Ultra-processed foods with Dr Andy Chan

Ultra-processed foods now make up over half of what many of us eat — and the health consequences are only just coming into focus. In this episode, we reveal what’s really happening inside your body when you eat these foods daily. 

Dr. Chan breaks down the hidden links between UPFs, inflammation, and diseases like obesity, diabetes, and colorectal cancer.

You’ll hear why some foods that look healthy on the shelf may be doing long-term damage — and how the gut microbiome plays a crucial role in the process.

This is the research big food companies don’t want you to hear. If you care about what you and your family are eating, don’t miss this conversation.

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Transcript

Jonathan Wolf: Andy, thank you for joining me today. 

Dr. Andy Chan: Happy to be here. 

Jonathan Wolf: Now, I think you know, we like to kick off this show with a rapid-fire Q&A with questions from our listeners. I’ll just remind you of the rules: say yes or no, or a one-sentence answer if you have to. 

Are ultra-processed foods making us sicker at a younger age?

Dr. Andy Chan: Yes, probably. 

Jonathan Wolf: Could there be ultra-processed foods in a home-cooked meal? 

Dr. Andy Chan: It depends on how you define home-cooked. 

Jonathan Wolf: Is there a simple way to know if a food is ultra-processed? 

Dr. Andy Chan: I think there are methods we can use to help people identify ultra-processed food. 

Jonathan Wolf: Are ultra-processed foods engineered to make us want to eat more?

Dr. Andy Chan: Many are, yes. 

Jonathan Wolf: Could a child's diet impact their likelihood of developing cancer later on? 

Dr. Andy Chan: Yes. 

Jonathan Wolf: Finally, you can have a whole sentence, what's the most common misconception about ultra-processed foods? 

Dr. Andy Chan: That it's a binary thing. That there's either ultra-processed or healthy. I think there's a gradation.

Jonathan Wolf: Most of us have this idea that ultra-processed foods mostly come from a fast food chain or snacks that we buy from the corner store. 

But I was shocked when my producer told me, as we are preparing for today's show, that apparently there's some new studies that say around 50% of the food that we cook at home is now ultra-processed.

And so that says, it's not just when we're out and about, we actually need to be worried about what we're buying in the supermarket and taking home. 

Can you help us to understand what is ultra-processed food, and how is it possible that there can be so much of it at home? 

Dr. Andy Chan: Yeah, I mean, I think that this is evolving. I think ultra-processed food has been a moniker that's been thrown around to classify foods in a somewhat simplistic way.

I think you're right, I think in most people's conception, ultra-processed food conjures up images of the bag of unhealthy chips or Doritos or the fast food meal that you have on the go. I think those are kind of the classic conceptions of what ultra-processed food is. 

But I think that we are understanding more and more that ultra processing, and that terminology can be a bit misleading because I think there are different ways to think about ultra-processed food and there are different ways to think about food processing more generally, and also different ways to think about how those different components of food actually influence our health.

It is a field that I think has been changing over time. 

Jonathan Wolf: So you're saying it's not just Doritos? What is it? 

Dr. Andy Chan: All food, to some extent, that is purchased, that is somewhat ready-made or has been prepared to be easily consumed, has a level of processing. And so there are industrial processes by which the food industry has put food and made it more accessible for people to eat in modern society.

I think that the classic conception of ultra-processed food is that it is food that has gone through some level of processing beyond its sort of original form to become more convenient to eat, and also oftentimes made to be more palatable. Meaning the ingredients have been put together to make them more tasty, and more attractive for people to eat.

So it oftentimes does come with a level of processing that makes them more highly preserved, which means they're usually more nutrient-dense. So there's more kind of calories in the food. Also they're made to be tastier so that people can eat them and enjoy them in a more sort of quick fashion.

Jonathan Wolf: Andy, I was growing up in the eighties, and people are definitely talking about junk food in the eighties. So is this just a new term for something that is the same that we've always had? 

Was I eating as much ultra-processed food in 1980 as my kids are likely to be eating today in 2025?

Dr. Andy Chan: It’s gradually increased to some extent. 

I think that when we use the terminology ultra-processed food to incorporate this conception of a level of industrial processing and hyper palatability, I think that has gone up over the last several decades, even from the 1980s.

So clearly, junk food and things that we were eating even back then were ultra-processed for sure. But I think because there's been more of an emphasis on providing food that is easier to consume, that is more convenient, that enters into food that we wouldn't classically consider to be junk food.

So I think there is a level of ultra-processed food that's more hidden than it had been in the past, and that has gradually risen.

Now we estimate that, for example, in the U.S. population, over 50% of the food, maybe even up to 75% of the food that we actually consume, would be classically considered ultra-processed food. 

