ZOE Science & Nutrition - Harvard Doctor: Obesity, cancer, and the real cost of convenience food | Dr. Andy Chan

Episode Date: May 29, 2025

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.  Our guest is Dr. Andy Chan, a Harvard professor and leading expert on gut health and cancer prevention. He heads the Clinical and Translational Epidemiology Unit at Massachusetts General Hospital and has published over 400 scientific papers. 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. Unwrap the truth about your food 👉 ⁠Get the ZOE app 🌱 Try our new plant based wholefood supplement - Daily 30+ Follow ZOE on Instagram. Timecodes 00:00 How much of our food is ultra-processed? 02:24 Can UPFs increase cancer risk in children? 04:48 Why our kids get sicker, earlier 07:12 How convenience took over our food choices 09:36 Are food companies engineering addiction? 12:00 UPFs and early onset cancer 14:24 Why calorie counting misses the point 16:48 Can a mother’s diet shape her child’s future health? 21:36 Is a poor diet as harmful as smoking in pregnancy? 26:24 Preservatives vs calories: what’s more harmful? 28:48 Brand new science: not all UPFs are equal 31:12 ZOE’s new processed food risk scale  38:24 Why UPF labels are misleading and confusing 40:48 A simple trick: how to spot UPFs on food labels 43:12 Should schools and offices be UPF-free zones? 45:36 How to shape your kids’ eating habits for life 📚Books by our ZOE Scientists The Food For Life Cookbook Every Body Should Know This by Dr Federica Amati Food For Life by Prof. Tim Spector Free resources from ZOE Live Healthier: Top 10 Tips From ZOE Science & Nutrition Gut Guide - For a Healthier Microbiome in Weeks  Mentioned in today's episode Trends in Adults’ Intake of Un-processed/Minimally Processed, and Ultra-processed foods at Home and Away from Home in the United States from 2003–2018, 2025, The Journal of Nutrition Ultra-processed food intake in toddlerhood and mid-childhood in the UK: cross sectional and longitudinal perspectives, 2024, European Journal of Nutrition The Healthfulness of the US Packaged Food and Beverage Supply: A Cross-Sectional Study, 2019, Nutrients Ultraprocessed Food Consumption and Cardiometabolic Risk Factors in Children, 2024, JAMA Network Open Maternal consumption of ultra-processed foods and subsequent risk of offspring overweight or obesity: results from three prospective cohort studies, 2022, British Medical Journal Have feedback or a topic you'd like us to cover? Let us know here. Episode transcripts are available here.

Welcome to ZOE, Science and Nutrition, where world-leading scientists explain how their research can improve your health. Today, Harvard Medical School Professor Dr Andy Chan reveals new research showing that around half the calories that we eat at home are ultra-processed. around half the calories that we eat at home are ultra-processed. Even the meals that we trust as homemade and healthy – stir-fry, salads, even Grandma's famous soup – could be hiding lab-engineered ingredients you'd never expect. Now we serve this food to our families every day, but at what cost? Andy's research exposes how ultra-processed foods don't just lead to obesity. They rewire appetite and may even accelerate early onset cancer. He challenges the myth that younger people can eat anything and still grow up healthy.

But there is hope. Andy reveals the worst ultra-processed offenders, the easiest food swaps, and how small changes by parents, schools, even policymakers could rewrite the future of our health. Dr. Andy Chan is a professor at Harvard Medical School, a doctor at Massachusetts General Hospital, and leads a team tackling early onset cancers. As a member of ZOE's Scientific Advisory Board, he's here to arm you with the latest research so you can make smarter food choices. Andy, thank you for joining me today.

Happy to be here. Now, I think you know we like to kick off this show with a rapid fire Q&A with questions from our listeners. And just a reminder of the rules, say yes or no or a one sentence answer if you have to. Okay. Are ultra-processed foods making us sicker at a younger age? Yes, probably. Could there be ultra-processed foods in a home-cooked meal? It depends on how you define home-cooked.

