, you know, caffeine is not quite at the level of sweetness, but it's one of the most studied compounds on earth kind of thing. We've looked at it for a long, long time. And there are recommended guidelines for caffeine consumption of about 300 milligrams a day for an adult. And I wonder if by the time you hit five cups, you're probably exceeding that level. And essentially, while you might be getting some benefits of polyphenols, you're beginning to see the downside of excess caffeine. And that's the sort of the tipping point, maybe. Yeah, no, I think that sounds very plausible. So we've got this magic drink that's pretty cool, full of fiber and polyphenols and all the rest of it.

And it tastes good, James, which I think is very important. How's it made, right? You said it starts with a plant. I think for most of us, that's not really how we think about it. And how does this process both affect its taste and also what impact does that then potentially have on its health? Maybe you can sort of walk us through that from these plants somewhere warm. Sure. Well, I'll start at the highest level. We mostly grow two different species of coffee.

There's one that's considered superior, which you might have seen sort of coffee shops using as a term, which is Café Arabica. So they'll say 100% Arabica, which is sort of the better of the two species. The other species we know as Robusta, it grows at lower altitudes. It's much hardier as a plant, in part because it produces twice as much caffeine, because caffeine, as I said, is an insect repellent. And so cheaper coffee actually has a lot more caffeine

in it, which I think is something people don't really think about. And if you think about jumping to the end, cheaper coffees like Robusta tend to end up in things like instant coffee. So you're getting a higher dose of caffeine per sort of other potential benefits. Typically speaking, I think some of the other things that are listed like antioxidants, I don't know where you stand on those, are seen as lower in Robusta than Arabica. So generally speaking, higher quality coffee is considered better all around in a way. It's more complex, it's denser, it's better. So

that's the starting point. We then take this fruit, we harvest it ripe, we squeeze the seeds out. The fruit's like a small grape and inside there's two seeds like a peanut, so facing each other. And that's why if you look at coffee beans, there's a sort of smooth side and a round side. Those ultimately get sort of processed and sorted and shipped to the country that will consume them usually. And that's where we would roast them. So they don't get roasted until they're usually in the country of consumption. Roasting has a massive, massive impact on the chemistry of the coffee bean. The thing that's good about it is that we create flavor at that point. If you try and drink raw coffee, it's not good. It's disgusting. It's just a hard plant seed. It has none of the flavors of coffee that we sort of experience. It's got,

you know, lots of things in there that seem good, but a lot of those react away during the roasting process. So when you roast coffee and it can take anywhere from 90 seconds to 20 minutes to roast coffee, when you roast it, there's a sort of cascade of reactions that take place. So James, you're basically cooking these seeds. Is that what's going on? Yes. Yes. So it's coffee roasters are sort of a hybrid of a very powerful oven and a tumble dryer. So you're sort of rolling these beans around in the heat. And then what coffee roasters are doing is very carefully controlling how much heat's going in because small changes to the rate at which you sort of roast the coffee has a massive impact on taste. And when you talk to people who

deal with chocolate or with malt, they're just like, no, no, you just get it to go brown and it's finished. Coffee is very fussy in terms of the roasting process. So it's hard to do well. From a taste perspective, and this is kind of important, the longer you roast coffee, the less acidity it will have because some people struggle with the acidity of coffee. It's going to be a thing, a topic for a little bit later. And the, but the more bitterness you will generate. And so roasting coffee is a kind of balance between keeping enough acidity that it feels interesting as a drink, because a little acidity in food is a wonderful thing, but not overwhelmingly sour, which people don't really like, but also not overwhelmingly bitter.

And some people enjoy darker roasts than others. There's no correct roast level from a taste perspective, but that's the trade-off. You'll lose complexity, lose acidity, and gain bitterness the longer you roast coffee. So that's roasting, which is a complicated thing. So a good brew, getting a bit nerdy, but if you started with 20 grams of ground coffee, you want about 20% of that to end up in the cup below. That's a good starting point. That's a good extraction. And we can measure that. We get very nerdy about that. How much water you use to do that makes different drinks and is kind of up to you. If you use just a little bit of water, that's kind of an espresso.

