Meet the Solutionists transcript and episode notes - season 4, episode 6

Mark Scott 00:01

This podcast is recorded at the University of Sydney's Camperdown campus on the land of the Gadigal people of the Eora nation. They've been discovering and sharing knowledge here for tens of thousands of years. I pay my respects to elders past and present, and extend that respect to all Aboriginal and Torres Strait Islander people.

Steve Simpson 00:26

Your biology has been hacked. Quite simply, it works. It's just not working in the modern food environment because we've constructed it in every respect, not to allow it to work and limit what you eat. It's designed to encourage you to eat more.

David Raubenheimer 00:47

What we've done is we've established the mechanisms through which processed foods leads to dietary and health problems. Why it is that we eat too much, and how that relates to our natural, evolved biology.

Mark Scott 01:10

So what's for dinner? We all think about what to eat several times a day, and sometimes the choices are endless. How do you choose what to eat? Are you influenced by your budget, where you live, your unique health needs, or by the other people sitting at your dinner table? You'd think we'd have figured out how to eat well by now, we have apps that count our calories for us. We wear fitness trackers that tell us how much energy we use. We have entire sections of bookstores and libraries dedicated to nutrition, and a whole online industry that wants to tell you how to eat. But how is all that information actually helping? Humans have been eating and surviving for much, much longer than we've known what a calorie is. Animals also eat well. They know how to choose what's good for them, and as far as I can tell, they don't have access to dietitians and calorie counters. So how do animals know what to eat? And can they teach us to eat better, too? Professors David Raubenheimer and Stephen Simpson have been working together to answer these questions for more than 30 years. David is the Leonard P Ullmann Professor of Nutritional Ecology in the School of Life and Environmental Sciences and nutrition theme leader in the Charles Perkins Centre at the University of Sydney. Steve is Academic Director of the Charles Perkins Centre and Professor in the School of Life and Environmental Sciences. So gentlemen, you published a book together in 2020 and it starts with the story of Stella. David, can you walk through what Stella taught you?

David Raubenheimer 02:51

Stella was a young adult female who anthropology student Kaylee Johnson, was interested in studying her diet over a long period. So rather just a day's record of the diet, as was standard in the field at the time, she thought, well, it's really important to get an indication of what the longer term composition of a diet is. So she selected 30 days. Did a very detailed study in which she got to know Stella very well. She followed Stella throughout her eating day, recorded everything that she ate, and then she took samples of the foods back to the chemical laboratory to analyze their nutrient content. Now, Stella ate a wide range of foods during those 30 days, approximately 90 different foods, and she ate different combinations of those foods on different days. But when the data came back from the chemical analysis lab, we saw a remarkable result, despite having eaten such a wide variety of foods, the nutrient composition of a diet in terms of a very important nutritional ratio, the ratio of protein to carbohydrates and fat stayed almost identical on a daily basis. What this taught us was that Stella was remarkably good at selecting a balanced diet. The most remarkable thing is she didn't do that using diet calculators or even consulting a dietitian or reading up in books, because she couldn't do that. Stella was a baboon and not a person. And the message from that study was that other species of primates, apparently, unlike ourselves, are really good at instinctively balancing their diet. They've evolved a biology that enables them to do that in very complex food environments.

Mark Scott 04:44

Steve, baboons are clearly highly intelligent animals. How are they doing this? Are they reasoning? Are they passing on learned behavior like humans do? How did Stella Do this? Do we think?

Steve Simpson 04:56

So Stella did what every other successful organism that's ever lived on Earth has managed to do solve the problem of nutrition. Nutrition is a complicated problem, and it requires balancing dozens of different nutrients and different quantities eating foods in appropriate mixtures, all the while avoiding becoming food yourself from something else. And all of the animals that we've ever looked at, from baboons all the way down to slime molds, can do this, and they do it, as we demonstrated in the lab, because they have appetites that control the intake of key nutrients. They don't just feel full or hungry in a general sense. They don't count calories. What they do is they measure specific components. They measure their intake of protein, carbohydrate, fat, the three major macronutrients and at least some of the micronutrients, such as sodium and calcium, and there are specific appetites that control the intake of those crucial nutrients, and everything else in the diet comes along for the ride.

