Prof Felice Jacka on Food, Mood and Mental Health

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Hey guys. Crib and governor from the Gut Health Gurus podcast. I've got a background in food science and I have an extremely special guest today. I've been trying reach out to this amazing woman for some time, Professor Felice Jacka. Thank you so much for coming onto the show.

It's a great pleasure.

And Felice, the first time I came across your work was last year in the Gut Brain Axis conference in Paris. And you had some incredible support during that conference and there was guys like Professor Ted Dyden, Dr. Imran Meyer, and they were speaking about your smiles trials and that's the first time I ever come across your work. And I was just mind blown about the extent and the repercussions of what you were able to achieve. Firstly, huge honor in terms of being a hero. You're certainly one of my heroes in Australia in that Gut Brain space. How we typically like to start our podcasts is, is to get it from the horse's mouth. Who is Professor Felice Jacka?

Well, I am the director of the Food and Mood Centre here at Deakin University in Australia, which is unique in the world in its focus on nutritional psychiatry. And in a way, I suppose we kind of founded the field. I'm president of the International Society for Nutritional Psychiatry Research. We've got our second major international conference happening in October, October in London. But my early career, my first degree was in fine arts. So I had no intentions or interest in studying science. But because of my personal experience of, you know, quite serious clinical, depressive and anxiety disorders, during my early years I was very interested in studying psychology and I went back in my early 30s to study psychology and I'll just get rid of that. I had two small children, so I did it very slowly. But during that time I realized that I wasn't really interested in being a counsellor But I was really interested in research and particularly in medicine and sort of the biological aspects of how the brain and the body talk to each other. And then I started to do some interning work with a new psychiatric research unit that had been set up here in the Geelong area. Professor Michael Burke is one of the leading. I think he's like number two in the world, most cited psychiatric researchers. He's extraordinary man and he's former president of the International Society for Bipolar Disorders. And I started sort of interning with him while I was still an undergrad. And we really are on the same page. We like to do things in a similar way. And very quickly I got a grant that allowed me to start doing RA work here. And I realized I really loved research. And so I went on and did my honours degree. And then doing my honours degree, I was looking at osteoporosis and depression and a lot of sort of about endocrinology. I kind of had to teach myself medicine, really. But I started to realize there was nothing in the psychiatry research area that had looked at nutrition and what the possible links were between nutrition and mental disorders, particularly common mental disorders. And I was fascinated by this because at the time there was a real. This burgeoning area called psychoneuroimmunology. So looking at how the immune system speaks to the brain and how it is so relevant in mental disorders both as a cause and a consequence of particularly depression at this stage. And at around the same time, we started to get some fairly very interesting data coming out of the US from neuroscience. So this whole area of neuroscience had really opened up with the recognition that there are at least two areas of the brain where you actually put on new neurons over the course of your life. You know, it wasn't just you were born with a certain complement of neurons and you only lost them as you drank too much or whatever. And one of the key areas is the hippocampus. And the hippocampus is very central to learning and memory. But also we were increasingly understanding very important in mental health. And it's one of the key targets of antidepressant medications, for example, and that if you manipulate diet in animal studies, you very quickly manipulate the function of the hippocampus via these proteins, these neurotrophic proteins sort of up or down regulating the expression of those proteins. So this was another strand of information that suggested that nutrition should be important in mental health. And yet there'd been very few studies done. There'd been a few kind of not very good supplement trials. There'd been a few epidemiological studies looking at individual aspects of diet, say folate or fish consumption, but that doesn't capture the totality of what someone eats. And so it's a very limited way of approaching this. But also the whole field had been, I guess, had fallen into disrepute that, because at the very early stages there was a lot of very bad science done, a lot of open label trials and a lot of extrapolating and overselling and, you know, the field really needed some scientific rigor. So I proposed to undertake a study looking at the link between the quality of people's diets and their clinical depressive and anxiety disorders, of course, taking into account all of these things that might influence that relationship, such as people's education and income and their body weight and other health behaviours, etc. And, you know, Michael was supportive, but he thought I was a bit bonkers, I think, frankly, very skeptical