Is there a simple way to know if a food is ultra processed? I think there are methods we can use to help people identify ultra processed food. Are ultra processed foods engineered to make us want to eat more? Many are, yes. Could a child's diet impact their likelihood of developing cancer later on? Yes. Finally, you can have a whole sentence. What's the most common misconception about ultra-processed foods? That it's a binary thing, that there's either ultra-processed or

healthy. I think there's a gradation. Most of us have this idea that ultra-processed foods mostly come from like a fast food chain or like snacks that we buy from the corner store. But I was shocked when my producer told me, you know, as we were 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, you know, 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 understand like what is ultra processed food

and how is it possible that there can be so much of it at home? 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. So you're saying it's not just Doritos, what is it? All food to some extent that is purchased,

that is somewhat ready-made or has been prepared to easily consumed has a level of processing. And so there are sort of industrial processes by which you know The food industry has put food and made it more accessible for people to eat in sort of modern society I Think that the the sort of 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 and 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 and also they're made more nutrient dense, so there's more kind of calories in the food, and also they're made to be tastier so that people can eat them and enjoy them in a more sort of quick fashion.

And Andy, I was growing up in the 80s, and people are definitely talking about junk food in the 80s, so is this just like a new term for something that is the same that we've always had? You know, was I eating as much ultra processed food in 1980 as, you know, my kids are likely to be eating today in 2025? It's gradually increased to some extent. I think that when we use the terminology ultra processed food to incorporate kind of 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 kind of more hidden than it had been in the past, and that has gradually risen. So now we estimate that, for example, in the US 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.

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

driving some of this increase. And then I think there has been, I think, this idea that over time, as people have become more accustomed to kind of the taste, if you will, of ultra-processed food, our palates have maybe adjusted such that people are now seeking out those kinds of foods more and more as kind of foods that they enjoy

and sort of trigger some of the reward mechanisms in our brain to make us sort of seek out these foods. 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. And we've seen that clearly in the classic Western countries or countries that are sort of high income,

but that's gradually becoming more prevalent in other parts of the world. And that's reflected, I think, in sort of 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. I'd like to share something exciting. Back in March 2022, we started this podcast to uncover how the latest research can help us live longer and healthier lives. We've spoken to leading scientists around the world doing amazing research. And across hundreds of hours of conversations, they've revealed key insights that can help you to improve your health. If you don't have hundreds of hours to spare, no need to worry.

At the request of many of you, our team has created a guide that contains 10 of the most impactful discoveries from the podcast that you can apply to your life. And you can get it for free. Simply go to zoe.com slash free guide or click the link in the show notes and do let me know what you think of it. Okay, back to the show. And Andy, when I hear you talk about sort of convenience and changing taste, it feels like this is all driven by like 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 like 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 any of the health impacts that might come from UPF. Is that all scaremongering or is this true? 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. And 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.

And 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. I actually had a conversation with a food scientist who worked for a company that I won't name who described just year after year, testing different variants. And 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 like 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?

Yeah, I mean, I think there's very clear evidence that that's happening. I think we're also seeing 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.

And 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. 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? I think it looks like that may be the case. I think it seems like, you know, the early evidence is that these drugs are, you know, also affecting our preferences in terms of the kinds of foods

we're choosing to eat. And that may have to do with kind of the shift in sort of our brain gut access and trying to sort of shift our preferences as to the kinds of foods that make us feel full and the kinds of foods that we enjoy. There's something slightly crazy here, isn't there? So we eat all of this food that, you know, we were never evolved to really eat steadily over 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 on the supermarket stores would probably never get us there in the first place. That's how I understand it. There's a bit of a swing, you know, I think it's an interesting way to look at it. But I think, you know, it's the population shifts that I think are what drive maybe what we're seeing being offered more and more by the food industry. It's really interesting.