Mark Scott 06:14

So you've got this framework for understanding nutrition, which basically is that animals know how to do this instinctually. I want to talk a bit more about that in the moment. But, but how did you two discover each other and your interests in this work together? It goes back to Oxford?

Steve Simpson 06:32

Goes back to 1987 a morning in Oxford, where we were both in the field, in Wytham Woods, which is a medieval oak and beach woodland outside of Oxford, probably the most studied piece of natural ecology on the planet. It's given rise to many of the foundational understandings in ecology derived from studies in this particular woodland. It's a really extraordinary place. We had a group of first year undergraduates, and our job was to take them on their first field course. And David had arrived quite recently from Cape Town to commence a PhD. I was a young faculty member, and he and I met for the first time, started talking. Realised we shared an interest in nutrition. We realised that nutrition was one of the three foundational principles in biology, sex, death and food are the three things upon which all the three, the big three, but of those big three, nutrition had a rather lesser status. It was considered Home Economics, or agricultural production of animals, and the net result of that was we felt that it had really slipped down the hierarchy, so we decided to reinstate nutrition, and to do so from the foundations that are provided by Darwinian evolutionary biology. So we wanted to reconstruct nutrition, and that got us very excited. We ignored the students. They wandered around aimlessly in Wytham Woods. By the end of it, David and I were working together, and over the next couple of years, we started working on the big problem of nutrition, and to do that, we chose locusts.

Mark Scott 08:27

And why locusts?

Steve Simpson 08:30

They’re a great model for various reasons. One is, if you want to ask the question, is an animal able to make wise and sophisticated nutritional choices, you would probably not choose the locust because they have a reputation for eating everything, and they do in vast numbers. Billions of locusts will strip their agricultural fields and they cause devastation. But we set about asking the question, well, okay, they eat everything in front of them. Are they really unable to make wise nutritional decisions? And if they're able to do it, why can't everything else? And the answer was that yes, indeed, they can. So they're very picky, sophisticated feeders. They eat exactly what they need to eat to redress nutritional imbalances. They know what they're doing, and you can get access to an animal like that. You can delve into its central nervous system. You can record from its taste receptors and show how they're changing in response to what it's eating. You can translate that into their behavior, and ultimately you can translate that into the ecology, and that's the power of a simple animal and the power of a biological approach, which, as David said, integrates deep investigation at the level of molecules and neurons all the way through to food environment. And the locusts sort of allowed us to do that.

David Raubenheimer 10:03

They were also well funded at the time because of the locust problem in agriculture.

Mark Scott 10:08

Right, money. Follow the money.

Mark Scott 10:17

We've talked about baboons, we've talked about locusts, but even blobs of slime, protein seems to be a driver of their appetites. What exactly is protein and why is protein such a driver?

Steve Simpson 10:30

It's one of the three, another big three, this time the macronutrients, which are the energy yielding nutrients that make up the majority of our diet, and that's fat, carbohydrate and protein. But protein not only yields energy if you burn it, which is what our bodies do during metabolism, it also contains nitrogen in the form of these amino acids. And unless you're able to extract nitrogen from the atmosphere. And some plants can do that, and bacteria can do that. We're not able to do that. You have to eat it. And if you're going to have to eat your nitrogen, you need protein.

David Raubenheimer 11:12

You also go and store it, very much like fat. You can store energy in the form of fat, but protein, you need to meet your requirements on a daily basis,

Mark Scott 11:21

You need to find your supply and consume the right amount. It's so complex. We read so much about, you know, so many different nutrients and the different functions that they have, but that complexity doesn't seem to bother the animals. How is that possible? They have targeted, nutrient specific appetites?