and, you know, kind of patronising. But I pressed on and I was lucky enough to be do my PhD in a large cohort study of people who were very representative of the wider Australian population. So they're selected from the electoral rolls and they span the full adult age range, so it's a very representative. And we also had very good quality data. We did proper structured clinical assessments on these people. I personally did over 500 on the women in my PhD. And of course I had to look to the nutrition field to look at the new ways of understanding diet and dietary patterns and using new statistical approaches that allowed you to capture the whole of diet and not just bits and pieces of it. Because, of course, if you eat, for example, a lot of magnesium, you're also probably eating a lot of folate and a lot of other things, and you need to understand the totality of that to be able to really start to look at links properly. So, anyway, I did my PhD and found indeed the associations that I expected between diet quality and common mental disorders. And because it was the first major study and it had very good quality methodologies, it was actually published on the front cover of the American Journal of psychiatry, wowed in 2010 by Medscape as the top psychiatry publication of that year. And it had a very big impact. And on the basis of that, what I was able to then do was go around the world to many different research groups where they had big epidemiological studies and they had variously collected information on diet and mental health and all of those other factors, but they'd not ever thought to put them Together. And I was able to leverage on the sort of the publicity around my PhD study to go and approach those groups and say, can we collaborate? Can I look at your data and we'll test this hypothesis? And so doing that, I was able to, within a very short period of time, relatively speaking, generate the first studies to look at this link between diet quality and common mental disorder in adolescence. And of course, this is the primary age of onset. And if we're thinking about prevention, and I think about everything with my prevention hat on. I'm former president of the alliance for the Prevention of Mental Disorders in Australia, so I've done a lot of work in the prevention field, and there's a very clear link. Even if you take into account things like chaotic family environments and family socioeconomic status, everything else, then to go back even further and look at the start of life and go, okay, the Barker hypothesis and all of the work there tells us that early life nutrition really matters to physical health across the lifespan in children. But is this also true for emotional health? So we looked at this in more than 23,000 mothers and their children in Norway. We looked at mother's diets during pregnancy. We looked at children's diets during the first few years of life, and then we looked at children's emotional regulation over the first few years of life, and again found these very clear relationships independent of all of these other factors that we needed to consider. So we were able to really establish the field. And of course, other people were starting to get on board and going, oh, we've got those data. We could look at this as well. And so more and more studies were coming out, and they were really consistent in their finding, which was that the quality of your diet is very clearly related to whether or not you develop depression in particular. Now, this is critically important for two reasons. One is that unhealthy diet or poor diet, because of the influence of big food and the industrialization of the food system and the way our food landscape has changed across the globe, unhealthy diet now is the leading cause of premature death in men across the globe, and number two in women. Now, at the same time, mental disorders, particularly depression, account for the leading global burden of disability. So they're massively expensive, they're massively impactful. The fact that the two things are linked gives us a completely new way of thinking about the problem of mental disorders. And, you know, in psychiatry, we've had no new treatments for depression for decades. We really struggle to address it properly. People with depression, you know, some will respond to antidepressants, some will respond to psychotherapy, but for many people, they're left with symptoms or they're not helped at all. So this, of course, was really important. And now we're at the stage where we have, after 10 years, several meta analyses where you bring together all of those observational data and look at the figures, and we see that a healthy diet, no matter how you measure it, whether it's a traditional Mediterranean diet, whether it's a healthy version of a Norwegian diet or Japanese diet, or, you know, however you measure it, it's associated with about a 30% reduction in the risk for depression. And of course, we were also starting to delineate these, the ways that things might be working. So we published the first study in humans to look at what we see in the animal studies, whether diet quality is related to hippocampal volume. And we saw very clear relationships. And that's now been replicated into far larger samples. But of course, what was lacking was the intervention study, because you can say these two things are very clearly and consistently related, but that doesn't mean that one causes the other. And you need a randomised controlled trial to be able to test