Updated 10th April 2024

The surprising way coffee can improve your health

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Coffee is one of the most popular drinks on Earth, making caffeine the world’s most widely consumed psychoactive substance.

Over the years, coffee has been demonized as a threat to cardiovascular health. But more recently, bigger and better scientific studies have challenged this idea.

In this episode of ZOE Science & Nutrition, we’re joined by two coffee lovers: Prof. Tim Spector, ZOE’s scientific co-founder, and James Hoffmann, author of How to Make the Best Coffee at Home.

James has been immersed in the world of coffee for more than 20 years as an award-winning barista, entrepreneur, and coffee consultant. He brings a wealth of in-depth knowledge and practical experience to the table.

When researching for his book The World Atlas of Coffee, James investigated the wide variety of coffee cultures and rituals around the world — all very different, though they orbited around the same beverage.

“This is a health drink. The evidence is really clear: It can reduce heart attacks by 25%.” – Prof. Tim Spector

Because caffeine increases heart rate and blood pressure in the short term, experts initially believed it could damage your cardiovascular system.

But according to Tim, coffee is a “health drink.” So, what changed?

He explains how better studies have shown that coffee actually reduces the risk of developing a range of heart conditions.

While we don’t have all the answers, the health benefits likely lie in coffee’s complex chemical nature. Made by fermenting beans, it's a heady soup containing thousands of compounds. 

Surprisingly, coffee is also high in fiber — around 1.5 grams per cup, which is more than a glass of orange juice. Three cups equates to around one-quarter of your daily recommended fiber intake.

In the Western world, many of us are fiber-deprived. So, coffee’s fiber content helps explain some of its benefits.

Plus, coffee contains a range of polyphenols. Plants produce these compounds to defend against environmental stresses. When you consume them, they fuel your gut microbiome and can help reduce blood sugar and blood pressure. 

What about caffeine?

Caffeine is the most well-known compound in coffee. Like polyphenols, caffeine is produced by a range of plants. For some, it protects against predators, but it has a wide range of other jobs.

James explains how some flowers produce caffeine to help improve bees’ memories. This ensures that the bees remember the flower’s location, enhancing the likelihood of pollination.

Tim describes why some of us are more sensitive to caffeine, and why it can ruin a night’s sleep or cause more unpleasant effects. 

For instance, females tend to metabolize caffeine more slowly, especially if they take a contraceptive pill. Metabolizing it less quickly makes caffeine’s effects last longer.

Interestingly, tobacco speeds up caffeine metabolism, meaning you’d need more caffeine to get the same hit, and its effects wouldn’t last as long. Needless to say, we’re not suggesting you try this combination. 

But if you want to reduce caffeine’s impact in a healthier way, some vegetables, including broccoli, speed up its metabolism.

The really great news is that decaffeinated coffee offers the same health benefits as caffeinated coffee. So, if you want the positive effects without the buzz, decaf is a good option.

Coffee and your gut microbiome

Tim provides a sneak peek into the results of a study he’s been working on. The research, which used 40,000 stool samples collected by ZOE, identified a particular gut bacteria associated with coffee drinking.

The bacterium, called Lawsonibacter, is found widely in nature. It dwells in the guts of almost all adults in regions where coffee is drunk, but its numbers explode in coffee drinkers. 

This is the strongest link between an individual food or drink and a specific bacteria ever identified. 

As it feeds on coffee, Lawsonibacter produces certain compounds, such as quinic acid, which help reduce blood pressure. Quinic acid also encourages the release of insulin, which reduces blood sugar levels.

A mini-experiment

Coffee is hugely varied. The species of coffee plant, how the beans are roasted and processed, and the way they’re prepared all affect the chemical makeup of your cup of joe.

In this episode, James conducts a mini-experiment to demonstrate some of this variety. Sampling Aeropress, decaf, instant, and kombucha coffee, he explores their levels of caffeine and chlorogenic acids — a group of polyphenols.

Among other insights, we learn that instant coffee, whatever you think of it, does offer health benefits.

While instant is lower in polyphenols than other types of coffee, it has higher levels of fiber. 

If you don’t like coffee, you don’t have to start drinking it, of course. But if you enjoy it, you can do so guilt-free. However, as Tim explains, if you have unstable blood pressure, it’s probably best to opt for decaf — you’ll still get the same health benefits.

Show notes

Many of us love coffee, but we may not be aware of its health benefits. If you thought coffee was just a caffeine kick, think again.

In today's episode, Jonathan, Prof. Tim Spector, and coffee expert James Hoffmann explore the intricate relationship between coffee and health. They uncover truths and myths about caffeine and describe coffee’s fascinating role in improving gut health.

Tim also shares exciting news about soon-to-be published research. The topic: coffee and the gut microbiome. Plus, James brews coffee live in the studio and helps us understand the different coffee variants. He even dives into the world of coffee kombucha.

James Hoffmann is an English barista, YouTuber, entrepreneur, coffee consultant, and author. He came to prominence after winning the World Barista Championship in 2007 and is known as a pioneer of Britain's third-wave coffee movement.

Tim is a professor of genetic epidemiology at King’s College London, director of the Twins UK study, scientific co-founder of ZOE, and one of the world’s leading researchers. 

Mentioned in today’s episode: 

How to Make the Best Coffee at Home by James Hoffmann

If you want to uncover the right foods for your body, head to zoe.com/podcast, and get 10% off your personalized nutrition program.

Find top tips for gut health from ZOE Science and Nutrition — download our FREE gut guide

Follow ZOE on Instagram.

Is there a nutrition topic you’d like us to explore? Email us at podcast@joinzoe.com, and we’ll do our best to cover it. 

Episode transcripts are available here.

ZOE Science & Nutrition

Join us on a journey of scientific discovery.

[00:00:44] Jonathan Wolf: Welcome to ZOE Science & Nutrition, where world-leading scientists explain how their research can improve your health. 


I'm your host, Jonathan Wolf, founder and CEO of ZOE. Today, we reveal how selecting the right coffee could improve your health. Espresso, instant, AeroPress, cold brew, decaf, the list of coffee options is endless. But which chemical compounds hold the secret to coffee's health benefits? And how many are in your cup of coffee? 


Today, we're joined by world renowned coffee expert James Hoffmann, who's set up a mini-laboratory right here in our studio to help us investigate. Alongside James is my scientific co-founder at ZOE, Professor Tim Spector. Tim is going to share groundbreaking findings from his brand new scientific study on coffee's impact on our health. 


James Hoffmann is the best selling author of How to Make the Best Coffee at Home. Tim is one of the world's top 100 most cited scientists and a professor of epidemiology at King's College London. James and Tim, thank you for joining me today. 

[00:01:53] James Hoffmann: Happy to be here. 

[00:01:54] Jonathan Wolf: I think that you probably know that we like to start with a quick fire round of questions.  A yes or a no, or if you absolutely have to, a one sentence. You up for it? 

[00:02:04] James Hoffmann: Yes. 

[00:02:06] Jonathan Wolf: All right, I'm going to start with you, Tim. As you know, I don't actually drink coffee. But if I started to drink coffee, could that reduce my risk of heart disease? 

[00:02:13] Tim Spector: Absolutely. 

[00:02:15] Jonathan Wolf: James, is instant coffee unhealthy? 

[00:02:19] James Hoffmann: No. 

[00:02:20] Jonathan Wolf: Tim, if I want to improve my gut microbiome, could drinking coffee help? 

[00:02:26] Tim Spector: Yes. 

[00:02:27] Jonathan Wolf: James, is it true that the darker the roast, the more caffeine in the coffee? 


[00:02:36] James Hoffmann: There's disagreement.  


[00:02:38] Jonathan Wolf: Okay. And finally, Tim, are you going to share the results of a brand new research study on coffee with us today?  


[00:02:46] Tim Spector: Maybe, if you're nice to me. 

[00:02:48] Jonathan Wolf: If I'm really nice?  


[00:02:49] Tim Spector: We'll see. 

[00:02:51] Jonathan Wolf: Hi, I hope you're enjoying listening to James and Tim's fascinating insights into the health benefits of coffee. We want this podcast to reach as many people as possible as we continue our mission to improve the health of millions. Seeing this show grow is what motivates the whole team at ZOE to keep up the hard work of creating new episodes each week. And the best way to get YouTube to show this podcast to someone new is if you click the subscribe button right now. 


So if you're enjoying this episode, please hit subscribe and make sure to turn notifications on. Thank you, and back to the show. 

Brilliant! Okay, very interesting to get into that. And look, James and Tim, it's fantastic to have you back on the podcast, and this time in person. And a few of our listeners who have been with ZOE on the podcast from the very beginning will know that this is actually the second time you've come on the show. 