It's a very strong end product. If you use more water to do the same thing, that's more like a filter coffee. And that's as delicious, but just a different kind of beverage. So there's no correct strength, but there is kind of good or bad brewing and extraction. And Tim, I hope you are measuring out the exact grams of water that you're adding onto your coffee, because I think James is going to be disappointed in you otherwise. That's my key takeaway at this point. There's actually more caffeine, if I understand it, in a weak filter coffee than there is in an espresso. And so most people assume that a strong Italian espresso is going to keep them awake more than

a sort of American style coffee. But when I did the calculations, it appears to be the opposite, better off with an espresso if you want to reduce your caffeine. How does that work? It's a good question. And what's frustrating is you'll regularly see studies published where there seems to be no correlation between the beverage and the caffeine quantities. They'll sort of secretly shop a bunch of chains in the UK and the caffeine content will be all over the place. Caffeine is very water soluble. So essentially the primary correlation is going to be how much coffee was used to make this drink. Now, in Italy, a single espresso might come from just seven grams of coffee.

So you think, oh, not too much caffeine. But they tend to use a good amount of Robusta in their espresso blends, which has a lot more coffee in there. So with filter coffee, you might be brewing from, say, 15 grams of coffee for a 250-mil cup. But that might be high-grown coffee, a pure Arabica, so not as much caffeine in the raw material. But that's the primary sort of correlation. How much coffee did you use? How much caffeine was in that coffee? Ultimately, the beverage is going to do a pretty good job of extracting the caffeine, regardless of whether it's a small drink or a big drink. So that's the sort of thing to think about when you're considering how much caffeine you're

drinking. So it's pretty hard to tell for the average consumer and just beware and assume the worst if you don't want too much. One step of the process I just wonder if you could touch on is near to my heart is fermentation. I know you love the roasting bit, but before that stage, the fermentation, how important is that in the whole flavor combat? Is it as, you know, like for chocolate, does it have such a big effect or not? So yes, yes, fermentation has a very big effect on flavor. I think just to give context to it, a lot of decisions that coffee producers are making is not around taste. It's about getting the best return they can on the crop that they've grown.

So most fermentation techniques are about reducing incidences of defect or sort of flaws in the coffee. There's a few different approaches. So as I said, we have this cherry, this fruit, and sometimes we're going to squeeze the seeds out and they'll still be covered in a little bit of sticky fruit flesh, for want of a better term.

And what they would do is let that ferment for maybe 24 hours, either, you know, covered, but with access to air or sometimes anaerobically, sort of covered in water, to break that down so that it's easy then to wash off. So you sort of have a clean seed to dry before export that doesn't have much sugar lying around that won't go moldy, that won't have any kind of flaws come into it. And just for a second, just because we talk about fermentation from time to time, but can we explain a bit for our listeners what's going on when we say it's fermenting for 24 hours? Can we explain a little bit more what's going on? Primarily what's happening, and a lot's going on with fermentation, so it's never something to say simply this. What we're trying to do is break down pectin in this particular case. So pectin is the sort of fruit fiber that's stuck to the seed. So what's happening there is microbes are breaking that down, consuming that sort of

sugar if I want to have a better carbohydrate, I suppose at this point, essentially causing it to break down. There are flavor byproducts as a result, and there's an impact on all sorts of things from acidity to sort of just sort of the fruitiness of the coffee in some cases. In other cases, this process does require quite a lot of water, and coffee has historically grown in places that maybe don't have a lot of access to water. There, historically, you would have seen that fruit picked and just dried as a piece of fruit, which is hard to do.

There will be some fermentation there that historically is kind of closer to kind of a controlled rot, for want of a better word. It's a kind of chaotic fermentation to just let a piece of fruit dry in the sun. It's much harder to control, but once you've dried it down, you can sort of hull that sort of dry husk of the fruit off and you've got access to a dry seed. The fermentation process, once coffee roasters get a hold of it, we talk about it just from a flavor perspective. So we'll talk about the sort of more tropical fruit notes of a dry process or a natural process fermentation, whereas we might talk about the kind of cleaner, more refined kind of juicy berry fruit notes or kind of grape or apple or those kind of fruit notes that you would get from more of a washed processed coffee.