Jonathan Wolf: So that's clearly a lot more than just the bag of Doritos and the candy that I'm thinking about. Why is it so prevalent in our diets today? What has been changing over the last 40 years? 

Dr. Andy Chan: Well, I think there has been a greater emphasis on convenience, I think. Because we have obviously seen our societies become more complicated in terms of the things that people are doing. 

I think in general, people are busier and multitasking during the day in terms of work, doing things at home. I think all those kinds of things have compounded to put a greater priority on having foods and meals that are easier to prepare. And reduces the burden on us in terms of time for food preparation, food shopping, and putting meals on the table. 

So I think that level of convenience and the need for that has, has risen, has been driving some of this increase.

Then I think there has been, I think this idea that over time as people have become more accustomed to the taste, if you will, of ultra-processed food, our pallets have maybe adjusted such that people are now seeking out those kinds of foods more and more, as foods that they enjoy and trigger some of the reward mechanisms in our brain to make us seek out these foods. 

So I think there's probably a combination of societal shifts in terms of what we prioritize in our meals, and also just changing taste in terms of what we enjoy eating. And that, I think, has adjusted over time.

We've seen that clearly in the sort of classic western countries or countries that are sort of high income, but that's gradually becoming more prevalent in other parts of the world. 

That's reflected, I think, in a global trend toward increasing consumption of ultra-processed food, and also with that has come maybe some global trends that we've seen in disease incidents. 

Jonathan Wolf: Andy, when I hear you talk about convenience and changing taste, it feels like this is all driven by active choices by us as consumers when we go to the supermarket. 

But I've definitely heard other guests talk about the role of the food corporations themselves in terms of maybe engineering these foods to make us want to eat them more, or just figuring out that they can save money or make the food in a particular way. 

Where they're not really worrying very much about what any of the health impacts that might come from UPF, is that all scaremongering, or is this true?

Dr. Andy Chan: I think the truth is in between. I think it's a combination of people's choices, and the choices they're making about food in combination with what they have access to, and also in combination with sort of what is being provided to them commercially. 

Obviously, those things work hand-in-hand and so as people's tastes change over time and the kinds of foods they seek out change over time, it obviously changes the calculus for people who manufacture foods, and for people in the food industry to provide foods that meet customer wants and needs.

Then, to some extent, that also feeds into itself, where I think some of these companies and some of the people who are responsible for our diets are gradually making changes to also try to encourage people's food taste to go in a certain direction. 

Jonathan Wolf: Actually, I had a conversation with a food scientist who worked for a company that I won't name, who described just year after year, you know, testing different variants.

The test is really straightforward. It's like whichever variant, when you go and do a taste test, people just eat more of, that's the one you ship. 

So, each year, they're very cleverly using all this food science to try and figure out how you can eat a few more cookies or a bit more of this thing.

Now he was just one person. But is that a part of what's driving this? 

Dr. Andy Chan: Yeah, I mean, I think there's very clear evidence that that's happening. 

I think we're also seeing it kind of in the opposite direction. I think we're seeing, obviously, some evidence that an increasing proportion of the population being on some of these new anti-obesity drugs like GLP agonists.

Those drugs are probably also changing consumer preferences in terms of the food they're eating. 

So I think there's evidence that the food industry is looking at that carefully, and trying to decide whether they need to also adjust some of the offerings they make available to the population. So they're meeting those changing preferences. 

Jonathan Wolf: And if you start going on those drugs which make you less hungry, does that mean that you're actually sort of craving these ultra-processed foods less, is that what you're saying? 

Dr. Andy Chan: I think it looks like that may be the case. I think it seems like the early evidence is that these drugs are also affecting our preferences in terms of the kinds of foods we're choosing to eat. 

That may have to do with the shift in our brain-gut axis, and trying to shift our preferences as to the kinds of foods that make us feel full and the kinds of foods that we enjoy.

Jonathan Wolf: There's something slightly crazy here, isn't there? So we eat all of this food that we were never evolved to really eat steadily over the years. It makes us sick. We end up in this horrible sort of hunger cycle that can end up with us living with obesity. 

Then we take these marvelous new drugs to sort of switch that off so that we no longer want to eat the food that, if they weren't selling in the supermarket stores, would probably never get us there in the first place. 

That's sort of how I understand that. 

Dr. Andy Chan: There's a bit of a swing. I think it's an interesting way to look at it, but I think it's the population shifts that are what drive, maybe what we're seeing being offered more and more by the food industry.

Jonathan Wolf: It's really interesting. I know your studieslot look at those overall population shifts. So I'd actually love to go down to this individual study that you published very recently, on ultra-processed food that you ran at Harvard. 

