The shocking way ultra-processed foods damage your brain

There’s been a surge in our consumption of ultra-processed foods, especially in the United Kingdom and the United States, where these foods contribute about two-thirds of people’s caloric intake.

Also a cause for concern is emerging evidence of ultra-processed foods’ detrimental effect on our brain health and overall well-being.

When most of our calories come from ultra-processed foods, the risk of chronic physical and mental health conditions escalates.

Scientists are now uncovering the intricate mechanisms behind this relationship. And they're particularly interested in the effects of these foods on our brains.

In today’s episode, we welcome back Prof. Felice Jacka, OAM. Felice is an Alfred Deakin professor of nutritional psychiatry and the director of the Food & Mood Centre at Deakin University, in Australia.

She’s also the founder of the International Society for Nutritional Psychiatry Research and the world’s leading researcher on food’s impact on our brain and mental health.

Now, Felice is back on the show to delve deeper into the effects of ultra-processed foods on the brain, specifically the hippocampus, an area responsible for learning and memory.

Mentioned in today’s episode: 

Learn more about Felice on the Food & Mood Centre’s website.

Follow Felice on Instagram.

Episode transcripts are available here.

Is there a nutrition topic you’d like us to explore? Email us at, and we’ll do our best to cover it. 


[00:00:00] Jonathan Wolf: I'm your host, Jonathan Wolf, founder and CEO of ZOE. Today, we learn the shocking damage of ultra processed food on your brain in the US and the UK. A staggering two-thirds of our food intake comes from ultra-processed food, and this is rising fast. Scientists are only just now starting to understand just how bad this food is for our health, and particularly for our brains.

In this episode, we'll take you through the latest scientific evidence and find out how to minimize the damage of ultra-processed food on our brain.

Today, professor Felice Jacka is back on the show. Felice is the Alfred Deacon professor of nutritional psychiatry, the director of the Food and Mood Centre at Deacon University, in Australia, and also the founder of the International Society for Nutritional Psychiatry Research. Above all, she's the world's leading researcher on the impact of food on the brain and on mental health.

Felice. Thank you for joining me today.

[00:01:11] Felice Jacka: It's great to be here

[00:01:13] Jonathan Wolf: Wonderful. Well, look, you are an expert here now, so why don't we jump straight into our quickfire round of questions and we got a lot of questions from our listeners this time and just remind you about the rules. We want a yes, a no or a maybe if you, if you have to, you ready for it?
Yeah. Brilliant. Can eating ultra processed food rewire your brain?

[00:01:37] Felice Jacka: maybe.

[00:01:39] Jonathan Wolf: Are the parts of our brain responsible for memory and learning affected by ultra processed foods? Apparently.

[00:01:45] Felice Jacka: Yes.

[00:01:46] Jonathan Wolf: 10 years ago. Did anyone other than you believe that food affected our brains and our mental health?

[00:01:53] Felice Jacka: Not to any great degree.

[00:01:55] Jonathan Wolf: Should we be worried about the impact of ultra processed food on the brains of our children?

[00:01:59] Felice Jacka: Oh, definitely.

[00:02:01] Jonathan Wolf: So that's a lot of scary things. I'm hoping you're gonna give us a little bit of positivity. If you stop eating ultra processed foods, can your brain heal?

[00:02:10] Felice Jacka: it looks like it.

[00:02:11] Jonathan Wolf: Brilliant. And last question, and you know, you, you're allowed a sentence now.

What's the most surprising thing that you've learned from your research? Looking at the link between diet and our brains.

[00:02:22] Felice Jacka: Just how big an effect size it is. So how large an impact it seems to be

[00:02:29] Jonathan Wolf: So you're saying like the food food really has a big impact on our brain

[00:02:32] Felice Jacka: apparently, based on the data we have so far,

[00:02:35] Jonathan Wolf: Felice, that's a lot of stuff and we're gonna dig into that over, uh, over the rest of the podcast. I'm really excited we're getting to do this in person because we did our first podcast about a year ago. It was over Zoom. You were in Australia, which is where you are based, and we had this like fascinating conversation about.

The links between diet and particularly mood and sort of mental health conditions like depression and anxiety. And I recommend to any of our listeners who haven't heard that, if they find this podcast interesting, which they will to, to really go back and we said at the end that it would be really fun to do some more research together.

I'm incredibly excited that you're actually here in London because you spent the last two weeks in our London office here at ZOE sort of planning out a whole series of new studies that we can do together to really try and look at the impact of food and mental health in the brain on on large populations.

So thank you for coming here. Thank you for agreeing to sort of help push forward this area of research together and how much fun to actually be able to do it in person.

[00:03:33] Felice Jacka: It's great and I love being here and you know the weather's wonderful and it's great fun to work with the ZOE team. So I'm having a ball.

[00:03:39] Jonathan Wolf: No one is gonna believe you in London. Now you've said the weather was good

[00:03:42] Felice Jacka: Yeah it’s been great.

[00:03:43] Jonathan Wolf: You brought the Australian weather with you. So I think today what we'd like to do is really dig into how ultra processed food affects our brains. Mm. And I think that this is one of the top topics that I think a lot of scientists are talking about now, but I think many listeners are gonna be really, really shocked, to be honest.

'cause even the idea of ultra processed food is something that's very new. We did a recent episode of this podcast with with Tim Specter and Dr. Chris Van Tulleken talking about ultra processed food. But I'd love to start actually just with a bit of a recap, because this is a new concept. I didn't understand what this was like until a couple of years ago.

People start to explain like, what do we mean by ultra processed food and how's that different to just sort of regular processed food?

[00:04:28] Felice Jacka: Well, the definition of ultra processed food means food that has basically been, if you call it food deconstructed from its original ingredients and put back together again, and it usually has a list of. Other ingredients that are not found in Whole Foods. So things like artificial sugars, for example, food colorings, preservatives, emulsifiers, these types of things.

So those foods make up a very large proportion of Western diets these days. And often people think that it's only really obvious things like, you know, crisps or ice cream, these sorts of things. But it's actually. Often pre-prepared, ready-made meals that you might find in the freezer. A lot of things in the supermarket, some commercial breads are very heavily processed.