that. That's incredibly challenging in nutrition because you can't blind people to the group that they're in. There's all sorts of issues and, you know, adherence, the whole thing. But I just finished my PhD. I was in the first year of my postdoc and I wrote the grant application for the SMILES trial and I really had hoped to get the funding in the first year. Sorry, I'm just going to get rid of this so that we stop getting interrupted. The first year we weren't successful, but the next year I managed to get the funds and we went where angels fear to tread and tried to do the study. And it was incredibly difficult because we'd hoped to recruit about 180 people with major depression, and instead we could only recruit after three and a half years, about 67 people. And so there was, I think, a lot of skepticism on the part of the medical fraternity. So no one was directing their patients to us. But there was a lot of skepticism about people with suffering from depression, you know, would this help them? But we did manage to do the trial and when it came time to publish the result to do the analysis, we absolutely, we're not expecting to see a significant difference between the groups. And there were two groups that we randomly assigned people to. One was social support, which we already know is helpful for people with depression. And the other was dietary support with a clinical dietitian. And when we did the analyses, we were just completely stunned because we saw a really major, major difference between those two groups. And in fact, about 30% of those in the dietary condition went on to have full remission of their depression, which is really extraordinary compared to 8% in the social support condition. But what was key with the SMILES trial was a few things. One was that there was a very clear and tight correlation between the degree of dietary change and the degree of improvement in people's symptoms. So basically, the more they improved their diet, the better off they were in terms of their clinical depression. Second, these changes weren't explained by changes in body weight. The average BMI in the people in the study was about 30. And that didn't change. It wasn't explained by other changes, say for smoking or exercise, etc. But very importantly too, we did two key pieces of economic evaluation. One was to test how expensive our diet was compared to the diet that people were eating when they came into the trial. And we showed that our diet was actually cheaper. But secondly, and I think this is really key, we did a formal economic evaluation with health economists and they showed that there was a massive cost saving by taking this approach to treating depression. There was a cost saving of roughly 3,000 Australian dollars for those in the dietary group because they lost less time out of role and they saw other health professionals less often. So it's saying that this benefits the whole purpose and their functioning in all aspects of their life. A few months after we published our study, people we know in South Australia published the results of their study where they did a very similar thing, but they did it in a larger sample size in a group based setting. And they found very similar results to us. And they also showed this tight correlation between the degree of dietary change and the degree of improvement and that it was highly cost effective. So this, and then just very recently in JAMA and we wrote an editorial for this, there was a, a study published, an RCT of a dietary approach in people with depression and obesity in the US and also showed that it improved depressive symptoms. So there's been three studies now that have targeted people with depression with a dietary approach. But what we also have is a very substantial literature where dietary approaches have been taken to treat, say, metabolic endpoints or other disease endpoints in people who don't necessarily have clinical depression, but they happen to have measured their depression and anxiety as part of the intervention. And we've just published in the last month or so A meta analysis on these data. So bringing together everything that we know, if you change people's diets, particularly if you use a nutrition professional to help them to change, you get a benefit to depression. If you change people's diets, you get a benefit to depression. And this is in the clinical space. So that's what we call level one evidence now, where you have a meta analysis of randomised control trials. And this goes along with the many, many studies and meta analyses now that show that diet, that exercise and physical activity are both important prevention strategies and also treatment strategies, and also the emerging literature around cigarette smoking. And that not only is it a risk factor for emerging mental health problems, but if you give up, you get a benefit to your mental health as well as your physical health. So we're now leading a group who are putting together a set of international guidelines for lifestyle psychiatry. So really embedding lifestyle medicine as a fundamental principle in psychiatry. And this is of course not to say that you would take that approach instead of other treatments, but rather that this should be the foundation, which actually in the clinical guidelines in Australia, it's already written in there. But the lack of training for health professionals means that that's not implemented. So we're hoping that international clinical guidelines might start to shift policy and practice.