But the vast majority of listeners will not have heard you before, because it was at the very, very beginning. But for those who have been listening before, don't worry, because this time we are in for a treat, because James has brought in some amazing technology, and we're actually going to be doing some science here in the studio, and therefore understand some more about what's really going on inside a cup of coffee. 


And we also have a second really fun thing, which is that I know that Tim has been working on a brand new peer reviewed paper about the health benefits of coffee. So I'm really excited to hear about this. 

But before we get into either of those things, can we actually just start right at the beginning with, with James? 
Like, why are we all so obsessed with coffee?  


[00:04:31] James Hoffmann: That's a good question. It's delicious and I think it's, you know, caffeine plays a massive role. Inevitably, it's the world's most popular psychoactive drug. But I think coffee has sort of woven its way into our cultures all over, around the world in different ways. 


The U.S. is a very different coffee culture to the U.K., to Italy, to Australia or Scandinavia. I think we enjoy the feeling of drinking coffee, but I think we enjoy the act. The sociability or the ritual or the break or all of those things of drinking coffee and hopefully it's good for us. 

[00:05:01] Jonathan Wolf: And Tim, what are the health benefits that these people might be receiving? What are the things, what are the key things in coffee that sort of could be affecting this?


[00:05:14] Tim Spector: Well for many years, we thought coffee was bad for us because short term, it increases your heart rate, increases your blood pressure. For decades, people said this is a rather dangerous thing to be having, don't do too much of it, you're going to have a heart attack. 


Then they started doing some proper studies and it was shown that you actually, based on over 25 studies, you can now see a reduction of about 25% in your risk of a heart attack or heart disease. So then you're saying, why would that be something that short term might be slightly stressing your system is actually long term good for you. 


And I think it's seeing coffee as this whole, coffee as this fermented plant that has microbes acting on it, has hundreds, thousands of chemicals produced from it, and it's probably a combination of all those things that gives it this health benefit, such as the fiber in it. 

And we used to not think of coffee as a fiber rich drink, but we now know that broadly you can get about 1.5 grams of fiber out of a cup, which means if you're having three cups a day, that's, you know, 4.5 to 5 grams of fiber, which, you know, it's a quarter of your daily fiber intake in the U.K. and the U.S. 

[00:06:39] Jonathan Wolf: I always find it extraordinary because I always somehow in my mind, think about fiber as being this roughage like bran. Or like, you know, the stuff that my grandmother, you know, might stir into a glass of, of water.  


[00:06:54] Tim Spector: Yeah. And two cups of coffee is more than a banana in terms of fiber.  


[00:06:57] Jonathan Wolf: But the point is it's a drink. So like, where's all that? You know, where's all the solid bits of fiber, and this is because my understanding of fiber isn't quite right, is it? 


[00:07:05] Tim Spector: Well, that's right. Well, fiber can be in drinks, and can be small particles that are still going to have a similar effect when they reach the lower part of your intestine, where all the gut microbes, and there are soluble fibers, and there are insoluble fibers, some of them might be invisible. 


[00:07:22] Jonathan Wolf: So I think that's the way it's actually dissolved into the drink. So there can be fiber in something you can't even see, which is… 


[00:07:26] Tim Spector: We always think about it like eating spinach or something, but actually it's not like that. And there are lots of different ways that we can get fiber into our body. 


And until recently we didn't appreciate this. It's not in most nutrition textbooks as a health drink. There's more fiber, you know, generally in coffee than an equivalent amount of orange juice, for example. 

So it's not sufficient. I'm not saying you can live just on coffee and have a good diet, but  given that, you know, in the West, we're very fiber deprived. It's actually perhaps the thing that's just keeping us going on this very low fiber diet and making up, you know, perhaps a quarter of a third of our fiber amounts. So it's the fiber. 

It's also these individual chemicals that we're still just getting to understand and this range of polyphenols that are in the coffee beans, some of them are enhanced by the microbes as they ferment it and those are released and those have direct effects on our, on our body. Some of them can reduce blood sugar and reduce stress and actually reduce blood pressure and things like this. 


So it's a complex area, but I think we're suddenly putting it together from a drink that was demonized as being very harmful to us, to something that actually could be beneficial. 

And the other interesting thing is we always thought it was about the caffeine. And the studies have now clearly shown that you get nearly as much benefit on the heart with decaffeinated coffee. 
Again, it comes back to this idea of how we see foods, as we always think of them as one thing. Coffee is all about caffeine and, you know, lemons is about vitamin C and we forget everything else. But clearly there's all this other stuff going on in that food that can give us these huge benefits. 


We all react very differently to caffeine. And that's a whole other series of events, men, women, whether you're on the contraceptive pill, whether you're drinking alcohol, whether you're having broccoli at the same time as it, all kinds of things can influence how the caffeine in the coffee is having an effect on you. 


[00:09:47] Jonathan Wolf: People who are sleep experts tend not to be as keen on coffee as the two of you, because what they see is the impact of caffeine on sleep and that poor sleep has these terrible health intake. So they vary, in my experience between,  you should never ever drink coffee whatsoever because that's terrible, to, Okay, you can have coffee, but you know, you need to cut it off at midday or something depending upon your sleep. So what you're saying is that…

[00:10:10] Tim Spector: I've got it the wrong way around. 

[00:09:47] Jonathan Wolf: Have you?  


[00:10:13] Tim Spector: So the things that affect coffee metabolism, so the speed at which coffee is broken down, therefore it doesn't hang around and keep you awake or has this effect on your body, it's reduced by alcohol. So, coffee metabolism is reduced by alcohol, so it lasts longer, but it's sped up by vegetables like broccoli. 


[00:10:36] James Hoffmann: So, but it's something like broccoli sprouts, which are even higher in sulforaphane. Yeah. That would be even better? 

[00:10:43] Tim Spector: Yes, in general, if you're having a lot of vegetables, That's going to have that effect.  


[00:10:48] Jonathan Wolf: So if I'm, like, overwhelmed and can't go to sleep, I eat a big plate of broccoli. Just a lot of cruciferous vegetables and then suddenly I'm gonna fall asleep. And if any listeners feel it doesn't work, they can write in.

[00:10:58] Tim Spector: You can also have a cigarette. That is also good. So that's why cigarette smokers actually need more coffee to get that same caffeine hit. 

[00:11:05] Jonathan Wolf: So to be clear, we are not in fact promoting that you should have a cigarette, but you are saying that people…

[00:11:10] Tim Spector: I'm just demonstrating how chemicals, and all food and things we eat and drink are all chemicals. 


[00:11:15] Jonathan Wolf: But what you are saying actually is that if you are a smoker, the coffee doesn't work as well. Is this why you need more coffee in order to get the coffee to work?  


[00:11:24] Tim Spector: Yes. Yeah, you're going to probably have twice as much coffee to have the same caffeine hit than if you're a non-smoker. 
And that's in males. Actually, if you're female, the metabolism is generally lower, so caffeine has a longer effect on the body. And if you are on the contraceptive pill, it also increases it further. So, metabolism is decreased, so it lasts even longer. So, females on the contraceptive pill, even a small amount of caffeine can really last a long time. 


It can be counteracted by smoking and broccoli. But, so just showing you how everyone is different. Again, it comes back to this personalization and, you know, not only in taste, but also, the effects of these chemicals. And that's just one of the chemicals we're talking about. 


[00:12:16] James Hoffmann: I think it's the great frustration of coffee conversation is the substitution of coffee and caffeine. You know, it's this incredibly well studied drug. We know a lot about caffeine, but. It's not all that coffee is but it ends up being all that we talk about most of the time when people want to talk about coffee and health. 


[00:12:32] Jonathan Wolf: Do we understand why coffee is full of not only caffeine, but all of these other polyphenols? What is it? Most of us think about coffee as being either something ground that we buy from our grocery store or maybe we think about it as like this blackened thing that looks a bit like a bean but we definitely don't think about it as a plant or anything else what what's the… 

[00:12:54] James Hoffmann: The caffeine's easier to sort of understand the presence of. It's primarily produced in the coffee fruit. So coffee beans grow in sort of a cherry. It's about the size of a small grape with two peanut-like seeds in the middle. So if you look at a coffee bean, there's two flat sides that would typically face each other.

As a defense mechanism the plant produces caffeine to act kind of as an insect repellent, for want of a better term to discourage insect attacks on the fruit. That's really why it's there in the quantities that it is. Therefore, you tend to see species of coffee that are hardier and more robust. One of which is Robusta, grows lower, more insects are present, twice the caffeine levels of something like Caffea arabica, which grows higher up and obviously has less challenge, and so it needs less defense. 