[00:05:12] Jonathan Wolf: one of the terrifying ones that, you know. Yeah, I, I'd never thought about. Right. You sort of think like, you know, that, you know, McDonald's or a packet of Oreos, like obviously that's not good for you and you know that it's very artificial. But the idea that something like bread, which just looks like bread might be ultra process, is there's something quite scary about how this is, is hidden and it doesn't look.

[00:05:35] Felice Jacka: yeah, I think we have to be a bit cautious 'cause there's many breads that would fall into that category. And this is the problem with the NOVA classification system

[00:05:43] Jonathan Wolf:  and will you explain for a minute what the Nova classification is.

[00:05:45] Felice Jacka: so there's four categories in Nova. So Nova was developed by Carlos Montera and his group in Brazil, and it really speaks to everything from category one, which is the completely unprocessed things like an apple, right through to category four, which is the ultra processed food.

The definitions are there to help guide discussion, help guide policy, but I think it's not totally strict. There's a lot of things that accidentally get swept up into that fourth category, so we always need to have a bit of nuance, and I know that Carlos and his team have talked about this a lot, that it's really not just about individual things and maybe choose that bread over that bread.

It's much more about food systems and food politics and how industry is really. Captured our global food system and displaced indigenous food cultures and certainly in western countries like the U S A UK Australia, but increasingly in countries that have had a far more traditional and really strong food culture.

So we need to change the settings in industrialized systems in the west and also prevent this takeover of the systems.

[00:06:56] Jonathan Wolf: So these sort of, with these foods that have got all of these ingredients you can never find in your kitchen, which is like the simple rule that some people have said to me that I find quite helpful as a way to try and navigate this

[00:07:07] Felice Jacka: So I guess you wouldn't be wanting people to absolutely panic and there'll be a lot of foods that might accidentally fall into that fourth category, like say whole meal breads that will still have healthful properties, but.

As a general rule, we understand what those ultra processed foods are. They are the things where you pick 'em up and you see this long list of ingredients on the back that you don't recognize, and it's things like preservatives and emulsifiers and all of those sorts of things.

[00:07:33] Jonathan Wolf: And we’re spending a lot of time with ZOE actually to try and do like better classifications of this because this is early science. And so what's useful I think for scientists isn't the same as just if you're a listener and you want to understand when you go to the grocery store what to buy, you wanna know for certain is this ultra processed or not.

And so this is clearly one of the, the challenges.

[00:07:51] Felice Jacka: I think it's interesting to know too, I saw a statistic the other day that the very large proportion of ultra processed food intake in the UK is coming from these processed breads that you get in the supermarket. Whereas in Australia, only 4% of the intake comes from. Spread. So I think there's probably differences in either what's available or the way they're produced in different countries as well.

So it's difficult to talk about this without really thinking about the setting.

[00:08:19] Jonathan Wolf: I'd love to talk a bit about what it does, and then maybe we can come back at the end to like, what can people do as well as maybe what can we all do together to sort of change the sort of food that that's available. And so I think that, you know, the starting question to go back to your rather scary quickfire answers is like, Why does the food I eat have anything to do with my brain at all?

I think lots of people will start with like, you know, I eat the food, it goes into my gut. I can sort of understand how maybe that might make me put on weight or yeah, but like, is my brain all sort of fixed and done by the time I'm 20? Or isn't this all a bit crazy?

[00:08:59] Felice Jacka: Well, a lot of people will have heard of serotonin because it's, it's called the, the happy neurotransmitter, but it, it's a bit more complex than that, of course. Um, a lot of the serotonin that is produced in the gut just stays in the gut.

It's just used as a local messenger. Type of molecule, but your gut microbiota produce a lot of different neurotransmitters, including serotonin.

[00:09:21] Jonathan Wolf: And what is a neurotransmitter?

[00:09:23] Felice Jacka: Well, a neurotransmitter is a molecule that helps a neurons. Brain cells speak to each other, but it also,

[00:09:29] Jonathan Wolf: So our gut bacteria producing chemicals that actually change the way that our, like brain neurons

[00:09:36] Felice Jacka: Well, I think it's important to say that we don't have that level of knowledge yet, so it's still very sketchy because of course, you're talking about something that is the most complex thing we know of in the, the whole universe, actually the brain, but certainly the neurotransmitters that are produced by gut bacteria, and they actually do produce neurotransmitters.

So even if you have like, Kombucha or something. You could be drinking actual neurotransmitters that have been produced by these bugs, which is very cool, but we don't think they themselves cross the blood-brain barrier. They do lots of different things within the body, but one of the things the gut bacteria do is help to metabolize something called tryptophan, which is part of what you eat.

It's an amino acid, and in doing that, they influence the amount of serotonin that is produced in the brain, so they don't. Produce the neurotransmitters directly that inf um, make their way to the brain. But they do play a part in that. But the other thing that the gut microbes do, and also that food does it seems, is influence the hippocampus.

Now, the hippocampus is a very cool area of the brain. When I was younger. I think neuroscientists and everyone believed that you were born with your full complement of brain cells, and as you grew older, they only got less.

[00:10:57] Jonathan Wolf: and I have to say Felice, you know, I'm 48 now and I. Do feel that, you know, in the last 15 years I definitely haven't grown any brain cells and it feels like they're just sort of slowly decaying a little bit. So you sort of try and compensate with wisdom. But it definitely feels to me that way as though, you know, I'm not maybe quite as sharp and I'm slowly don't feel like I'm, it feels a bit like the rest of your body.

Like at this point you try really hard to keep it stationary. But it's completely the opposite of like my 15 year old where like he wakes up every morning and he seems to have like, You know, put on another half a kilo and you can see like his brain like getting, you know, smarter and more complex.

[00:11:34] Felice Jacka: Yeah. And well, you, the brain at that age is undergoing a pruning process and, you know, a refinement process

[00:11:41] Jonathan Wolf: I'll tell him that.

