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

0:00Welcome to ZOE Science & Nutrition, where world leading scientists explain how their research can improve your health.

0:14The case against the Western way of eating is stacking up. Heavy and saturated fats and refined carbohydrates. It's been linked to heart disease, stroke and other chronic diseases. We hear a lot about potentially healthy alternatives, like the Mediterranean or Japanese diets. But today we're talking about another diet that you probably haven't heard of, but seems to have some astonishing and fast-acting health benefits. The traditional African diet. Rich in fibre, grains, fermented food and plants, this diet has never been properly studied or understood until now. Today, we're joined by one of the scientists behind a groundbreaking study that has just been published in Nature just a few weeks ago, exploring the traditional African diet.

1:01Dr. Kui Ryan de Mast is an infectious disease specialist at Radvald University Medical Center in the Netherlands. And by the end of today's episode, give a better understanding of how the traditional African diet improves our immune system, our metabolism, and our gut microbiome. And some simple tips on food swaps that you can make right now as a result.

1:23Kweerain, thank you for joining me today. Thank you. Lovely to be here. And Tim, thank you for joining me as well. Likewise. So Kweerain, 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 sentence answer if you absolutely have to. You're 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?

2:06Sadly, yes. Is a traditional African diet healthier than the Mediterranean diet? Not necessarily. All right. And Kwe Raine, 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 Quiraine 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.

2:48And actually, it's that ultimate combination where they put the fresh bread and the chocolate together and they make a pain au chocolat or, you know, chocolate croissant, 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 a scientist behind the very first significant clinical trial of the sub-Saharan African diet, published in the world-leading journal Nature just a few weeks ago.

3:20But 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 heart disease cancers autoimmune disease 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.

4:04And it's 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 really absolutely vital for us moving forward to really redesign the way we eat and think about food. I really 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?

4:41That'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 Ansel 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, et cetera, and plenty of olive oil, and found they had a third of the rate of heart disease of the average American.

5:22And so it was this idea that we should be somehow mimicking what they were eating in southern Europe, in Greece, in Italy, in southern Spain. And if we could recreate that 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 doesn't mean that's now the healthy diet places like italy are getting increasingly obese and having problems as well.

6:07So 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 Kui Rain, 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 dietary patterns across the different regions 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, teff in Ethiopia.

7:06And these are very, I would say, interesting small grain cereals with many health benefits. But also, they have a rich tradition in Africa in using fermented foods. They also have a lot of porridge, don't they? The thing we don't do is that they put all different grains into some gruel 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 a 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 did our studies, people consume two, sometimes three times daily.

7:45Indeed, the porridge is made of maize or from millet. But you see in many areas that they have their local porridge, can be made from maize, can be made from sorghum, 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 if it dropped on my head. Could you describe for listeners who maybe are not familiar with like a millet or a sorghum, what are they similar to that we might be used to finding in a Western supermarket? To be honest, I can't really say like compare it to what we're used to here in Europe or in a Western supermarket.

8:22But they are extremely interesting, these grain cereals, because they're so nutritious, contain lots of fiber, more than, for example, wheat. They're rich in polyphenols. They also have a low glycemic index. So you don't see 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. The goal of eating 30 plants a week might sound like a big endeavor, but I wanted to tell you that it isn't actually that hard to achieve. Regular listeners to this podcast know that we often talk about eating 30 plants a week and we stand by it so much that our gut health scientists actually created Daily 30, which is a gut supplement that makes it really easy to do.

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10:37By the way, Whenever we talk about Daily 30 as a good source of fiber, we're required to say that it contains four grams of total fat per serving. Obviously, that's all amazing healthy fats from plants. Ready to start improving your diet this week? All it takes is a scoop to make every day a good gut day. Just go to zoe.com slash daily30 to start adding it to your meals and try the fiber maxing trend for yourself. And right now, we're offering our listeners a free Zoe tin and magnetic scoop with every order. So order yours today at Zoe.com slash daily30. So there are many grains that our ancestors used to eat, and 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.

11:27But if you go to other countries, you'll see all these varieties of these 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 big commerce, global commerce. So this is why when you go to Africa, you'll see a lot of these regional grains that we don't see anymore in the rest of the world. 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.

12:01Yes, correct. Yeah. But we haven't traditionally eaten them. 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 eating millet or sorghum indeed. And what made you want to study this African diet, Kui Rang? Well, it's one of the reasons it's my own observation. So I've been collaborating with a university hospital in Northern Tanzania, KCMC. So it's the foot of Mount Kilimanjaro. And I've been collaborating with them for almost 20 years.

12:42So 20 years 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 non-communicable diseases or lifestyle diseases. So there's a lot of obesity, a lot of type 2 diabetes, people with cardiovascular disease, kidney failure. So we are interested in what does it cause these changes in disease patterns and my department, our research focuses on factors that regulate your immune system.

13:32We've been doing different studies in the Netherlands 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, in Tanzania, to look what are the factors that regulate your immune system because if you talk about cardiovascular disease, for example, we know that there is an essential role for inflammation. And so we conducted some years ago a larger study, over 300 people, healthy people. 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.

14:19And what stood out was what people eat. these studies where you look at we call them cross-sectional studies so you look at one time point so we had a clear hint that the change in diet between people living in the city and people 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 confirm that it's indeed diet so that's why we did this intervention study And Kui-Rain, can you maybe draw a picture for the many listeners who have never been to Tanzania? What was it like when you first visited 20 years ago? And what is it like now?