So I'll just press pause just for a moment so we can dig into a couple of questions that I have as a follow up. So the first question I have is in terms of these dietary changes that you made during the trials and just for the layperson listening to the podcast, what are some of those strategies that people could implement at home to improve their mental health?

Very, very basic stuff. It's swapping out refined grains, you know, white bread, refined cereals, those sorts of things for whole grains and for diversity of whole grains. So, you know, oats and barley and millet and brown rice and black rice and those sorts of things. It's increasing the number and the diversity of vegetables and fruits that people take in. These, of course, really important sources of fiber. It's increasing or introducing legumes, so chickpeas and lentils and these other really critically important sources of fibre. It's using olive oil instead of, you know, say butter or other seed oils. It's starting to include fish in the diet a couple of times a week for those long chain omega 3 fatty acids. But also very, very importantly, it's reducing the intake of the extras foods. And what we know from the literature is that both not getting enough of the good stuff. So the foods that are high in fibre and high in polyphenols and healthy proteins and fats, and also quite independently having ultra processed foods in as part of your diet, they're both independently related to worse mental health outcomes. So fundamentally speaking, say for example, you've got a young person who's getting lots of veggies and fruits at home, but is then going off and having lots of of junk food before, during and after school, that's still going to be a big problem. And conversely too, if you've got an older person, for example, who's not necessarily going out to maccas every week, but they are having a very limited white foods diet, that's also a problem. So both of those things are important. We don't know which is more important than the other. Both increasing the stuff that we know is really important for gut and brain health and the second is reducing the stuff that we know is really damaging for gut and brain health.

And in terms of the studies and the different age groups that were looked at, is the findings relevant to say, children, adolescents and older people?

We haven't done intervention studies in children and adolescents yet, but that would be an obvious next step. But based on the very extensive and consistent observational evidence, we would say that the same thing may apply, but we don't know until we do the research.

And just as a side note, is something like, because you looked at various lifestyle factors as well during your time, is sleep a consideration as well?

In some of the epidemiological studies where those data were available, they were looked at as well and didn't seem to be involved in that relationship. And the other interesting thing about the observational data is that body weight is not involved in the relationship. So while we know that obesity is linked to an increased risk of depression, and depression can often lead to obesity, the body weight does not seem to explain this diet mental health association. So I think that's really important in the intervention studies. I'm not sure whether sleep was taken into account. I don't think it was in our SMILES study. That would be an interesting thing to investigate, but I would be very doubtful that that would play a major role in it. I think sleep's incredibly important and certainly if you don't sleep well, then your diet is usually poorer. But in the association, I would doubt, based on the existing evidence that it's a major player, maybe a small part of it. Sure.

And I can't help but be intrigued about these guidelines and protocols that you, you guys have developed in terms of psychiatric treatment from a lifestyle perspective. Are you able to share a few of those protocols? Okay, so it's still in development?

Very much in development. We're going to be doing this as a joint venture between the Australasian Society of Lifestyle Medicine and the World Federation for the Societies of Biological Psychiatry. So they have a committee that puts out international guidelines. So we'll do this as a joint venture.

Awesome. I'm so excited to see what you guys come up with because I think it's going to be really important for practitioners as well. So in terms of adoption of your studies, what's your general feeling about the overall medical community adopting.