And there's a hybrid that you might see called a pulped natural or a honey coffee where you sort of have this mixture of things and it has an impact on sweetness, on texture of your cup of coffee, that kind of mouthfeel, how full, how rich does it feel? But obviously there's a lot more going on under the surface. And generally these are natural microbes just in the environment or do people add specific ones to the mix? Historically it was natural natural microbes. These days, some of the modern winemaking techniques are coming in, and there's sort of additions of some bacteria or enzymes to accelerate aspects of fermentation there, which is kind of interesting. And so there's now much more controlled fermentation or intentional fermentation happening. But ultimately,

to go all the way back, historically, it was about how do I get the most valuable crop at the end of this with the least cost to me because you know coffee is far far far too cheap and so we're sort of forcing people to make these kind of decisions because they're trying to squeeze as much value as they can out of it. And one thing that's come up I'd love to explore a little bit more is fiber. When I think about fiber I sort of think about the stuff that you can't easily digest so I would would naturally thought, well, that's all the stuff that's left behind in the process that you're talking about, James, right? You said, I think that like two thirds of this wasn't going to dissolve into the hot water. So I was like, okay, I get that. That's fiber. You chew on it. It tastes terrible. Most of us have probably had coffee grounds in our mouth

before. I think what's really surprising is to say, well, in the coffee itself, after I've put it out and assuming that it's not a Turkish coffee with all of it stuck at the bottom, I would have thought, well, there's no fiber in that. That sounds sort of mad. So Tim, James, can you help us to understand what this is and how fiber is, I guess, not as straightforward as maybe we'd assumed? Yeah, it's a bit of a misconception to think of fiber as this sort of husk that can't be dissolved or digested and just passes through you. And the old concept of roughage was this old-fashioned science of how we discuss fiber. Actually, it's incredibly complex and understudied. And there's soluble forms that do dissolve in water. And there's forms that dissolve in fats. And there's forms that stay insoluble

and just sort of end up as a slime inside your gut that do lubricate the gut. So there's all different types of fiber. And this is, I think, what we're just talking about here. And clearly, there's multiple forms of fiber within something like coffee, and that's why some gets left behind, but a large amount does get drunk and get into your intestines. Yeah, I think I was sort of genuinely shocked by this research. I think I'd lived a life of, you know, I might have experimented with some resistant starches before, and, you know, that's not much fun to put a drink and kind of consume. So the idea that I could get a couple of grams of fiber from coffee seemed actually quite

shocking to me. You know, it's a good amount of what is dissolved from the sort of coffee grounds is fiber, and I had no idea. Yeah, just to put it in context, the average American or Brit, I can't remember which one it is, had somewhere between 13 and 15 grams of fiber a day. And a decent filter coffee will have something like 1.5 grams of fiber. So if you manage to get 10 cups of coffee, you'd be getting all your fiber that way. And it just shows you that just having three cups of coffee is about a third of

your daily intake. Although we know that we need double that really for good health. So 15 is not the target. It's like the sort of the low level that most of us are taking. Yes. But for many people, it's the main source of their fiber at the moment, which is quite worrying. That's amazing. And Tim, I just want to pick up on something else you said, where you said there's many sorts of fiber in coffee. So it's not just one type. That tends to matter, right, as we think about food. Could you explain a bit more?

And does that tie into some of these surprising health properties of coffee? It may well do, yes. The complexity of fiber means that this is made up of different compounds, different chemicals, and all of different compounds, different chemicals, and all of these are, in fact, food for our gut microbes. So each different type of fiber that is something that reaches the lower part of our intestines, our colon is where the gut microbes are, serves as a food for a particular highly specialized microbe that wants that one. So there might be several types of soluble fiber in coffee, and each one of those attracts a different set of microbes and different species. And we know that this diversity is really important.

So even within one plant, like a coffee bean, there are multiple sources that will feed many different types of microbe. And we know the more diversity of species you have in your gut, the healthier you will be. So it's a great example of how in the past, we haven't really understood this and how the new science is revealing these exciting insights into why something like coffee, which we thought was bad for us, is actually good for us. And when we look at how coffee affects us, I mean, we've touched on two things already. You've talked about caffeine and then you've talked about sort of this fiber.

Are those the two ways that coffee affects us? Are there other ways that coffee affects us when we drink it? Well, it obviously has this effect on our brain. And we normally have these chemicals in our brain putting us to sleep. And so clearly one of the things of coffee is to neutralize these chemicals, these adenosine molecules. And it acts as a block of that so that you can alter the normal tiredness cycle. And this is why coffee wakes you up 20 minutes after taking it. And that's very part of this neurochemical aspect of it, which is mainly related to the caffeine component.