But yeah, that's the primary reason caffeine exists. Caffeine is produced by other plants.  


[00:13:47] Tim Spector: Yeah, tea leaves as well, so I mean, green tea, things that, I mean, not green, more the black tea ones, for the same reasons.  


[00:13:55] James Hoffmann: Yeah, and there's another argument that some flowers produce caffeine, and it's one of those sort of situations where everything becomes crabs, in that different plants through different pathways have ended up producing caffeine almost for different purposes. 


There was one study that showed caffeine improved bee memory. And so things like orange flowers produce caffeine, and that's the speculation in that it improves the sort of quality of pollination as a result.  


[00:14:19] Jonathan Wolf: So the bees can find their way back to the flower.  


[00:14:22] James Hoffmann: That's the theory, which I think is kind of amazing. 


[00:14:23] Tim Spector: What are they going to do to the caffeine? 


[00:14:24] James Hoffmann: Either way, I mean, it worked.

[00:14:26] Jonathan Wolf: I like that. And polyphenols themselves are also, what I understand, defense chemicals, is how I've heard you and others describe them, Tim.  


[00:14:33] Tim Spector: Yeah, this is, again, it's an incredibly broad family, but in general, these are chemicals produced by plants to defend themselves not only against insects, but it might also be against high winds or could be cold or it could be strong sunshine or you know. It could be to change the way predators, you know, the taste and things that are for predators. 

But generally it's a defense mechanism for plants that ends up having a side effect of being beneficial for our gut, our gut microbes. That's how nature has come full circle.


[00:15:13] Jonathan Wolf: Now, I know Tim, you know, you teased us a little bit, but you have got a really exciting new paper. Can you tell us a bit about it?  


[00:15:22] Tim Spector: Okay I'll give you a little teaser anyway. So it's still under peer review, it hasn't come out yet. But this is work I've been doing with the fantastic Nicholas Sagata in Trento and his team there, plus with the 40,000 plus of the ZOE sample. So people have been giving their stool samples and we've been comparing them with their drinking habits and their food habits. And now we've got this huge sample, both in the U.S. and the U.K. and we've actually looked at other populations around the world.

We've found that of all the food and drink associations that we linked up from our questionnaire to the microbes, the one that comes top of the list, that pops up every single time was a microbe that is associated with coffee.  


[00:16:11] Jonathan Wolf: It's amazing. So literally, the thing that we could most clearly have a one on one relationship between bacteria and food was actually a drink. 


[00:16:18] Tim Spector: Exactly. It's like a forensic test, you know. Rather than doing questionnaires, you just take a bit of that stool sample, you extract the DNA and you find this microbe called Lawsonibacter named after Dr. Lawson. And it's inevitably linked to the consumption of coffee. And that was so strong it was, you know, we had this list of all these other ones and many of the foods are all mixed up and you don't get a clear signal of any one microbe. 


So it seems very specific. It really doesn't seem to eat anything else. So it's been hanging around for us humans to produce coffee, imagine. And this microbe is pretty much In everybody in the U.S. and the U.K. Even if, like you, you're not a coffee drinker, you'd still have low levels of this microbe and you say, why is that possible? You know, I haven't had coffee for 20 years. Well, it's all around us, this microbe, because we've all got it. Because half the population now are coffee drinkers, it's in people's breath, their saliva, you know, we swap microbes of the people we share houses with. So nearly everyone has low levels of it, except young children. 


So when you're born, infants don't have it. So they're acquiring it from around the place and then it stays dormant until it starts being fed coffee. And then it grows up and gets to these enormous levels and what's really interesting, then it feeds off the coffee. And then we found that it then produces these chemicals that through the fermentation process turn out to be really healthy for us and have been shown to reduce blood pressure and reduce blood sugar and things. 

So all this is going to come out in this paper, but it is absolutely fascinating because other countries that don't have a history of eating coffee don't have this bacteria at all. 


[00:18:20] Jonathan Wolf: It's like a panda. You know, and the panda only eats one thing, we all know that it only eats bamboo, and you're saying that, maybe it's not quite as extreme as that, but basically, this Lawsonibacter lives on the fiber that comes off coffee. Is that what you're saying? 


[00:18:39] Tim Spector: Yeah, that's right. But it seems to be able to survive without it, in a very sort of suspended animation form. 


[00:18:45] Jonathan Wolf: So it can sort of get by a little bit enough. But it's not, it's a very small fraction of your microbiome. 

[00:18:50] Tim Spector: And it won't reproduce, it won't be happy until it finally gets you know, that shot of its first cup of coffee. And then it takes off and then it produces all these healthy chemicals that we know from the epidemiology are actually reducing our risk of heart disease and generally helping our metabolic health and perhaps helping our blood sugar levels. 
  


[00:19:12] Jonathan Wolf: This is a bit like a, you know, don't they say a dog can be vegetarian, so it could live on it, but it's pretty miserable, that's not clearly what it is. But then finally you give it a steak, and it's like, okay, I'm off. I'm stretching the analogy a little bit, but it's sort of somehow they're managing to survive a bit, because if there was no food it could live on, it wouldn't be there. 
But basically, this is the thing that it has the ability to really thrive on, and presumably better, therefore it can break down the coffee stuff better than all the other bacteria in your gut. 

And so you often talk about this idea that there are, you know, it's sort of like an ecosystem like in the jungle or in a coral reef with everything specialized. 
And so here you've actually found this bacteria with this really clear one to one relationship.  


[00:19:54] Tim Spector: Yeah, it's the strongest signal we've got in all the foods and drinks.


[00:19:58] Jonathan Wolf: And has anyone done that before? I mean, is this now the, are there many examples already of where people have been able to find these links? 


[00:20:06] Tim Spector: No, I think you know, we're not the first to find this microbe. It's been shown in some small studies, but they didn't really know it's global epidemiology patterns and I think showing how it affects normal people and the idea of people who don't drink coffee still having low levels I think is really cool. And also the other thing we've found is that it still likes decaf as well, so it's not as fussy.

[00:20:34] Jonathan Wolf: I think there are many listeners who might be quite fussy about their decaf versus the caffeine. But this is an example of where you're saying it's not the caffeine in the coffee that this bacteria cares about. 

[00:20:45] Tim Spector: No, and again it's not the caffeine that has the sort of, seems to have the health benefits either. 
So, you know, it's all these other chemicals that are produced. So the microbes are dialing into, we don't know, one of the many fibers in coffee and we don't know exactly which bit it's particularly targeting. But it then thrives on that and uses that as an energy source and produces lots of other really fascinating chemicals that help our bodies. 


[00:21:15] Jonathan Wolf: I could just for a minute, because I think for somebody listening to this, I think they'd be like, okay, I understand that I've got this bacteria inside my gut that eats coffee. Help me to understand though why that then creates any health for me as the human being. Like I can see it's good for the bacteria but why is that good for me with the bacteria inside me? 


[00:21:37] Tim Spector: At a global level, you're having something as a source of fiber, which means in general, lots of microbes are benefiting and general gut health is improved. But in this specific one, which we've got a nice example here, it's showing that eating the coffee, the bits that get to the lower intestine have been mashed up a bit, but they're still mainly intact. 


And this Lawsonibacter is attaching to it, breaking down some of those sugars in the fiber, and as a by-product is producing these key chemicals. There are probably many of them, but we've isolated a couple of them. 

One of them is quinic acid, which is a well known constituent of coffee, but it's producing it in large amounts, so it's perhaps liberating it and sending that into the blood. And we know that chemical when you take it out of the system, you put it into animals and things. And some human studies will do things like increase insulin levels and reduce blood sugar levels. That's a good thing. So these chemicals are generally having good effects on the body. 
And all these chemicals used to be called antioxidants. 

[00:22:50] Jonathan Wolf: And sorry, that was quinic acid, is that what you said? Yes. So that's a specific example of something you can measure that has really been created by this particular experiment?  


[00:22:57] Tim Spector: Yeah, it's just one example. I mean, there's, again, you know, our technology only allows us to sort of get a small microscope on one bit of it. 
There's probably lots of other things happening. But that's a really nice example of high levels of this quinic acid are related to the presence of the Lawsonibacter. 

So, it's not just the presence of coffee, it's when you've got high levels of that microbe. Microbe plus the coffee equals this other chemical, which is something that normally you wouldn't get in your body. 
And that chemical, just like going to the chemist and get, if I went to the chemist and then got some quinic acid and said, okay, that's going to be good for my blood sugar, my metabolism, and there might be other ones that are also good for reducing your blood pressure long term, who knows, reducing other stresses in the body, anti inflammatory effects. 