[00:11:43] Felice Jacka: But what neuroscientists discovered probably the end of the 1990s. That we have this region of the brain called the hippocampus. Now it's only tiny. They're two little bits that sit together in the middle of the brain

[00:11:56] Jonathan Wolf: Felicia's holding over. For those of you just on audio, she's holding her hands like very small. 

[00:12:00] Felice Jacka: yeah, they're probably a lot smaller than that

[00:12:02] Jonathan Wolf: Like really small.

[00:12:03] Felice Jacka: But they, this hippocampal area of the brain seems to be very important in learning and memory. Okay. It also seems to be really important in mental health. So there are particular proteins that grow new neurons in the hippocampus, so the hippocampus can actually grow and shrink over the life course.

[00:12:23] Jonathan Wolf: And is that unusual?

[00:12:25] Felice Jacka: It's the only bit of the brain that we know of that does this, where you can actually grow new neurons and it can get larger.

[00:12:31] Jonathan Wolf: So the rest of my brain, I am right. Basically, it's not growing anymore. All that's happening is it's sort of, I'm losing capacity.

[00:12:38] Felice Jacka: does look like that. And people, as they get older, their hippocampus shrinks and that's when you start losing your car keys and forgetting your kids’ names.

[00:12:45] Jonathan Wolf: And this is linked to dementia.

[00:12:46] Felice Jacka: strongly linked to dementia, but of course it's linked to learning and memory right across the life course, so it's relevant for children as well. Their ability to learn and remember it's relevant to, you know, people in middle age in their jobs and their. You know, ability to function in the world.

Now, what we see over and over again is that the quality of people's diets is linked to the size of their hippocampus. Now we'd seen for many years. I,

[00:13:10] Jonathan Wolf: just wanna stop you for a minute 'cause you just said something really radical and I just wanna make sure that, 'cause you just said the hippocampus is sort of central in our learning and memory. It's the only part of our brain that keeps growing, um, that can grow as we get older. And then I think you just said very casually, but I just wanna pick up, oh, and by the way, the size of it is, Like directly related to the diet

[00:13:31] Felice Jacka: That's exactly right. So when, when the hippocampus was identified as this region of the brain that grows and shrinks, part of that was because they could see that people with major depression, for example, had a smaller hippocampus. And when they were successfully treated, the hippocampus got larger. But there was actually a whole lot of really cool research in animals in the early two thousands, and it's one of the reasons I got.

Really interested in this idea of nutritional psychiatry, where they could manipulate the size of the hippocampus and also the animal's sort of learning and memory by manipulating exercise, which affects the hippocampus and diet and showed. Really quite profound effects. So in 2000, I think it was about 2013, I did the first study in humans to look at this.

So we'd been working with this large epidemiological study. So that's when you're just observing people, you're not intervening, you're not doing an experiment. And it was a large cohort of people in Australia and we'd already seen that the quality of their diets was linked to the risk of them developing depression for the first time as they got older.

Independent of a really wide range of really important, you know, socioeconomic factors, income education, these sorts of things, and then recognizing that there were brain scans done on a small cohort of the older people, about 250. I thought, oh, let's. This is a great opportunity. So we actually looked at the hippocampal size of people as a function of their diet quality.

And of course we took into account depression. We took into account all of those other factors, and what we saw was a very clear link between the size of P People's Hippo Camp High. Their diet quality, and it wasn't just a tinsy little effect size. It was, it was equivalent to about 60% of the shrinkage that you see in the hippocampus as people get older.

[00:15:29] Jonathan Wolf: That's amazing. So you're saying 60% are. Of the, the amount that somebody's this part of this critical part of your brain shrinks is down to whether or not you are having like a good diet or, or a bad diet.

[00:15:40] Felice Jacka: Well, this is observational, so we can't say, definitely it's causal, but it was a very clear dose response. Since then, there's been two other studies. One done in the UK with the White Hole two cohort that showed the same thing. Diet quality, very clearly linked to people's hippocampal volume, particularly alcohol.

If you drink, it looks like you'll have a small hippocampus, even a small amount, which is a bit depressing.

[00:16:07] Jonathan Wolf: That'll depress Tim, who's always looking for a reason to say you can have one glass of red.

[00:16:13] Felice Jacka: And then in the Netherlands, they did an even larger study, more than 4,000 people, and showed that the quality of people's diets was linked to not only the hippocampus, but other regions of the brain and total size, gray and white matter volume, taking into account all these other factors. So it looks like diet is really clearly linked to your hippocampus. Now, this is incredibly important when you're thinking about your brain power. Now it's not just learning and memory. The hippocampus seems to be a key part of our emotional regulation systems.

What we see in animal studies is if that the animals are manipulated so that they can't produce. The protein that makes the new neurons in the hippocampus, antidepressants don't work. So there's some thinking that actually the hippocampus is a key way in which antidepressants can improve mental health.

But the other thing the hippocampus does is it helps to regulate your appetite.

[00:17:16] Jonathan Wolf: It sounds like it does everything.

[00:17:17] Felice Jacka: Well, it's a really, you know, your brain is amazing, right? Yeah. And it does all sorts of things. And a lot of what we know is coming from animal studies. 'cause you know, you, it's very difficult to chop humans' heads off and have a good look at their brains.

[00:17:30] Jonathan Wolf: good to hear

[00:17:30] Felice Jacka: Yeah. We do have two very cool studies though, that have actually manipulated diet just for the short term in young, healthy people. So

[00:17:41] Jonathan Wolf: tell us about them.

[00:17:41] Felice Jacka: So these two studies were done in young, healthy. Lean people, right? So they're not overweight, obese. In the first study, they gave them just over four days, a breakfast of toasties and a chocolate milkshake.

[00:17:58] Jonathan Wolf: And Toasties is,

[00:18:00] Felice Jacka: just like, you know, a toasted sandwich, probably with cheese or something in it. But in one group, their version of that was very high fat, high sugar, and the other version of that wasn't, and they were randomly assigned to both. And what they saw was within four days, they could see an impact on this hippocampal related learning and memory tasks in these young people.