Steve Simpson 11:40

They do so. So what we discovered early on was, rather than having 100 different nutrient appetites for all the micronutrients, all the vitamins, all the minerals, as well as the macronutrients, what animals have done, and not just animals, slime molds and non animal organisms too, is to focus in on a small number of nutrients that are really important, nutrients, and design specific through natural selection, specific appetite control systems for each of these and normally those appetites work together. So they'll work together to help guide the animal that little bit like a nutrient seeking missile. It'll chase a target which is its requirement, what it needs now, what it needs now. And it'll chase that target in multi nutrient space, if you like. And by doing that, it will attain, without thinking about it, a balanced complement of nutrients, and it'll thrive and reproduce and so forth. But what we discovered was that if you put those appetites together in a different environment where they can't all achieve a balanced outcome, they have to compete with one another, then you end up with problems. So one of the appetites is going to be stronger than the others, perhaps. And if that's the case, then it will have the whip hand when it comes to how much total energy the organism eats. And the whip hand we found in a whole series of species is protein.

Mark Scott 13:20

So say humans are like every other animal, we have the same innate ability to eat the right diet without even thinking about it. But why doesn't it feel that way? Why do I find it so difficult to eat well?

David Raubenheimer 13:32

You find it so difficult to eat well because the biology that you share with other species is expressing itself in an environment that has been distorted by a human constructed environment, principally by industrially manufactured foods.

Steve Simpson 13:50

Mark Scott 14:17

So the environment has changed faster than we've been able to evolve to deal with that changed environment. So to what extent has that environment been the driver of the modern obesity crisis that we see now?

David Raubenheimer 14:31

To a massive extent. The problem is that foods are engineered processed foods are engineered by food engineers in corporations specifically to, as Steve said, to override those regulatory mechanisms that tell us when we've eaten enough, because eaten enough is not a good business proposition for processed food manufacturer, eating more is a better proposition. And so foods are among the strategies that are used to lower the protein content of processed foods that has a two fold benefit. One is that protein is an expensive macronutrient, so at lowest costs and makes particular manufacturers foods better competitive. And the other is that we like the other species, many of the other species we've studied, we regulate our intake most strongly around protein, and so we eat more of a food that has less protein in it. And there are many, many other strategies that are now well understood that make the foods around us competitive in a commercial sense, often at the expense of health, including obesity.

Mark Scott 15:40

Possibly a naive question. Can that be replicated with other animals if, in fact, you create an environment where you're reducing protein levels and not getting that level of feeling satiated by eating? Do you see the same diverse outcomes?

Steve Simpson 15:56

You do exactly, and that's what we saw right at the outset with our locusts studies. And I guess if there was a particularly eureka moment in our careers together, it was when we looked at the data on human obesity over the last 60-70, years. It began in the 1950s really, and then it went up and up and up and the waistline of the planet got bigger and bigger, and that was driven, very clearly, driven by our eating more calories rather than expending too few. So it was mainly driven by the entire intake side of the equation, and those calories were in the form of fats and carbs. Industrially processed fats and carbs. Protein intake stayed almost the same. Hardly changed at all. And the prevailing view was that, well, none of the calories came from protein, so we didn't get fat from eating more protein. It's fat and carbs. And then there was a 40 year fight over whether it was fats or carbs. That was the problem, and we came along as a couple of entomologists and said, well, hang on, if protein hasn't changed, maybe that's what's driving the extra fats and carbs. We're trying to maintain that intake the same in a world where it's being diluted by fats and carbs, and the culprit is therefore the protein appetite interacting with our changing food environment. We published that in 2005, the year I arrived at the University of Sydney, and since then, we and many others have collected, now an incontrovertible base of evidence that shows that that's the case, and we've delved into the molecular biology of the appetite control itself, and David particularly, has done this extraordinary work looking at how the food system has interacted with this biology to cause these terrible problems.

Mark Scott 18:06

So when we're off shopping and we're heading to the supermarket, taking your research insights in mind, how do we go about that exercise?