So it's one of the first examples we've got of a constituent of food that reacts with a very specific bacteria to produce these chemicals. And this is really giving us this whole picture of how our food, interacts with our gut microbes to produce, you know, they are basically these mini-pharmacies and each of them is producing an incredible little drug that we couldn't dream of producing ourself. 
They know exactly the right dose. They know what to give it. And evolution, everything has done this to us. And it, it's a way that we can now, well there's a glib term that food is medicine, you can clearly see, yeah, you know, a coffee bean is a way of delivering something like quinic acid in exactly the right doses for your body if you have, you know, three to four cups a day. 

[00:24:42] James Hoffmann: So can I get into the weeds just slightly here? Is that okay? You probably know much more about quinic acid than I do. I'm vaguely familiar with quinic acid but I want to split out into coffee. I want to sort of just as a question, separate the fibers, which would be very different compounds to the polyphenols. 


Because when we come to doing a little bit of science later on, I can look at one of these things. I can't look at the other. And so talking about quinic acid specifically makes me feel like polyphenols are a key constituent of the diet of this thing. Because I know that when you roast coffee, you degrade some of the polyphenols in the roasting process. 


And one of the byproducts actually of roasting coffee is quinic acid. And so there's a sort of curve and a relationship there. So I'm wondering if it is the polyphenols in coffee that the Lawsonibacter is interested in, or the sort of specific fibers present in coffee that I think are reasonably distinct to coffee. 
I think they've got slightly, I don't know enough about fiber. I know the names of some of the coffee fibers, but I don't know that much about them. 

But they're, they're kind of, to me, they're sort of separate things. And if you look at sort of measuring the presence of either in coffee, they don't necessarily correlate. 
And that you can have lower fiber levels, but quite high levels of chlorogenic acids specifically, are the kind of polyphenols most commonly found in coffee. 

[00:25:59] Tim Spector: And so which is a precursor of quinic acid. 

[00:26:01] James Hoffmann: Right, yeah. So, that's the bit where I'm like, if I'm trying to theoretically optimize to feed this thing as much as possible, I would think differently if I'm thinking about how do I get at the maximum polyphenols versus the maximum fiber. 


And so that's why I'm kind of interested in its specific diet, whether it's, we're not sure, it could be a little of both, or it's more one than the other. That's kind of what I'm interested in as a bit of a nerd right now.  


[00:26:26] Tim Spector: Well, I don't think anyone knows the exact proportions. My understanding of this is it's a bit of both. That polyphenols are used as an energy direct energy source for microbes to allow them to reproduce and do their thing. 


And one of their things is to drill into the fibers and extract again, nutrients from that and then produce other ones as a by-product. So it's, it's probably a bit of both. 

It's going to be a while, I think, before we work out those proportions. Also, generally, most of these work in combinations in teams and guilds, so it's very hard to work out who's doing what. 

This is quite a rare example where you've got, you know, what seems to be nearly a sort of one to one type system here. But, of course, coffee isn't one thing.  


[00:27:26] Jonathan Wolf: So I have a simpler question, you know, but my simpler question is does this mean I have to start drinking coffee? 


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[00:27:38] Tim Spector: No. I think there's other ways you can improve your health. But I think, for those people who don't like the caffeine, decaf coffee really should be more of an option. And I think we ought to be exploring other foods and drinks that do contain some of these good things so that your body can still produce this substance like this quinic acid. 


And I think that's where a lot of this new science takes us. There could well be a way of making a blend of coffee, for example, that you liked. That we changed its taste profile so it was less bitter for you.  


[00:28:22] Jonathan Wolf: What's interesting, I don't think we've discussed this before but I gave up coffee more than 20 years ago and it was part of dealing with a lot of food intolerances that I got so I was definitely drinking lots of coffee at 21, I got these food intolerances after I was very sick with mononucleosis, glandular fever. 


And a few years after this, as part of trying to deal with this, I gave up coffee. And one of the things I found was that coffee was definitely triggering a whole bunch of digestive problems. And apparently this is, you know, it's quite common, so I remember, it's one of the things that the doctor had talked about trying and it's not necessarily the caffeine actually, because same impact really with decaf. 

And so this is part of what I gave up along with this whole process of giving up this vast amount of food and ending up on this sort of really miserable, very processed diet. But interestingly, what I did find was I ended up sort of just drinking more tea that pulled up my level of caffeine. 
And I think I found a happy medium, which is that there's a lot of caffeine in a coffee. And I actually found that there was a lower spike. 

So it's not that I gave it up because I hated the taste, but I am sort of curious, I think a lot of people listening are saying, do I have to drink coffee for health, or is this more of saying like, actually you should think about this as a healthy drink, as opposed to the way that people have thought about it before as unhealthy. ,

But it's not saying you have to drink it if you don't want to, but it is definitely contributing to the way we get fiber and all of these positive things, or is this like, wow, this is like a silver bullet. If you're not drinking coffee, you should really try quite hard because of how good you think it is.  


[00:30:03] Tim Spector: I think it's nuanced. I think I wouldn't want anyone to regularly eat or drink things they didn't like. Food is to be enjoyed and savored and that is the most important thing and everyone has food preferences. We've done our twin studies to show some people you know, have a sensitive palate. They don't like those bitter flavors at all, and genetically their threshold is very different to someone else. So realize we're all different. Don't start forcing people to do things. 

But at the same time, this is a health drink. The evidence is really clear that if you can reduce heart attacks by 25%, you know, that's pretty cool. 
If you can do that and there's not many other ways, something so simple, you can actually achieve that. 

So I would say to people who haven't had it like you for. You know, 15, 20 years, try it again occasionally, or try different ways of having it, or think of all these vitamins, supplements, multivitamins that people take, they don't really like taking them, but they do it because they think they're doing some good and there's no evidence whatsoever. 


Here you have, you know, you could take a shot of espresso and it's, you know, easier to take the most vitamins and you know, a couple of those a day and you're getting huge health benefits. 

So I think just revisit it and realize that you can overcome these thresholds, these bitterness thresholds, by constant use. It'd be hard if you now because you've been off it, but there might be other ways. of doing it, perhaps, you know, and that spoonful of sugar will probably, the balance will still be positive, you know, maybe not with six sugars, but…


[00:31:52] James Hoffmann: Modern coffee in particular has focused on reducing bitterness and improving flavor as a kind of outcome, and I think we see lighter roasted coffees that have less bitterness to them, the way that we prepare coffee. 


You know, I think really well made coffee is not that bitter compared to badly made coffee. I think the thing that's notable about humans is that we're pretty blank slates and our preferences are learned. And while we have different perceptions of things like bitterness, when it comes to flavor, if you want to learn to like something, well, you can just choose to learn to like it. 


Like you can acquire a taste if you want to, we do it all the time. No one enjoyed their first lager. No one enjoyed their first lager. It's awful. No one enjoyed their first coffee. But we go back and we choose to acquire tastes. 


[00:32:33] Tim Spector: So genetic studies have shown the threshold is there for bitter taste. So if you don't like coffee, you don't often like red wine as much as white wine. 
You might find broccoli and brussels sprouts hard to have. And this is more common in females. And also dark beers. So they tend to go together, these profiles. But as James is saying, you know, you can get used to it very easily. And most of us do that as students.  


[00:33:04] Jonathan Wolf: We have basically the world's foremost expert on coffee, and we're going to do something fun. 


Now, just before we do it, could you explain, does the way in which you make your coffee have a big impact on both the taste. But also sort of tying into what Tim is talking about, does it impact, therefore, the health of these things, the fiber and the polyphenols we've been talking about?  


[00:33:25] James Hoffmann: Yes a lot. I mean, taste is the most important thing for someone like me. But yes, if you take some ground coffee and you brew it, you are dissolving things from it. And a good percentage of coffee is not soluble. You could brew it forever, keep running water through it in a little drip machine, it would still be there afterwards, it's simply not soluble. 

It will dissolve in the water. It's you know, it's kind of like wood, what is left over, in a simplified way.  


[00:33:53] Tim Spector: The good bits are in the bitty bits. 


[00:33:53] James Hoffmann: Yeah, so you can wash out and dissolve into your brew water about 30% of the grounds. And so if you took 100 grams of ground coffee, brewed it for ages, dried it out afterwards, you'd have 70 grams left. Okay. Right, and the 30 grams max would end up in a cup. 

Ideally, you don't want 30% of the coffee. Some things you just want to leave behind, actually, that don't taste great. Generally, we want between probably 20 and 23, 24% of the coffee dissolved in the cup below. 