And that's something that can have benefits, but also can have side effects as well. And we had a lot of questions on this, actually. How much is too much coffee? And I think that's related particularly in that context of sleep, but in general. And then a lot of questions about the time of day to drink coffee. And maybe, you know, maybe start with James, because I suspect, again, this is a cultural thing as well as a scientific thing, isn't it? The show you're listening to right now that's providing you the latest evidence-based health and nutrition information from the world's top scientists

while making it takes a lot of time We think it's well worth it all in the name of improving your health All we ask in return is this Send a link to this podcast to someone you think would benefit And if you haven't already click follow this podcast wherever you're listening right now. Okay, let's get back to the show. So like I said, with caffeine itself, there's a sort of broad guidelines 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 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, percent is a lot but for the average um weekend gym go well i 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 one percent it's brilliant i've got my uh i've got 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 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 that 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 know that you can test your genes for coffee now if you go to something like 23andme which gives you a rough idea of you know it doesn't explain most of the variation it will 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, yeah, 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 to this so that you need higher doses to actually keep you awake.

That's the other factor here. Although I'm not saying we should be giving all our kids large express. I was going to say, is that is that 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, you know, the Italian breakfast might be the might be the solution we'll have to see.

Sounds like we need to do some. 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. So it can be an uncompromised taste experience or barely compromised one. Most of the time, it's not that. I was going to say, I think for many people will be surprised by that. I think it's got a reputation, I guess, like many other sort of processed foods as sort of much worse for you. So I think hearing someone who's such an aficionado be so positive is surprising. Tell us a little bit more about that, I think. It may open up a lot of ears i suspect to maybe rethink this no no i think from my point of view i'm going to be talking about sort of specialty coffee very much still so this is going to be sort of smaller companies roasting coffees from distinct places you'll see farm names or sort of more

precise regions on the bag as i said this this process of decaffeination actually changes the density of the coffee bean it It becomes more porous. So it roasts very differently. And many roasters don't pay enough attention to this because they don't see it as an important product. There's a sort of snobbery against decaf inside the coffee industry too. But there are people who are passionate about decaf because this is coffee for people who just like the taste, not even the caffeine. They're just there for the taste. And they get a rough deal so yes if it's roasted fresh and if it's roasted carefully it can be good

it will look like a darker roast than it is because it's less dense the oils will come to the surface of the coffee bean it'll look like a dark roast it's often not actually but it goes stale really fast because a lot more air can get into the inside of the coffee bean it's just much less dense so if you are buying it as whole bean using it within two three weeks and and sort of grinding it fresh each time you'll have a great experience if you're buying pre-ground decaf from a supermarket unfortunately that is it's a subjective thing i would say stale it's food safe it's totally fine to consume but it is not what it once was from a flavor perspective so freshness is is the key it's the secret buy decaf from a passionate roaster who wants to sell you decaf some roasters are sort of death before

decaf and others are like no no no this should be great let's make it great and james do you let decaf pass your lips on a regular basis? Absolutely. I definitely suffer from caffeine. So my cutoff is about three o'clock in the day. I tend to drink no more than three cups of coffee a day. Doing tastings, we don't, you know, it's like a wine tasting. You're not drinking it. You're typically spitting it out afterwards. So I'm quite cautious around this, but there's times at four in the afternoon where I just want a coffee. I want that sort of moment, that sort of ritual of coffee. And so I drink decaf and I really enjoy it.

It can be really good. Instant decaf. Are you going to give us a comment on that? That's, oh, I could, but it's complicated. So there exists in the world high convenience decaf, but that's as far as I'll touch on. So it's possible, but highly rare. And Tim, any of you from on your side on decaf? Is it as healthy as caffeinated coffee? That's a great question. And 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 while we're talking about sort of making of the coffee, we got to the roasting in the end, maybe to sort of come to the final question thinking about it again from a health perspective we're generally hearing that instant coffee is probably not very good once we're outside of instant coffee does it matter there's a lot of false stuff saying that drip coffee was particularly bad for your heart and this all came from studies in scandinavia where this is very common. But I think all those were found to be spurious. So the current evidence doesn't really distinguish the types of coffee in terms of the heart disease.