David Raubenheimer 18:16

Well, what our research suggests is that the simplest and most effective way to choose a diet sensibly is to minimise the proportion of highly processed foods that contribute to your diet. We can all recognise them. We've got a good idea of what they are. Once we've done that, the like way we like to think about it is that other species, the reason they're so good at choosing a healthy diet is that they live in a balanced food environment. We live in an imbalanced food environment because of processed foods, but we also live in a home where we can regulate the proportion of different food types to which we are exposed. If we can minimise the amount of processed foods that come into the house and leave it up to our appetites to do as they've done for the past many 1000 years, and continue to do in other species, we'll balance our diets using the biology that evolved for that purpose.

Mark Scott 19:14

A lot of the articles we've seen even in in the last year about expressing concerns about highly processed food that correlates with where your research has been taking over recent decades.

David Raubenheimer 19:25

Very much so what we've done is we've established the mechanisms, some of the mechanisms through which processed foods leads to dietary and health problems, why it is that we eat too much, and how that relates to our natural evolved biology, and most important of all, as Steve said, that it's not our biology that's broken, but it's that aspect of our food environment that is broken, leading to the problems.

Steve Simpson 19:53

So we like to say, eat with your appetites and shop with your brain.

Mark Scott 19:58

So you take your brain to the supermarket Steve these days, and every shelf seems to be loaded with protein added food. You know, three decades ago, it was low fat. Now it's protein enriched, protein enhanced. How does that work with the science of food?

Steve Simpson 20:14

Well, this is very intriguing, because that whole movement, I'm afraid we have some responsibility for this, because our early work demonstrating that protein was a satiating nutrient that we showed protein leverage if you dilute it, that will cause you to eat more. That was picked up very early on, and we had a lot of interest from the protein industries, snack food industries all the way through to the producers of animal protein, which we declined to engage because we wanted to retain our academic independence, but nonetheless, it generated a whole set of things, including lifestyle interventions, new products, high protein this, high protein that. Meanwhile we asked ourselves the question, okay, animals don't like eating too little protein, and that's fine. You can understand why, because they can't reproduce, maintain themselves, grow, but they also don't like eating too much, which is why, if you increase its proportion, you eat less, and you can lose weight. Why is that? So that's another evolutionary question, and we set out to answer that, initially in flies and then in mice, and then in studies on human populations. And it turns out, there's a cost to eating too much protein, our body regulates its intake, not too little, not too much. And if you eat too much protein, it drives a whole series of pathways which lead you to grow, to not look after your cells, to not clean out the protein rubbish that accumulates in your cells as you go through the day, and there's a harm associated with too high an intake of protein. Those people who are particularly attracted to the notion of a very high protein diet don't like that side of what we do. They like to concentrate on the other side. But nonetheless, like many things in biology, it's a balancing act, not too much, not too little.

Mark Scott 22:26

I want to come back to how we know what the right amount is for us, but just on that, the protein added element to foods, the extent to which it feels like almost taking protein out of context, to sprinkle it on top of a food that it doesn't naturally kind of fall into. Does that? Does that diminish its impact? Is for protein to have impact? Does it need to be authentically in the food that we're eating?

David Raubenheimer 22:51

Yes it, it does. The problem is that the response that Steve has described is a continuation of what caused much of the problem to begin with, thinking about single nutrients. Is it fat or is it carbs? Well, what we have done is raise an awareness that there's a third macronutrient that's really important, and that's protein. So the narrative has now become, no, it's not fat or carbs, it's protein. But the problem is that foods are very, very complex things, and if you tweak one thing, you automatically tweaking the proportions of other things within that food. It's like herding cats. So if you just increase the protein content of processed foods that might provide what is known as a health halo, the impression for consumers that this is a healthier food to eat, and in some respects it might be, but the other respects in which it's not, for example, processed foods are typically very low in fibre, and we require relatively high fibre content in our diet, or in micronutrients, vitamins and minerals and so forth. And those real foods come in packages that contain all of those things in the kind of balance, but also the form, as you say, integral to the food itself, rather than added as purified substances. And our bodies are designed to interact with foods that contain a wide range of nutrients that are presented in that more natural, integral form, rather than just add it on top.