[00:18:23] Jonathan Wolf: Wow. So they changed the breakfast and in four days, in

[00:18:26] Felice Jacka: Four days. And then the second study, and this is in  d them to have Belgium waffles or something similar for breakfast and to have the rest of their meals from these food chains.

The other group were given the, the healthier version of the same breakfast, and then told to continue their diets. Now, it should be said, these people all had reasonable diets to start with. They weren't eating a whole lot of junk food. Similarly, after a week, they saw the same impact on hippocampal dependent learning and memory tasks, and it seemed to be particularly pronounced in those who had a very strong glucose response to the diets.

[00:19:13] Jonathan Wolf: So like not good control of their blood sugar. Is that what that is?

[00:19:15] Felice Jacka: That's right. Yeah. So what also happened in those, in both of these studies is that people consuming these unhealthful foods also had lower appetite regulation. So we know that people, when they're eating ultra processed foods, they seem to eat more. Even when they say, oh, the food is just as tasty. Or, you know, and we know this from randomized control trials in the States.

Very famous trial done by Kevin Hall, but we don't really know why. Well, in these studies it looks like I. It affects the hippocampus and it seems to do so through glucose regulation, and that seemed to affect appetite. So people were more likely to want some more of these types of food. So it's saying that what you eat has a really important influence on your hippocampal volume and your hippocampal function, which could affect your learning, your memory, your mental health, your appetite regulation.

In the second study, they tested people again. Three weeks later when they'd reverted back to their normal healthy diet, all of those deficits were gone. So it suggested once they stopped eating those foods, they actually, their brain kind of went back. Maybe the hippocampus is very plastic, so I probably grew some more neurons.

[00:20:40] Jonathan Wolf: And so what would this mean over timefully? So imagine that, you know, I eat a diet of ultra processed. Food for the next decade and, and you don't like, what does this mean in the long run? 'cause you talked about like these sort of short term effects on sort of maybe some something you can measure in your hippocampus, but what would it actually mean to somebody in terms of their health and capabilities?

[00:21:06] Felice Jacka: Well, we know from, again, the epidemiological literature, so this is when you don't intervene, but you're just looking at people, large groups of people that you are assuming a representative of the population, and we see right across the world this clear link between the quality of their diet and their risk for these common mental disorders.

So that's depression and anxiety. These are very common. They're very, very burdensome. So at the population level, it looks like right across the life course, if people are eating a less healthy diet, it has an influence on mental health.

[00:21:39] Jonathan Wolf: And what about other brain, 'cause  you were touching a bit on things that go towards dementia. Do you see that as well, or is that We

[00:21:45] Felice Jacka: see that diet and also the things that are linked to diet like blood glucose and body weight and blood pressure. They're all very clearly linked to dementia risk. And we know globally that poor diet is pretty much the leading cause of illness and early death.

[00:22:01] Jonathan Wolf: And I think a lot of people listening know that, that seems quite clear, but I think they'll be surprised by the link to. Dementia. Mm-hmm. Um, just in the same way, I think that they will be surprised about the link to depression anxiety if they didn't listen to, to the podcast in, in the past. Yeah. I feel like that is not well known.

[00:22:19] Felice Jacka: no it's not. And it's interesting because when these huge studies, like the global Burden of Disease study, estimate the burden that comes from poor diet, they are not necessarily including brain disorders, like neurodegenerative disorders. They're certainly not including mental disorders, but they're also not including things like ADHD and autism.

And now it looks like there's a pretty clear link there as well.

[00:22:48] Jonathan Wolf: So tell us, tell us a bit. I mean, maybe tell us a bit more about all of this, because I think that. You're right. Almost nobody talks about this. And even the scientists that we have on, uh, on our shows in general, there is still this thing in science, I think, about this huge divide between people talking about anything to do with the brain and people talking about any other part of the body.

And I've had explained to me by doctors that this also follows the way that like the medical profession still has this like really big divide. Yeah, sure. Between sort of psychiatry on one side and everything else. Yes. And so it's great to have you here a. Like, how serious are these risks? I guess? I think many people, you know, my grandmother had Alzheimer's.

Yes. Um, and it was sort of a fast onset, you know, as for everybody, like devastating impact on the family, you know, devastating impact on my father. It's still like his number one fear in life is that he's going to have the, the same thing. And, and I think for many people it feels as though. This is something you have no control over.

Yes. I think that's a story that I have understood. I think my father understands, whereas I think many people feel, I think rightly, given all the, the evidence that, you know, diet and exercise can have a lot of impact on your risk of strokes and, and diabetes. So I mean, is there actually, like how real is this linkage?

[00:24:05] Felice Jacka: Well, it's very consistent and the difficulty is, of course, doing an intervention, like a trial over a long period of time. You can't really give someone junk food diet for 40 years and follow them for 40 years and look at how likely they are to develop dementia.

[00:24:20] Jonathan Wolf: And that’s what some people might say, that's exactly what we've done across the world as an experiment on all of us.

[00:24:25] Felice Jacka: Yeah. Well that's that's very true. The other interesting thing about dementia is it's not just excess body weight or high blood pressure. High blood glucose that seems to be involved in the risk for dementia. And again, these are just associations and so many things are involved in the risk for any illness in humans.

It's often very difficult to narrow right down and and say, okay, this specific thing. But certainly that is a very clear and very consistent finding in the literature that these factors are linked to the risk for dementia. What I'm really interested in more recently is the oral microbiome and how that might be linked to dementia risk.

[00:25:03] Jonathan Wolf: So these are the bacteria in your mouth.

[00:25:06] Felice Jacka: That's right. It looks like there are particular microbes that may set up shop in the neurons of your brain because they can get there pretty easily through, you know, and your brain lays down these plaques. You know how in dementia people have these. Plaques on their brain, and that's one of the hallmarks of dementia.

And there's thinking that these are, these plaques are actually antimicrobial and it's your brain's attempt to get rid of the infection sitting in the neuron. Now, this is very new research. It's very speculative, but I think it's super interesting because the oral microbiome we already know is very clearly linked to.

