ZOE Science & Nutrition - How your food choices affect the planet

Episode Date: September 15, 2022

Our planet is overheating. Human society is creating too much carbon dioxide, stopping the sun’s warmth from escaping back into space. As earth gets hotter, its ice caps are melting, causing sea levels to rise, and submerging entire communities. Floods, droughts, and wildfires are already becoming much more common. Some effects of climate change are now irreversible, but there is still hope, and adjusting what we eat might play a bigger part than you’d imagine. In this episode, Jonathan speaks with a pioneer in science who will help you understand how your eating habits affect the planet, so you can make informed decisions about the foods you eat and how you prepare them. Sarah Bridle is a professor of food climate and society at the University of York in the United Kingdom. She is on the vanguard of a new field, and her research carefully measures the exact effects of the foods we eat on climate change.  Download our FREE guide — Top 10 Tips to Live Healthier: https://zoe.com/freeguide Timecodes: 00:00 - Intro 00:10 - Topic introduction 01:34 - Quickfire questions 03:14 - Why does climate change matter? 05:40 - Why does food matter for reducing climate change? 07:44 - Understanding how different foods affect the climate 11:32 - Do I have to go vegan to help stop climate change? 13:14 - Are all meats equal in terms of their climate impact? 16:20 - How do by-products of animals impact climate? 17:22 - Carbon footprint of milk alternatives 19:51 - Is a baked potato good for the planet? 21:42 - Other things that impact climate change to consider 23:33 - Food miles vs air miles? 26:48 - Are avocados killing the planet? 28:05 - Avocados’ water consumption 28:44 - Packaging 34:34 - Food waste 35:20 - Can a sustainable diet be affordable? 36:39 - 3 things to do to reduce your impact on climate change 38:58 - Summary 40:22 - Goodbyes 40:49 - Outro Episode transcripts are available here. Follow Sarah: https://twitter.com/sarahbridle Get Sarah’s book here. Follow ZOE on Instagram: https://www.instagram.com/zoe/ This podcast was produced by Fascinate Productions.

Welcome to ZOE Science and Nutrition, where world-leading scientists explain how their research can improve your health. Our planet is overheating. Human society is creating too much carbon dioxide, stopping warmth from the sun escaping back into space. As our planet gets hotter, its ice caps melt, causing sea levels to rise and submerging entire communities. Floods, drought and wildfires are already becoming much more common. I'm recording this during sweltering heat on the hottest day in the UK's history.

Some of the effects of climate change are now irreversible. But there is still hope. We can all play our part to avoid total disaster. And guess what? Adjusting what we eat might be a much bigger part of this than you'd imagine. This is a very important subject, so I'm delighted to be joined today by Dr. Sarah Bridle, Professor of Food, Climate and Society at the University of York. Sarah is a pioneer in this new field, and her research carefully measures the exact impact of the food you eat on climate change. This episode will help you understand how your eating habits affect the planet, so you can make informed decisions

about the foods you eat and how you prepare them. Professor Sarah Bridle, thank you for joining me today. It's a pleasure. Thanks for having me. Let's start as always with our quickfire questions. So the first is, do I have to go vegan to save the planet? No. Oh, I thought maybe we all had to be vegan. All right, let's go on to the second question. Is a baked potato a great food to reduce my carbon footprint? Oh, I'm really torn on that one. I'm going to go for the one sentence answer, which is yes, but it depends on how you cook it, what you eat it with.

And that was a trick question because we've been talking about the baked potato earlier as an example of how this can be difficult. So we'll come back afterwards to why a baked potato, which after all is a locally grown food, it's a vegetable, sounds like it can be difficult. So we'll come back afterwards to why a baked potato, which after all is a locally grown food, it's a vegetable, sounds like it should be perfect. So why sometimes this is more difficult than you think. What would you say to someone who thinks there's little point in changing what they eat to combat climate change? Well, I think the main thing people don't really know is actually food contributes about a third of all climate change. And so actually what you eat and the choices you make turn out to have quite a big impact depending on what we all do collectively

together. Brilliant. And I have a second question. Sarah, what's the one thing I can do today to help save the planet? Well, finding out about the foods that you eat that are the most impactful for climate change and then thinking about the quantities and maybe the frequency of those foods. And for most people, on average, in the UK and the US, for example, that tends to be animal products. So what of those might you maybe eat a bit less of? And then what else could you add in? Maybe some fruit and veg and things that are more healthy and good for the planet at the same time. Brilliant. Okay, so why don't we start at the very beginning, Sarah? Why does climate change matter at all? Well, so we're heating up the planet. That's the sort of global heating kind of element of climate change. And that heating of the planet is actually causing extreme