[00:34:22] Jonathan Wolf: Right, so you want all of it dissolved in. You want to get somehow the good bits, but leave some of the not nice tasting bits. 


[00:34:27] James Hoffmann: Generally. And there are some very bitter compounds that tend to come out at higher extractions that people don't enjoy. However, if you don't get enough out of the coffee, you tend to get a lot of the acids, and not a lot else. And it's a bit like lemon juice rather than lemonade. Like, good coffee should have some balanced acidity, give it a kind of freshness to it, add some flavor. 
But badly brewed coffee will just be sour, unpleasant, and to be avoided. 

And so, firstly, you want to get the extraction right for the taste perspective, and that's how finely you grind the coffee. Obviously, the more surface area you expose, the easier it is for the water to get in and pull out the things that you want. 
Because there's a correlation between what you're extracting in terms of taste and what you're extracting in terms of the soluble fibers and things like the chlorogenic acids, a well brewed cup of coffee will have more of everything good. More taste, more chlorogenic acids, more polyphenols, therefore, and theoretically, a little bit more fiber, too. 


So, all in all, you want to get your money's worth. You've bought some nice coffee, there's good stuff in it, you want to make sure you're getting it all out. So that's the goal of good coffee brewing.  


[00:35:30] Jonathan Wolf: So, I understand you have brought along a sort of mini laboratory, to show us how both a professional would sort of test for these compounds, but then we can also talk through for us to understand, and we are going to have a sort of tasting and science experiment at the same time. 


[00:35:50] James Hoffmann: Yeah, I think it's interesting. I have a little portable caffeine meter that has the benefit of also giving me an output of chlorogenic acids present in the brew as well. It'll be in milligrams per deciliter, so per hundred milliliters. We can scale it up to a normal cup of coffee for people in a minute. 


But yeah, it'll give you an idea of something like instant coffee versus fresh brewed. What are the differences there? And then we can have a look at instant as well, which is a lot of people's choice, and talk about some of the kind of theoretical benefit that instant might have, or might not have. 


[00:36:21] Jonathan Wolf: Got it. So we're going to try it. Let's just run through. What are the different things that you're going to brew us up.

[00:36:24] James Hoffmann: So I'll make you some regular, fresh, well grown Arabica coffee. I've then got some good decaf coffee and I can talk about decaffeination, because I think it's something people want to know more about and sort of fear a little bit, because they see chemistry and get a little bit nervous. 
And then I've got some instant, too. And instant's super interesting on a technical level. However you feel about the taste, I'm going to try and stay away from the politics of the taste of that. But we can actually look at some of the chemistry of what you get in there or what you don't get in there. 
 


[00:36:52] Jonathan Wolf: Got it. And I think we might have a coffee kombucha as well, is that right? Oh, good. 

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All right, James, so we've got the equipment out, which now looks very impressive. Can you tell me what you've got?

[00:38:05] James Hoffmann: Sure, this is called an AeroPress. It was invented by the guy that invented the Aerobee, and it's kind of a bit like a French press and a paper filtered brewer all in one. So I'll put ground coffee in hot water, let them steep together. There’s a paper filter at the bottom here, and at some point I'll press it, and so it'll separate the grounds from the liquid. 


I will add some coffee, which I ground just before I got in a cab to come here, so it's nice and fresh.

[00:38:25] Jonathan Wolf: And you're just throwing in a random amount of coffee?  


[00:38:29] James Hoffmann: I would use, as a ratio, 60 grams of coffee per liter of water that I want to brew. So I'm going to brew 20 grams of coffee to 330mls.  


[00:38:38] Jonathan Wolf: And you very, the answer is you very carefully measured the amount of coffee and you're going to put in just the right amount of water, is what you're saying. 


[00:38:40] James Hoffmann: Yeah, it just, I like using weighing scales because most of the time I'm making coffee before I've had coffee and I don't want to guess or have to think and I like a weighing scale for telling me what I have to do and I just make the number happen. So that's why I'm, I'm big on scales. 

[00:38:57] Tim Spector: And this is for an Americano? 


[00:38:59] James Hoffmann: So this'll brew like a filter strength brew, yes. So close. Americanos tend to be fractionally stronger, but like a drip coffee kind of strength seem to be the easiest thing. 


[00:39:03] Jonathan Wolf: And while you're pouring, tell me about the water, because one thing that did entertain me is that James arrived with his own water. 


[00:39:10] James Hoffmann: I don't know how much you want to know about water, because it's a miserable subject, but the minerals in water play a big role in extracting the flavors, so they are involved in essentially dissolving some of the stuff that we want. 

But then there's also something called alkalinity, or a buffer, if you want to get into the chemistry, which will affect your perceived acidity. 
And too much buffer makes everything taste a bit brown and dull. No buffer makes things taste very sour and unpleasant. 

So, I brought water that had an ideal amount of minerals in terms of calcium, and an ideal amount of buffer, so that we get some acidity, but not too much.  


[00:39:45] Jonathan Wolf: So you won't take the water out of the tap, you have to get your own specially modified water to make the coffee the way you want it to taste. 
 


[00:39:52] James Hoffmann: London water tastes good but it has a lot of calcium and a lot of buffer in it too. So, it tends to make all coffee kind of taste a bit the same, which is a shame. And so I, you know, I've paid for the good stuff. I want it out and I want to enjoy it as much as possible. Making your own water is a little bit extreme I agree. 


[00:40:12] Jonathan Wolf:  I'm glad you're still at the point where you can see it, a little bit at least. The entertainment that I'm taking from the fact that you not only brought your own coffee, which seems very reasonable, but brought your own water which I think is acceptable, but verging on the slightly eccentric.

[00:40:23] Tim Spector: And what about adding salt, you mentioned? 



[00:40:24] James Hoffmann: So, yeah, salt's interesting. Salt's a great little hack, in that for the majority of people, it's not everyone, table salt acts as a bitterness suppressor, right? It's one of the reasons you often see salt and dark chocolate together, actually. It makes them more palatable, as well as enhancing flavor, too. 


But if you are served miserably bitter coffee, you know, the kind of the real filth in a hotel breakfast kind of coffee, a tiny sprinkle of salt. And I mean a tiny, you know just a little tiny sprinkle, stir it in you'll be shocked at the, it sort of mutes the bitterness quite impressively and increases let's say palatability. When you just need the caffeine, I want to help get you there. This shouldn't need salt, I would hope.  


[00:41:05] Jonathan Wolf: And so talk me through, the hot water's been sitting there right now, and you described before about how the fact that the ground coffee has a lot of things inside it which are going to start to dissolve. So is that what is going on?

[00:41:17] James Hoffmann: Yeah, right. So, you know, essentially the water's pulling these things out of the cells that we've sort of exposed through grinding the coffee bean. 


[00:41:22] Jonathan Wolf: And so the longer you leave it, the more is being dissolved out.


[00:41:26] James Hoffmann: Yes, there's a point at which you have diminishing returns and it's not worth waiting much more. So I'm just giving a quick mix before I press it down and then we'll press it through and we'll have a brew. Now this is paper filtered. From a health perspective, the data seems to suggest that actually paper filtered is healthier for you than unfiltered. 


I think it was a big Scandinavian study that sort of showed that the peak health sort of heart health benefits came with filtered coffee. I think there's a couple of lipids in coffee that was sort of filtered by paper that show a correlation to an increased rate of serum cholesterol. I just enjoy it more if I'm honest. I enjoy the clarity of flavor.


[00:42:01] Tim Spector: I'm not sure it's that convincing now because these are intermediate effects on lipids and as we're saying lipids are complicated. So short term change in lipids doesn't mean necessarily long term health. So I stick with the one you prefer.  


[00:42:16] James Hoffmann: I think now what I'm gonna do is just do a little caffeine test on this, and then I can dispense to you. 


[00:42:21] Tim Spector: That looks quite weak to me. 

[00:42:16] James Hoffmann: It's a light roast, so this is actually from a Scandinavian coffee company, and Scandinavians are famous for their light roasts. But it should have a little bit more fruitiness to it, lower levels of bitterness from being a lighter roast. So for the, I don't like coffee, you could approach this more as like a strange fruit tea
 mentally and see how
you get on with that.


[00:42:39] Jonathan Wolf: I'm very excited. I mean, I'm definitely drinking the coffee that has been made in this exquisite fashion.

[00:42:46] James Hoffmann: So I'll just give it a quick stir just to get a better sample.  


[00:42:49] Jonathan Wolf: And James, you've brought a piece of technology here. Do you want to talk us through for those people who are just listening on audio? 
What are you doing?  