Cardiovascular health, we've done research to show that it's linked in a dose response manner. The number of oral health conditions are linked in a dose response manner to depression risk.

[00:25:56] Jonathan Wolf: Dose response is?

[00:25:57] Felice Jacka: It means that if you had two oral health conditions, your risk or your, your likelihood of having de depression was down here.

But if you have eight, you, it's up here and it goes up like this in a, a stepwise

[00:26:11] Jonathan Wolf: So it gets higher and steadily as you get more of these oral issues

[00:26:13] Felice Jacka: Yeah, that's correct.

[00:26:15] Jonathan Wolf: Then your risk of depression is just steadily going up and up and up like a graph that's sort of like a, that's, you know, straight line

[00:26:21] Felice Jacka: So the oral microbiome is, of course, directly has access to the brain, but it also makes, there's many pathogens that make their way to the gut. Particularly if you're on those PPIs, those proton pump inhibitors, those things that people take for gastric reflux, because that reduces the barrier that stops these microbes making their way to the gut.

[00:26:45] Jonathan Wolf: We actually had a podcast talkin about this and some of the downsides of taking these,

[00:26:49] Felice Jacka: That's correct. And we know that the oral microbes, like everything else, they seem to be influenced by the food that we eat. So this is another link to diet and another way

[00:26:58] Jonathan Wolf: it's not that this has always happened with these, these plaques in your brain. You're saying that the microbes in your mouth are themselves affected by what we eat, and then your, your information is

[00:27:09] Felice Jacka: But it, it's highly speculative at this point, but basically diet seems to be able to affect your risk or your, your mental and brain health via a lot of different pathways. A lot of this is based on animal evidence at this point, so we really need to do it in humans. We are doing a lot of research at the moment.

We've just finished a really, really cool trial where we've looked at the possible impact of the on the brain of fermented dairy, like, you know, kefir yogurt. We've also just finished a trial, which is sort of a proxy investigation of ultra processing. So you know when people are living with obesity or sometimes they have to have surgery and they need to lose some weight, and they get put on these very low calorie diets.

So 800 calories a day, really low, and usually they're put on these shakes and bars. These highly processed foods that say they're nutritionally balanced, they've got vitamins and minerals added, and they've got protein and all the right, they've even got fiber added to them. We worked with a couple of dieticians who've developed a range of pre-cooked and frozen products that are the same, very low calorie, but they're based on vegetables and legumes and things like this, so that people, because they were concerned that people going on these very low calorie diets really weren't doing their health any good.

So we randomly assigned 40 women to receive either the shakes and the bars or the whole foods over a period of time. And the primary endpoint was the gut microbes.

[00:28:48] Jonathan Wolf: So seeing what happened to their, to their bacteria. Yeah.

[00:28:51] Felice Jacka: Now I can't give too many results away because this is, we're only just analyzing the results now, but basically we do see pretty much what we would expect to see, and this, to my mind, reinforces that just because foods have vitamins and minerals added to them just because they have, you know, this nutritional profile that doesn't look like it's too bad.

These ultra processed foods, and here it could be everything from protein shakes and bars to whatever. I don't think that the body and the brain recognize them in the same way that they do Whole foods. If you think about Whole Foods like plant foods, right? It's estimated that there's possibly as many as 150,000 different phytochemicals in them.

Now we know about only maybe 20,000 if we are lucky, but that includes things like the polyphenols, the Flavanols, 150,000 of these phytochemicals that interact with each other in highly complex ways. Interact with every bit of your hugely complex body, brain in highly complex ways that we can't even begin to map.

Not to mention the food matrix. You know the way a whole food is put together by nature, all of that is lost when you process foods and when you deconstruct

[00:30:11] Jonathan Wolf: It’s crazy isn't it? It's now I drives 'cause I've, I've heard Tim and others talk about this and now it drives me slightly crazy. 'cause you see, you know, on some packaged food something says, you know, high in potassium or whatever. I'm, and I'm, and I'm now thinking, well, Well, that's fine, but apparently there's 150,000 other things that I need to get.

So this sort of focus on these individual things, it sort of shows you how we've ended up in this world where you have this food that's stripped back and then has, you know, 15 things in and then you wonder, I guess, how much we are missing as well As, you know, there's been a lot of focus on like the bad things in the ultra processed food, but clearly there's also this thing about this huge absence of all the things that our bodies are used to having.

[00:30:54] Felice Jacka: That’s exactly right and when even just think about fiber, fiber isn't just one thing. There's multiple, multiple, multiple different types of fibers. Everything from non fermentable to highly fermentable, everything in between. They're all treated by your gut microbes differently.

They all have different effects. You can't put that into a, a, a processed food and just say, well, it's got fiber in it. It's okay. Well what sort of fiber? You know, like where's the complexity of the fiber that your microbes are expecting to come in? And this is a major issue and it gets back again to the food system.

When do you think about the way the food industry, so our global food system costs the world around $20 trillion a year.

[00:31:40] Jonathan Wolf: 20 trillion dollars.

[00:31:41] Felice Jacka: 20 trillion American dollars.

[00:31:43] Jonathan Wolf: I don't even know how much that is, but it's a big

[00:31:44] Felice Jacka: Well, an equivalent would be the whole GDP of China is about 16 trillion a year, right? So this is huge. This is coming from the UN Food Summit. Now about 11 trillion of that is the impact on health, but about 7 trillion is the impact on the environment.

And these two things can't be torn apart because biodiversity in the environment. Influences the biodiversity in us, our microbes in our gut, in probably every part of our body in our lungs. The microbes we breathe in. Now, the soil, ideally healthy living soil, the way those phytochemicals get into the plants is via this very complex, tight relationship between microbes in the soil and fungi in the soil.

So nutrients. Phytochemicals make though into the plants from healthy living soil, the way our industrialized food is produced now, soil is dead. There's an estimation that over the next a hundred years, we'll actually lose about 30% of the food producing capacity of the soil across the world because of what we are doing to it.