I don't think we've done direct contrasting trials yet of different types of coffee. But I think if you go for the good quality ones, then you're much more likely to have a healthy outcome. I think you can go with your personal preference, you know, whether you prefer the percolator, the drip, or the espresso, there's no clear evidence that one is healthier than the other at the moment. And James, I think you said at the beginning that maybe we were free, but I find it hard to believe you haven't got a preference really. Oh no, like I have a preference, but I'm not going to say that's right that's a little too much strawberry but i like paper filtered coffee i like the clarity of flavor i don't like bits i don't

mind a french press sometimes but i just like clean tasting cups of coffee that's just for me but i like espresso which is sort of metal filtered too within the sort of coffee community there's still sort of rages a debate around, I think, lipids in coffee. Cafe All is one of them, and for the life of me, I cannot remember the name of the other one, because there have been occasional papers sort of correlating these to heart disease. But I know the world of correlating dietary cholesterol to blood cholesterol is a complicated world that I never, ever, ever want to get into. I think coffee drinking broadly seems to be healthy

and you know I think the bigger Scandinavian studies have shown coffee drinkers have lower all-cause mortality than non-coffee drinkers and that's good news to me it's not that I want to stop reading there but I think coffee is ultimately a good and healthy thing but like all things the dose is the poison so to speak so like a little moderation a little awareness I think for a lot of people I think that's where things run out of control, where they're like, oh God, I had five or six cups of coffee today. I feel a bit weird. I think being mindful around your coffee consumption is a good thing. And we haven't touched on a few other health side effects of coffee. Some people might notice they go to the toilet more, have a pee more when they're having coffee.

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. I will say the whole stimulating the bowels thing 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. Many people time their trips to the toilet by their coffee. That's right. So that's why they have to leave the house, you know, coffee before you leave the house, not when you're on the bus. I think that's right. And there are people, right, particularly people who have sort of digestive issues for whom coffee is a challenge if it's tied in with other things, right? And so it is definitely one of the things when you're going through exclusion diets and things like this that is often looked at. Again, I think, I guess that ties into this story about,

you can say that on average, something is healthy, but it doesn't always mean for you as an individual that it's the best possible thing that you can do. So the other topic, I think, we've talked a lot about coffee and what it does all on its natural state. If you can describe all the processing that's just been done as natural.

We had lots of questions about what happens when you start to add things to coffee. And basically the questions are all around dairy, right? Lots of people are used to drinking milk. And for many of us, when we go to a store to buy this, get a coffee, which is a latte or a super duper frappuccino. Is it still healthy, Tim? Well, you're still getting the same ingredients,

obviously, if you add milk to it, but you're getting the milk. So generally, my view on milk is that it's relatively neutral. It's definitely not a health drink. For some people, possibly slightly negative, but I don't think there's any evidence it disrupts any of the benefits of coffee on its own. It's obviously giving you some extra fats and some other calories and may have an effect indirectly. I mean, obviously, you know, I actually like the Italian way of having a macchiato where you basically just have about four drops of sort of frothy milk on the top, which has any, you know, just to take the edge off any bitterness. But the habit of having half milk

and half coffee, I think you do realize that having a lot of milk in your diet is probably not a good thing. And so I think people should perhaps cut back on the milk. But milk per se, I don't think is a major worry for most people. But of course, some people do have lactose intolerance in most parts of the world. So we have to be aware of that. But I think in general, the other, it's not bad. The only other caveat here is some people, if they're into restricted time eating, most practitioners will have a black tea or a black coffee and not think that they're breaking their fast. And if you add lots of milk to that, then it does definitely stimulate the insulin glucose pathways and so would break the

fast. So that might be just another consideration to get people to experiment with trying to get used to having coffee without milk. So I think many people in the UK and the US are not used to it. And I think it's something that just it's a bit of training and culture. You just go to the Southern Mediterranean, you just don't see people putting milk in their coffee unless occasionally at breakfast time and james any strong opinion from your side about it is it sacrilege to add milk to this drink no i mean milk is one of nature's great bitter blockers and so you know i think from that perspective it does a great job increasing palatability of what is ultimately often a very bitter quite harsh product the better the coffee, and better is a very difficult word to use here,

but generally lighter roasts, more expensive, higher-grown coffees have lower bitterness levels, and so they need less milk to become palatable. So there's a sort of benefit there to drinking quote-unquote better coffee or sort of more premium coffee from that perspective. I'm not a milk drinker.