[00:42:57] James Hoffmann: So it's a little bluetooth connected caffeine and chlorogenic acids analyzer. What I'll do is I'll pull a very specific quantity of coffee with a little pipette here, and I'll add it to a small solution that I'll shake together for a while, and then there's a chip that I insert into a machine, I cover a little sensor with the liquid, the reagent, and the coffee. And then within about 15 seconds, it'll tell me the caffeine content and the chlorogenic acid content. 


[00:43:21] Jonathan Wolf: Which is a sort of polyphenol? 

[00:43:23] James Hoffmann: So about, I think, 90% of the polyphenols in coffee are counted as chlorogenic acids. I think there are some others in there, but there's a very strong correlation between the quantities.

[00:43:30] Jonathan Wolf: The base is giving you a measure of the amount of polyphenols.  


[00:43:33] Tim Spector: Right. One of the major classes of polyphenols. 


[00:43:35] Jonathan Wolf: So there's loads of individual variants within that, but that's like a big category. How cool.  


[00:43:44] James Hoffmann: So I have to shake for 10 seconds.

[00:44:49] Tim Spector: Do you do this every time you go to a coffee shop? 

[00:43:50] James Hoffmann: No, no, because they're like five for a test, so. It's very quick. I mean, it's interesting. We did it, we took it to sort of different chains to look at the variants in, if you ordered an espresso, what's the caffeine dose going to be and how much is it going to vary? And the answer is massively. And caffeine is one of those things, and as much as it isn't all that coffee is, it is a big part of it. Where, it's the most popular drug, and we consume it in a completely unregulated way. 


If you order a coffee out, you've no idea how much caffeine you're about to consume. And I'm not sure that's good. If I'm, as much as I like coffee, I'm just not sure that that's a brilliant idea. 

[00:44:22] Tim Spector: It's like going to a pub and not knowing What percentage of alcohol is in that beer, isn't it? 

[00:44:27] James Hoffmann: Absolutely. 


[00:44:28]  Tim Spector: Any of these coffee shop chains, even in the same machine, same trained staff will produce a different…

[00:44:39] Jonathan Wolf: There's a high degree  of variation. It's not like when you're just drinking a beer or something that every glass of beer has the same level of alcohol. 

[00:44:43] Tim Spector: It's regulated. You've got to show on it how much alcohol is in that bottle. No, there's no testing in terms of caffeine.  


[00:44:50] James Hoffmann: Can I send this along to you if you want to have a little taste?  


[00:44:52] Jonathan Wolf: Yes, I would love to have a taste. Tell me how I'm supposed to taste my coffee. 

[00:44:57] James Hoffmann: If you have a glass that is sort of oval shaped, so to speak, yes, swirling it will give you a kind of nice headspace of aromas that you can smell if you want to do that. You don't have to do that. If you sip it, if you slurp when you sip, you will generally have a sort of more intense flavor experience as you sort of spray the coffee around it and send more stuff volatile. 

[00:45:20] Tim Spector: Like olive oil tasting? 


[00:45:19] James Hoffmann: Or any one, wine tasting, whiskey, everyone likes a slurp.  


[00:45:22] Jonathan Wolf: What I would say as someone who hasn't drunk coffee for a really long time is, smells really nice. Much less strong than I would normally expect from a coffee. And the color also, and Tim already sort of mentioned this, actually looks like it could be a tea. It's really not that dark. 

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[00:45:37] James Hoffmann: Yeah. So as a brew, this is on the very light, very fruity end. And you might think, oh, there's no caffeine in this then. No. So the caffeine level, we'll start there. That's the easiest thing. Because that's sort of understandable to most people. So that's 72 milligrams per deciliter. 


So if you drank, let's say a small, which would be 200 mls, that'd be 140 ish, 145 milligrams of caffeine. The daily recommended dosage for adult males is about up to 300 to 400 milligrams. 

[00:46:08] Jonathan Wolf: So that's almost half your amount, just in one small cup of coffee. 


[00:46:10] James Hoffmann: So three smalls over the course of the day would exceed your recommended caffeine dose. 
So it's actually surprisingly caffeinated, I would say. 

[00:46:19] Jonathan Wolf: So I'm going to drink this, but my caffeine is about to go through the roof. So if later I'm talking very, very fast at the end of the podcast, you'll know why.  


[00:46:26] James Hoffmann: You've got a small amount there. It's not a lot, but yes, that's a decent whack of caffeine. 


Chlorogenic acids. This will only be useful as we look at other things in comparison, I suspect. 166 milligrams per deciliter of chlorogenic acids here. So a decent dose, I would say, of chlorogenic acids. Which is good news. Because that's good for our Lawsonibacter, he's gonna be happy down there, or, it's gonna be happy. 


[00:46:51] Jonathan Wolf: So you're actually measuring all these polyphenols, and so this is what's going to be feeding these bacteria in the paper you were talking about earlier, Tim. 

[00:46:59] James Hoffmann: But the fiber content of this would be relatively low compared to something like a darker roast. I think there is more breakdown of certain compounds, in darker roasts, that make them soluble and easier to extract. 


[00:47:10] Jonathan Wolf: Take us to the next coffee.  


[00:47:12] James Hoffmann: Well, I brought some decaf next. Which I thought would be interesting because I'm curious to see how it stacks up. If you skip the caffeine, what are the polyphenol benefits like in a decaf? 

So this is coffee from Brazil. It's a decaf coffee. So you decaffeinate coffee before you roast it. So you take the raw coffee seeds and you decaffeinate those. There's a bunch of ways to do it that have various. Nice sounding names. All of them are safe, and I think people hear certain chemical names and inevitably freak out at the idea of ethyl acetate, which is often 

known as the sugarcane process because no one likes the name ethyl acetate. 


So yeah, I think decaf historically has been underrated. I think people don't think of decaf as delicious. I think people see a decaf as a compromise, which is a terrible shame. It's harder to roast as a coffee roasting company. It's harder to make it taste good, but it's actually very possible to make good tasting decaf. 


I think for a long time decaf drinkers have been undervalued. They are the true coffee lovers because they're not even getting the chemical hit out of it. They're just drinking it for the taste, and yet they are not well looked after. 

By the time I made you a flat white, most people would have no idea. If it was a good, well produced decaf, well roasted, well brewed, delicious. Absolutely delicious. I drink a lot of decaf now because I'm quite caffeine intensive and I value my sleep quite highly. And so my afternoons are full of decaf. 

[00:48:29] Jonathan Wolf: So this would  be a way basically to reduce a lot of, I guess, the main health risk about the coffee, right? Which is that it impacts your sleep, and we know how important sleep is. 


[00:48:36] James Hoffmann: Right. I'm precious about that. 

[00:48:39] Jonathan Wolf: And you still get, you said, Tim. Most of the health benefits.

[00:48:42] Tim Spector: Yes that's correct. You still get the heart benefits from decaf.


[00:48:45] Jonathan Wolf: And you're making it exactly the same way, and it looked to me exactly the same as the ground.  


[00:48:51] James Hoffmann: It doesn't need special treatment. Dose in there, right, and I'll give you a little mix and a share.  


[00:48:57] Jonathan Wolf: Excellent. And before we get to the answer, I'm going to ask Tim, so what is your guess in terms of looking at this on the fiber content and the polyphenols? How do you think it's going to compare with the first one?

[00:49:13] Tim Spector: Well, fiber should be higher. And we know that decaf coffee has the same fiber as regular. 
As a general rule, if things are more bitter, they're more, and more tannic, and more astringent on your tongue, and less smooth, they're more likely to be higher in polyphenol count. 

[00:49:33] Jonathan Wolf: It smells stronger to me, like, less sort of soft than the last.  


[00:49:38] James Hoffmann: There's a lot of reasons for that. It's a different roast level. It's a different country of origin. I was still saying low bitterness, quite gentle, friendly in that perspective. The polyphenols came in at about 158 milligrams per deciliter, so I would say not a statistically significant variation. The previous one was about 170, I think. So, high. Plenty of those things available there. 

I think the interesting thing for me about instant, as a contrast coming into this, is that instant cheats in an interesting kind of way. The manufacturer of instant is motivated by price more than anything else. And so what they need to do to keep this as cheap as possible is to yield as much as is humanly possible from the coffee beans that they start with. And so through a variety of processes that are only used by instant coffee manufacturers, they can get their extractions up past 30%. 


They can get it all the way up to about 55%, which means that they can get almost twice as much out of a coffee bean compared to normal people brewing at home. They do that by breaking down some of the insoluble stuff, they sort of hydrolyze it, and then it effectively acts as a bulking agent. 
And so you would therefore see higher, technically, higher fiber contents in instant coffee than you would see in filter coffee. 