With herbicides, you know, pesticides, artificial fertilizers. And also that intense cropping where we just take everything out of the soil, leave it barren, and then go put the same thing back in again. So we've completely got away from how soil used to. Help our food to grow. Now that food is eaten by us, it's also eaten by livestock that we then go on and eat and don't even let me get started on the industrialized production of chicken and pork and these things that have huge amounts of antibiotics in them, often to make them fatter.

Of course they make their way into us as well. Now everything in our industrialized food environment, including the environment we live in, the advertising, the food that's available to us, the subsidies that make these ultra processed foods just so much cheaper than whole foods and so much easier to get.

This is what needs to be changed. So, you know, I talk to people and I say, well, we know from the evidence that, for example, the diets that women consume when they're pregnant, Is linked to their children's emotional health and things like ADHD. We have to change our food environment so that. The population is eating in a way that supports the health of the population.

You know, there was a really interesting paper just published. It wasn't a scientific study, it's like a report in Norway. Norway has exceptional data because they have these registries that you can actually go and look at and and do scientific testing on, and they basically looked at the. Introduction of fast food restaurants into the population, which happened in about sort of the eighties in Norway, and then cohorts of children that grew up exposed to fast food restaurants.

So it wasn't directly linking consumption of fast food and, and children.

[00:34:46] Jonathan Wolf: Just the change in the environment. So what happened?

[00:34:48] Felice Jacka: And you see an increase in body size, of course, but also a decrease in IQ.

[00:34:57] Jonathan Wolf: Wow. And, and Felice, you're incredibly passionate hearing this, and I think what's striking is. You're a very serious scientist. You're really on the cutting edge of all this research around the brain and food, and you know, I heard your que your answers to the, the question at the beginning. You know, like many scientists, you're a little cautious about, you know, not wanting to say yes or no, but you sound pretty convinced here.

I mean, I think you sound pretty convinced that this ultra processed food really is having an impact. This isn't just a hypothesis without a lot of data. You sound like you say no. Like the evidence is quite strong enough. In the same way as it might have been with smoking. Maybe that's a good example. How would you compare this?

Like we said, wow, that smoking turns out really does have all of this bad impact. We really need to change things. We need to try and convince ourselves to stop. You know, my grandmother smoked for years. My mother smoked in her, uh, in her first few years, and then people realize, no, this is really bad. And so people try and shift and then of course we try to change the overall environment.

I mean, How serious, like how strong is the evidence, I guess, is this just like, oh, I think this might be the case, but really, you know, who really knows it's.

[00:36:05] Felice Jacka: a very interesting analogy because if you look at the global burden of disease study, so the largest health study in the world, it brings together everything we know from health studies across the world involves more than 2000 scientists. You know, we are doing some work for the Global Burden of Disease study now.

Tobacco smoking is up there in the top five risks for illness and early death, but it's up there with the other four factors, which are all diet related. So for at the global level, poor diet and smoking are roughly equivalent.

[00:36:36] Jonathan Wolf: The main causes of people dying earlier than they would otherwise

[00:36:37] Felice Jacka: That's right but at an individual level, people vary enormously in terms of their risk.

What you have to do is look at converging evidence, so converging evidence from all the epidemiology where you look at large populations and see these links over and over again. We did a systematic review and meta-analysis that. Looked at the link between ultra processed food intake and a whole host of outcomes.

Now, obviously body weight and size was one of them all. Cause mortality was increased by about 30%.

[00:37:08] Jonathan Wolf: So that's just dying

[00:37:09] Felice Jacka: That's just dying. Yeah. For anything. But also the risk for depression, it was associated with an increased risk of depression of about 24% I think.

[00:37:20] Jonathan Wolf: Which is a huge increase

[00:37:21] Felice Jacka:  it is. Yeah. And then, you know, we've just finished a study in Australia that's looked at this, again in a very large sample of I think about 20,000 people, and shown about the same increased risk of a measure of depression over time for people with a higher intake of voltage processed foods.

What's interesting in that study, Is that the people with the highest intake of ultra processed foods were also the most advantaged. So they weren't the poorest or the having the lowest income or the lowest education. It was actually those at the other end of the spectrum. But what was also interesting is that those people were actually having less energy intake, less saturated fat intake.

So it looked like these were like diet foods, these were the ultra processed foods with the added sugar, uh, the artificial sweetness and things like that.

[00:38:09] Jonathan Wolf: this is one thing that makes me really angry, which is how many people have been trying to do the right thing basically and follow what they think is good and like eat based upon the labels they see in the grocery stores they go into of like, oh, this is good for me and it's got this added thing.

Um, one of our previous guests said this brilliant thing, which is that basically any food that has a label on it saying that it's good for you. Isn't, and I thought that, that, I'd never heard that before. And then you realize it's basically, it's all of these ultra process, it's these breakfast cereals for the kids that say, you know, high in these vitamins and whatever, and Those are exactly the foods that…

[00:38:46] Felice Jacka: Look  I have had a bit to do with some of these industry players and the nutrition people who work for those big food corporations. They're generally traditionally trained dieticians. They may have been trained however long ago, and they genuinely think that because food has added vitamins, minerals, whatever, that it is a healthful product because that's based on what we knew back then.

[00:39:11] Jonathan Wolf: What practical. I'd love to switch maybe now like to practical advice. Practical advice. So maybe it's, let's start with children and then let's think about maybe for our listeners and also maybe also thinking about people as we get really quite old. Any practical tips for us about what we should do? How do we identify this U P F? What should we worried about and what could we do about it?

[00:39:30] Felice Jacka: The thing with these sorts of foods like ultra processed foods and these foods that have got a lot of added sugar and salts and fats, they're all designed to interact with the reward system of the brain. Well, they're probably not explicitly designed for that, but they do.

They interact with the reward systems of the brain and for children and adolescents. Those reward systems are particularly sensitive, if you like, and there is some evidence, I believe, that suggests that it is programming the immune system and inflammation and the reward systems of the brain when they're young, if they're exposed to it, so that they will want to keep eating those sorts of foods, they'll make those choices.