weather events as well. So droughts, floods, wildfires coming from that, for example. And actually, for me, with an obsession about food, the most worrying aspect of that is the impact of those extreme weather events and the general warming of the planet on food production. So food is being influenced and affected and harvests are being lost due to droughts, for example. And that is going to have an impact on how much we can feed the planet and how, therefore, potential issues with trading foods. Are people still going to be happy trading foods between countries after there's been a drought and affecting what we can grow? So there's really worrying implications of us all having a lack of food and potential conflicts, that sort

of thing. That definitely sounds about right. I guess a lot of people may be listening and saying, hey, the earth is going to get a couple of degrees warmer. Actually, plants grow better when it gets warmer, right? For those of us who are gardeners. So you might have thought, actually, there'll be much more food, but that doesn't seem to be the story that you're telling. Yeah. So it does depend on where you are on the planet. So there are some places, I think it's Iceland, which will be able to grow more food. But on the other hand, on average, globally, if we look at, for example, in the middle of continents, we've got a lot more heating there, 10 degrees heating there, even if you've only got on average a global increase of,

say, two or three degrees, it's a lot bigger in some places than others. And that on average is going to have a decrease in food production just due to the increase in temperature. And then if we also look at the extreme weather events, those are happening in a more coherent way. So due to the warming of the poles, we actually have more, for example, heat waves happening across, say, the whole of the northern hemisphere, which then mean that multiple food production places get knocked out at the same time, which then has a much bigger impact on how we respond globally. And I think many of us who are listening to this are definitely conscious that there are more extreme weather events than before. I'm sitting here in London, in my home up in the attic. When I grew up in London, I can tell

you, it was never hot in the summer ever. So no, it's going through this big heat wave at the moment, and it's pretty unbearable. So I guess, you know, I think there are many people who see that in their own lives. So climate change is obviously not good in general, specifically not good for food production. Why does food matter, however, for reducing climate change? Yeah, so actually, it turns out that about one third of all climate change is caused by producing food. And so actually, that's bigger. If we group it like that, that's bigger than, for example, transport or heating. So one third, that's amazing. That's like huge. Yeah, so that includes clearing land for agriculture, so deforestation. It includes

applying fertilizer to the soil to grow crops for animals to eat and for us to eat. And it includes the animals, the livestock, the methane emissions, for example, cow burps. And it also includes packaging, transportation, cooking and wasted food and all of those things in between. So a third of everything that we need to sort of constrain, if we're to avoid your rather sort of apocalyptic vision is down to the food we eat. And that sounds like that's actually bigger than the things we're often worrying about, like, you know, airplanes. And is that right? Yeah. So the rest of the climate change is largely caused by fossil fuels. But actually,

if we stop burning fossil fuels tomorrow, we'd still be left with most of that contribution from food, because that is actually coming from other causes to climate change. And if we actually stop burning fossil fuels, and we only had that food contribution, we'd still be on track for causing two degrees of warming by the end of the century from food alone. So we also have to address the food system. So even if we went to entirely renewable energy sources, actually, if you don't solve food, it's such a big part of this that we're still going to have the sort of heating that you're describing. Yeah. Well, yeah, two degrees by

the end of the century, and that's very unevenly distributed and really problematic. So Sarah, as always, these conversations are very cheery, really fast. So I'm sure everyone's always really keen to have you around for a dinner party. Let's talk a bit about where that is. And then I'm looking forward to getting onto the positive things that we could do. We always like to talk about sort of actionable changes. So I'm assuming that not all food is equal, right? So what are the foods that are really bad for climate? And this is what you have spent the last few years on. You've written this really impressive book, Figuring This Out, which is what made me realise just how complicated this is.

Help us to understand. Yeah. So first of all, a lot of people underestimate how different foods are in their contribution to climate change. So people sometimes often will get the right sort of ordering, but really underestimate how different they are. So if we have an eight ounce steak and chips for dinner and we compare that to having a jacket potato and a microwaved potato and beans for dinner, then those two things would be really different. And you'd have 20 times as much climate change from the steak and chips dinner as from the potato and beans dinner. So help us to like unpack that. So that's like enormous difference. Like where does that come from? They look like they're about the same size on your plate. How do you work this out? Yeah. So what people do is they go through