But there's a trade off. That's come from less coffee beans in the first place. And so, what I'll do is I'll brew this at a sort of matching strength to these here. And that'll give you a sort of matching strength, and then we can have a little look at the caffeine as well as the polyphenols. Interestingly, they recommend you brew instant quite weak. They recommend a 1% strength. I'll say 1 gram per 100 mls. Which is surprisingly weak.

[00:51:31] Tim Spector: That's why when I try a strong one, it's virtually undrinkable, isn't it? 


[00:51:34] James Hoffmann: It’s designed to be weak. To be produced quite weak.


[00:51:37] Jonathan Wolf: Now, just as you're making the instant, there'll be people listening to this who have no idea what instant coffee is. Could you just explain for a minute, it's sitting in a packet, it's lots of these little granules. 

[00:51:47] James Hoffmann: So instant coffee, the way you make it is, is basically you make a very large, very strong cup of coffee. 
And then you freeze dry, ideally, all of the moisture out of it. And what you end up with is a sort of solid clumped, powdered thing. And what they then do is turn it into a shape that mimics ground coffee to most people, to sort of remind you of ground coffee. But you could sell this as a pure powder, you could sell it as large, chunky flakes. 


[00:52:14] Jonathan Wolf: So really,
it's like dried coffee, and then you rehydrate it? Is that what you were saying?

[00:52:17] James Hoffmann: Yeah, it's like a stock powder. You know what I mean? And you were going to reconstitute it into water. 


[00:52:22] Jonathan Wolf: And when I was growing up, this was the primary way that people drank coffee in the U.K., but I know that in the States, where I also grew up, this was never really the primary way that people had coffee and they used to have sort of like a filter coffee in the house. 
Was the benefit of this really convenience? Is that where this comes from or… 


[00:52:41] James Hoffmann: That's, that's primarily it. There's no, you need a kettle. And you can just, you know, scale it very easily. You need to make ten mugs of it, one mug of it. It's just, you know, ten spoonfuls or one spoonful. It's very easy, but with all convenience comes compromise. 


And so as we suppress the price of this, the qualities of raw materials inside instant coffee will inevitably much lower. And then, that doesn't start you in a good place, and then it's manufactured to kind of maximum yield, not about maximum flavor. 

They do some clever stuff in that when you buy a jar, they'll have injected just under the gold foil lid on the top some aromas. They do an oil extraction and then they capture some of the aromas of fresh coffee and inject them under the foil lid so that when you pop it open, there's a release of aroma that reminds you of fresh coffee, even though those flavors were never present in the soluble material
underneath.

[00:53:36] Jonathan Wolf: This is like selling a house and you're told you should bake bread. And people are like, oh, I'll buy that house. It always smells of baked bread, but they don't realize. It doesn't come with the house. This is the coffee equivalent, is it?  


[00:53:47] Tim Spector: Pretty much.  


[00:53:49] James Hoffmann: Give you a quick stir. And we've made coffee, which is obviously much faster than me messing around with a coffee brewer. 
But, let's have a look at what we get as a result. So this is technically the same strength as the last thing I gave you. 

[00:54:05] Jonathan Wolf: Okay, well it is really dark compared to like the previous ones, when my hand was underneath it I could actually, it was just like a little brown. This is so dark I can't see my hand at all. 
So it, it's a completely different color and yet you're saying it's the same, it's still 1 percent of this water is made of coffee. It doesn't smell anything like the other two at all. It doesn't smell very much of anything, actually. 


[00:54:30] James Hoffmann: No because the process of brewing and freeze drying and you lose a lot, inevitably, in that process. Especially the aromatic stuff. This has used half the amount of coffee. To make it, essentially.  


[00:54:43] Tim Spector: So it's half the amount of caffeine they've just extracted more, like a sort of squeezing an olive, crushing a whole olive.  


[00:54:49] James Hoffmann:  Absolutely. And yield, 38. 8 milligrams of caffeine, so about half the caffeine of the first thing you tasted. 


[00:54:55]  Jonathan Wolf: Okay. So it's got half the caffeine. 

[00:54:49] James Hoffmann: Half the caffeine. 33.55 milligrams per deciliter of chlorogenic acid. 

[00:55:01] Jonathan Wolf: So only 20% of the polyphenols that we had in the previous two. 

[00:55:10] James Hoffmann: But lots of fiber. So that's a strange one. So, you know, if you're just chasing fiber in coffee, this actually is pretty good. Whether those are the right kind of fibers that are preferred by your gut microbiome, I couldn't say. B it's definitely lower in things like polyphenols.  


[00:55:24] Jonathan Wolf: What are your thoughts, Tim? 

[00:55:28] Tim Spector: I haven't had actually instant coffee for a long, long time. But actually it's not that bad. If you get the concentration right, you know,  it's perfectly drinkable. It's just it's just not complex. It doesn't have any of the other interesting aromas or flavors. 

[00:55:47] Jonathan Wolf: This is what I think of as coffee tasting. Like is the sort of thing you might have served at the end of some dinner.

[00:55:55] James Hoffmann: Yeah, this is the premium end of it instant I would say. Yeah it gets much worse. 
This is as good as it gets. But I would say, if you're chasing the health benefits of coffee, it seems to me that good quality coffee brewed fresh is the best of all worlds because you get lots of what you want and it tastes really good. And for me, that encourages both delight and more consumption. It's easier to drink a good quantity of this stuff if you really enjoy it. 


[00:56:23] Jonathan Wolf: So I think that was fascinating, and we have one left to go, don't we? Which is not really a coffee at all. 

[00:56:30] Tim Spector: Yeah, we were exploring other ways of having coffee if you don't like it, the taste in the original sort of beverage form. And so, as people know, I like fermented foods and drinks. And you can have coffee kombucha. 


And there's two ways of doing this. So kombucha is basically a fermented tea where you use a SCOBY, which is this blob like composite of fungi and microbes together in a, look like a bit of a jellyfish floating around. And they basically like eating tea and sugar. 

And once you've got a nice big healthy one, you can put it in a mixture of tea and coffee. 
And it will transform that coffee into something new and original that's got a tiny bit of alcohol in it. You can't generally taste it, 1%, a bit of CO2, and all these extra chemicals that make it healthy for you. And it's a probiotic coffee, could be the ultimate. It doesn't grow as well. It prefers tea to coffee, so you don't get as much, and they're harder to grow, so they're harder to find. 
And you have to then put it back into tea after it's done a bit of its coffee stint, you can't keep it going in coffee. 

And then, there's another way of doing it, which is what I do. Is make it in tea the normal way and then for a second fermentation you pour it off and you add a little bit of coffee flavoring with a little bit of extra sugar and that gives you all the coffee aromas and you've got a coffee beverage there that's got the combination of both the tea and the coffee and is really different but I find it delicious. 


[00:58:24] Jonathan Wolf: And James, have you had this before?  


[00:58:25] James Hoffmann: I haven't had this. I've had various coffee kombuchas over the years. 

[00:58:28] Jonathan Wolf: And so are you appalled by this idea, or excited, and can we pour  a bit and maybe try it? 


[00:58:31] James Hoffmann: Yeah, I can't actually measure it yet, because I need something that's not fizzy, because the gas messes with the pipette measurement. 
So we'll come back to it in a little bit. 

The challenge technically, or typically with coffee and kombucha, is that a good cup of coffee has quite a complex acid profile. A bunch of different acids in there, contributing to that, and sort of synergies between different acids can get quite complex. And so once you throw in acetic acid, that vinegar, You can really produce a very strange outcome. 
You know, it's mixing different vinegars. Doesn't always work out. And so I've mostly tasted pure coffee kombuchas with a sweetened brewed coffee. You know, and the SCOBY's gone to work just on that. And the acid outcome has been challenging. I'm very curious about this one though.  


[00:59:18] Jonathan Wolf: Alright, let's try it. 


[00:59:19] Tim Spector: Cheers.  


[00:59:20] James Hoffmann: Cheers. 


[00:59:27] Jonathan Wolf: Well, that's pretty weird. What do you think?  


[00:59:30] Tim Spector: Well, I've had these ones before. So the first time you drink it, it is, you're not expecting it. So it's a sort of coffee pop, isn't it?  


[00:59:40] Jonathan Wolf: Yeah. It's like a weird combination between like a fizzy sort of, I almost had like apple juice in my mind and coffee at the same time, which is a very strange combination.

[00:59:50] Tim Spector: So this is the second fermentation one. So it's basically a kombucha then done with a second ferment. 