Look, despite the fact that unhealthy diet is the leading cause of early death in men and number two in women, most medical practitioners get an average of two hours in training in nutrition during their, you know, their health training. This is a major issue and many people are aware of this. And there's a lot of stuff starting to happen overseas in terms of training, but that is yet to trickle through. And of course it's important to understand. Our meta analysis showing that dietary change improves depression was only published last month, so it's too early. So we've got a handful of practitioners around the world. Dr. Drew Ramsey @ Columbia University in New York is a very high profile proponent and he teaches this in the States, you know, to professional bodies. We're developing online training that people will be able to take and it will be accredited through the Food and Mood Centre and Deakin University that should hopefully be developed by the end of this year. So there's a critical need to get training in place. People like Dr. Rangan Chatterjee in the UK doing training in lifestyle medicine for medical practitioners. It's really important. 2015, I had some input into the updated clinical guidelines for the treatment of mood disorders put out by the Royal Australia New Zealand College of psychiatrists in 2015 and that now actually has it enshrines Lifestyle medicine, they don't call it that, but it's diet, exercise, sleep hygiene, smoking cessation and substances as step zero. It's the thing that practitioners should be doing when they first get a patient with a mood disorder. That should be step zero before moving on to other forms of treatment. But of course it's just not done because people don't have the training. And they might say something like, oh well, of course it's really important to, you know, have a healthy diet and exercise that doesn't do anything. People don't understand often what a healthy diet is because there's been many People who've had a vested interest in making that really confusing, including Big Food. And unless the health practitioner, whether it's a psychiatrist or a medical professional, professional of other sorts, really emphasizes it and gives people clear guidelines and writes it on a prescription pad, it doesn't change behaviour. So one of the other things we're doing is working to have a Medicare item for dietitians for people with mental disorders of all types. And the other point about this is that for people with what we call SMIs, serious mental illnesses, so that psychosis, the people with really serious and psychotic disorders, they have a lifespan that's on average 20 years shorter than the general population. And that's because of two things or three things, really. One is some fundamental problems with metabolism that tends to go along with these conditions. Two is, of course, the impact of the antipsychotic medications, which are just a disaster for people's body weight and metabolic health. And third is, of course, their lifestyle behaviors often go down the toilet when they're unwell. You know, they. They don't cook for themselves, they don't exercise, that sort of thing, and they smoke more now. This is why they die so much earlier and they're so much sicker. The fact that we're not addressing their physical health, first and foremost to prevent those things happening, when we know from very good research that's been done that you can support people with even very serious mental disorders to eat well and to exercise and to stop smoking, this is not being done as a standard treatment. It means that this just, this massive imperative from a parity point of view, you know, an equity point of view, that people with mental disorders are able to access dietitians and exercise physiologists and support for smoking cessation at the very first instance. And of course, even if you're looking just at depression, we know, and I say just as depression, of course some people can have very severe depression, but we know that if you have depression, you are already at much higher risk of cardiovascular disease and obesity and metabolic disease problems. So we would say it not just enough to screen people and go, well, you're depressed, but you, you are not overweight and you're not. Your blood sugar is okay. And so we won't even worry about that. We need to be implementing this from the first instance to prevent these chronic diseases developing. So even if you don't do it for your mental health, you do it for the physical health outcomes. So there is absolutely, unarguably, a very strong case for having lifestyle medicine and here we're not talking about alternative medicine or complementary medicine that doesn't have an evidence base. We're talking about lifestyle medicine, which has a very massive and clear evidence base, you know, around dietary improvement, exercise and smoking cessation. That should be the starting point and everything else, you know, you can build on.

That. Absolutely. Felice, I'm 100% with you on that. It's so important to start with that low hanging fruit. Let's segue a little bit onto. And this is what we do in my podcast all the time. We jump around like crazy. But I'm really fascinated because you mentioned something around prevention being something that's important to you now. How do we instill, I guess, the findings on your studies to say, for instance, a mum or a prospective mum? So how does these factors influence, say, for instance, a young child? Can moms do anything to improve the chance of, say, a child developing these type of illnesses? Can we catch it.

Early? So based on the available evidence, some people, we will be able to prevent some cases of mental disorders developing in the first place if children have a healthy diet from the start of life. But putting the onus on the individual without talking about the food environment and policy is a huge mistake. Humans operate within an environment and that environment has a massive impact on the choices they make. We know from history that when the food environment is a healthy one, that people's health at the population level is far, far, far better. And I talk about that in my book. We have just the first steps in Australia for our politicians to say yes. We will think about some of the recommendations made by the Obesity Policy Coalition around taxation of sugar sweetened beverages, limitations on marketing, limitations on availability, those sorts of things. That hasn't happened yet. All they've done is say, yes, we will consider it. The influence on big Food, on policy is just beyond belief. How massive it is. It's much bigger than the tobacco industry. We think that if people and if policymakers and individuals understand that a healthy diet is not just important for averting a possible cancer or heart disease diagnosis further down the track, or diabetes, you know, people don't pay attention to things that happen a long way in the future, if they understand that this is of relevance to children's emotional health and their cognitive health, their ability to learn and remember and grow their brains from the start of life, I believe that that is going to add a lot more weight to the push to radically improve our food environment, which is a.

Disaster.

Absolutely. For individuals and families to pay far more attention to The Dietary.

Guidelines. I'm totally with you. I mean, food in itself is so addictive. There's so many addictive qualities to food. And to put the onus in an individual, I think, is pretty unfair. I think we do need wider policy changes to address this.

Issue. Now, something about the individual that doesn't actually work either. We see that recommendations about what we shouldn't and shouldn't eat for decades, it hasn't made any.

