Can a traditional African diet help protect against inflammation? | Quirijn de Mast & Tim Spector

Can a traditional African diet really transform your health within 2 weeks? Within 2 weeks, African diets, they have many health benefits, but we looked at their local porridge when you eat them. We saw a clear reduction in inflammation, which is key to many diseases.

So, how do you make this porridge? I get that question quite often. So today we're joined by one of the scientists behind a groundbreaking study exploring the traditional African diet. Dr. Qui Ryan Deast is an infectious disease specialist and internist at Radval University Medical Center in the Netherlands.

We conducted a larger study in Tanzania. The people with a western diet their immune cells performed less well with Salmonella for example and the tuberculosis bacteria. And then we switch them to this traditional African diets. Even after a few days, you can already see changes in your immune system. Why is that? In the African diets, people would consume 90 g of fiber a day. Why in the western diet was 30 g a day? That's a big difference. And the people have the diversity in the different fibers they're eating, have the healthiest immune systems and guts.

Tim Spectre is one of the world's top 100 most cited scientists, a professor of epidemiology and my scientific co-founder at Zoe. The western diet is responsible for millions of deaths a year through the chronic diseases that it's causing. I think it is really exciting that we now getting a new idea of the mechanisms of why foods are good for you. It's not about the calories, it's about interaction with the gut microbes and our immune system. And quir, how have you changed your diet?

Welcome to Zoey Science and Nutrition, where worldleading scientists explain how their research can improve your health. [Music] Quain, thank you for joining me today. Thank you. Lovely to be here. And Tim, thank you for joining me as well. Likewise.

So, Qui Rain, we always start the show here with a rapid fire Q&A with questions that come from our listeners, but we have some very strict rules, very hard for scientists. You're allowed to say yes or no or a one-s sentence answer uh if you absolutely have to. You willing to give it a go? I'm ready.

Can a traditional African diet really transform your health? Yes.

Do you need to wait months before getting the benefits of an African diet? No, certainly not.

Tim, is the Western diet harming people? Sadly, yes.

Is a traditional African diet healthier than the Mediterranean diet? Not necessarily.

All right. And Quirra, for a Western listener, what's the most exciting thing about an African diet? I think what excited us the most as researchers was the clear effects, the immune effects of a traditional fermented beverage that we used in the study.

Everyone has their Achilles heel when it comes to sort of tempting treats and Quain was telling me that he was raiding the breakfast buffet of the hotel he was in last night. And it's funny because for me it's like fresh bread, it's chocolate and actually it's that ultimate combination where they put the fresh bread and the chocolate together and they make a pan of shakala or you know chocolate quason depending where you are and all of those are sort of key foods in the western diet and that diet in general features a lot of processed meat, high sugar drinks and refined grains. But I'm very excited to be talking about a completely different diet today and to be speaking with the scientists behind the very first significant clinical trial of the subsahara and African diet published in the world leading journal nature just a few weeks ago.

But just before we dive into it actually I thought maybe Tim you could just summarize what's the problem with the western diet. The western diet, also known as the SAD diet or the standard American diet, is basically responsible for millions of deaths a year through the chronic diseases that it's causing. So, obesity, diabetes, uh heart disease, cancers, autoimmune disease, uh mental health problems, you name it, this has been linked to our poor diets. So anything we can learn from other populations about how to manipulate or change our diets. Looking at other examples is really important for our health. And it's coming increasingly true that it's not just about the fats. It's not just about the calories. It's about something else in the food that is upsetting our immune systems and our bodies and our gut microbes in ways that in the past we haven't really thought about. So thinking about new mechanisms about how other diets might be beneficial is is really absolutely vital for us moving forward to really redesign the way we eat and think about food.

I already asked about this Mediterranean diet versus African diet because I think we hear about the Mediterranean diet often as the answer. Tim, why is that? That's probably because we've got most data worldwide comes from our study of the Mediterranean diets since the 1950s. We've been really looking at that as the model of why there was this big difference between North and South Europe in terms of heart disease. That's how it all started. And American researchers like Anel Keys did these big epidemiology studies following populations that were eating lots of dairy and fatty foods, but with large amounts of legumes and vegetables, fresh fish, etc., and plenty of olive oil, and found they had a third of the rate of heart disease of the average American. And so it was this idea that we should be somehow mimicking what they were eating in southern Europe in Greece and Italy and southern Spain and if we could recreate that in the in Northern Europe and North America then we would actually dramatically help improve our health. So that idea has been with us for over 50 years now. Although it's been very difficult to define the Mediterranean diet. And if you go to the Mediterranean now, you'll see pizzas and pasta and that isn't what they originally thought of as the Mediterranean diet. So this is the problem and that's been exported. There's pizza places everywhere in the world now. It doesn't mean that's now the healthy diet. Place like Italy are getting increasingly obese and having problems as well. So it's trying to define what are the key elements in these diets that are helpful rather than just saying, "Oh well, just eat like the Italians or the Spanish and you'll be fine."