Because I think it helps us to understand one of our most common listener questions, which is, are these ultra-processed foods making us sicker at a younger age? 

I understand that you chose a very particular group of people to study, namely, kids. Why did you choose to study kids? Because I think children are really active, so surely they can get away with eating a lot of this sort of junky food without bad effects. 

Dr. Andy Chan: Well, I think that this really came out of our desire to understand a little bit more about why we are seeing this trend in obesity rates.

I think we've clearly seen in the U.S. and other countries, that obesity has risen dramatically in the population. It's not just adults, it's also younger people. So we're also seeing rates of childhood obesity really rise dramatically as well. But, the reasons for why we're seeing that increase in obesity haven't been so clear. 

I think there's been an assumption that we're just eating more. But to the point, I think, in the last several decades, we've actually seen that probably caloric intake in general may actually not be shifting dramatically. That it's not just we're eating more calories, but that there might be some differences in the types of calories we're eating.

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So we really wanted to understand why are we seeing these dramatic shifts in obesity rates, particularly in younger people. In addition, we're also seeing that there are dramatic differences now in rates of chronic disease in younger adults that we haven't been seeing before. 

So we are seeing more and more rates of cancer in younger people. I think that that's an area that I'm particularly focused on, is trying to understand what are the reasons for why younger people are getting cancer.

So, because of that, I think that there is maybe this shift in risk factors that are happening at younger ages, that may be some of these things that we're thinking about as being risk factors for disease later in life are actually shifting into younger ages.

I think we need to really focus and have more attention on what younger people and children are being exposed to, and not just adults. 

Jonathan Wolf: Andy, is it only cancer that is increasing in younger people? 

Dr. Andy Chan: I think that's been the most dramatic change. You know, we're seeing dramatically increased rates of different types of cancer in younger people. I think that's been a very noticeable trend. 

But I think we're also seeing changes in other types of conditions as well. As a gastroenterologist, for example, we're seeing rises in inflammatory diseases of the bowel. We're seeing rises in inflammatory bowel disease, for example.

We're seeing obviously changes in overweight obesity over time. We're seeing also consequences of that rising over time, like diabetes, et cetera. 

So I think we're seeing a lot of these metabolic diseases, and inflammatory diseases happen at earlier ages, and that probably reflects what we're seeing in cancer as well.

Jonathan Wolf: When you say younger people, the older I get, the more I want that to include me. What does younger people mean as you're talking about that as a doctor and a scientist? 

Dr. Andy Chan: Yeah. I mean, I think for cancer in particular, we generally define early onset cancer in younger adults as being less than 50. Because in the past, I think we kind of considered cancer to be a disease primarily affecting people over the age of 50.

That's really why most of the cancers, the common cancers that we screen for, we start that screening at the age of 50. So I think in the common definition of early onset cancer for our studies, we've really been focused on people younger than 50. 

Jonathan Wolf: Could you maybe summarize the study, what you did, and the findings?

Dr. Andy Chan: Yeah, so we really were wanting to focus on, as you said, younger people, to kind of understand what are younger people being exposed to in terms of risk factors, and how does that affect not only their health as young people, but in later life. 

So we wanted to develop this study within a cohort of younger people that we've been following longitudinally since they were very young over time.

It's called the Growing Up Today study. And these are a group of children that have been followed because they were offspring of mothers who were already in a study, which is called the Health Study Two. And these were a group of female nurses in the U.S. that had been tracked with questionnaire data since the early 1990s.

Jonathan Wolf: This is the 1990s. So this is a 35-year study at this point. 

Dr. Andy Chan: Right. So we have a unique opportunity to look at this group because we have data on the mothers, and we also have data on their children, over the last 30 years. 

So having that combination of data is really unique and being able to then really pinpoint risk factors, not only in the kids when they're growing up, but also look at risk factors in the moms at the same time. Also, even some of the things they're exposed to when they were pregnant with those kids. 

So we have data on both the moms and the kids. So we really wanted to look at what the diets of these kids were like and what the diets of the moms were like, and assess whether diet and the things they were consuming affected their risk of developing overweight obesity later in young adulthood. 

We carefully looked at information tracked on what they were eating, and then assessed whether a substantial component of their diet was related to consumption of what we would consider ultra-processed food, and then assessed whether that consumption of ultra-processed food was associated with their likelihood or risk of developing overweight obesity in the future.

Jonathan Wolf: So what did you find out? 

Dr. Andy Chan: It was very interesting. I think we did find there was an association between child consumption of ultra-processed food and future risk of obesity. Perhaps that wasn't so surprising. 

But what was very interesting in particular was that it also was associated with the likelihood of their moms eating ultra-processed food during that period of time where they were raising their kids. It was sort of an independent risk factor. 