Difference. Totally. Everything stacked against them, from the marketing to the production of food. So I'm with you there. Something that's on my mind as well, that I wanted to ask was. So you mentioned, and we spoke before we started as well. Both of us have struggled with anxiety and depression, which kind of led us to, I guess, the path that we've both followed. I'm fascinated to ask. I've got to ask this question. So with your findings, have you been able to implement any of these strategies in your own life, and have you seen any improvements in your.

Condition? Definitely. So I probably developed, like many children, an anxiety disorder when I was in about six. I think that's the average age of onset for anxiety disorders, based on the US data. By 13, I was suffering from quite severe panic attacks without really knowing what they were or why, but they were pretty bad. And then my first episode of major depression was probably about 14, which is pretty typical now. By the time I was 19, I had a really severe episode at 19. I mean, I'd struggled through adolescence, and by the time I was 19, it was very bad. I was really, really affected, and it was affecting my life and everything else. What I found was. And I generally eaten pretty well because I grew up in a family where healthy food was kind of the norm. But what I hadn't done was exercise. And what I found was that I was really having trouble sleeping. So I started exercising to improve my sleep. And that was such a key change. I started running, you know, and I started to. I realized that I really enjoyed running. And I'm not talking marathons here. I'm just talking, you know, five kilometers around the lake. It had such an incredible beneficial impact on my sleep and on my mental health that I've really been, apart from a couple of, you know, little blips, I've been pretty well since then. So I haven't had those issues since then. So for me. And then, of course, when I was exercising and sleeping better, I would also choose healthier foods. And this is what we see from our data as well, when we help people to improve Their diet, they started exercising more, they stop smoking and they stop drinking so much alcohol. And so it has this flow on effect to the rest of your lifestyle behaviors. So I've stayed pretty well since my early 20s by, you know, healthy diet, exercise, prioritizing sleep, just the basics. I have been pretty good. So in my own life, yes, I've definitely seen the benefits of this approach and I still to this day, you know, exercise regularly to make sure that I sleep well. And I of course I love fruit and vegetables and healthy. So I really enjoy cooking and preparing.

Foods. That's wonderful. And that's so interesting because we've had Professor Ted Dyden who's another, I guess, psychiatry expert buddy of.

Mine. He and John Cryan. So John and Ted are really the world experts in the gut brain axis research. And John's coming out this week to stay with us. He's a really good buddy.

Of. Oh.

Wonderful. I've worked with Ted and John, we've collaborated on a number of grant applications and co supervision of students and things like that. And they're just marvelous.

People. Ted's. I don't know John, but Ted's a wonderful man. And I guess my point was he always also mentioned on the podcast and people can go back and listen to the episode, but he also mentioned about running, about his passion with running and how that's improved his health as well. So this is a perfect segue, I think, to talk about the microbiome and from your findings and your research and the studies that you looked at. Now how does your smile trials and dietary intervention relate to modulation in the gut microbiome which could lend itself to improving your mental.

