ZOE Science & Nutrition - How to build a better brain: The 5 foods you need to protect your memory, mood and to cut dementia risk | Prof Felice Jacka & Prof Tim Spector

Episode Date: July 2, 2026

Can food improve brain health, memory and mood?  In this episode, Prof Felice Jacka and Prof Tim Spector explore how diet, the gut microbiome and fermented foods may affect your mood, brain function and dementia risk. Drawing on clinical trials and research involving more than 10 million people, they explain why what you eat could have a much bigger impact on your brain than most people realise, and what the latest science suggests you can do about it. Felice, who helped create the field of nutritional psychiatry, explains how food influences the brain through the gut microbiome and inflammation. She and Tim explore why some foods change brain function, which support brain health, what the evidence says about ultra-processed foods, and why diet is becoming an increasingly important part of research on brain and mental health. Learn which foods to eat more often, which foods to reduce, and simple, affordable ways to build meals that support your gut, mood and long-term brain health. From whole grains and legumes to fermented foods and everyday supermarket and grocery store choices, by the end of the episode, you’ll have realistic advice that’s easy to put into practice today. If the food you eat today helps shape your brain tomorrow, what small change could make the biggest difference over the next year? 🌱 Try our science-backed and tasty wholefood supplement Daily30 🌿Let your gut microbes snack on the ZOE Gut Health Bar Get our brand-new app and Gut Health Test designed by world-leading gut health and nutrition scientists to build healthy eating habits 👉 Join ZOE Follow ZOE on Instagram. Timecodes 00:00 Intro 03:10 Why beans may boost mood more than cake 07:35 Can diet reduce your risk of depression? 10:10 Can changing your diet put depression into remission? 12:45 How does the gut microbiome affect the brain? 16:04 Can gut microbes transfer depression symptoms? 17:55 What gut bacteria are missing in mental illness? 20:16 Is food the most powerful tool for brain health? 22:11 The yogurt study that surprised neuroscientists 25:35 Can fermented foods help grow the hippocampus? 28:18 Why fermented foods may improve mood and energy 30:16 The gut-brain connection explained simply 31:13 How diet during pregnancy affects brain development 37:52 Are depression, anxiety and dementia connected? 39:27 What are ultra-processed foods really doing to your brain? 39:55 The major study linking ultra-processed foods to disease 42:31 Are some ultra-processed foods healthier than others? 43:44 Real food vs meal replacements: what happens to your microbiome? 48:29 The ingredient Felice Jacka tries to avoid 50:16 Do supplements improve brain health? 52:23 The best foods for brain health and mental health 53:37 How to eat for brain health on a budget 55:40 The simplest brain health advice you’ll hear today 58:40 The complete brain health and gut health checklist 📚Books by our ZOE Scientists The Food For Life Cookbook Every Body Should Know This by Dr Federica Amati The Appetite Reset by Dr Federica Amati Food For Life by Prof. Tim Spector Ferment by Prof. Tim Spector Good Mood Food (preorder) by Prof. Tim Spector Free resources from ZOE The Smart Snacking Guide: How to feed your gut, fuel your day, and snack without guilt The Hormone Harmony Guide: Tuning Your Body’s Internal Orchestra   Eating for Better Brain Health: Your brain-gut blueprint How to eat in 2026 - Discover ZOE’s 8 nutrition principles for long-term health Live Healthier: Top 10 Tips From ZOE Science & Nutrition Gut Guide - For a Healthier Microbiome in Weeks  Better Breakfast Guide Mentioned in today's episode The 'SMILES' trial, BMC Medicine (2017) Mood Disorders: The Gut Bacteriome and Beyond, Biological Psychiatry (2024) ZOE study: Fermented food improves mood, energy, and hunger Effects of a probiotic fermented dairy product on the brain, Gut microbiota (2025) Associations between diet quality and depressed mood in adolescents, ANZJP (2010) Ultra-processed food exposure and adverse health outcomes, BMJ (2024) Global Burden of Disease, The Lancet (2026) Folic acid, ageing, depression, and dementia, BMJ (2002) Transplantation of gut microbiota derived from patients with schizophrenia induces schizophrenia-like behaviors, Nature (2024) Have feedback or a topic you'd like us to cover? Let us know here. Episode transcripts are available here.

Welcome to Zoe Science and Nutrition, where world-leading scientists explain how their research can improve your health. Every meal that you eat is the start of a remarkable journey through the body. The food you eat is broken down into nutrients, absorbed into the bloodstream, and transformed into the energy that powers every heartbeat, every movement, and every thought. But what if food isn't just fuel? What if it's essential for how your brain operates? Every meal you eat also provides nutrients to the trillion of the world. of microbes living in your gut. And these tiny organisms aren't just passengers along for the ride. Like mini pharmacies.

They produce chemicals that send signals directly from your gut to your brain. And that begs the question, could what you eat shape how you feel? When we think about mental health and brain health, most of us picture medications, upbringing or genetics. We rarely think about breakfast. But what if the most powerful influence on how we feel is what we put on our place, every single day. Today, we're exploring the extraordinary connection between food and a healthy brain. And joining us is someone who has helped change this conversation entirely. Professor

Felice Jacker, Professor of Nutritional Psychiatry, and founder and director of the Food and Mood Centre at Deakin University. Her clinical trials were the first to show that a better diet could significantly improve symptoms of major depression, helping to launch an entirely new field of Science. She's now overseen a large team of scientists in Australia, transforming our understanding of the relationship between diet and mental health. And alongside her is Tim Specter, my scientific co-founder at Zoe and professor at King's College London. He's a world leader in microbiome science, and his personal research for the last few years has been focused on how the microbes in our gut affect our brain health. Together, we'll explore the latest evidence linking food and

brain health. Understand what has changed in our diet that has led to a huge surge in mental health issues. And most importantly, Felice and Tim will share simple, actionable advice that can improve your mood and support better brain health. Because their research suggests you can achieve big changes without perfection or restriction. Felice, thank you so much for joining me again on the show. Ah, such a pleasure. And Tim, thanks you for joining us. Looking forward to it. So you remember Felice, we always kick off the show with a rapid fire Q&A with very strict rules. A yes, a no, or if you have to a sentence. Yeah.