So Quirra, it's really exciting to have you here because I think we've tended to speak a lot about the Mediterranean diet across many different scientists on this podcast. This is the first time actually that we're talking about a traditional African diet. Could you start by just telling us what is a traditional African diet? It's not easy to define because there is not like a typical traditional African diet. I mean Africa is a huge continent and there's so much diversity in in dietary patterns across the different regions. Um that said there are some I would say some unifying themes if you talk about African diet. So many of the traditional African diets they're mainly plant-based that's one. So people consume a lot of legumes, traditional grains like millet, sorghum, te and ethiopia and these are very I would say interesting small grain cereals with many yeah health benefits. Um but also they have a rich tradition in Africa in using fermented foods.

Also have a lot of porridge don't they? They sort of the thing we don't do is that they put all different grains into sort of grl and porridge and that seems to be what I've noticed in Africa is the grain might be different but they still have a similar that's the base of many meals like we would have potatoes they have a sort of grain porridge. Yeah that's correct. So in Tanzania where we uh we did our uh studies people consume two sometimes three times daily indeed the porridge it's made of of mace or from millet but you see in many areas that they have their local porridge uh can be made from maize can be made from from sorum for example. So that's true. Yeah.

And you've mentioned quite a few grains that I'm not familiar with like sorghum I wouldn't know it if it dropped on on my head. Could you describe for listeners who maybe are not familiar with like a milled or a sorum? What are they similar to that we might be used to to finding in a in a western supermarket? To be honest, I I can't really say like compare it to what we we're used to in the in here in Europe or in Western supermarket, but they are extremely interesting these grain cereals because they're so nutritious, contain lots of fiber, more than than for example wheat. They're rich in polyphenols. They also have a low glycemic index. So you don't see this like this spike in glucose or insulin when you eat them. Yeah, they're kind of neglected I would say, but they have very interesting health benefits.

So there are many grains that you know our ancestors used to eat and we've we've all become very focused on these monocultures of just having maize and wheat as our principal ones and they're the ones we export. But if you go to other countries, you'll see all these varieties of these um cereals. And it turns out they're much healthier than the ones that we've evolved in that we're just more efficient for storing long-term and and and big commerce sort of global commerce. So this is why when you go to Africa, you'll see a lot of these regional uh grains that we don't see anymore in the rest of the world.

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And so I should think about these as being like the seeds of these plants, a bit like I might have with wheat. And these are traditional plants that as human beings we've presumably cultivated for very long periods of time in Africa. Yes. Correct. Yeah. But we haven't traditionally eaten them. If we are, you know, if you're listening to this in the States or Northern Europe or probably Australia or Canada or wherever, they somehow never really made the transfer with people as we came out of Africa. No, not that I'm aware of. So we don't have a tradition with with eating millet or or sorghum indeed.

And what made you want to study this African diet? Quirin. Well, it's one of the reasons is my own observations. So I've been collaborating with a university hospital in northern Tanzania, KCMC. So it's the foot of of Mount Kilamanjaro. And I've been collaborating with them for almost 20 years. So 20 years was my first ago was my first visit for I was doing a PhD on malaria and since then I've been a regular visitor and I do see clear changes in disease patterns over these past 20 years. So 20 years ago if you would look in the hospital there were mainly people with infectious diseases but nowadays you see this very rapid rise in people with yeah non-communable diseases or lifestyle diseases. So there's a lot of obesity, a lot of type 2 diabetes, people with cardiovascular disease, kidney failure, and so we are interested in what does it cause these these changes in disease patterns. And my department, our researchers focuses on factors that regulate your immune system. And we've been doing different studies in the Netherlands in in cohorts of healthy people and people with underlying conditions. But we thought it would be of particular interest to also perform these studies in Africa and Tanzania to look what what are the factors that regulate your immune system because if you look at if you talk about cardiovascular disease for example we know that there's an essential role for inflammation and so we we conducted some years ago a larger study over 300 people um healthy people So, and and some of them were living in a city, some of them were living in a rural area. And we looked at all these factors that might associate with the function of your immune system. And what stood out was what people eat. These studies where you look at, we call them cross-sectional studies. So, you look at at one time point. So we had a clear hint that the change in diet between people living in the city and people living in a rural area that that was one of the main factors driving inflammation and the function of the immune system. But we wanted to to confirm that it's indeed diet. So that's why we did this intervention study.