Health? Well, I think it's a very obvious link. We didn't at the time when we did smiles, we didn't know anything about the gut brain axis or gut bacteria or anything like that. So we didn't measure it, which is a shame. But here now at the Food and Mood Centre, we're running more than 20 research studies and the large majority of those, I think at least 15, we're measuring that triad of diet, gut health and mental health because just very fundamentally from, you know, from the most basics we know now, we're pretty sure from all of the very extensive animal data and the emerging human data that the gut and the resident bacteria are very important for both our physical and our mental health. So that's the fundamental. The second thing we know based on the evidence so far is that diet is probably the most important factor that affects the health of the Gut and the composition of the gut microbiota. We know from the few intervention studies in humans that you can change gut microbiota composition and the health of the gut, you know, signified by, for example, levels of inflammatory markers that are linked to bowel cancer within a very short time frame. So the two case studies I'm thinking of here, one is that they took 10 people and they put half of them on a meat and, you know, animal food heavy diet and the other half on a diet that was high in plant foods and fiber, etc. And showed a very rapid change in their microbiome with apparent improvements in those in the plant based diet with more short chain fatty acids, etc. And a reduction in the animal based diets. And then of course, that other very important study, I think, where they looked at African Americans and they looked at South Africans and they showed very big differences in the health of the microbiome and of course their diets, and then they swapped their diets for two weeks and showed that the gut health, including the inflammatory markers, went right up in the poor South Africans and went down in the African Americans. So we know from studies such as those that you can change your microbiome and the health of your gut very quickly by changing your diet. Now, there's no one prescriptive diet for your gut. What we know is that your gut needs fiber. That's first and foremost, and it needs a diversity of fiber. And the second thing is it needs polyphenols. And the emerging literature suggests that it also needs certain types of fats and doesn't like other sorts of fats. So it really likes poly and monounsaturated fats that you would get from, say, fish and olive oil and nuts and those sorts of things. Doesn't love lots of saturated fat, but again, saturated fat, you know, comes in many different forms and many different food matrices. And I think we need to get well away from talking about individual nutrients and focus on food and whole food. And in that regard, Michael Pollan just said it all when he said eat food, meaning real food, not too much, mostly plants. If you want, you can eat some meat. You can, you know, there's a huge amount of variation in there, but just try and get the fiber into every meal that you have and the polyphenols as.

Well. And this. Is there a clear mechanism of how these short chain fatty acids and polyphenols actually.

Work? Oh, gosh. Well, there's many, many, many. So for those who don't know the very fundamentals are your gut microbiota. Their primary activity is to break down dietary fiber that our human enzymes can't break down. So when you eat, say, fruits and vegetables, whole grain cereals, legumes with lots and lots of plant fibres, they make their way down to the gut. The bacteria ferment them to break them down, and doing that fermented fermentation process produces all of these metabolites, all these different molecules. Now, they do so many things in the body and we're only just starting to understand them. One of the key things they do is they modulate the immune system. They're incredibly important in modulating our immune system, both within the gut environment, but also for the wider body. The other thing they do is that they interact with virtually every cell in the body via what are called G protein coupled receptors, and they therefore influence how genes behave, what things are turned on and off. So they influence every cell in the body. Data so far from animal studies suggests that they also influence the integrity of the blood brain barrier, that they are important in brain plasticity, that hippocampal growth that I talked about, that they may be important, important in neuroinflammation. So inflammation in the brain. They certainly affect metabolism, which is linked to mental health. So they do many, many different things, but if you don't have enough dietary fibre, they can't do that. This is the issue that we're seeing in the west, is that we're having not anywhere near enough dietary fibre or enough diversity of dietary fibres. Our gut microbiome diversity, which is a marker of good gut health, is going down and down and down, and we're seeing an increase in the. These mucus degrading bacteria and a decrease in, you know, just the diversity in a whole lot of microbes that we used to have when we were living a traditional lifestyle. Based on the current evidence, and of course, we need much more data, particularly from humans, that's enormously problematic and may, in fact put us at jeopardy, particularly if, you know, nasty new viruses come along or if you encounter a new food source or you have to make a rapid change to your diet to survive in a change in a cataclysm, for example, having a diversity of microbes makes it much more likely you're going to be able to adapt to that. So there's a whole lot of reasons why we should be very concerned about the reduction in the diversity and the health of our microbiome. And diet is the quickest and the most full way of making an improvement very, very quickly. To your gut.

Microbiome. Absolutely. And how about the neurotransmitter story? What's the deal with.

That? Well, when microbes ferment dietary fiber, they produce neurotransmitters, and they also change the environment to mean that your body's own production of neurotransmitters is changed. Now, the production of neurotransmitters, we don't know what that means. We know that more than 90% of serotonin, for example, is produced in the gut. But we don't know that that actually gets into the brain because of the blood brain barrier. But what we do know is that the bacteria in the gut influence the metabolism of tryptophan. Tryptophan is a precursor of serotonin. So by doing that, they influence the, the levels of serotonin in the brain. But what I find fascinating is, so for example, gaba, which is sort of like this anti anxiety neurotransmitter. When you have a fermented product such as kefir, which I love, or sauerkraut or something like that, you're actually consuming gaba because the bacteria, they produce these neurotransmitters and that ends up in the food that you're eating. So many people think that they should be having fermented products because of the live bacteria that are in them. But many of these fermented products actually don't have much in the way of live bacteria because the bacteria have eaten all the substrate, whatever that is, sugar or dairy sugar or whatever, and then they've died off because they've got no more food left. It doesn't matter, because what you've got in that product then is all of those metabolites that have been produced during the fermentation process. And you also have dead bacteria. We know that dead bacteria have a lot of bioactive properties as well. So there's a lot of good reasons, we think, to consume fermented foods regularly. But the data are very sparse. And this is something where we're also doing research is to look in great detail at the impact of fermented foods on the gut and related markets in the blood. But also then as a stepping stone to doing randomized control trials of fermented food products for depression and.