Are you willing to give it a go? Yeah. Can some people with depression be successfully treated by changing their diet? Yes. Can eating fermented foods lead to measurable changes in our brain? Yes. Are supplements necessary to maintain brain health? No.

should we avoid eating all ultra-processed foods? No. And finally, what's the biggest myth that you hear about the links between food and mood? This is up to the individual. That's their responsibility to eat well. And if they don't and they're depressed, then it's their fault. That's a really big myth. That's really problematic.

I think it's the myth that it's the mood that influences what food you eat, rather than the reality that it's the food that is the major driver of your mood. I think most people listen to this can remember a time when they've eaten something delicious and it's made them happy. And before I met you, Phileas, I would have thought about a piece of birthday cake or perhaps a nice glass of wine is a thing that would make me happy. But when you came on the podcast a few years ago, you told me I should really be imagining a can of beans.

Yeah. Hopefully cooked in a nice way. Coaked in a nice way. And honestly, when I heard that, I thought that it sounded crazy, right? Like, who would swap, you know, birthday cake for like a meal of beans to actually make you happy? But after a lot of personal experimentation, I've actually come to the conclusion that you're right. Now, I don't think I should be surprised that what you were telling me made sense because you've almost single-handedly invented this field of nutritional psychiatry. And so it's a real pleasure to have you alongside my co-founder Tim, because over the last few years, Tim has become more.

and more focused on this question of the role of the microbiome on mood and brain health. So I think having the two of you here is like a powerhouse. Felice, could you maybe just start by telling us how you first became interested in what seems sort of crazy that there's a link between food and mood? So I came into psychiatry research pretty accidentally, sort of by the back door. I did a psychology undergrad, and then I became really interested in statistics. And so I made my way to a newly established psychiatric research unit. and they had some data and they said, would you like to analyze it?

So these were psychiatric data and I burst into tears and said, yes, please. I was in my undergrad then. So I went on and I did a number of papers using data from this really big cohort study. And I became aware that there were all these dietary data there as well as the clinical interviews to assess depressive and anxiety disorders. When I came into psychiatry research, I was fascinated to realize that there just wasn't an evidence base that had linked food to mental and brainhound. health. But at that same time, so this is like the end of the 1990s, early 2000s, there was an

increasing focus and interest in psycho-neuroimmunology. And that's basically how your immune system and your mental and brain health are linked in a bidirectional way. And of course, you know, what you eat is a really powerful driver of your immune function. And I knew that. And around the same time, there were all these data coming out of animal studies, neuroscience in the States, from a particular group, showing that this newly recognized area of the brain that could grow new brain cells was very important in learning and memory, but also seemed to be important in mental health, could be modified by healthy or unhealthy foods, manipulated. So here was another piece of the puzzle.

And then, of course, understanding that epigenetics, you know, your genes weren't just set in stone, they could be turned on and off by environmental exposures. And diet was one of the exposures that switched your genes on and off. So there were all these parts of the puzzle where I knew that bits of your physiology that are firmly linked to mental and brain health were influenced by diet. So why weren't we looking at it? And it was really just that whole paradigm in psychiatry where nothing that happens below the neck is of particular interest.

And we really hadn't started looking at the gart or any of those sorts of factors. So I set out to try and understand this better, and everyone thought I was a bit, you know, woo-woo. But luckily, we had really, really good quality data. I mean, they were observational. It's not an experiment, you know, we're just collecting data from people. But really importantly, we had the data that we needed to properly test the hypothesis because we didn't just have very good quality dietary data and very good quality psychiatric assessments. But we also had very good data on socioeconomic status, you know, people's income and their level of education, their body size, their other health behaviours, all the things that we need to take into account if we're looking at this relationship.

So then I was able to actually go and test this for my PhD, and it ended up being a very high-in study. And so from there, I was able to build the evidence base around how diet quality was linked to mental and brain health right across the life. calls from the very start of life to the end of life across different countries. So it doesn't matter whether in Brazil or Norway or Japan or where have you, higher diet quality, you know, a healthier diet that's got more of the whole foods in it tends to be associated with about a 30 to 35 percent reduced reduction in risk. A 30 to 35 percent reduction in what sort of conditions? In the risk for depression. There was some evidence for anxiety as well, just hadn't been studied as often.

But this was, again, independent of all those other factors we talked about. Really importantly, it's not explained by body weight. People always think, this is another one of the myths, that that link between diet and mental health must work through body weight. You know, you eat badly or too much and you have a higher body weight, therefore you become depressed. Now, that's nothing to do with it. We see this link at every single level of body weight.

So this isn't just about the fact that you're living with obesity or you're overweight and that's making you depressed. No, that's right. It seems to have nothing much to do with it at all. And then, of course, we went on, we ran the Smiles trial, which was the first experiment to see whether we could actually alleviate even severe major depression by improving diet quality. And in that study, the average body mass index was about 30.

So it was in the obese, overweight category right at that point. That didn't change. People didn't lose weight. And the improvements we saw in their mental health, which were really large, that didn't correlate with body weight change. And Feliz, can you explain simply what that smile study was? Because I know that this is viewed as a sort of rather breakthrough study up until now everything was just observational.

And you said, I'm actually going to do like a proper randomised control trial. It was a crazy postdoc in the first year of my postdoc thinking, well, we've got the evidence now from the observational literature, from all these populations, from children up to older people, across countries. But we really need to know if this is a causal relationship. That means does diet not just correlate with mental health, but does it affect mental health? So I developed this protocol for a randomized controlled trial. And basically what that meant was we recruited people with moderate to severe major depression.