And quir can you maybe draw a picture for the many listeners who have never been to Tanzania? you know, what was it like when you first visited 20 years ago and what is it like now? Because you're painting a picture, I think, of a lot of modernization and a rise in diseases. I think will probably be surprising to most listeners. Yeah. No, it's totally different. So, um, so Tanzania is a country in East Africa. It has a steady economic growth. So, it's now a middle inome country. Um, more and more people living in cities. And in these cities, life is like yeah, what we know from the western world. People are surrounded with processed foods. There is fast food on each street corner. There is snacks everywhere. So they're now eating hamburgers and French fries and lots of processed food in packets produced by Yes. big companies. Yes. Every street corner has brightly colored stalls with, you know, soft fizzy sodas of every single bright color of the rainbow. Really fluorescent colors. The thing you notice most when you go to these countries and yeah, these snacks that last for years that never go off. Big food companies have got there first. They've made sure that these foods are everywhere and they're cheap and available. And another thing is that that I notice is that so 20 years ago people would walk a lot. Uh but nowadays there are motorcycles everywhere. You know these these motorcycles important from China and tuk tuks people have much more sedentary lifestyle. So these are two major changes. And what's interesting in the in in Kilimanjaro region where we did our study. So we have a town it's called Moshi but at Moshi lies at the foothill of of Mount Kilimanjaro but very nearby on these foothills of Mount Kilimanjaro. People still leave live kind of a traditional life where they still exercise a lot, they walk a lot but also they preserve their traditional diet. So that makes this a very interesting area to look at the effects of lifestyle changes and dietary changes on health. It's almost like a time machine where you can look back into a diet of um people living in sort of preodern uh western lifestyle. And then literally next door you've got people who are now living the sort of diet that you would be living if eating if you were in New York or London or or Amsterdam. Exactly. Yeah.

I had no idea how fast that change was happening and I think I'm also rather shocked to hear how much these sort of western disease we we tend to think about them as western diseases right the diabetes and the obesity and you're saying that now in Tanzania which is only 20 years ago you're saying that almost nobody was eating these foods and you really see the impact already today on things like obesity. Oh absolutely. So in an urban population, so people living in cities, 30 to 50% of the adults are overweight or or frank obese. 30 to 50% 30 to 50%. So that's it's immense. It is immense. So it's a huge challenge for for health care nowadays. And generally when I've when I've been to Kenya and Tanzania, they believe that western food is more likely to be healthy for them and because it's seen to be associated with being rich and wealthy and therefore more advanced. Even if it comes in a bright green packet, it's seen generally as something that you should aspire to. So there's a big gap in in education about what is what is good and bad.

Well, I think you've painted a really powerful picture for why you'll be really interested to understand whether the diet change is what's sort of behind this change in health that you're you're describing. And I think we've got a bit of a picture also of what this African diet is. And it's clearly very very different from the Western diet. Your team was the first ever, as far as I know, team to sort of comprehensively try and examine the effect of a traditional African diet with a very strong sort of study structure where you could really actually do an intervention and see what happened. Could you describe in in sort of in simple terms what the study was and then we'll go on and talk about what you found out. Yeah. So we selected a group of healthy young men and um half of the men were living in the city and they were consuming a western type diet while the other half half of the of the young men they were living in a rural area. So up Mount Kilamanjaro somewhere almost 2,000 mters. So what we did we set up a study site up on Mount Kilimanjaro. So, kind of a pop-up restaurant on almost 2,000 meter altitude. Pop-up restaurant. I love it. With a with a cook, the rural living man, we would switch their diet to western type diet. So, the they would come three times daily to our study site to our pop-up restaurant. Uh they get breakfast, they get lunch, they get dinner, and so and then we we we measured uh the function of their immune system. We did that with blood tests and we sampled their microbiome. And we did that at the end of the two week intervention and then they would switch back to their habitual diet. But we resampled them four weeks later because we were also interested in the longer term effects of this such a short Yeah. intervention. And in the cities we did the opposite. So the the man they had a had a western type diet and so we switched them to this traditional Kilimanjaro style diet. So we gave them lots of beans, traditional grains, the millet, sorghum porridge for example again with the same resampling four weeks after the end of the intervention. We did exactly the opposite. So we switched basically their diet. So western to traditional and traditional to western.

Do you remember roughly the difference in fiber consumed per day? Yeah. So in the heritage diet, uh the people would consume Yeah. roughly 90 grams of of fiber a day, while in the western diet was roughly 30 grams a day. Wow. That's that's a big difference. And just so people know, the average American uh in the in the West has about 15 grams of fiber per day. So 30 is actually a recommended level. So it's it's not bad, but you got three times that in the African diet. That's amazing. Yeah. So I'm just doing my little mental maths. You're saying that traditional African diet goes from like 15 grams you see in America on average all the way up to 90. So it's like six times more fiber they're eating every day. So you know, we talk a lot about deficiency, but that relative level is extraordinary, isn't it? Absolutely. Yes.