[00:59:56] James Hoffmann: For me, I like my ferments to go a little longer. I feel like this is quite a gentle one. I want more acid.

[01:00:00] Tim Spector: It’s a bit light. But I think it's a beginner's one. 
And for someone who doesn't like coffee, could you drink that?

[01:00:06] Jonathan Wolf: Yeah, I could. It's actually, I mean, it was weird the first time, but could I drink that glass of that? Definitely. Well, while we're waiting to measure it, because you said it's too fizzy to get the polyphenol answers, I had a couple of final questions I'd love to answer. 

The first is like you, you've given us all of these different types of coffees. I think lots of people were listening to this and saying, imagine that I'm going into a coffee shop rather than making this at home. What is James's top tip for picking the best coffee in that situation?  


[01:00:37] James Hoffmann: First and foremost, I'm going to be pro independent coffee shops. They have a different motivation. 
They're trying to win you over with the quality of the product, not with convenience and familiarity, which is how chains tend to work. So it's worth the gamble to find a good independent coffee shop. They'll care more about the coffee. It'll be fresher. It'll probably be of higher quality. It'll probably be theoretically higher in things like polyphenols, which that's a broad statement and I'm very nervous making it, but you would hope that would be the case and so that would be the first thing.

And then I think you know as long as coffee is well brewed which again independents these days tend to do well. Whether it is a flat white or it is a filter coffee or it is a straight espresso It's actually a matching kind of extraction of the raw material across all of those things. 
And so, you should see the benefits kind of regardless of your preferred drink. But you know, people or independent businesses are excited to talk to you about what you like and help you find something that you like. And it's always worth a conversation and finding your local sort of place. I think we don't have that feeling as much anymore of like your local coffee shop. 

And that's a shame if you know, that's the thing independence offer over chains to his community space experience. So yeah, all those things is why i'm pro independent business.

[01:01:50] Jonathan Wolf: And one question that we were asked a lot from our listeners was what about people with high blood pressure? So Tim, you've been talking about all the great health benefits of coffee, but you also mentioned I think that historically people were told not to drink coffee because it raised blood pressure if you have high blood pressure. What is your advice?  


[01:02:10] Tim Spector: I think if your blood pressure is not under good control, then you have to be very careful with coffee and caffeine. But all the studies suggest that if you're just starting to drink coffee, it's only the first few weeks that your blood pressure will go up, and then it stabilizes. 


So I wouldn't advise anyone just to completely change their diet or anything they're doing if they don't have stable blood pressure. Get it stable and then start to slowly introduce coffee into your diet. It's not, as far as I'm aware, a contraindication if your blood pressure is well controlled. I monitor my blood pressure and coffee has no effect on that. And there's some evidence that long term it might actually reduce your blood pressure.  


[01:03:03] Jonathan Wolf: Got it. So you're saying if someone's listening to this and they have high blood pressure, but it's under high control and they like coffee. You're not saying it's not don't worry about it, they don’t have to give up.

[01:03:11] Tim Spector: No. Though there were old studies They're out of date. They showed that people who hadn't been exposed to coffee if you give it large doses, short term your blood pressure can go up. So obviously if you know, you have a problem, short term you don't want to have that problem. But if it's well controlled then no real problem long term.

And long term we know from all the epidemiology that for the average person, they will get derived benefit long, in terms of their heart health, you know, the caveat as always is where everyone is an individual and all our responses are going to be different. 
We can't give advice that is going to apply to absolutely everybody. We're talking at this point averages.

[01:04:04] James Hoffmann: And there's always decaf. 

[01:04:05] Tim Spector: Yes. So that is always decaf. And I think it was the blood pressure story was mainly about the caffeine side of it. So as we've heard, decaffeinated coffee is safe. The chemical processes are now considered very sophisticated, safe. There's plenty on the market, find one that you like, no need to have caffeine.

I think everyone's got to work out, you know, the lots of factors that affect your caffeine metabolism, work out what suits you, experiment, find out, you know. But for many people it does get them going in the day and gives them a clarity of thought, you know, in their thought processes and other things that are important and that's why I have coffee in the morning, but I don't have it at night. 


[01:04:42] James Hoffmann: Right, let's see what we've got. Okay, interesting. So caffeine first. This came out at about 33 milligrams, so actually comparable to slightly less than the instant, but comparable to actually a normal strength instant. Chlorogenic acids came out at 55.87. So, you know, 55 to 60 probably realistically, which is I thought decent actually, like better than instant and certainly more enjoyable and fun to drink. So yeah, interesting.  


[01:05:20] Tim Spector: Okay, so more, more polyphenols than instant coffee and…  


[01:05:24] Jonathan Wolf: But still a lot less than the coffee. 


[01:05:27] James Hoffmann: But there may be, I assume, some polyphenols from the tea in there as well, which may not be picked up by this if they're not specifically chlorogenic acid. So probably a broader profile.  


[01:05:36] Tim Spector: Suggesting it's a healthy drink as well. Yeah.  


[01:05:40] Jonathan Wolf: I would like to do a quick summary, and today has been really fun because we got to do a science experiment while we were doing this. I think the key takeaway is that coffee has been really reassessed from something that we were being told was really unhealthy to something that we now understand is actually healthy. 


And that, how we understand that is very much about the way it has the impact on our microbiome and how our microbiome then affects us. And so there are two different components in the coffee that are really important. One is the fiber, and one is the polyphenols. And interestingly, there's lots of fiber that is soluble, which is not how I have ever really thought about fiber. 


And so we heard James making the coffee and you could see like the hot water going in sort of sucking all of this fiber and polyphenols out of this ground up bean from a plant. And that interestingly, there's this great new paper which we will share as soon as it's peer reviewed and published, which shows that this is then feeding one particular bug that we've now discovered, which I think Lawsonibacter, did I just about manage to pronounce that Tim? 


[01:06:49] Tim Spector: Yep. 

[01:06:51] Jonathan Wolf: Which we can see, basically, is like a test for whether or not you drink coffee. So I will get my microbiome retested tomorrow and we'll see whether it's, I think it takes a bit longer than that, probably right, Tim? Which then creates these chemicals as a result of eating this coffee, which we understand. 

I think you mentioned this thing, quinic acid, is just one example of something that we know then has these positive impacts in our body because it sort of passes through into our blood. 
So that's very exciting. 

This does not mean you have to drink coffee. There are other ways that you can get fiber and polyphenols, but it means that if you do like coffee, you should be feeling good about this. And that interestingly for, you know, a lot of people in the U.S. or the U.K., the amount of fiber from your coffee, if you're drinking three or four cups, you say could be very significant because our total fiber intake is so low. 


And then we did this wonderful test, where we tried a variety of coffees. And one of the things that was really striking to me is that the decaffeinated coffee scored just as highly on this polyphenols count as the caffeinated coffee, which is not at all how I would think about it. I sort of put it in my mind as a bit like instant coffee, not really very good for you. 


The instant coffee, on the other hand, was much lower on the polyphenols. You've really lost a lot. And then we tried this fun coffee kombucha, which is definitely not something I suspect most of our listeners are regularly taking. And interestingly, there were really polyphenols in there. And so I think that's really fun to see some real, like, that scientific measurement right now that there are some of these good things in that drink. 


And so the net result, I think, is don't drink the instant coffee. Do go to an independent coffee shop. And after that it's a lot about your taste choices and don't at all feel scared about taking the decaf. Because in a way you avoid the caffeine and you're still getting most of these health benefits. 


And I look forward, there will presumably be more papers to come as we understand more about caffeine and as the number of participants in ZOE grows.


[01:08:55] Tim Spector: Yeah, we'll be able to do one on tea hopefully soon. 

[01:08:58] Jonathan Wolf: I'm all up for that one. Wonderful. Thank you so much, James. 

[01:08:59] James Hoffmann: Thanks for having me back. 


[01:09:02] Jonathan Wolf: And thank you, Tim. 

[01:09:04] Tim Spector: Thank you.

[01:09:08] Jonathan Wolf: Thank you for joining me on ZOE Science & Nutrition today. It's been really fun to learn about the different types of coffee, their beneficial compounds, and Tim's new research on coffee and the gut microbiome. It's even tempted me to drink coffee myself, a little bit. Now, if you're interested in finding out more about your own gut microbiome, something that I do regularly, then you can learn more about becoming a ZOE member, getting your gut microbiome tested, and receiving personalized advice on how to eat the best foods to support a healthy gut. 


You can also get 10% off your membership. Simply go to zoe.com/podcast. As always, I'm your host, Jonathan Wolf. ZOE Science & Nutrition is produced by Yella-Hewings Martin, Richard Willan, and Tilly Fulford. See you next time.

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