Now, many of these people have been sick for a very long, time. They were very, very unwell, a lot of them. Most were on other forms of treatment already. I just hadn't worked, and half of them were randomly assigned to get social support. The other half saw a dietitian. So in the Smiles trial, what we did was we measured their depression severity. That was their main outcome. And at the end of the trial, we saw that there was a very large difference between the two groups. So about 8% of the people who got social support, their depression went into remission and roughly a third of those who got the dietary support, their depression went into full remission, which is really remarkable for a group who'd been sick for a long time

very often. So that's a huge difference. You're saying like 8% got the social support, but like a third of people actually came out of depression as a consequence of changing what they ate, but nothing else. That's right. The degree to which they improve their diet quality, correlated really tightly with the degree to which their depression improved. Tim, I'd love to hear your thoughts on this.

Another notification. Something else to add to the to-do list? Is it work? Is it life admin? Or maybe another email from your boss? Your heart rate might be quickening at the thought. After all, life is full of little moments that add to our mental load. If you're feeling wired, tired, irritable or on edge, that's your hormone. responding to everyday stresses.

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That's why gut health experts, Zoe, and reproductive health pioneers, Hurtility, have teamed up to create a free guide, grounded in science, to help you decode what your hormones are trying to tell you. You'll find out how stress responses can impact your body and how diet influences hormones, metabolism and mood.

You'll also find delicious recipes that support these systems. Learn more about your hormones today and download the free guide at zoe.com forward slash hertility or click the link in the episode description. Felice's trial was one of the reasons that, you know, it's got me really interested in the brain again. And I think what we're seeing here is how potentially important food is as a brain medicine. And this is like, you know, the elephant in the room in psychiatry and psychology that

nobody is trained in metabolic health, in nutrition. Don't even think about it. Patients with brain or mental health disorders often have the worst diets because people looking after them are not trained in any way in nutrition. they don't even make the link that there's any connection there at all. And yet this is one of the most powerful interventions that they can do. And the science is catching up now with the observations. So we've had these rather crude observations.

We had the science that's, you know, from my point of view, the microbiome science has been there for a while. And a lot of that has been in mice. how you can produce anxiety or depression in mice just by swapping around their gut microbes from one to another, you know, in a way, a bit like mental health problems being an infectious disease, which I think is kind of a freaky sort of viewpoint, but that's what these mouse models show. But until we've shown it in humans, it's never really real. And so linking all that stuff with the changes in the Smiles trial,

really to me makes it much more concrete that we have here, you know, a real reality that we know that our food improves your gut microbiome and that then improves what's going on in your brain and those signals to the brain. And it's so important because you're, we know that the gut is the major source of information to the brain. So I think it's, you know, the most exciting area in science at the moment is this gut-brain connection that we're re-evaluating all the time. And it's bringing in all this new neuroscience, particularly on inflammation, which we've talked about on this show a lot, how important it is to keep inflammation levels low. And we know that people with depression and mood problems have raised inflammation levels on

average. And all of us actually, you know, in the Western world, have raised inflammation levels compared to people in other countries. So this link that what's going on in our choice of food is changing to our gut microbes, they're then producing these chemicals which send signals to the brain. That brain then interprets that as being unwell. And then we go into this cycle of depression behavior, which is a protection for the body.

So there's the other way of thinking about, you know, we know that inflammation is a protective response. What's happening is inflammation in the brain is also a protective response. It's just inappropriate. It's just doing it at the wrong time. But it is incredible. There's so few studies out there because this whole field, particularly the clinical area, has been cut off from the rest of medicine. You know, why do we put people in mental hospitals? Why are they separate? The worst diets are in mental hospitals. And in some surveys, they've shown that long-term, psychotic patients, about 70% of them have type 2 diabetes.

And the doctors looking after them are not trained in looking after diabetes or metabolic health at all. And the whole thing is just perpetuating everyone being made worse by their environment rather than better. And we know the drugs we've got, unfortunately, they help a few people, but they have really failed to live up to our hopes. and they haven't really changed in the last 50 years. I sort of want to wind back sort of quite early

where you talked about what we've discovered in mice and you sort of mentioned in passing, Tim, is mental health and infectious disease? I think you were saying that they've done tests in mice where by changing the microbes inside the mice, they were actually changing... They're transplanting them from one mouse to another. So using this model of these...

sterile mice, you can implant microbes from a stressed, anxious mouse into a sort of neutral mouse with no microbes, and that new mouse will then display the same anxious brain symptoms as the initial one. So I was being a bit joking about infectious disease, but normally if you've got microbes from someone else and it causes a brain effect, you know, you could call it infectious in some ways, just like we've talked about obesity potentially or type 2 diabetes being infectious because microbes are responsible for it. I mean, it's not in that sense. Did you know that you can do it with humans too? So if you take poo from people with major depressive disorder or with schizophrenia and you put them into mice compared to poo from healthy

people, you can induce what's called the behavioral phenotype. Basically, you can make a mouse behave as if it has depression or schizophrenia, you can see some of the biochemical changes. Yes. You could do this with hypertension. I find it really wild that you could take poo from someone with high blood pressure and give it to a mouse and induce hypertension in the mouse. So what this is suggesting is that there's a causal effect happening here, that the microbes are causing this condition or phenotype if you're talking about animals. You're saying you could take, like the poo from somebody who has a mental health issue, like a serious one, like depression or schizophrenia, you can give it to mice that don't have any microbes,

and they basically become schizophrenic or depressed. The mouse version of it, that's exactly right. Or display symptoms that were in that direction. And some of the changes in their blood as well, which is also really interesting when you think about, like we did a really large systematic literature review. We looked at all of the data, all of the studies. that had taken someone with major depressive disorder or bipolar disorder or schizophrenia and compared their microbes to somebody without those conditions.