We also had a third group in our study and there we made use of a traditional fermented beverage that's commonly consumed in this uh Kilimanjaro region and this drink is called embe that's the local language also commonly referred to as banana beer and it's it's a beverage made of bananas uh so they they kind of mash bananas so make banana juice and then they add some millet it and then this is uh fermented um by some you have some local producers and then people typically yeah drink for sometimes half a liter a liter a day. So in our third group we had men with a western type diet and we gave them this fermented banana beverage for one week. Did you try it yourself? I tried. It's quite sour, isn't it? It's very sour. Yeah. Yeah. So you really have to get used to the taste. And is it as is it as an alcoholic as a beer? Yes, it is. It has a low alcohol content. So, it depends on the the time of the day that you drink it because it gets stronger during the day. It gets stronger during the day because the fermentation is ongoing. So, like how alcoholic in the morning and how um so it varies but usually in the morning it's about 1%. But it cannot it it can increase to up to 3%. Got so in the morning that doesn't sound very alcoholic. You're not likely, I guess, to have a lot of hit. At 3% and you drink a liter, you're going to feel might make you sleepy in the afternoon and evening. And it sounds like you're not really selling it that it's going to take over my local wine bar from the taste. Is that people say, "Well, it depends on the on the the local producer. Some are well known to to make it also more sweet. So, it depends on your producer." But yeah, for me, when I have tasted several times, yeah, it's for me it's pretty sour. Well, I want to find out what it does for me and then we'll be figuring out how to source a tasty version.

So, Quir Rain, I think you set up sort of described this study with these three arms. The people like halfway up Kilimanjaro switching to a western diet. The people in the city who've been eating a western diet for a long time now switching back to that traditional diet. And then a third version where you're saying they're on a western diet, but you sort of reintroduce this fermented beverage. I guess you're sort of giving them away free basically giving away free beer each day. Is that uh correct? Yes. What did you discover? So in the the people with a traditional diet who switched to a western type diet, we basically saw that they develop more inflammation. That's the main finding within two weeks. Within two weeks. So we looked at at several aspects of the immune system. So if we looked at the circulating immune cells in the blood, we saw that they became more activated. Also, they started to produce more yeah inflammatory proteins in the blood. And third, we isolated the immune cells from the blood and we we we stimulated these immune cells so in the lab with with microbes. And what we noticed is that these immune cells performed less well. Um so on the one hand they developed inflammation but on the other hand if you stimulate the immune cells with microbes you see an yeah a poor response and quirin these are like bad microbes you're talking about sort of microorganisms causing salmonella or yeah we we indeed with salmonella for example and and the tuberculosis bacteria two weeks on the western diet you gave them tuberculosis and they like didn't deal with it as well. Yeah. And this this shows that there is kind of an immune disbalance. And on the one hand, the immune system produces too much inflammation. So it's like ramped up really. So it's like Yeah. So it's getting excited in a general way. Yeah. But it's not very effective when you actually give it a real villain to attack. Exactly. Precisely. So the switch to a western diet had quite some negative effects on the on the immune system basically.

Well in the people that we switched from a western diet to a traditional diet we saw the opposite. So we saw a clear reduction in inflammation which is good. And in the third group the people with a fermented banana beverage it also had mainly an anti-inflammatory. on inflammation inhibiting effect and we saw that the immune system was much more imbalanced. So these were the main findings and could you separate out whether this is an effect of the bad effect of the western diet or the lack of good effect of the African diet? How do you separate those in your mind? It's hard to separate but I think it's it's it's certainly both. Yeah. Right. So that if if people had carried on eating their African diet, they might have been able to tolerate a little bit of western diet and sort of vice versa. Yes. And with the banana beverage alone, is that enough to solve everything or was that not as good as the people who moved on to sort of the the full African diet? Well, it's you do see some different effects. the banana beverage could correct some but I think there were additional effects of of the switch to the to the traditional diet. So the combination would be perfect. And in fact it's interesting our colleague Christopher Gardner did a study at Stamford where they compared uh in Americans high fiber diets against high fermented food diets and they found different immune profiles of the two. So it's there are different processes involved. Both are beneficial, but the fermented food has a big impact of its own. And that that's certainly something we've done some studies in Zoey as well with our citizen science. People having extra fermented foods do get benefits that look as if they're different to the the ones of just by increasing your fiber intake or your plants. So lots of different mechanisms being brought into play.

What are your thoughts on this study and and and the rather amazing results after just two weeks? I don't like to ever read too much into one study, but it is actually backing up uh a few older studies that have weren't as sophisticated that did something similar. So where they've swapped uh some Africans for some American diets uh and just looked very crudely at their microbiome and that improved when they went on to the African diet and got worse on the American diet. And of course this Stanford study where they compared fermented foods and fiber. So it is very consistent and it I think it is really exciting that we're seeing that we now getting a new idea of the mechanisms of why foods are good for you is that it's not about the calories. It's not about the fats. It's not about the vitamins. It's about their interaction with the gut microbes and our immune system and how that is so crucial to nearly everything in our health. If we can get that balance right, then you know we can actually start to control these diseases that we've let go rampant. And I think this is the really important message from from these these kinds of studies about learning these new mechanisms. And as you said, it's not just about ramping the immune system up, it's getting the right balance so that on the standard American diet, our immune systems are just going crazy attacking everything, but they're not very effective. So we're getting more infections and the body is being confused by all these immune signals and not repairing damage, you know, leading to all kinds of metabolic problems. So yeah, we we need to learn from these studies and learn, you know, what the best foods are to eat so we can help ourselves.