[00:40:07] Jonathan Wolf: And is this all or nothing? Or can anyone listen to this? Say, you know, either for myself or for my family, maybe I can't cut out all of these ultra processed food. You know, if is, is there a certain amount, you know, does it, is it better if you reduce it?

[00:40:23] Felice Jacka: Definitely. And so what we've seen in our latest study, so this big sample of Australians, is that it's only those in the very top quartile, like that top 25% of consumers of ultra processed foods that had the increased risk for depression. Now you want to normalize healthful foods.

We recognize that so many people have challenges with access, maybe storage, maybe food preparation, education. It's gonna take time to overhaul our whole global food system. There's huge pushes on to do this. There's. Big players and things happening at the, the level of both industry, but also government that I'm hopeful will start to feed into changes in the way we produce foods, changes in the way we market them, all the rest of it.

But governments have to get real about food policy because we're talking about the whole health of the population. But in the meantime, if people are consuming these foods, even just small reductions are gonna help.

[00:41:24] Jonathan Wolf: And let's say someone's listening to this now and you know, we've talked quite a bit about children, but let's say I'm a 48 year old listening to this and I would like to cut down on UPF, but I don't even really, I don't even know what UPF I'm, so it's sort of like, oh my God, I've suddenly just discovered I've been smoking.

I didn't even realize I was, what's the, the way to start down this path? If you're advising someone who’s listening and wants to go and do something

[00:41:49] Felice Jacka: Yeah. I think, I believe that there's apps that can help, you know, like swap sort of apps where that you can go, okay, I was gonna choose that, but actually I'll get that instead. Reading the labels, they're always designed to be very, very difficult to understand

[00:42:03] Jonathan Wolf: And what would be your simple..

[00:42:05] Felice Jacka: would just be if you, if you pick up and it's got a label with lots of different things in it that you don't recognize, then don't choose that. One of the important things that we did with our SMILES trial was we estimated the cost of the diet that we were advocating compared to the cost of the diet people were eating when they came into the trial.

So people coming into the trial had lots of ups, lots of discretionary foods. And we estimated the cost very carefully of their baseline diet, and then we looked at what we were advocating for and our diet was actually cheaper. Because what we were saying was things like frozen vegetables, they're fantastic.

They're nutritionally, often even superior. You don't get the food wastage. You have them available the whole time, and they're really inexpensive, relatively speaking, tinned and dried legumes. These are your absolute gold in the food department because they're so cheap

[00:43:00] Jonathan Wolf: And these are beans and chickpeas and things.

[00:43:02] Felice Jacka: Beans, chickpeas, even green peas.

You know, mushy bees go for it because they have so much fiber, so many phytonutrients, and they are very cheap and easy to prepare. Tinned fish. I love the precut salads that you get at the, at the supermarket. I live on those. During the week. I literally get the precut salads, especially if I can get the ones that have got like, I don't know, kale and beetroot and all sorts of different, like that rainbow, because then I know I'm getting lots of phytochemicals.

I stick 'em in a bowl. I have a tin of chickpeas or something like that on top. Sometimes I'd put in like a small tin of fish or something, mix it all up. Lots of extra virgin olive oil, which is a really important source of these phytochemicals and some balsamic vinegar. And there's a meal, you know, and if you wanna add in, like, you know, make it a bit fancier and herbs and things like that, that increases those phytochemicals too. But super easy

[00:43:59] Jonathan Wolf: So good for your health and sounds really tasty as well.

[00:44:01] Felice Jacka: Really tasty and really quick. So, and I like quick,

[00:44:06] Jonathan Wolf: I think that is brilliant advice. I mean, maybe final question, I think, um, 'cause we've, we've, we've talked about many stages of life, but you haven't really talked about older age. Um, is it all too late if you're listening to this and you are already, you know, 80.

[00:44:24] Felice Jacka: I think it does matter a lot. So there's been a couple of really important studies done where they've looked at the gut microbes. So we know that in general, A healthy diet means that you have a more diverse gut microbiota and your gut microbiota. Diversity is in turn linked to things like frailty, which includes measures of cognitive decline, and they showed that when people moved into nursing homes, the diversity of their microbes really reduced because their food diversity really reduced, and that was associated with increased frailty and more cognitive decline.

Now we don't actually know over what sort of timescale, you know what we eat

[00:45:00] Jonathan Wolf: to make sure I'm understand, you're saying like basically, again, like the bad food leads to bad microbes, and when you're older you get, you know, your cognition, your brain function is getting worse than other people. So actually it's incredibly important as you're older to think about this and therefore to do something positive to support you with the right food. 

[00:45:18] Felice Jacka: What we see is, you know, when we think about those junk food diets that affected the hippocampus and learning and memory in just such a short timeframe, within a week, within four days, we also see that you get improvements in that within a very short timeframe.

And if we look at the literature from the dietary interventions for depression, we can see in as little as three weeks these really major changes

[00:45:41] Jonathan Wolf: That's amazing. So within three weeks, potentially, if you really change your diet, you could really feel better mentally.

[00:45:47] Felice Jacka: your hippocampus is super plastic. And one of the interesting things I, I think, is that your skeletal muscles, so the muscles that you build, if you're going to the gym, lifting weights, whatever, they actually produce the proteins that help to grow your hippocampus.

So when you're going and you're lifting your weights, you're directly increasing the size of your brain. So that's really cool.

[00:46:07] Jonathan Wolf: That's amazing. So I don't think, most of us don't think when we're going to the gym that we're, in fact we have this bias, right? That, you know, you're, people go to the gym all the time. This is only when I was a kid. I think it was like, well that's not, you know, it's like people not really. Thinking about their brain and now you're saying actually they're working out their brain as well as their

[00:46:21] Felice Jacka: It looks like it. Yeah. Based on the information we have so far. But it does look like you can affect change in your hippocampus and your ability to learn and remember and your potentially your mental health really quickly. And that makes sense. If you think about, you know, you put in food if it's high in sugar, It gets absorbed by your short bowel, doesn't even make its way to, the large bowel, gets straight into your bloodstream and your blood glucose increases and that seems to create inflammation.