Now, as you would expect, there's differences between the microbes of people who do and don't have a serious mental illness. But what I was really interested in was whether there were some commonalities, were there some common features about the microbial profiles of people with, serious mental disorders. And that's exactly what we saw. What we saw was consistent reductions in the microbes that produce buterate. Now, butyrate is a really powerful anti-inflammatory molecule. And you'll often see that the people with some sort of an illness will have reductions in these buturate producing bacteria. But they also had increased levels of lactic acid producing bacteria.

And now in people with serious mental disorders, you will see increases in lactic acid in their blood and in their brain. And that's complicated, but there's something around the way that your body produces lactic acid, the way the bacteria does. It suggests that there's something about the microbial profile that's producing too much lactic acid that's feeding in potentially to the disease profile. The third thing we saw was differences in bacteria that produce these neurotransitaphobic. transmitters called GABA and the glutamate pathways. Now, these are really dysregulated in people with serious mental disorders. So again, we don't know if it's cause or effect, but the fact that these bacterial differences mapped on to the biochemical changes that we see in people with serious mental disorders is really telling, I think. I'd add another one to that is that

the other consistent message you get is that you get microbial patterns that are pro-inflammatory. Yeah. So they're driving the immune system to produce protein markers that you might see in the blood of things that we've talked about, CRP in the past, that are just slightly high, not clinically really high, but just above the surface. And so this is a consistent pattern across all brain disorders. Yeah.

Is that there's something going on in the guts of these people that must be sending messages, you know, up to the brain to say, you know, be on. on alert here, you know, you've got to work harder. There's something going on that isn't right in addition to the changes you've suggested. And could you help our listeners just to piece this together because we started with a small study saying that if you change what you eat, then actually can have this profound change, each and on somebody with very serious mental health issues. And now we're talking about how these microbes in our gut seem to be really important. We're linking the two together. We now know that, yeah,

If you improve your diet significantly from the poor diet that most people with brain disorders are on, that will shift your gut microbes. And those microbial shifts are in a certain direction that it can produce these healthy chemicals like buterate, or they're going to produce anti-inflammatory compounds that are going to counteract the inflammation. And these then have effects on the brain and can improve a lot of the symptoms. That's essentially what we're summarizing from all kinds of different evidence, although no one study has done at all. But the other exciting thing is, effect size of, say, a diet, a healthy diet on brain symptoms, are not trivial. We're seeing effects, just to put it in context, that are bigger than you would get with starting an antidepressant on average.

So we know that some people do well on antipresents, but many people don't. If you take the average, you're going to do better with a diet alone than an antidepressant. And obviously, everything, it's all personal. And your study didn't directly show that because it was in addition to an antidepressant. Yeah, that's right. But there are other studies out there suggesting that these effects are really big. I know that everyone listening to this is like, okay, I want to start talking about the actionable advice about what I can do. But before going to there, I'd like to talk about some of the really interesting science.

So both of you have been involved in, I think, underpins the advice that you might give. And I think what's already come through from what you're talking about is that you seem very clear about this big picture link between, like, the food you eat and microbes improving your mood. But like exactly how that works, it's a lot of the challenging work that, you know, you and other scientists are doing to pin it down. The team said you've done a recent study involving fermented dairy. Yeah, yeah. It's a pretty cool study. we teamed up with one of our big dairy companies in Australia. And they have a product on the shelf, which is a yogurt.

It just has an added probiotic bacteria. It's one of the really common ones that you'll see in a lot of yogurts. We wanted to do a placebo-controlled trial. Now, of course, if you're having yogurt, it's not just got the flavor, it's got the texture, it's all sorts of things, but they made a really great placebo. So what we did is we randomly assigned 40 healthy women. So these weren't women with depression or anything else. They were healthy women to have either the yogurt drink or the placebo over a period of eight weeks.

Now, this wasn't a large amount, just a little tiny sachet, 130 mils that you got from the supermarket. And we did brain scans on them. And we also measured other things like microbes and their blood and things like that. But keeping in mind, they were healthy people. So we didn't expect to see huge change in those things. But what we saw at the end of the eight weeks, and we worked with neuroscientists who know much more about this than we do, really, and they were kind of blown away because if you remember me mentioning this part of the brain called the hippocampus that is really key,

it's really key into learning and memory. It seems to be really important in mental health. We think it's one of the main ways in which antidepressants actually work is by increasing the size and the function of the hippocampus. So the hippocampus is a tiny little well. It's actually two structures and it's got a bit of a shape like a seahorse and the Latin word for sea horse is hippocampy or something like that. So that's where it gets its name. We used to think that your brain just lost all its brain cells, not all of them, but lost brain cells as you went along and you didn't get any more new ones. And then neuroscientists started to spot this area that seemed to actually grow and shrink. So it actually would grow new neurons. Particular

of proteins would help to grow the neurons. I think about them like manure for the brain. The hippocampus is important in certain types of memory, particularly the short-term memory, and it also seems to be important in mental health, because when you look at the way SSRI's work, antidepressants, one of the things they seem to do is to increase the proteins that grow the new neurons. So they increase the manure for the brain. It's also involved the hippocampus in satiety, the sense that you've had enough to eat. And the studies that were done previously in the healthy adolescence, when they were just given these junk foods for a week, or even just a few days, and they showed that there were impairments in these cognitive tasks that are

linked to the hippocampus, they also showed these impairments in satiety. So people weren't feeling full. They wanted to keep eating. And I think maybe the hippocampus is part of that. story, so it's something we really are focusing on now. We've already shown, and others have now shown the same thing, that people with unhealthy diets have a much smaller hippocampus, which is really key because as you get older, your hippocampus shrinks. And because it's so important to learning and memory, this, we think, is involved in part of that, you know, loss of cognitive ability as you get older. Now, what we saw in this dairy trial was that after eight weeks of these small sachets a day, that the women who got the real stuff, they had an increase in the volume of their

hippocampus. It actually grew, this is what we saw after eight weeks of them consuming this. We didn't see that happen in the placebo group. We also saw that there was more connectivity between the hippocampus and the frontal loat. So this is the bit of your brain that's sort of guides your higher order thinking and planning and this sort of thing. So it's suggesting, you know, improvements in brain function. And then what we saw was in the microbes, an increase in the bacterium that was the probiotic bacterium in the yogurt, which is what you would expect. But that correlated really clearly with that increase in connectivity between the hippocampus and the frontal lobe. And we also saw suggestions of more glutathione in the brain. Now, glutathione. Now, glutathione,

is your brain's natural antioxidant. So it helps to protect your brain. And it looked like the women who got the real yogurt, compared to the placebo, had higher levels of glutathione in their brain as well. And so what is that glutathione going to be doing for me? Well, it protects your brain. It's your body's own antioxidant.