So what the kids were kind of exposed to in the household seemed to actually have a direct influence on whether they were subsequently at higher risk of developing obesity.

We did some additional work looking at the association of moms' diets when they were pregnant with their kids. There seemed to be some association there, not quite as strong, but it does look like early life factors, and particularly maternal risk factors, seemed to be important in determining a child's health over time.

Jonathan Wolf: I heard you mention that it's not just that you're eating more calories if you're eating this UPF, if I understood rightly, that the quality of the food is something that, you know, you were saying actually really makes a difference, and could you help us to understand that?

Dr. Andy Chan: I think what it implies is that a kid's diet has to do with what they're eating, but also has to do with what other foods are being consumed in the house and what they're exposed to. 

So, everyone's diet is also in part, not just their individual food choices, but also what food they have access to. So the idea that a household's access or a household's propensity to be eating ultra-processed food influences our later health, I think, is an important message. 

In addition, I think that it sort of shows kind of a practical association, but also there's biological questions as well. Are there exposures that might be related to differences in exposure to ultra-processed food?

For example, in utero, a mom's diet, does that influence their kids' health. Yes, certainly in the short term, I think we know that a mom's diet obviously affects the newborn period, but does it also have potential effects downstream from that? 

It does raise interesting questions about that, because it is possible that some of the short-term dietary exposures that someone is exposed to when they're in utero, what we call biologically imprinted. Such that it has an influence on their later health status. 

That's, I think, a really interesting possibility and one that's being explored more and more.

Jonathan Wolf: I think you're saying that the food that a mother is eating while she's pregnant could actually affect the health of their child 20 years later. And that if they're eating lots of these ultra-processed foods, that could actually be harming their health 20 years later?

Dr. Andy Chan: It's very possible. I mean, I think that that's really the hypothesis that we're pursuing, trying to disentangle how much of that is what the kid's exposed to, and what they're doing, from what their mom's doing is part of it.

But also, understanding is there an independent effect of what the mom's doing that still has a lingering effect on the child when they get older. And I think that that's the thing that we're really trying to tease out. 

Jonathan Wolf: So, the first thing that I always think whenever this comes up is, it's really, really tough being a mother. There's so much guilt about trying to do a good job when you're pregnant, and then you know when the baby's born, and you're supposed to breastfeed. 

Every time we have this sort of conversation, that is almost just layering on more guilt. On the other hand, I think it's important to understand what the science is saying.

I think we're used to the idea that you shouldn't smoke when you're pregnant. I don't quite understand how it works, but it seems clear that smoking is really bad, and it's not bad just for the nine months that's going on, it's sort of obvious that it's not setting your baby up well.

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I think lots of people will be really shocked to say that UPF foods would be bad. Because I think we mainly associate with, you're just going to eat too much of this, right? It's sort of too yummy. And so you're going to like overeat, and so you might put on weight as a result.

But saying that it's actually long-term harmful sort of makes it sound more in the category of smoking or alcohol rather than, you know, don't eat too many calories. 

Dr. Andy Chan: Yeah, I think it's, it's a very complicated issue, and I'm glad you raised that. 

I think one of the things that we are trying to really avoid is this idea that, you know, there's a stigma around diet and people's food choices. I think that's not our intention whatsoever.

We recognize that mothers, and certainly people in general are doing the best they can, in terms of making food choices. And sometimes, those food choices are dictated by other factors that they don't have control over. 

The kinds of foods that are available to them, in terms of food access, in terms of both economic issues around food access and also economic issues, and where they're living, and their ability to access fresh foods. 

Those are all factors that I think are beyond the control of an individual, but I think it does also suggest the need for us to look at this more closely. 

Because I think if we start to see evidence that maybe some of these factors are important to consider when someone is pregnant, or when they're raising their kids. 

It does have implications for the recommendations we make, both to individual people, but also what we'd recommend as a society, and what we are, what we're willing to offer people as a society, and what we should prioritize as a society in terms of access to food, et cetera. 

There is sufficient evidence to really consider that there is implications for people at every stage.

Jonathan Wolf: So the learnings from this are just as relevant at the point that you are an adult… 

Dr. Andy Chan: At every stage of life, whether you're male or female. I mean, I think these are the kinds of things that we're understanding.

Jonathan Wolf: So at this point, you said you've got this study, and you're eating all of this ultra-processed food is not good.

Do we have any understanding why that is the case? Because I guess that would then help us to understand better what needs to be changed. 

Dr. Andy Chan: Yeah, so I think that's the key question. That's the key next step.

So I think we alluded to this at the beginning, is that we're understanding that ultra-processed food, I think is a useful framework, but I don't think it's sufficient for us to really get at what's cause and effect and also really get at what are the underlying reasons or mechanisms by which some of these foods may be causing health problems, like obesity or cancer. 