It seems to influence your hippocampus really quickly. If you eat good things, fiber and the polyphenols and the healthy fats that we know that the gut microbes need. Once it gets down to the large bowel, all those bacteria get to work and produce all these thousands of molecules really fast. And that influences all these systems in the body.

Our immune system in particular, our metabolism and our body weight, our, the way genes are turned on and off the mitochondria, the way you know neurotransmitters are produced in our brain. It all happens really quickly. So that's really exciting 'cause it means you can make changes today and have an impact really fast.

[00:47:28] Jonathan Wolf: I think that's a brilliant place maybe to wrap up because I think quite a lot of this is slightly, slightly depressing, and so I think to finish with this idea that actually you could make a change right now if you. Into this and within three weeks you could really feel an impact on your brain. Yeah. Is rather magical

[00:47:42] Felice Jacka: Even less than three weeks potentially.

[00:47:46] Jonathan Wolf: Wonderful. I'm going to try and do a little summing up. It was a bit complicated today, so correct me if I get anything wrong. I think we started by just saying that we're now starting to understand that ultra processed food is not just something that might be affecting our weight and some of those sort of cardiovascular risks like heart disease and things like this, it's actually directly affecting our brain and therefore affecting, uh, not just our mood, but even our, our cognition that you think a lot of that is, Is influenced sort of directly through the microbiome and all of these bacteria who apparently make these magic neurotransmitters, which I don't really understand, but they sound like they're very important.

as one of the ways it sort of links from what we eat through to things that are going on inside our brain that there's a particular part of our brain called the hippocampus. Which although it's very small and Felice, I remember and you had your, like your hand, like it's very small, but apparently controls almost everything like learning and memory and appetite control.

and amazingly it's the only part of our brain that can actually grow, you know, once we're an adult and which is sort of constantly changing and that the. The quality of the diet we have is directly linked to the size of this hippocampus. And so you can see that basically people with a bad diet and lots of ultra processed food that actually you can, you can see in real time the sort of hippocampus, shrinking.

And that's linked to a lot of bad things as well, like dementia. And on the other hand, there is this possibility to improve your diet. It's not too late. You can actually grow your hippocampus. So I love that. It's a bit like going to the gym, but for your, for your brain. Overall, the impact of this ultra processed food, it looks like on a global scale is as bad as smoking.

And that that is the only other thing that's sort of as bad as this. And then I think we talked a bit about sort of different life stages that you said to me, I was right to be worried about, you know, my little girl. Because with Children's, incredibly important, this sort of, this huge amount of their diet that is ultra processed food today that, um, once again it's like a.

A tough story for pregnant women because you're saying, well, actually like what you eat does affect your children's mental health. And there's already, I think, always so much pressure on pregnant women having seen my wife go through this, but also what they're, but obviously critically, what they're eating afterwards is so important and above all, try and get 'em to eat as much an adult diet rather than thinking that we should have all of these like highly processed special foods for, um, for children.

And at the other end with older people, actually again, like the positive story is you could potentially really improve your cognition and frailty. By eating the right food and on the reverse, like the sort of food that you might be given in on a hospital or a care home could actually like be leading to really fast decline.

And then I think the final thing that you said, I thought was brilliant, I had heard of is potentially you could exercise to improve your brain and that there is actually this direct link. Uh, so you know, if you could cut down the ultra processed food and improve the exercise, you are actually working out on your, on your brain in the same way as you are working out  in your body.

[00:50:47] Felice Jacka: Yes, I would. I would agree with a lot of that. I would say that a lot of what we know from association studies, which talks about averages across the population, so we can't say about any individual, the degree to which this is gonna influence them. A lot of what we know comes from animal studies, so we still need a lot more work in humans.

But if we bring all the evidence together, it looks like diet really does matter to mental and brain health, right across the life course from right the start right to the end. The degree to which it matters, we don't know yet. In regards to smoking, I think at an individual level, junk food is probably not as bad as smoking, although it might be at the global level.

It's certainly diet and cigarette smoking are pretty much the leading causes of illness and early death. So there's a lot that we still don't know. But if we bring together all the evidence from human and and laboratory studies, We see that it's all converging on this idea that what we eat is just as important for our mental and brain health as it is to our physical health, right across the life course.

And that makes sense because mental and physical health are really just one and the same thing. We are one highly integrated, highly complex system.

[00:51:57] Jonathan Wolf: I love that story, Felice, and I think in terms of getting more evidence, I hope we're gonna be able to announce to our whole ZOE community soon some new studies allowing us to do some of these interventions and understand more in sort of the large populations, which are normally so hard to do.

So lots of people, how what we can, affect our our brain health, our mood, our cognition, because it seems like one of the reasons we don't understand this is just, there's been incredibly few studies until very recently.

[00:52:28] Felice Jacka: What we need to do is push our politicians to help us help the whole population to have access to better, healthier food through food policy. We need to have proper food policy. It shouldn't be up to the individual to have to make those really hard decisions every day about what to eat because it's confusing and industry has had a vested interest in making it confusing.

[00:52:57] Jonathan Wolf: Felice, there's a wonderful place to finish. Thank you so much. Really excited by the studies that we have planned together and excited to talk about some of these new studies that will be coming out in the next year.

[00:53:07] Felice Jacka: We've got a lot coming out in the next year, so watch the Food and Mood Center space.

[00:53:11] Jonathan Wolf: We will, and we'll have links on the show for all of this. Thanks.

[00:53:15] Felice Jacka:  Thank you. That was great fun.

[00:53:18] Jonathan Wolf: Thank you, Felice for joining me on ZOE Science & Nutrition today. If you want to understand how to cut down on ultra processed foods and support your brain with the best foods for your health, then you may want to try ZOE's personalized nutrition program.

You can get 10% off by going to As always, I'm your host, Jonathan Wolf. ZOE Science & Nutrition is produced by Yella Hewings-Martin, Richard Willan, and Alex Jones. See you next time.