It protects you against inflammation and immune irritation of it. You actually could see a real difference in terms of things that are going on inside the brains of people who eating this yogurt versus this sort of fake alternative. Yeah. And that was both that this important part, the one part of your brain that can like create more connections and everything, the hippocampus was actually more connected, but also

it was creating this chemical glutathione. Glutothion. Glutothion, which is good. Helps to protect my brain. That's right. So it looked like there were aspects of the brain that you would expect would result in better brain power were there. So larger hippocampus, more connectivity with the frontal lobe, also more glutathione, which protects your brain from oxidative stress. So these are all good things.

Now, we need to do it in a much larger sample because that was a small sample and it was also women who were really healthy. So there wasn't this remarkable difference that you might see if you were looking at it in a group of women, say, with major depression. Because we know that when people have major depression or another serious mental disorder, on average, they'll have a smaller hippocampus. If they are successfully treated, the hippocampus grows again. But as I said, diet really affects the size and the function of the hippocampus, so does physical activity. But it could also be, you know, having written a lot about fermented foods, it could be, it's acting on the immune system. So we know that people who aren't.

used to it and suddenly get fermented foods. We've done this big Zoe trial where we had 6,000 people taking fermented foods. And in the first week or two of taking it, 50% of them who were taking three or more a day fermented food portions, 50% of the show an improvement in mood and energy in that time. And this is in huge numbers of people, whereas the people who only managed one fermented food got less, so there was a dose response effect, which means that the more foments you were taking every day, or the more regularly you were taking them, the greater chance you had of having a significant improvement in mood and energy. And energy is very much, this fatigue or energy is very

much a brain symptom. We now know that. We used to think it was something to do our muscles or, you know, it was something to do the menopause or whatever, but it all comes back to the brain. about our perception of our environment. And we believe that most of these fermented foods have a major impact on the immune system. We don't understand all the mechanisms, but we do know that it reduces markers of inflammation. So it's quite possible in addition to this specific effect on this little sea horse type area of the brain. It could have a general calming of inflammation of the brain, which we now know is really important. So it brings in this whole other idea of anti-inflammatory effects being good for things like depression.

The more we discover, the more complex it gets. That's definitely the story of nearly everything in science, but particularly the brain. And I think it's, you know, we may want to just go back a notch and just say, okay, a healthy brain is one that has, you know, hardly any inflammation in it. It's getting the right signals from the rest of the body. body, it gets its main signals from the gut. The gut gets, you know, it's healthy signals if it's eating the right foods and the microbes are converting that into the right chemicals. So that, I think, to me, is the crucial link. And I think once we make this link between

how that affects mood, and we're seeing this in lots of trials, whether it's the Zoe trials, whether it's, you know, your studies, I think we're getting this consistent, message that we have to look after our guts if we're going to look after our brains. And it's not just limited to depression and anxiety. Everything I've looked at, every mental health disorder has an element that you can link back to gut and diet or inflammation. So there've been many, many, many studies now from all around the world showing very consistently and comprehensively that the diet during pregnancy is linked to child emotional

behavioral outcomes over the first few years of life. It's linked to language acquisition, and it's linked now to ADHD and autism. Now, we've worked a lot in this space, and we work with colleagues all over the world. Those findings are very clear. What we think is going on, or at least part of the story, is that mothers who are eating an unhealthful diet during pregnancy, they have a less diverse or a less healthful microbiome. That we see is linked to emotional behavioral outcomes. But what we're also seeing is that those mothers have higher levels of inflammation. So higher levels of something called glycae.

So glycai is a marker of inflammation. And what we see is that mothers who have unhealthy diets during pregnancy, more Western foods, salt processed foods, they have higher levels of glycae, and that in turn is linked to slower brain development or slower language acquisition in infants. You're giving this example about, you know, pregnant women and their children, but listening to, I assume that's just an example, like that if I'm eating that diet as a, you know, a 50-year-old man or I'm eating that diet as a 14-year-old child, this is going to be having

these effects on my microbiome and then my brain and then my mood. Is that correct? We've done many, many studies looking at, for example, adolescence. That's about the age of where really critical vulnerability in teenagers, particularly girls. And we know in young adolescents, there are dose response relationships again, so more of one leading to more of the other, between the level of unhealthiness in their diets and their mental health, independent of their family backgrounds, they're, you know, family functioning, socioeconomic status, all of these things. And we see this, whether it's in very early childhood, in adolescence, in adulthood, in older people. Very, very consistent findings. We're consistently seeing these links between the

aspects of the gut microbiome and people's mental health across the age range. But again, going to the start of life, we're seeing it involved in neurodevelopment. And if you go back to the animal studies, we certainly see that that's the case. So all of these signals are pointing in the same way, which is the food we eat is critical to our microbiome and all of the molecules that it produces. This has a very important effect on inflammation, which is really important in virtually every chronic condition that you can think of, including mental health problems. It has an impact on the brain, whether it's the blood brain barrier, the hippocampus, all of these other systems, including the way your genes are turned on and off, how your mitochondria function,

the little energy generators in your cells, all of these different things are affected by your microbes. Tim, we've obviously talking a lot about mental health issues, obviously police focus a lot on depression. I know that you talked about anxiety and all these sorts of things. Let's say someone's listening to this and they're not worrying about that, but they are worrying about brain health more broadly. Is that something completely different in terms of like these brain health?