It's not for me. And maybe my mind was poisoned early. The beginnings of coffee culture said, this is the 1500s, coffee and milk gave you leprosy. That was a widely held belief in a great deal of Europe in the sort of middle of the 1600s, really. That was a sort of no-go, which I found kind of fascinating. So that seems like a good reason to keep the milk out of one's coffee then. We've obviously evolved our understanding since then, but it's just a sort of fascinating tidbit from history. But then, but it's just a sort of fascinating tidbit from history. But yes, like I totally understand the sort of why people reach for milk,

why they reach for cream, why they reach for sugar. But I think that this is the upside of quote unquote, better coffee, so to speak. What that's trying to achieve is more flavor, less bitterness. So that's the thinking there. In the UK, a lot of coffee you get in coffee chains is not very good, is quite bitter. And in a way, drinking it with milk may be the only palatable way to have it. And it's a bit of a vicious circle because the more people buy lattes, the more they make the roast bitter to compensate. So it'd be nice to start getting people to experiment without it and see what the coffee really tastes like that they're trying to get at. I would agree 100%. But I would, you know.

Brilliant. Well, I think that's been an amazing tour. I think we can keep talking about this for hours, but I'm just going to try and sum up the sort of wide ranging conversation we've had. So first we started with, you know, coffee is actually the seed of a tropical plant, which is not how we tend to think about it. And then amazingly, the caffeine that we are all in search of is actually an insect repellent. Coffee is healthy. So ignore everything that we might've been told in past years. And the big reasons that we think behind that is about all the fiber that you get from it, and particularly these polyphenols that Tim was talking about. There's a complex process of making it. There are two sorts of plants. And I think James has said the Arabica is the better plant and also lower caffeine, which is interesting as you think that it's not always the same

caffeine across these. There's a fermentation process involving microbes and then you roast it, which apparently is a bit like cooking something in a tumble dryer, which is a wonderful image that I'm going to try with my son later. And that the roasting from James's perspective is sort of the most important step here for really affecting the flavor. Is that right, James? I think probably so, yes. There really is fiber in this and the fiber is not just roughage. So the reason why you might be struggling with this is because I've got the wrong vision. A lot of fiber can be soluble in water. So if you're having three or four cups of coffee, you know, you might be struggling with this is because I've got the wrong vision. A lot of fiber can be soluble in water. So if you're having three or four cups of coffee, you might be getting close to half of the average fiber intake in the US or the UK. So that's quite a lot, but

coffee has a lot of impact on us. The stimulation comes from a lot of chemicals, but particularly caffeine, it really does affect your sleep. James says you can make your coffee the way you like. So there is not one single answer, although I think we all heard that he does it with filter paper. So I'm sure we're all going away thinking that's obviously the best way really. Decaffeinated coffee is not as bad as perhaps we've been led to believe by sort of thinking about as very cheap coffee. Fine, I think we talked about milk and Tim said, you know, it doesn't do any harm to the health properties of the coffee. You're just adding milk almost as if you drink it on the side.

And on the health side, milk is neither a super health drink nor something that's really bad for most people. It's sort of neutral. So you can think about that. Just before we go, I have one final quick question from one of our listeners, George on Instagram, who said, does coffee dehydrate you? Which is something that people talk about a lot on social media. What's the answer? 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. Wonderful. James and Tim, I really enjoyed that conversation. Thank you so much for taking time to talk about this wide range from health to taste. And I think everybody will be going away and drinking a cup of coffee right now. This was great. Thank you for having me. Yeah. Thank you very much. Bye-bye.

Thank you to James Hoffman and Tim Spector for joining me on Zoe Science and Nutrition today. We hope you enjoyed today's episode. If you did, please be sure to leave us a review and subscribe. If you're interested in learning more about Zoe and the best foods for your body, you can head to joinzoe.com slash podcast and get 10% off your personalized nutrition program. Finally, if this episode left you with questions, please send them in on Instagram or Facebook and we will try to answer them in a future episode. As always, I'm your host, Jonathan Wolf. Zoe Science and Nutrition is produced by Fascinate Productions with support from Sharon Fedder and Megan McPherson here at Zoe. See you next time.