It's a useful starting point and a useful framework for us to think about it. But I think we have to do more to understand why it's potentially triggering disease risk, and also what components of ultra-processed food are of specific concern.

For two reasons. One, I think it helps us understand more about disease biology, but second, I think it helps us deliver a little bit more specific, and precise, actionable information for people, so that we can be more deliberate in our recommendations, going forward.

Jonathan Wolf: And what are the theories that I guess you are pursuing? Because I'm pretty sure, Andy, from our many conversations, that you're going to have a bunch of theories about why that might be the case, and that presumably will help you to think about the future studies you're going to design. 

Dr. Andy Chan: Yeah. So, I mean, the question about ultra-processed food is, is it just a question about calories, and food density, and hyperpalatability, is it just that that's why ultra-processed food may be causing these harms? 

In which case, I think our strategy would be different than if it has to do with some of the individual components of ultra-processed food that might be causing a problem.

Like, for example, are there specific things that preservatives in food are actually triggering, that are independent of the calories? 

So, for example, emulsifiers that are being used increasingly to make foods more stable, and make them more palatable. Are emulsifiers potentially doing something specific, independent of the calories?

There is evidence, for example, in animals, that emulsifiers may be for example, affecting our colon or intestines in a way that's detrimental. It could be causing some low-level inflammation, it could be causing difficulty for our gut bacteria to survive in a healthy way.  It may be shifting our microbiome in an unhealthy way.

So, specific components of what we do to process food may be particularly important to identify. Because if that's the case, then we can be more actionable about trying to tailor our guidance to say, let's try to limit the amount of emulsifiers that we're eating, and do more in a way to control that. 

And also understand ways of approaching food to allow us to preserve food in ways that are different.

Jonathan Wolf: I know you're a good scientist, and therefore always cautious about jumping ahead of where everything is proven, Andy, but listening to you, it sounds like you're pretty sure it isn't just calories, as you are talking about this.

Is that right?

Dr. Andy Chan: I don't think it's just calories. I think that it's probably other factors as well, and so that's one of the things that we're obviously trying to drill down on.

Not all food processing is bad. I think there are levels of food processing that are actually probably neutral in terms of health. So, I think we can't lump all food processing in the same category. 

I think we need to classify food processing in different ways to allow us to potentially be more nuanced about our recommendations, and also accept the fact that, to some extent, in our modern society, we can't all just be making food from scratch all the time.

Jonathan Wolf: And I know from the team at ZOE, when you start to really look into the food, that you can see there are two foods that are currently classified as ultra-processed food. One of them might have a small amount of one sweetener, and another one might have 30 different things, each one of which would be viewed as a component that would be UPF.

So there's this huge variation, isn't there, about what's really in our diet, which currently is, unless you can go through all the food labels and understand what they mean, which I think unless you're a leading nutritional scientist, like nobody can, it's all hidden and very confusing.

Dr. Andy Chan: Yeah, it's really a challenge. I think it's not realistic to say you can't, or shouldn't eat any food that has any level of processing. I think that that's an impossible situation to put somebody in, and it's not feasible, and it's probably detrimental to be trying to make that recommendation.

I think we need to be, again, more realistic and also create opportunities for us to understand better what are truly the health effects of ultra-processed food, and are there some ultra-processed foods that are particularly bad. So that we can use this kind of foundation of how we're considering ultra-processed food and deliver something a little more precise.

Diet's important at any age, and so even if you're not seeing immediate health consequences to your dietary choices, there is potential to improve our diet for our future health, which I think is a good message to have. 

I think also, it sets people up for eating in a way that will sustain them through adulthood, so they can continue in a healthy dietary pattern throughout adulthood, which I think is a good message.

I think we're all understanding that this is complicated, and that there are things we can do at every stage of life to improve our health, and that biology is by no means predetermined. 

Jonathan Wolf: So I think, Andy, what you're saying is, the good news is, if I'm listening to this, and I am 60, and I've been eating a diet that's really high in ultra-processed food, for as long as they've been putting ultra-processed food in our diet, it's not too late.

Dr. Andy Chan: I don't think it's too late at any age. I think we just are trying to raise awareness of the importance of thinking about dietary choices at every age. 

But I think clearly, the evidence shows that it's never too late to really adjust one's diet, and also really think about the possibility that if we are parents, that our own dietary choices may have an influence on our kids as well.

Jonathan Wolf: I think, as you know, Andy, one of the things that we've been working a lot within ZOE over the last couple of years is trying to better understand the relative levels of this UPF. For the reasons you've described, that the tools that we've been using up to now just haven't really differentiated it very well.