outside of mental health, or is it the same? I think it's all part of the same spectrum, and I think we need to stop seeing mental health issues as 360 separate symptoms and start seeing this as one organ. And equally for depression or dementia, the brain is reacting in a way that is inappropriate for our age. and the genes and risk factors for all these are very similar, which tells us there must be common ground. And therefore, in all of these studies, you see poor diet as always there every single time. And the data is just as strong for avoiding dementia as it is for avoiding

depression. Yep. And it's all being backed up by the science. The genetics has not shown there are separate diseases. They've shown at most there are two types of brains. disease genetically. We're susceptible to all these things, but it needs another trigger, and it looks like diet is the number one thing that we can intervene on and make a huge difference. It's no surprise that one of the big risk factors for dementia is type 2 diabetes, and type 2 diabetes is totally preventable by diet. So everything keeps coming back to the same message that just hasn't got through to, you know, the medical community. Think of the friend who starts every morning with coffee,

forgets to eat lunch, grabs a supermarket sandwich between meetings, and then crashes on the couch at night with takeout and a glass of wine because they're too exhausted to cook. Send them this episode. It might explain why they haven't felt their best for a long time. I promise you, they'll thank you. Could I come back to something that you've both touched on,

but I feel like we've sort of not addressed head-on, which is ultra-processed food. What are you seeing? Well, ultra-processed food is food that if you look at the packet, it has a very long list of ingredients. It has a substrate that might have once been food, but it's been heated and extruded and changed to be completely unrecognizable.

We believe, we hypothesize that there's something about the actual processing itself that might be problematic, or the level of processing that might be problematic. We published this huge umbrella review a couple of years ago in the British Medical Journal, created news all over the world showing that 70% of the health outcomes that we studied were linked to a higher intake of ultra-processed foods. 70% with particularly strong evidence for death, any cause of death, for cardiometabolic diseases, so heart and diabetes diseases, and common mental disorder.

depression and anxiety. 70% of the health outcomes that we looked at were linked to a higher intake of ultra-processed foods. Could you help me to understand what that means? Epidemiology. So it's moving from little trials to big observational studies and compilation of multiple trials. Putting them all together. So, you know, our study was what's called an umbrella review. So we brought together all of the meta-analysis that had already been done.

So when you get small trials and you put them all together, and you come up with a summary statistic, like a number that tells you something about how one thing is connected to another, we took all of the meta-analyses and brought them together. So we had data from more than 10 million people in this large umbrella review. And in our umbrella review, we looked at a whole heap of different health outcomes, and we saw that 70% of them will link to higher intake of ultra-processed foods. So when, for example, you look to individual cancers, you might not see that all of the cancers were linked to ultra-processed food intake, but quite a number were.

So that's the sort of, when we talk about health outcomes and the number that we looked at, 70% of them were linked to high-oldrocess food. And the ones with really strong evidence, where there were just lots and lots and lots of studies saying the same thing was around any cause of death. so life limiting, cardiometabolic diseases, so that's heart diseases or metabolic diseases like diabetes, high blood pressure, etc., and common mental disorders, depression and anxiety. Some people in the science community don't believe that ultra-processed foods that don't have unhealthy nutrient profiles

should be demonized. What they say is if the food has a healthful nutrient profile, then it should be considered as food. So we set out, again, tiny little study to test this hypothesis. Now, a really good example of a nutritionally balanced ultra-processed food are the meal replacements, the shakes and the bars that people are often going on when they need to lose weight quite quickly. basically these meal replacements become their food. We know that they're really helpful at helping people to lose weight. But we think that as a really good model of a nutritionally balanced ultra-processed food, they could be used in science because they've got low levels of sugar because they've got artificial sugars.

They've got added vitamins and minerals. They've got added protein. They've got added fibre. They're low in fat. So they're nutritionally balanced is what they're. called. We compared them to very low calorie real food diet, so legumes and vegetables primarily. So we recruited nearly 50 women living with obesity who needed to go on to these very low energy diets. And for three weeks, they got either the packaged, you know, pre-cooked food, which was

primarily legumes, vegetables, whole foods, or the meal replacements, the OptiFast. What we saw after just three weeks was that the women who had the real food with the legumes and the vegetables, the diversity of their microbes really increased. Whereas the ones who got the optifast, the microbes, there was evidence of a decrease in their microbial diversity. Now, critically, both groups lost weight. So it wasn't about they lost the same amount of weight. But it does suggest that even when they're nutritionally balanced, your gut microbes are interpreting them differently. If you have real vegetables and legumes, so plant foods, what you're getting as well as the vitamins and minerals and the protein and the fibre and these carbohydrates, these macro and micronutrients,

you're getting them in a way that nature has provided them. So you're getting them within their own food matrix, which we think is really important, in the combinations that nature is intended, which we think is really important. But we're also getting the phytochemicals. So phytochemicals are things like people think about them as antioxidants or polyphenols. There may be as many as 150,000 of them. Now it's likely that we co-evolved to have receptors to these phytochemicals in plant foods. And we're not getting them at all when we're getting ultra-processed foods. There's no phytochemicals in those.

The food matrix is lost. And we're not getting the fiber and the vitamins and the minerals in the form that nature has provided them. Yeah, because the difference is in these ready-made supplements, they might have one type of artificial fibre, whereas if you're having a range of plants, you'll be getting hundreds or thousands of different types of fibre. So it's not giving the gut microbes the same food. It's like going to a zoo and just giving all the animals the same food, whereas in the natural way, you're giving a mix of a thousand different foods. And so bringing this back to my brain health, you're saying this experiment was a way to sort of demonstrate that the issues for my brain are not simply that I'm eating food, which has got like lots of sugar in it or lots of salt.