I know your studies a lot look at those sort of overall population shifts. So I'd actually love to go down to this individual study that you published, you know, 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 like, are these ultra processed foods making us sicker at a younger age? And 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. Well, I think that this really came out of our desire to understand a little bit more about why we're seeing this trend in obesity rates. We've clearly seen in the US and other countries that obesity

has risen dramatically in the population. And 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 you know, 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 be not 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. So we really wanted to kind of 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're seeing more and more rates of cancer in younger people. I think that that's an area that I've particularly focused on is trying to understand what are the reasons for why younger people are getting cancer. So because of people, I think that that's an area that I've 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 maybe some of these things that we're thinking about as being risk factors for disease later in life are actually shifting into younger ages. So 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.

And Andy, is it only cancer that is increasing in younger people? 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 sort of metabolic diseases and inflammatory diseases happen at earlier ages. And that probably reflects what we're seeing in cancer as well. And when you say younger people, the older I get, the more I want that to include me. What do younger people mean as you're talking about that as a doctor and a scientist? 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. And that's really why most of the common cancers that we screen for, we start that screening at the age of 50. And so I think in the sort of common definition of early onset cancer for our studies, we've really been focused on people younger than 50. Could you maybe summarize the study, what you did and the findings? 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 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. So 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 Nurses' Health Study 2. And these were a group of female nurses in the US that have been tracked with questionnaire data since the early 1990s. So this is like a 35-year study at this point. 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 tracked over the last 30 years. And so having sort of 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. And also even some of the things they're exposed to when they were pregnant with those kids. So we have kind of data on both the moms and the kids. So we really wanted to 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. So 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 associated with their likelihood or risk of developing overweight obesity in the future.

So what did you find out? 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. And 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 mom's 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 seem to be important in determining a child's health over time. I heard you mentioned that it's not just that you're eating more calories

if you're eating this UPF, if I understood rightly, that sort of the quality of the food is something that you were saying actually really makes a difference. And could you help us to understand that? Yeah. I mean, 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 kind of what they're exposed to. So sort of 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 their later health, I think, is an important message. In addition, I think that that shows a practical association, but also

there's biological questions as well. Is 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 kid's 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? And it does raise interesting questions about that because it is possible that some of the sort of 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. And that's, I think, a really interesting possibility and one that's being explored more and more. I think you're saying that the food that a mother is eating while she's pregnant could actually affect sort of the health of their child like 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?

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 sort of what the kids exposed to and what they're doing from what their mom's doing is part of it, but also, you know, understanding is there an independent effect of what the mom's doing is part of it, but also, you know, 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. I mean, so the first thing that I always think whenever this comes up is it's really, really tough being a mother. Like, there's so much guilt about trying to do a good job, you know, when you're pregnant and then, you know, when the baby's born and you're supposed to breastfeed and every time we have this sort of conversation that is almost just like 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 sort of clear that smoking is really bad and it's not bad just, you know, for the nine months that's going on. It's sort of obvious that it's not setting your baby up well. I think lots of people will be really shocked to say that you PF foods would be bad because I think we mainly associate with you're just going to eat sort of too much of this, right? It's sort of too yummy. And so you're going to overeat and so you might put on weight as a result, but saying that it's actually like long-term harmful sort of makes it sound like more in the category of smoking or alcohol rather than, you know, don't eat too many calories.

Yeah, I think 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 and we recognize that mothers and certainly people in general are doing the best they can in terms of making food choices and sometimes, you know, 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 sort of recommendations we make both to individual people, but also what we recommend as a society and 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. So the learnings from this are just as relevant at the point that you're an adult. At every stage of life, whether you're male or female. I mean, I think these are the kinds of things that we're kind of understanding.

So at this point, you said you 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. 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. And what are the theories that I guess you're 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 as you think about the future studies you're going to design. Yeah. So, I mean, the question about ultra-processed food is, is it just a question about calories and food density and sort of hyper-palatability? 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 kind of 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. And 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. The show you're listening to right now that's providing you the latest evidence-based health and nutrition information from the world's top scientists. While making it takes a lot of time, we think it's well worth it, all in the name of improving

your health. All we ask in return is this, send a link to this podcast to someone you think would benefit. And if you haven't already, click follow this podcast wherever you're listening right now. Okay, let's get back to the show. 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're talking about this.