15:01Because you're painting a picture, I think, of a lot of modernization and a rise in diseases. I think it will probably be surprising to most listeners. Yeah, no, it's totally different. So Tanzania is a country in East Africa. It has a steady economic growth. So it's now a middle-income country. 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 are snacks everywhere so they're now eating hamburgers and french fries and lots of processed food in packets produced by yes big food companies yes every street corner has brightly colored stalls with soft fizzy sodas of every single bright color of the rainbow really fluorescent colors the thing you notice most when you go to those countries and yeah these snacks that last for years that never go off big food companies have got their first they've made sure that these foods are everywhere and they're cheap and available and another thing is that that I noticed is that so 20 years ago people would walk a lot but nowadays there are motorcycles everywhere you know these these motorcycles important from China and tuk-tuks people have a much more sedentary lifestyle so these are two major changes and what's interesting in the Kilimanjaro region where we did our study so we have a town it's called Moshi but it Moshi lies at the foothill of Mount Kilimanjaro.

16:39But very nearby on these foothills of Mount Kilimanjaro, people still 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 people living in sort of pre-modern 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 Amsterdam.

17:20Exactly. 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 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 percent of the adults are overweight or frank obese 30 to 50 percent 30 to 50 percent 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 been to kenya and tanzania they believe that western food is more likely to be healthy for them 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 is something that you should aspire to.

18:23So there's a big gap in education about what is good and bad. Well, I think you've painted a really powerful picture for why you'd be really interested to understand whether the diet change is what's sort of behind this change in health that 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.

18:59Could you describe 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. Half of the men were living in the city and they were consuming a Western-type diet while the other half of the young men they were living in a rural area so up mount kilimanjaro somewhere almost 2 000 meters 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 men we would switch their diet to western type diet so So they would come three times daily to our study site, to our pop-up restaurant.

19:47They get breakfast, they get lunch, they get dinner. And then we measured 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 intervention. And in the cities, we did the opposite. So the men, they 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.

20:31Again, 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? Yes, when the heritage diets, people would consume, yeah, roughly 90 grams of fiber a day. While in the Western diet was roughly 30 grams a day. Wow, that's a big difference. And just so people know, the average American in the West has about 15 grams of fiber per day. So 30 is actually a recommended level. So it's not bad, but you've got three times that in the African diet.

21:16That's amazing. So I'm just doing my little mental math. 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 Kilimanjaro region. And this drink is called Mbege, that's the local language, also commonly referred to as banana beer.

21:55And it's a beverage made of bananas, so they kind of mash bananas, so make banana juice, and then they add some millet. And then this is fermented by some local producers. And then people typically drink for sometimes half a liter or 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, so you really have to get used to the taste. and is it as is 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 because the fermentation is ongoing so like how alcoholic in the morning and how so it varies but usually in the morning it's about one percent but it can increase to up to three percent because in the morning that doesn't sound very alcoholic you're not like i guess to have a lot of hair at three percent in your 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.

23:34So, Kwee 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. And I guess you're sort of giving them away free, basically giving away free beer each day. Is that? Correct, yes. What did you discover? So in the people with a traditional diet who switched to a Western-type diet, we basically saw that they developed more inflammation.

24:11That's the main finding. Within two weeks? Within two weeks. So we looked 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 inflammatory proteins in the blood. And third, we isolated the immune cells from the blood, and we stimulated these immune cells, so in the lab, with microbes. And what we noticed is that these immune cells performed less well. 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 queerane these are like bad microbes you're talking about sort of bad microorganisms causing salmonella yeah we indeed with salmonella for example and and the tuberculosis bacteria two weeks on the western diet yeah 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 the one hand the immune system produces too much inflammation so it's like ramped up really so it's ramped up 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 switch 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 so an inflammation inhibiting effect.

26:11And we saw that the immune system was much more in balance. 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 certainly both. Yeah. Right. So that 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 full African diet?

26:53Well, you do see some different effects. The banana beverage could correct some, but I think there were additional effects of the switch to the traditional diet. So the combination would be perfect. And in fact, it's interesting, our colleague Christopher Gardner did a study at Stanford where they compared in Americans high fiber diets against high fermented food diets. And they found different immune profiles of the two. So there are different processes involved. Both are beneficial, but so the fermented food has a big impact of its own. And that's certainly something we've done some studies in Zoe as well with our citizen science.

27:36People having extra fermented foods do get benefits that look as if they're different to the ones just by increasing your fibre intake or your plants. So lots of different mechanisms being brought into play. What are your thoughts on this study 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 a few older studies that weren't as sophisticated that did something similar. So where they've swapped some Africans for some American diets and just looked very crudely at their microbiome, and that improved when they went onto the African diet and got worse on the American diet.

28:15And of course this Stanford study where they compared fermented foods and fiber so it is very consistent and I think it is really exciting that we're seeing that we're 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's been confused by all these immune signals and not repairing damage you know leading to all kinds of metabolic problems so yeah we need to learn from these studies and learn what the best foods are to eat so we can help ourselves 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.

29:37And you were talking about obesity and diabetes and heart disease and all these things that we know, you know, 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 measuring? Because that's not immediately clear to me. No, so we know that inflammation is key to many diseases, like indeed, like cardiovascular disease, cancer, dementia, name it. On the other hand, what we're more and more starting to understand is that if you have a chronic inflammation... And Quirain, when you say chronic inflammation, what does that mean?

30:21chronic inflammation is that your your immune system is chronically activated so 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 alarm's going off all the time 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 how to efficiently attack some microbe and we think this then disrupts metabolism our mitochondria and affects all kinds of diseases is because the body's just running really inefficiently.

31:16I 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 love that analogy of like the wrong petrol in the car. I suddenly think 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 me. On the other hand, And 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?