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Can the two of you help me to understand the link between this immune system response that you were measuring and then the impact on people's long-term health and you were talking about obesity and diabetes and heart disease and all these things that we know you know we we are likely to die of in the west you know we're not very likely to die of an infectious disease anymore. How is that linked to sort of this immune system that you were you were measuring? Cuz that it's not immediately clear to me. No. So, we know that that inflammation is is key to many diseases like indeed like cardiovascular disease, cancer, dementia, name it. On the other hand, what we we're more and more starting to to understand is that if you have a chronic inflammation and quir, when you say chronic inflammation, what does that mean? Chronic inflammation is that your your immune system is chronically activated. So, um, yeah, that's basically long term. It's quite normal to have an immune system that every now and again pops up because it sees a threat, but it goes back to its normal levels. What we're seeing now in western populations on these bad diets are levels where it's continually being triggered. It's like, you know, your fire alarms going off all the time. Uh not just the weekly test, it's like on all the time. So, the body can't focus. It can't concentrate because it's just got all these alarm signals. It doesn't know where to go and repair things. It doesn't know uh how to efficiently attack some microbe. And we think this then disrupts metabolism, our mitochondria, and affects all kinds of diseases because the body is just running really inefficiently. I think that's the way to think about it. It's like you're just putting the wrong petrol in your car and so it can never really function properly when the whole system is just ramped up. It's just like you're revving the car too much. I I love that analogy of like the wrong petrol in the car. I suddenly think I I'm I'm getting it.

So on the one hand that sounds very depressing if you've been on the western diet your entire life like like me. On the other hand I think you're saying that in just two weeks switching to this African diet you could really see a measurable improvement. Like was that meaningful? I think it's meaningful. So it shows that even after a few days that you can already see changes in your immune system and that's what we also know from from earlier studies to be honest. So we know that it doesn't take very long to see effects if you change your diet. I think it's amazing.

Before we switch on to sort of like what can this mean for listeners, are you able to understand what the components of the diet are that are affecting the body? So you switch this, you know, this whole diet for for one group, another group just given them this uh banana beer. Do we understand at all, you know, what's going on? What parts of the what what are the characteristics I guess of this African diet that are being so much healthier? Yeah, I think it's the combination. So it's not just one type of food like which did the magic trick. So it must be the combination. So I think the foods that were important in the traditional diet. So it's the the traditional grains which contain lots of of fibers but also the legumes which are fiber richch and traditional vegetables they were eating lots of fruits they contain anti-inflammatory uh products called polyphenols also the fermented products they used so they contain some live microbes who could could have beneficial effect on the on the gut microbiome uh so I think it's the combination

I remember when I was um spent some time with the Hadza tribe uh which is just about 6 hours from where your experiment was. They had a lot of these berries and that was a big part of their diet was these tiny little berries which were the precursors of many of our cultivated berries and they had something like a thousand times the levels of polyphenols that ours do. And the other thing they were eating at the Hadza was digging up tubers. Yes. um things which we'd now know as things like yams, bit like these root vegetables which become potatoes but actually they're much more nutritious than potatoes. Was that part of their their diet in in this group of Tanzanians? Yeah. So we didn't give them them berries but what we did we gave them indeed like roots and tubers cava taro. So, so absolutely there's some variance uh which is is a important part of the regular traditional diet and baobab was that no we in this region there are not too many baobobs so baob fruits were not part of this they cut down the trees unfortunately so they don't have them but yeah that was their porridge that that had as their daily porridge was the baobab which is um interesting but yeah this porridge seems to be the the binding thing across Africa that it's a very really easy way to get the fiber into your body quickly.

You know, I think of a porridge as something or an oatmeal as something that I I get in a packet that I rip the top open, I pour into a bowl, I put in some milk, and I put in the microwave for a minute and a half. I have a feeling you're describing a slightly different porridge or oat milk. How do you make this porridge? So, the the porridge they most commonly consume ugali. Traditionally, it's made from from unrefined maze and they add some water and they boil it and then you get this kind of stiff porridge. But you do have variants. So in our study, we also as breakfast we we we served uh participants a porridge made of of millet for example. So you just use millet, you add water and you you boil it and you make it into a porridge. So, it's almost like making like rice or a sort of sticky rice and you're just keeping the liquid in it. I'm imagining as soon as you say porridge or oatmeal that I'm adding sort of dairy milk, but actually it's just really sort of boiled to break it. Yes. It's Yeah, it's the grain plus water and a bit of heat or a lot of stirring. The Hadza didn't really use they didn't have a lot of boiled water. So, you know, they would just add normal water to crushed bits of the baobab into these little cubes and basically with 10 minutes of just beating it up, it would it would just become this creamy thick liquid. And I think this is the general way that for millennia we've been eat consuming these these foods which we've sort of forgotten. Your type of porridge, Jonathan, is highly refined. They've stripped off anything on the outside that would stop it becoming instantly absorbed into your body. All those good bits have been thrown away. You're just left with a very sugary center bit that dissolves instantly in the water or microwaves away and then goes straight, you know, to produce sugar in your system. Whereas these old ones have got all that coating there that is part of all these what we're now discovering are the crucial bits. That's really interesting. We did a podcast on oatmeal where we actually got to do a live experiment looking on what was happening to our blood sugar as we were eating these different sorts of oatmeals. And I feel here you're describing something which is a whole level both more nutritious but also less processed than you know any sort of oatmeal you know forget about the stone ground version. This is sort of like more fibrous to start with. It sounds like a grain which is itself is probably you know closer to its original form in nature I guess than the sort of oats and um grains that we typically eat in the west if I may add Jonathan what's so what's worrisome is that more and more people are making these porages from imported refined maze for example so Africa has imported lots of of staples nowadays refined maze wheat rice it's cheaper So their their local agriculture indeed um it's it's transitioning more and more to to monocrops and also cash crops for exports. So so tea, coffee production. So lots of these maze nowadays is being important because countries like the US have an excess of maze and they get subsidies from the government to produce it really cheaply and they end up dumping it in third world countries where it overtakes the traditional uh types of grain and the local farmers you know who growing it can't compete and so they're they're sort of being forced to transition into these less healthy grains that they're not traditionally used are cooking with anyway and have all these health disadvantages. So yeah, it's it's a real sort of geopolitical problem at the moment and and when there's famines, it happens even more. Yeah. So there was a very yeah rich tradition of smallcale subsistance farming, but it's really declining nowadays.