Is that right? I don't think it's just calories. I think that is 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, you know, probably not neutral in terms of health. And so I think we can't lump all food processing in the same category. So I think we need to classify food processing in different ways to allow us to potentially be, that you can see that there are two foods that are currently classified as ultra processed food.

And one of them might have a small amount of one sweetener and another one might have like 30 different things, each one of which would be viewed as like 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 sort of, you know, unless you can go through all the food labels and understand what they mean, which I think unless you're like a leading nutritional scientist, like nobody can, it's all hidden and very confusing. Yeah, it is. 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, hopefully, 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. And I think also it sets people up for eating in a way that will sustain them through adulthood so they can kind of continue in a healthy dietary pattern for 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. So I think, Andy, what you're saying is the good news is if I'm listening to this and I'm 60 and I've been eating a diet that's like really high in ultra processed food, you know, for, you know, as long as they've been putting ultra processed food in our diet, it's not too late.

Yeah, I don't think it's too late at any age. I think, you know, we just are trying to raise awareness of the importance of thinking about dietary choices at every age, but I think clearly 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.

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. This is 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 app to be able to start to distinguish between different levels of UPF and also understand whether something actually has UPF at all. And we're 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.

Yeah. And 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 starting 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? 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 sort of 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. And so 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.

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. Specifically these colon polyps, yes. Yeah.

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, you know, playing a role in this risk? 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. Yeah, I think so. And then the other component of that research, which I think is sort of consistent with what you're doing at ZOE,

is trying to not just use these very UPF, but trying to understand are there specific types of UPF that may be more harmful than others. So, you know, 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 EPF, there's probably differences in the potential detrimental effects. And so, you know, 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, you

know, overweight, obesity, or biological markers of heart disease or cancer? And Andy, this is because UPF is very complicated, isn't it? It could be like 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? Yeah, and we don't know what steps in that process are harmful.

And what has been created, is it necessarily harmful? It may not be. So I think we need to test that. So it's going to be keeping scientists busy for a long time? I think so, yeah. Brilliant. Well, I would like to transition now to sort of actionable advice. You know, 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, you know, for myself and probably for my family. But we also started by saying, well, like half the food that you're cooking at home probably has ultra-processed food in it. So is it inevitable or is there things that people could do to reduce their consumption that don't require some completely radical change to how they live?

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 kind of 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. And 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. And when you say prepared, would taking a packet out of the fridge and putting it in the microwave and turning it on for three minutes as the meal, right?

Does that count as, is that the making it at home? Is that gonna- No, I mean, prepared from raw ingredients, prepared from its original ingredients, as opposed to something that you're sort of heating up. 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, like 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 and 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? I think it's the 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, you know, scratch.

So if you're making spaghetti and meatballs, if you're using, you know, fresh tomatoes, as opposed to a bottled sauce, I think that clearly differentiates a group of food choice that's higher in ultra-processed food, the canned sauce versus something that's lower in ultra-processed food. And when you look to the data from your study, are there particular things that are really driving this sort of high levels of ultra-processed food that people might be eating and that they're saying this is the stuff that you should be trying to figure out how to reduce? 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 were 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? Do you know someone who wants to improve their health and doesn't know where to start? Why not share this episode with them right now? It's a chance to help them see what's really on their plate,

backed by the latest science. They'll thank you for it. Are there any other tips you would have for people beyond saying like the more that you can make it from scratch is going to be better that could help with reducing cupia? I mean I think in general when you're looking at the foods you're buying, you know checking the ingredients list is certainly, you know, 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, you know, just a smaller number of ingredients and sort of things that are, you know, easy to recognize. So the more sort of ingredients on a list and the more kind of 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. I find that a very helpful rule of thumb if I'm you know if I'm not using the app because yes you see all these things you have no idea what they are it's a little bit of 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 at home, whether that's like 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 to eat at lunchtime when you're at work? Yeah, I mean, I think that that's obviously another layer to this. I think sort of 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 and 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 available in grocery stores, but also foods available in things like cafeterias and canteens and schools. And 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. And I think that that's a society-level thing also that could have a meaningful impact. I understand that in the States, for example, the rules about what you need to put on the 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. You just say like, I know it's safe.