Anxiety. Wow. I literally cannot wait to see the actual data because I'm a huge proponent of especially kefir milk. Kefir was the one product that really turned things around for me in terms of my own personal struggle with anxieties and.

Depression. Interesting. Yeah, we Hear this a lot and we're in the process of doing.

That. Yeah. And to your point, on the postbiotics or the metabolites that are produced by the microbes during the fermentation process, there's even all these functional peptides, especially with.

Kefir. There's tons and tons of review paper on this if you're interested. It's in the literature. I can send it to.

You. I would love to have a read of that and I can link it to the actual podcast as well. But Felice, we're pretty much coming up to time. There's a couple of rapid fire questions just to close the loop because we have a community of about 10,000 people in a Facebook group and I did post that we're going to have you on to the podcast and they did send me a few questions to ask. There was a lady in there, what's her name? Ellie De Jong. She said she was a research assistant of you and to say.

Hi. Oh, okay. Yes, I think she's changed her surname. I remember Ellie from when I was doing my honours year, I think a long time.

Ago. Yeah, she said to give her a shout out. So here you go, Ellie. And I think you answered the question in terms of adults, adolescents and children. You covered the public mental health service reaction to your work. So let's talk about your book. So you've written this amazing book called Brain.

Changer, the British version. It's about to be published on July 26, so it'll be published in the UK and Europe. And the lovely Michael Mosley's given me a quote and endorsement for it. So bless him, he is a big fan of the research that I've led and he has endorsed that. So that's great. So that'll be published very soon. But it's been available in Australia since February or beginning of March.

Really. And we always finish the podcast with the question because it is a gut health gurus podcast. So we always come back to gut health. So if there was one thing, Felice, that a listener listening to the show could do to improve their gut health. And I'll also add in mental health, because we're talking mental health, what would it.

Be? Start eating beans. If you're going to just get one thing, start eating legumes. So lentils and chickpeas and black beans and red beans and stick them in everything. You know, stick them in your spaghetti Bolognese. Just you get a tin, chuck it in, you get a salad, chuck in a tin of lentils. Like it's the peasant food. And it is so cheap and easy and tasty and so good for your gut.

Microbiome. Wonderful advice. Such good, good source of fiber as well. And if people want to reach out to you, what's the best place they can get you on in terms of social.

Media? I'm on Twitter. I'm just starting to do Instagram. We've got the Food and Mood Centre website and we're just about to really zhuzh that so it'll be bigger and better. And we're, you know, gonna restart all our blog posts and things like that. So that's probably the main way. There's a Food and Mood Centre Facebook page as well where people can have questions and things. So we do our best. Although, you know, we're under a lot of time constraints because we're running more than 20 different studies and we're really, really focused on trying to answer questions that are of real relevance to people's daily.

Lives. Wonderful. Felice, thank you so much for coming onto the show. It's been an absolute blast and pleasure and absolute honor to have you as a hero. So thank you so much. My pleasure. Thank you.

Felice. No.

Worries. I hope you enjoyed this episode of the Gut Health Gurus with Professor Felice Jacka. What a fascinating conversation. And if you want to show some support, head over to Apple Podcasts and leave us a five star review and a kind comment. Now, if you're interested in making kefir, kefir is one of the best things you can do for guts, health and also your mental health. Head to www.nourishmeorganics.com and in the search bar, just search for kefir and you'll find everything about kefir, all the products and use the code Gut health gurus for 10% off until next.