It's actually that the ultra processed food itself is worse because it's missing a whole bunch of things that like my microbes and my brain need. And so we need to start thinking not only about like improving your diet in the sense of having less. sugar, but like directly the ultra-processed food may be plain and important part of it. Am I understand that right? That's right. And I mean, obviously it's early days. This is one small study. It's a proof of concept.

There's so many aspects to ultra-process foods because apart from in this study, it was nutritionally balanced. But then we're talking about what it doesn't have. But in many ultra-processed foods, in fact, pretty much all of them. And even in non-altre processed foods, actually, we're getting a huge number of things that we think are detrimental to the gut. So one of them is emulsifiers. And if you look on any packet nowadays,

you know, emulsifiers of different sorts, sometimes they've got a number, but they are in everything. And the animal science suggests that what they do is they impair the gut lining, which we know is really important to keep healthy. People have known about cancers and obesity, and that's hit the press.

What hasn't really hit the press is how important these foods affect brain diseases. diseases. And putting it into a big context, too, we've just had the latest study on mental disorders being published in the Lancet from the massive international global burden of disease study. So this study looks at health data from right across the world, and it looks at the burden of different health conditions, and as well as looking at risk factors for those health conditions. And what it's concluded yet again is that mental disorders account for the leading cause of disability across the globe. So it doesn't mean that they necessarily cause early death,

although in some cases they do, but it's that disability where people can't engage in the world in the way that they would like to, education or work or family activity, whatever. And when you look at mental disorders, by far the majority of that burden is accounted for by depression and anxiety. I'd love to talk about like, okay, somebody's listening to this, now they're really convinced that this can really make a difference to their brain health and mental health. So if I was trying to reduce this, but also not become terrified of everything that might be in the supermarket, what should I focus on? Well, for me, what I do as a shorthand is to just look at whether there are emulsifiers present in the food, and I tend to avoid the ones that have

got emulsifiers. Now, that's a really simplistic way, but it's something that's really useful. for when you're rushing and you're really busy and everything else? I use my Zoe app if I'm in a store to just look at the barcode and tell me what is the rating for that because nearly all food is processed to some extent. And you can score it into four categories. And I'm only really worried about the top two categories. So low processing risk doesn't really worry me. I'm not obsessed with it.

And all of these foods, you could have them occasionally. It's not a big deal. But if you have it regularly, as many people do, as part of their diet every day for breakfast or for lunch, they're getting meal deals. They're in this rut. So I would tell to everybody, the first thing is get out of that rut, change your breakfast, change a sandwich, you know, think about your evening meal and try and cut out ready meals. Avoid anything that has a massive health claim on the front. You know, and if you look at children's yogurts or most breakfast cereals, and they're full of health claims, and that is a big red flag. They're trying to get you to buy this rubbish, and it's going to cause inflammation, glucose spikes, and mess up your brain. And so we've talked about ultra-processed food.

Are there any other foods that you would tell somebody to focus on if they're trying to improve, you know, their mental health and their brain health in terms of stopping? Processed meat and sugar-sweetened beverages are associated. associated with increased risk and fibre and whole grains associated with decreased risk. I would love to talk now about what you add in. Let's start briefly with something that isn't food, which is supplements. There's some very weak evidence for some supplements alongside other treatments in mental disorders, but they're not incredibly strong. Do you take any supplements? I don't take any supplement. I take vitamin D in wintertime in Australia.

because we live in the cell. That's all. And Tim, what about you? I'm interested in omega-3, and it has been shown that in people with low levels, it is beneficial to take omega-3 supplements, but I always prefer to take the food. So I take sardines and anchovies and measure my blood levels.

Now, the other thing I've started taking recently is folic acid, which we know works very well in pregnancy and protecting the baby's brain and development. So we know it has a major effect on the brain. And there's a number of studies now showing that is preventive for depression and potentially other brain diseases. And the third thing that I've sort of dabbled with, not quite convinced yet, is creatine. And we've talked about this on the show, whereas there's some evidence, there's pretty good

evidence that it builds muscle, not very much, but it does build it. and there's weak evidence that it might prevent against dementia. So I'm looking at the evidence, but I haven't yet jumped in to say, I'm going to take this regularly. You know what I didn't? It's not a supplement, but to prevent dementia, I had my shingles vaccine. That's a great point. Vaccines have been shown to reduce dementia.

So you say what should we take? Well, you should definitely take a shingles vaccine if you're offered it, and you should also take your annual flu jab because that has been shown to reduce dementia. Amazingly, no one really understands why, but it's a bit like fermented foods. Your immune system is being tickled by these vaccines. Let's move on to food and what you should add into your diet. Let's take it in turn. What would be your key prescription for this?

Well, based on the emerging evidence from the studies that we're doing, I would have said legumes before, but now I'm saying whole grains. So whole grains come up again and again and again as the strongest correlate of better health outcomes, whether it's physical health or mental health. And what's a whole grain? So they're things like oats, not the really processed ones, a very unprocessed ones, barley, rye, spelt, quinoir, you know, these types of things. Well, I don't like to pick out one food because I don't believe in superfoods. So I would go back to our sort of mantra, let's eat the 30 plants a week and vary it. And, you know, I'm finding I'm now getting up to nearly 50 plants on many times.