So, you're seeing this big transformation, it sounds like, just literally over the 20 years that you've been visiting, from this very traditional diet to a diet that looks rather similar to the one that, you know, I might be eating from my local supermarket. Correct. Yes.

So, I think the results of the study are amazing. I think the fact that you can see an impact just in in two weeks is fascinating. And I know that Tim is incredibly excited by your fermented test as well since he is Yeah, definitely want to try that one. is the world's biggest uh promoter of more fermented food. I would love to now sort of try and transition into actionable advice for our listeners. And so, you know, they're not living in Africa. This is not probably their traditional diet for the vast majority of people who are listening. So, I'm really interested maybe start by just describing a little bit more like what you might eat in a day on a traditional African diet and then I'd like to start to talk about what what could that mean for someone listening and how could they try and get the benefits from this given the reality of what you might get from your local supermarket. So, what could we learn from from their diets? Um, so I think point one is their biodiversity. I think Africa they they have thousands and thousands of of very interesting edible plants. Many of them still underutilized. We don't know their health effects yet. I mean there's so much we can still learn uh diet-wise from from all the indigenous knowledge from Africa. So I already mentioned these these traditional grains. I think they're very interesting. one of these traditional grains, te it's it's more and more being used here and also claimed to be one of the you know, the called superfoods and quirine how do you how do you spell te e ff so it's an ancient grain coming from Ethiopia which is supposed to be one of the precursors to to wheat and what we're we're currently having as our main grains and you can get te flour here now uh you can make breads with it and with e corn as another sort of ancient grain that I think you also see in Africa, don't you, as well? Yes. Yeah. So, yeah. So, going back to these ancient grains rather than this this highly uh evolved wheat that we currently have in it in its in its current form going back many generations could actually help us, you know, even just making bread in better ways. Yeah. That's why in Ethiopia it's being used to make um they ferment actually the the te and make it into a kind of a bread. It's called Ingera and that's their main staple and it's interesting. It's it's also it's gluten-free and as said contains a lot of fiber, a lot of polyphenols. Um so that's one thing. So the traditional grains but also um I think there are some some green leafy vegetables which are interesting. An example that's commonly being consumed in in Tanzania looks like a spinach. It's called amarant. It's also sometimes called or referred to as African spinach. Yeah. And last it's it's the fermented products. Although I there are of course yeah important challenges. I mean um if you would like to consume like a banana beverage that we used in our study. Yeah. It's difficult with all the the regulations that we have. So because you yeah here it should be pasteurized and then you lose Yeah. you basically you kill a lot of the microbes that are in these fermented beverages. But the example might be kombuchas or other things that we do have in the west that could have similar uh advantages if they have many yeast and microbes in them like I I guess this this did you do any microbiome testing of the beer? Yeah, we uh well there are some some we know some from from earlier studies from literature. So it's indeed it contains a lot of lactobacill and also sacrome sizier which is kind of a a good yeast a healthy yeast. So it's important for for your gut microbiome. And that said I mean I think it's yeah if you look we have some earlier data from from from the microbiome of people in this in this region. And what what was very interesting is in that people consuming this traditional diet that we found quite some yeast in their microbiome and yeast I think their their role is really underestimated in in in the role in gut health. They're only you know a very small percentage of the of the microbes in our gut microbome are yeast but yeast have such a yeah strong immune modulating effects. You know with our current industrialized diets the loss of of yeast in our microbiome could have a strong health effects.