Yeah. I mean, I think that there is, you know, going to hopefully be, you know, 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 it also has to do with what you're

buying in a fast food restaurant. Yeah. I mean, if you can't even with what's in the grocery store, but it also has to do with what you're buying in a fast food restaurant. Yeah, I mean, if you can't even know what's in the food, you definitely don't have any choice, right? To avoid it. And you can hide a lot, obviously, in food. Yeah, I find this, and it's obviously worse in the US 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 UPFs they're eating? 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, what you're putting in the house obviously will be a good way

to sort of 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 sort of food choices. I think if you make choices individually to eat in a certain way, I think your kids will sort of 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 a sort of initial educational step that you can make. 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 like, I have all of these gut microbes inside me

and they need to be fed. And 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 like additive. So it's rather than like taking everything else away.

It's like, well, you know, you haven't had, you know, any apricots and you want to make sure you feed your good bugs. And interestingly, it's a much more powerful story than you just have to do this in order to be healthy. You know, like it doesn't really make any sense. So that would be the one other one I would say genuinely I have seen have an effect on at least my kids behavior.

That's interesting, spending it in a positive way and also kind of take advantage of like kids good nature and benevolence to do good. Yeah, we're very big believers here at Zoey about like, you want to think about what you add and what is positive because ultimately this is about making like lifelong changes that you can support. And also food is meant to be enjoyed, right? So if you like make everything seem miserable, then it's sort of like you take away

one of the great pleasures in life. I think we can probably get rid of a lot of UPF though, without losing a lot of the pleasures in life, but I think that makes sense. And yeah, I'm gonna try and do a quick summary from today. And thank you so much for taking us through this study. The thing that sticks in my mind is like most shocking is consumption of ultra processed food is associated with a higher risk of tumours 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 that ultra processed food is an important risk factor. So it's not just that you're eating too many calories. It's not just that you're going, maybe you've got higher rates of obesity because of calories, but actually it's ultra processed food itself is having an impact. And we're eating a lot of it.

I was hearing like 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, you know, 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 like the choices we made when we were children or you know, what our mother ate.

You know, 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. And then we talked a bit about what can you 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 sort of a guide that this is clearly an ultra processed food. But critically, I think, Andy, what you're saying is, anytime you can sort of make it at home rather than it be completely pre-prepared, you're likely to reduce the level of ultra-processed food a lot.

And you gave this example a couple of times, which I think most people were really shocked to think that sort of a tomato sauce would be ultra-processed, right? That seems really natural, but it's interesting. Like a couple of times now you can, that's an example, is like don't use the sort of pre-prepared tomato sauce. If you could just make it from like chopped tomatoes, that's actually gonna make a big difference

in the level of UPF you're eating. That sounds like a good summary. Now, if you listen to the show regularly, you already believe that changing how you eat can transform your health, but you can only do so much with general advice from a weekly podcast. If you want to feel much better now and be on the path to live many more healthy years, you need something more. And that's why more than a hundred thousand members trust Zoe each day to

help them make the smartest food choices. Combining our world-leading science with your Zoe test results, Zoe is your daily companion to better health for life. So how does it work? Zoe membership starts with at-home testing to understand your unique body. Then Zoe's app is your health coach using weekly check-ins and daily guidance to help you shift your food choices to steadily improve your health. I rely on Zoe's advice every day, and truly it has transformed how I feel.

Will you give Zoe a try? The first step is easy. Take our free quiz to find out what Zoe membership could do for you. Simply go to zoe.com slash podcast, where as a podcast listener, you'll get 10% off. As always, I'm your host, Jonathan Wolff. Zoey's Science and Nutrition is produced by Julie Pinero, Sam Durham and Richard Willen. The Zoey's Science and Nutrition podcast is not medical advice and if you have any medical concerns, please consult your doctor. See you next time.