There’s this famous scale called NOVA that I'm sure you can talk about much more than me, which was the first attempt to try and explain whether something was UPF or not. But it's a fairly crude way to understand things, and didn't really tie up to a lot of the data that we were actually seeing on individuals and the impact on the microbiome.

So, I'm very excited that we're about to release that into the app, for anybody using the ZOE app to be able to start to distinguish between different levels of UPF and also understand whether something actually has UPF at all. 

We are hoping that's going to help to sort of start to push this forward, both in terms of how we're publishing it scientifically, and looking at that, and also just helping people to make better informed decisions.

Dr. Andy Chan: Yeah. 

Jonathan Wolf: One of the reasons that I know that you think it matters, and I'd love to talk about that, is you're working on this team that's studying the rise of these early onset cancers. 

Part of what you've been saying to me is that you think that diets, in general, and potentially UPFs in particular, might be part of this rise.

Dr. Andy Chan: Yeah, I think that that's definitely something we're seeing in the data. I think in some of our early studies, we're starting to see evidence that consumption of UPFs does have a role in the likelihood that someone's developing an early-onset tumor. 

So we, in particular, for example, did a study to look at the consumption of ultra-processed food in younger adults, and did see that there was an association between that consumption, and the likelihood of having a colon polyp, which is a precursor to colon cancer at a younger age. 

I think that that's provocative and interesting data to suggest that some of the trends we're seeing with obesity, and its link to early onset cancer, may in part be related also to diet and ultra-processed food consumption.

Jonathan Wolf: And Andy, you're very calm as you say that, but if I just understood what you said, you're saying consumption of UPF, like eating more UPF, is associated with a higher risk of my getting tumors in my body?  

Dr. Andy Chan: Specifically, these colon polyps, yes. We don't want to be alarmist. I think these are colon polyps that are not cancers, these are cancer precursors. 

So in large part, they're being diagnosed by individuals, and being removed to prevent that cancer from developing. So I think there is still something actionable for people to do.

But I think it does raise this question again of, we see this in humans, can we also see if this is something that holds up in some of our animal models, and our experimental models to kind of get at the mechanism again, to understand sort of why that might be something we're seeing.

And is there something specific about the foods that are playing a role in this risk? 

Jonathan Wolf: I mean, it does sound like yet another data point you're presenting to us here about why you'd rather be eating less UPF, and that it is doing something to us. It isn't simply just that it tastes so good that we're going to eat more of it.

Dr. Andy Chan: Yeah, I think so. 

And then the other component of that research, which I think is consistent with what you're doing at ZOE, is trying to not just use these very broad categories of UPF, but trying to understand, are there specific types of UPF that may be more harmful than others? 

So, I think as we mentioned, the NOVA classification and some of these early classification schemes are really good starting points, because it helps us to frame the question, and it helps us to do some of the initial work in this field.

But I think we are at a point where we're starting to identify, within categories of NOVA, within categories of UPF, there's probably differences in sort of the potential detrimental effects. 

So, we, for example, want to take some of these UPF categorizations and see do they link up with specific changes in some of the biological markers of overweight, obesity or biological markers of heart disease or cancer?

Jonathan Wolf: And Andy, this is because UPF is very complicated, isn't it? 

It could be that there's all these different preservatives, and all these emulsifiers, and all these sweeteners, and then there's the stuff that they don't even have to put on the label. To do with just, how they might take a raw material that seems normal, like, I don't know, a grain, and they can sort of smash it up, and reorganize it, and they can still call it a grain, but actually it doesn't look anything like the chemical did before. 

So that's a lot to try and figure out, isn't it? 

Dr. Andy Chan: Yeah. And we don't know what steps in that process are harmful, and what has been created isn't necessarily harmful. It may not be. 

So I think we need to test that. 

Jonathan Wolf: So it's going to keep scientists busy for a long time.

Dr. Andy Chan: I think so, yeah. 

Jonathan Wolf: Brilliant. Well, look, I would like to transition now to actionable advice. 

I think anyone listening to this is probably saying, you know what? I definitely wouldn't want to increase the amount of ultra-processed food I'm eating, and I'm interested in reducing it, for myself and probably for my family.

But we also started by saying, well, half the food that you're cooking at home probably has ultra-processed food in it. So is it inevitable, or are there things that people could do to reduce their consumption that don't require some completely radical change to how they live?

Dr. Andy Chan: Yeah. I think I wouldn't say 50% of the food we're cooking at home is ultra-processed. I would say 50% of the food we're consuming as a society may be ultra-processed. 

I think in general, kind of a rule of thumb that I like to think about, is that if you are able to make it at home on your own, in a way that would appear to be in your kitchen, that that probably is a diet and a food choice that is less likely to be ultra-processed.