In many countries doctors are trying to eliminate yeast from people's guts uh because it's been got a bad name. So the the candida you can many specialists say oh it's all down to having too much yeast in your your gut and what we're hearing the latest research is saying the opposite is true. You need more yeast in your guts to give you really good immune benefits. Having yeast in my gut could be a good thing. Absolutely. Yes. Uh all the evidence is pointing in that direction. There are a few rare exceptions where you get yeast overgrowth but for the vast majority of time we want to have more yeast. We want to stop killing them and we want to be eating foods that introduce them into our guts. We don't know enough about them, but we think they have a crucial role for our immune health and dampening down inflammation. So, this is fascinating thing we come back to on this podcast a lot where maybe originally with good intentions, we've ended up eating something completely different from the diet that we sort of evolved with and then we're having like these terrible side effects is how I understand this. that you can see within sort of two weeks from switching like back to a more traditional diet or away from the traditional diet towards our new sort of industrialized big food driven. Yeah. And and we got to realize is that we've also lost a lot of our microbes because we all originated originally from Tanzania or Kenya, that bit of East Africa. And when you look at those indigenous populations, they have twice as many species as we do in the West. And that includes the yeast and other parasites as well as the regular microbes. So we've lost a lot. We need to learn again to relearn how to regain them and how to keep them happy.

So, I'd love to talk maybe Tim you can share having listened to this a bit more about what a listener might be able to do if they're saying I would like to eat more in line with the African diet and maybe take me through some like easy swaps listening to this that you might be able to make maybe you know starting with where somebody may be today. Yeah. Well, I think the first lesson is you got to increase your fiber intake. In in this study, we compared, you know, 30 grams a day, which is the recommended level, you know, up to 90 grams. So, we need to go beyond the recommended levels of fiber in the West. And can you give some examples of what that might mean for somebody maybe eating the traditional very meat heavy processed? The more meat you've got on your plate, the higher it is to increase your fiber because there's no there's no fiber in meat dishes. So, if you're just having dairy and meat, you're getting no fiber at all. So reducing that and upping your level of high-fiber vegetables is what you need to be doing. And in Africa they have a lot of legumes and that's the easiest way to get both protein and fiber. So legumes are beans, they're lentils, you know, there's hundreds of varieties of these sort of plants that we don't eat nearly as much as much of as we should be and they're all pretty much good for you. Getting a mixture of them is great. We've been talking about some grains that are quite exotic to most of us in terms of what we buy from the the supermarket. You know, if I was instead eating different sorts of beans or chickpeas or lentils or things that you know are more familiar uh in terms of being able to get them in tins from the supermarket, are they likely to have similar effects or are they likely to be much less effective than this this African diet that we're talking about? No, I think they should be pretty much as effective. What we also need to realize is that Africans have their own gut microbiome. Each population has their own specific microbiome. Remember, we're only share,

You know, less than 20% of our microbes interact with each other, even within the same country. Because we're going to share it less with someone in another country. So, um, we mustn't assume that what works perfectly in one population will work for everyone else. But we can take some general principles, and I think that's really important. And realize that it's also personalized. Um, so, but so I think we can take some broad principles here, see which ones do cross countrywide borders, and use those examples.

So, fiber seems to work everywhere. How you get it is, is, is may depend on what's good in your country and how your microbes get on with them. There is a clear seasonal effect on what people eat. So it really depends on harvest time, availability of fresh products, for example, fresh crops. So people change their diet throughout the year, which is so different from my experience, which is even through my life. I remember as a kid feeling that the fruits and vegetables in the supermarket changed through the year, and now actually, whatever you want, strawberries, asparagus, is there all year round. It's just flown from some different part of the world.

Yeah, correct. Well, that's true in the UK, it's true in the US and other similar countries. But if you go to the southern Mediterranean, it is very seasonal. You know, they have certain fruits that they only have in winter. You know, your apples and your pears, and they will have, you know, the peaches and other things, but you wouldn't get them out of season, and they don't eat them out of season. So, so that might support more diversity of microbes because I'm having these different things that my different bugs like.

Exactly. You're not having the same fruit every single week of the year. So, what's interesting, Jonathan, so in our earlier study in Tanzania, we found this very clear seasonal effect also of the function of the immune system and of inflammation. And we could relate that to the products that people would eat during, you know, after the wet season and after the dry season. So when you have the fresh products, then we would see that the immune system, the inflammation would go down. So you wouldn't expect that in an area so close to the equator as they're changing their diet, and particularly when they're eating more fresh produce, you actually see that their inflammation decreases and their immune system is sort of working better. Yeah. So after harvest, when all the, when they have all these fresh products and fresh vegetables, we saw a reduction in inflammation.

That's amazing. Yes. That could be due to things like the polyphenols being at their highest level in the really fresh produce, when they're really bright and they've got all the defense chemicals in there. And the longer you leave them, the more you lose those defense chemicals. So we don't yet know that this is speculation, but it's really fascinating these observations.