So that will naturally incorporate things like whole grains, et cetera. So the more diversity, the more likely you are to get all the nutrients your brain needs. And fermented foods. Fermented foods comes in a close second. Yeah. And I think we should all be having some fermented. foods in our diet because it works in a different way on the immune system. And there's probably the two key fundamentals we should be all doing. If someone is listening to this and they're saying

this all sounds great, but I need really cost effective ways to be able to improve my diet. And one of the reasons that I, you know, I'm eating lots of this ultra-processed food is that it's cheap and it sort of can, you know, it lasts, all the rest of it. What would you suggest? Food has to be accessible. It has to be easy to prepare and it has to be affordable. What I do is I do on the weekend a big crock pot. I change the grains every week, but often it's things like barley in there. Legumes of different sorts. I'll put in different dried legumes. These are super cheap. Barley is super cheap. And then I can use frozen vegetables. They're really cheap and they're often frozen, really just after their pick. So they can maintain,

actually, their nutritional density plus the whole grains, plus the legumes. And I think that that's a really simple, extremely cost-effective way of having super fast food available to you for the week. I think it's a great question. How do you get people on a bad diet with some mental health issues to eat better. And that's why actually come up with a cookbook of over 100 recipes and tips about what to keep in the larder, how to batch cook, how to use frozen foods, frozen vegetables that canned things that cost very little. And when you do that and you start thinking about it more rationally, you actually reduce what you're spending on your food. You just got to plan it right. You just got to say, I've got to change some of my habits.

Let's have a new look at this. So hopefully people who want more detail can go and get some new ideas on how they can change what they're eating on a regular basis in ways that's really going to improve their mood and their brain. We want to change people's habits for a lifetime. And so it doesn't make it it takes time to get there. That's not important. It's just making these permanent changes. So to finish for Lee's, if someone is listening to this, but maybe they feel a bit overwhelmed by where they are and the challenges in their life. and how busy they are, what would you maybe recommend as one small change that they could

sort of start with tomorrow that might really make a difference? I think I'd suggest a mental change because when you think about the incredible complexity of the brain, it's the most complex thing that we know about, the incredible complexity of food, plus all the misinformation that's flying around as well as the really good information, the complexity of the gut microbiome and the science there, all that complexity could just blow your brain up and you could just think, well, I'll just give up and walk away and keep eating the chips. What I'd say is that's all complicated, but what you need to eat to feed your gut microbiome is super simple. So it's just lots of plant foods of different sorts. I think probably throw in some

fermented foods. You don't have to be a vegan or even a vegetarian. Just try and avoid the foods that are in packets with lots and lots and lots of different ingredients if you can and focus on the ones that are whole. And they can be frozen. They can be. tin, they can be dried, they can be cheap. Brilliant. I would like to try and do, I don't even call it a summary, maybe pick out the highlights that have rested here in my mind and maybe try and focus on, particularly on the actionable advice at the end.

The thing that immediately comes to mind is you can give mice something like schizophrenia and depression simply by giving them the gut microbiome of the human being with those. And I think it does really break this whole idea that I grew up with that these are things that adjusts in your head and then not like in your body. And it really tells you also just how important your microbiome is and therefore your food. So I think that's crazy. It also, I guess, makes you realize that people with these mental disorders, like they have a very different gut microbiome.

The second thing I'm really struck by is something you said, for least, that mental disorders are the largest cause of disability in the world today. So this isn't just like a niche thing. That's huge. And that's before we even talk about people who are maybe high, functioning, but feel anxious or stressed. And then the other thing, Tim, that you said, which is that mental health and brain health like dementia are really the same thing. The impact of food on our mental health is huge, that you can basically give people a change

in diet and a third of them can stop having depression symptoms is remarkable. And that works as well as, you know, all the drugs and things we have. The other thing I think that came who really strongly is ultra-processed food as an issue is really real. And you said you did this massive new study and 70% of bad health outcomes, including mental health and cancer and heart disease, are linked to an increase in eating ultra-processed food. So you just see what a big deal it is. But I think the good news is then you said, like, there's a lot you can do.

So this also isn't something that you're just stuck with. On food, I think that, you know, the rules are the same things we talk about all the time. Think about 30 plants a week, particularly think about these plants that are going to really feed your microbiome, whole grains, barley, quinoir, unprocessed oats, legumes like chickpeas and beans, fermented foods. But also think in this case about specific foods that you want to reduce or try and keep really low. So particularly cut out the worst ultra-processed foods. Tim says, don't worry about all of them, but like the high risk and the medium risk you really want to take out. Felice says, you know, you turn it over and say, does it have an emulsifier? Okay, I'm going to try and avoid.

Then on other things, cut out ready meals, cut out sugary drinks. Process meat, sausages, salamis, these hamses, it's a really big deal. And Tim, finally, he said, you know, any food with a big health claim on it for you is a really easy way to say, like, I just wouldn't eat that. And then finally to finish, Felice isn't taking any supplements. Both of you are trying to eat a lot of oily fish to keep your omega-3 levels up. So that's a sort of food as supplement. Tim has started taking folic acid. And you both said, actually, just amazingly, think about vaccines.

Shingles vaccine, flu jab, that might be the biggest thing you can do actually to, like, protect your mental health, which is amazing. I never would have thought about it. Protect against dementia, specifically. When you think about mental disorders, there are so many risks that we have very little control over. Now, the fact that something that 100% of the population does several times a day is actually a modifiable factor in the risk for these common mental disorders, which account for this huge global burden, this is critically important. So this is actually really exciting.

It's something that we do have some control over, but it should not be up to the individual. We need to change the system. We need to change our environment so that. Less healthy foods are not the default. Just a final note, I think if everyone realizes the link between what they're eating and their mood, they would actually be really motivated to change what they're eating. I'll end this episode with something I think you'll like, a free Zoe gut health guide. If you're a regular listener, you know just how important it is to take care of your gut.

Your gut microbiome is the gateway to better health, better sleep, energy and food, the list just goes on. But many of us aren't sure how to best support our gut. I wasn't sure before doing Zoe, which is why we've developed an easy-to-follow gut health guide. It's completely free and offers five simple steps to improve your gut health. You'll get tips from Professor Tim Specter, Zoe's scientific co-founder and one of the world's most cited scientists, plus recipes and shopping lists straight to your inbox. We'll also send you ongoing gut health and nutrition insights, including how Zoe can help. To get your free Zoe gut health guide, head on over to zoey.com slash gut guide. Thanks for tuning in and see you next time.