That being said, I mean, there's things that we're probably cooking at home that do have levels of processing, but I think for the most part, those are easier for us to identify. 

I think in general, if we're creating food in our kitchen, and it's something that we prepared in our kitchen, it probably is less ultra-processed.

Jonathan Wolf: And when you say prepared, we're taking a packet out of the fridge and putting it in the microwave and turning it on for three minutes as the meal. Does that count? Is that the making it at home? 

Dr. Andy Chan: No, I mean prepared from raw ingredients. Prepared from its original ingredients as opposed to something that you're sort of heating up.

Jonathan Wolf: Yeah. Got it. Because I think one of the things that we've seen is that those sorts of ready-prepared meals could often be incredibly high in ultra-processed food. Much more than you would expect.

I think part of this is because they're trying to sort of preserve it all, and make it last much longer than it would do if you made your spaghetti meatballs or whatever it is at home. 

The fact that it looks like a sort of home-cooked meal, is that enough to know that it doesn't have quite a lot of UPFs in it? 

Dr. Andy Chan: I think it's a first step, but I think a more precise way would be if you could make it from ingredients that are more likely to come from scratch. 

So if you're making spaghetti meatballs, if you're using fresh tomatoes as opposed to a bottled sauce, I think that clearly differentiates a food choice that's higher in ultra-processed food. The canned sauce versus something that's lower in ultra-processed food. 

Jonathan Wolf: And when you looked at the data from your study, are there particular things that are really driving this high level of ultra-processed food that people might be eating, and therefore, you're saying this is the stuff that you should be trying to figure out how to reduce?

Dr. Andy Chan: Yeah, I mean, in that study as a starting point, we were just using the NOVA classification. So we hadn't yet gotten to the point where we're able to kind of drill down into more specifics. 

I think that would be kind of the next step is again, trying to understand more about, within these categories, these broad categories of ultra-processed food, can we untangle something that may be more specific?

Jonathan Wolf: Are there any other tips you would have for people beyond saying, the more that you can make it from scratch is going to be better, that could help with reduced UPF? 

Dr. Andy Chan: I mean, I think in general, when you're looking at the foods you're buying, checking the ingredients list is certainly helpful.

I think if you're seeing a lot of things on that ingredient list that you don't recognize, I think that's generally a sign that that probably is more ultra-processed than something that has just a smaller number of ingredients, and sort of things that are easy to recognize. 

So, the more ingredients on a list, and the more chemical names you don't understand, I think that's a general rule of thumb to kind of give you a sense of what's more ultra-processed than not. 

Jonathan Wolf: I find that a very helpful rule of thumb, if I'm not using the app. Because yes, you see all these things, you have no idea what they are, and it's a little bit of a red light, right? It's like, I don’t know why that should all be here. 

Now we're talking a lot about what individuals can do. Is there anything about the food environment as we're outside our home, whether that's the school, or maybe there's a canteen at the place that you work, or even just thinking about the sort of restaurants that you're going to eat at lunchtime when you're at work.

Dr. Andy Chan: I mean, I think that that's obviously another layer to this. I think delivering individual recommendations for people and things that we can do as individuals is important, and that's a first step. 

But I think we can have a broader impact by trying to be better at tailoring the kinds of foods that we are offering people in their home and in their work environment, in their communities.

And that, I think, has to do with being more thoughtful about availability of food in different communities. So, making sure that we're making efforts as a society to provide better access to food that is less processed, to people in different communities. And that has to do with foods, you know, available in grocery stores, but also foods available in things like cafeterias and canteens, and schools.

Then also I think being careful to think about food labeling, and making sure that we're being very thoughtful about food labeling and what foods are labeled, and making sure that they're labeled accurately. And, trying to, I think, raise a little bit more awareness about what are things in foods, that we're eating on a regular basis.

I think that that's a society-level thing also that could have a meaningful impact.

Jonathan Wolf: I understand that in the States, for example, the rules about what you need to put on a label, even what you need to tell the FDA about, basically means you can add all sorts of ingredients into your food. You don't need to tell the FDA, and you just say, I know it's safe. 

Dr. Andy Chan: Yeah. I mean, I think that there is, you know, going to hopefully be a little bit more transparency about food labeling going forward.

I think as we start to understand more about the impact of processing on our health, that will hopefully come with a little more attention to what we're requiring people to provide in their labeling. 

That's a clear kind of step that I think we should be thinking about taking. And I think that has to do with what's in the grocery store, but also has to do with what you're buying in a fast food restaurant.

Jonathan Wolf: Yeah. I mean, if you can't even know what's in the food, you definitely don't have any choice to avoid it. 

Dr. Andy Chan: And you can hide a lot, obviously in food. 