You've mentioned polyphenols quite a lot. Can you remind our listeners what they are and why they might be declining after I take this plant from the field? Well, polyphenols used to be called antioxidants, but they're chemicals within the plant that are there to keep it safe from damage from sun, from wind, and also predators. And it turns out that when we eat these plants, we ingest them, and they act as fuel for our gut microbes. They can process them and then convert them into energy, and they use it to then replicate. And it turns out that their effects on the body are really via the gut microbes. There's very few effects that are direct. So the gut microbes are there to break them down. So they're very keenly sensitive to the levels in them. And we know, we did a podcast, if you remember, Jonathan, on olive oil, and know that as soon as that olive oil is made, the polyphenol count is at its highest. So it's really quite bitter, makes you cough, flavors. But if you leave it a year or two, it's only down to half the levels. So we know there's a general dropping off in the chemicals. They just like to be there on the living plant and then they decrease. Same with wine. So you really want to be having the fresher the vegetables, the higher the polyphenol count. Um, and that's generally true. So these stored ones made in factories. So that's why most commercially produced foods have very little polyphenols in them unless they've added them back in.

And, Quinn, imagine somebody's listening to this and said, I'm going to try this tomorrow. I'm going to try and make my own version of your study, switching towards this traditional African diet, adding in all of these different foods that are going to give them much more fiber and polyphenol and all the rest of it. You were able to measure a change in two weeks. Could they expect to see or feel any results at home if they did this?

Yeah, I think so. So I think they can feel a difference in, for example, their bowel habits, you know, with increased fiber intake. But maybe people also start feeling more fit after, yeah, indeed, a short time.

And how have you changed your diet? I get that question quite often. Well, unfortunately, I haven't started yet brewing my own banana beer at home. But how I changed my diet is, so I, I clearly increased my intake of vegetables, tried to eat more legumes, have more lentils, um, reduced, like we reduced meat intake, limit processed foods. I was quite surprised. I mean, I hadn't, yeah, expected these effects that we observed in these studies. So, I mean, I work as an internist. I knew, of course, the importance of what you eat, but that the effects are so pronounced, I hadn't expected, to be honest.

Final question. Let's imagine that our listener finishes this episode and they immediately call their friend to share just one thing, which is like the most impactful thing from your research that could help them improve their health. What would you want that one thing to be? I think what we've seen in Africa and what it learns us is the importance of switching your Western type diet to a whole food plant-based diet. It has such a clear, yeah, health benefit. So that would be my take and my message from this study. You see across Africa, meat intake has really increased in recent times, but traditionally, I mean, they didn't eat that much meat.

I would like to try and do a quick summary. I mean, the first thing that pops up to mind is that for your research, what you did is you built a pop-up restaurant halfway up Kilimanjaro, which is the most entertaining study I think we've ever had on the podcast, in order to understand how the traditional African diet works. And what you found is that switching to it in just two weeks can transform the way that your immune system works, such that it's much better if you move away from a traditional Western diet. On the other hand, rather depressingly, you could be on this traditional African diet for 20 years and just two weeks on this sort of highly processed Western diet, and suddenly, you know, you test what happens if you come into contact with something like tuberculosis, and your immune system is working much less well. So that's really extraordinary. And the other thing I took away is that the sorts of diets that people are eating in Africa has transformed in the 20 years that you've been visiting. And so actually, many people are now eating exactly the same sort of highly processed food that we're all eating in America or Britain. And with that, you've seen this explosion of diabetes and obesity and heart disease. And so there isn't just this one good diet like the Mediterranean diet. There's probably a set of these traditional diets, but they have a lot of things in common. And the key things I guess that I took away from this is they have a very big variety. And Tim, you said this thing about like your microbes are fussy. So you need to have a wide variety of different fibers to feed all of these different microbes. And your African diet has all of those different plants, many of which we just have sort of lost in the diets that we eat today. But also interesting, you did the specific test around fermented drink, this embay, the banana beer, and you found that even if you were still on the Western diet and you just added that, it had a really beneficial impact. So again, something that's come up, you know, quite a few times on the podcast with completely different sorts of fermented foods is that it has this really beneficial impact. You talked about polyphenols, so it's not just the fiber in the food or the diversity. It's also these polyphenols, these sort of defense chemicals, and that what you saw was that when the diet is fresher, and so these have been sort of harvested more recently, actually that lowers your inflammation and improves your immune system. And in terms of what you could do, I took one takeaway is I want to go and try and see if I can source teff, this ancient grain that apparently I could find, you know, quite possibly in my supermarket as an alternative to wheat that I could try for baking. But also in a simpler way, I don't need to eat these very specific millets and things that might be unfamiliar. Actually, beans, chickpeas, lentils, all of these things that I can find in a tin in my supermarket, you know, if I were to use a lot more of those, I can get much closer to this African diet, but with food that's familiar. And I think what I heard is you think I could have the same benefits that you saw in this study, you know, halfway up Kilimanjaro.

Correct. Yes, fully agree. If you enjoyed this episode with Quir Rin and Tim about the traditional African diet, I know you'll love watching this conversation with Cambridge professor Charles Yo, debunking Western health fads and weight loss myths from crash diets to calorie counting.