Steve Simpson 24:23

It comes right back to what we were saying at the outset about if you have a small number of appetites and you attend to them, then all the rest comes along for free in a natural food environment, because you can rely on the correlations between the things you're regulating and all the other stuff you need, fibre, minerals, vitamins and so forth. But if you atomise food, deconstitute it, and then put it back together again in unnatural combinations, you strip out all the other things that your. body and your appetites have come to require through correlation, you've smashed those correlations, and that's what the processed food industries have done. They've atomised and then reconstituted foods.

Mark Scott 25:15

So what are we to do? Should we be counting our macro nutrients?

Steve Simpson 25:21

I don't think you need to count anything listen to we need to read, learn how to listen to our appetites. Now there's a beautiful example when it comes to protein. When you're protein hungry, our research at the Charles Perkins Centre has shown your liver releases a hormone called FGF 21 that makes you crave savory flavors, umami flavors, and that's the way your body tells you what to select in your food environment. It also makes you less prone to want to eat sweet things, so it's helping balance your diet. The trouble is, if you've got that craving for savory and the nearest thing is a bag of potato barbecue flavored potato crisps, that's a protein decoy. It tastes like protein. It's got all your umami flavor characteristics that we've evolved to associate with high protein foods, but it's just fat and carbs. And you've been you've been hacked. If you listen to your protein appetite and you want something savory, then you pick high quality protein rich foods, whether they be lentils or meat or whatever it happens to be. It could be vegetable in origin or animal. It doesn't matter, you'll get the protein that will satisfy that response, reduce your FGF 21 levels, and then you won't feel the craving anymore.

Mark Scott 26:56

Just one last question, Steve, for you. You're wrapping up this year as director of the Charles Perkins Centre, and one of the driving forces of that Centre has been multi-disciplinary engagement, and we talk a lot about that at the University of Sydney and on this podcast as well. You take the issues we're talking about today. How does multi-disciplinary research really open up solutions to the kinds of challenges we're talking about.

Steve Simpson 27:22

We’ve lived this journey, and it's required us to go from baboons to slime molds to populations, to clinical studies, to molecular biology, to bioinformatics, to engineering, to follow the leads that have led us to where we are now in this sort of holistic understanding of nutrition, with these, we think, anyway, profoundly important basic understandings of principles underpinning it. So as a pair, we've been able to span disciplines, but to have the opportunity to really engage at scale. The Charles Perkins Centre gave that in a way that would not, quite literally, would not have been possible anywhere else in the world.

David Raubenheimer 28:12

It’s also a very, very important frontier in modern science, because many of the unsolved problems lie between disciplines. Disciplines are very strong. They're solving problems within themselves. But the world doesn't respect academic disciplines. Climate change doesn't, obesity epidemics, don't they just happen, and we need to equip ourselves to tackle them, not only within but really across disciplines as well.

Mark Scott 28:43

That's professors David Raubenheimer and Steve Simpson from the Charles Perkins Centre at the University of Sydney. And if you want to know more about the science connecting eating and good health, you'll like our episode of the solutionists with Luigi Fontana.

Luigi Fontana 28:58

Colour restriction with optimal nutrition is the most powerful intervention to delay aging. So in animal models, you can increase lifespan up to 50%. It's like if a human being, instead of living 80 years, would live 131 years in good health.

Mark Scott 29:21

You can listen to that episode of The Solutionists right now and make sure you're following the show so you don't miss an episode. The Solutionists is a podcast from the University of Sydney, produced by Deadset Studios. This episode was recorded at the Faculty of Arts and Social Sciences media room and our thanks to the technical staff here you.

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Meet the Solutionists, with Mark Scott

Why you should be eating like an animal

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