Jonathan Wolf: I find this, and it's obviously worse in the U.S. than it is in Europe. In this particular context, it's a bit shocking, honestly.

Now, if someone's listening to this and they're saying, it's really clear for me. But I'd really like to try and also improve the habits of my kids. Are there any habits that you could somehow try and instill that might help them to reduce the amount of ups they're eating? 

Dr. Andy Chan: Well, as parents, I think we do have control over what's in the house, right?

So, depending on the age of your kids, your kids are probably consuming largely what's available to them easily, around them. So what you're buying and what you're putting in the house, obviously, will be a good way to provide some safeguards in terms of what kids are exposed to and what they're eating.

I think your kids will also obviously be able to gauge your own food choices. I think if you make choices individually, to eat in a certain way, I think your kids will see that and hopefully, that'll be a model for their own dietary choices when they get older.

And then I think if you are involving them in food choices that you're making when you're shopping or when you're at a restaurant, and giving them some explanations around what you're choosing, I think that also is an initial educational step that you can make. 

Jonathan Wolf: I love all of those.

The one other one I would add, that I have found most effective, is if I think about my daughter, who's still five, the thing that she's found really powerful is that I have all of these gut microbes inside me, and they need to be fed. They like these plants, and fruit, and vegetable, and that's what they need.

That has been a much stronger argument for her to think about why she needs to have that as part of her food. So it's additive. So it's rather than taking everything else away, it's like, well, you know, you haven't had any apricots, and you want to make sure you feed your good bugs.

Interestingly, it's a much more powerful story than you just have to do this in order to be healthy. You know?  It doesn't really make any sense. So that would be the other one, I would say, genuinely, I have seen have an effect on at least my kids' behavior. 

Dr. Andy Chan: That's interesting. Spin it in a positive way, and also kind of take advantage of kids’ good nature and benevolence to do good. 

Jonathan Wolf: Yeah. We're very big believers here at ZOE about you want to think about what you add, and what is positive. Because ultimately this is about making  lifelong changes that you can support. 

And also, food is meant to be enjoyed, right? So if you make everything seem miserable, then it's sort of like you take away one of the great pleasures in life.

I think we could probably get rid of a lot of UPF, though, without losing a lot of the pleasures in life. But I think that makes sense. 

Andy, I'm going to try and do a quick summary from today, and thank you so much for taking us through this study. 

I think the thing that sticks in my mind as most shocking is consumption of ultra-processed food is associated with a higher risk of tumors in my gut, in my body.

That's pretty shocking because I don't think anyone listening to this is going to feel that that's what they want to have happen as a result of their food. So this UPF thing is real. 

The diet that we eat when we're children, or even when we're pregnant, affecting our kids, can then have this real impact on health 20, 30, 40 years later.

And that in particular, what you've been discovering is the ultra-processed food is an important risk factor. So it's not just that you are eating too many calories, it's not just that maybe you've got higher rates of obesity, because of calories, but actually this ultra-processed food itself is having an impact.

And we're eating a lot of it. I was hearing 50 to 75% of the food that we're eating today is ultra-processed, and a lot of it is hidden. So it's not in the Doritos bag anymore. It's actually in the dinner that looks really nice that you bought at the supermarket that's in the fridge and you're going to put in the microwave or the oven.

On the positive side, what you've also said is, we're not doomed by the choices we made when we were children, or what our mother ate. If you're listening to this 40, 50, 60, 70, 80, it doesn't matter. You can actually change your diet today, reduce those ultra-processed foods, and it really will have an impact on the future.

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And then we talked a bit about what you can do, and I think we talked about the fact that today it's hard to understand whether something is ultra-processed or not. 

I discussed the fact that for people listening who are using the ZOE app, that actually there's this new capability to do that. But in general, it's been hard. 

The best thing you can do is just turn it over, and look at the ingredient list, and if there's a lot of things you can't recognize, that's a guide that this is clearly an ultra-processed food.

Critically, I think, Andy, what you are saying is anytime you can make it at home, rather than it be completely pre-prepared, you're likely to reduce the level of ultra-processed food a lot.

You gave this example a couple of times, which I think most people were really shocked to think that a tomato sauce would be ultra-processed. Right? That seems really natural.

But it's interesting, a couple of times now you’ve given that as an example is don't use the sort of pre-prepared tomato sauce. If you could just make it from chopped tomatoes, that's actually going to make a big difference in the level of UPF you're eating. 

Dr. Andy Chan: That sounds like a good summary. 

Jonathan Wolf: If you enjoyed this episode with Andy, I highly recommend our previous conversation with him, which you can watch here where we dive into the rise of colon cancer in younger people.

Thanks for watching, and see you next time.