and they look at all the different things it takes to produce that food and they add all those contributions. Now, if we look at something like steak, then there's several different contributions. One of the biggest ones is actually that about 5% of all the calories eaten by a cow are burnt out as methane, which is a really powerful greenhouse gas. And then we've also got the manure coming from the cow that also contributes methane to the atmosphere. And there's also nitrous oxide from when that goes into the soil. So there's a few different ingredients that all add up to being to that factor of 20. And so you've got the cow burping the methane. I'm guessing that's not the main contribution to the 30% of all of our food. So what else matters as we're thinking about

food? Presumably it's not like cow is bad and everything else is good. There's presumably more going on here. Exactly. Yeah. So it depends a lot on how you produce the food. So if we think about the cows, for example, then those cows, if they're grown on deforested land, if they're grazing land that's been recently cut, the trees have been cut down to clear land for agriculture, then we would think of that as a lot of greenhouse gas emissions from the carbon dioxide released by those trees when you cut them down. So we've got deforestation as it makes a big difference to those numbers. But we've also got, for example, if that manure is going to be spread and be out on the fields and decomposing as nature set it up,

then that's going to cause less emissions than if that manure is stored for a long time, which happens, for example, with intensively reared dairy cows, the manure is stored for a long time and that produces a lot of methane when it's stored for a long time. So there's different ways that you can produce that beef and that has an impact on that number. So you've basically done this incredibly complicated calculation of all the little elements and it's not just the direct amount of carbon dioxide here you're talking about, but actually, you know, if they cut down a tree, then you've lost the tree. So you're calculating all of these different factors to understand what the total impact is for an

individual food. Exactly. Yeah. And so have you been able to get calculations for all the different common foods that we eat? Yeah. So, I mean, this is collating work done by hundreds, maybe thousands of people even to do this across all different types of food. And so if we think about the potato, for example, or crops that are grown for human or animal consumption, the main issue there is going to be if you put fertilizer on the soil, so putting nitrogen on the soil, for example, that then interacts with microbes in the soil. So putting nitrogen on the soil, for example, that then interacts with microbes in the soil. It may be a link to microbiome, you never know. The microbes in the soil, which then turn that into nitrous oxide, which is a powerful greenhouse gas. And so it only comes down to

quite often microbes in the soil and also the microbiome inside the gut of the cow, which is converting some of that food into methane. I think when I'm listening to this, and I suspect how it listens as well, it sort of starts to say, well, so I need to be vegan then to stop climate change. You're telling me this meat is really bad. Is that the conclusion? Well, actually, when I first heard about all this, I went vegan for a year because I was so shocked about the impact of my diet and I wanted to do something to help. But actually looking back on it, probably stood there, unpacking my suitcase from a transatlantic trip with the oven on, with my jacket potato in the oven,

probably popped to the shops to get some green beans flown in from somewhere and felt very smug about all the great things I was doing to help with climate change. But actually transatlantic flights, driving to the local shop in the car for one food item, flying food items in for eating and putting the oven on for two hours all caused more climate change than say, you know, a small piece of meat. So it's not

as clear cut as being vegan. But it's also I used to love having milk in my tea. And I felt very sad because I gave this up for that year. But actually, you know, a tablespoon of milk in a cup of tea, you know, it's a drop in the ocean, as it were. It's not a large fraction of your daily climate impacts of your food. So whatever you're eating, it's contributing to climate change a bit. And having a very small amount of things isn't going to make necessarily a massive difference to your overall footprint. So there's no need to be absolutist about it. I think that's a really great message because I think it matches in a lot what we talk about here in general, as you think about food, that there's, you know, there's no such thing as a bad food when we're thinking about health, it's about thinking about your entire diet. And I think there's something quite

nice in a space where there tends to be very strong polarization around views that you're saying, actually, it's maybe not quite as extreme, you don't necessarily have to give something up completely. It's more about understanding quantity. Could we talk about meat for a minute? Because I think one obvious question as I'm hearing this is, are all meats equal in terms of their climate impact for people who are eating meat? No, they're not all equal. And so if we think about the most commonly consumed meats, then beef and lamb would be at the higher end. That's because they're ruminants, because they've got this particular stomach arrangement. If we look at other animals that are commonly

consumed, most of them aren't ruminants. So they're things like pigs and chickens, for example. And the climate impact of those will be three or less times smaller per gram. And is that all because of this methane that you were talking about before? Yeah. So the contributions to climate change are different for different animals. If we look at something like chicken and pigs, actually, then a large fraction of the climate impact is coming from producing the food that they eat. And can you explain that for a minute? So if there's not this methane specific thing, why is it any worse to eat a chicken than it is to eat a carrot? Yeah. So it's the quantity of food

that animals need to eat. So if we're looking at something like pigs, for example, then they need to be fed seven calories for every calorie that we get from the pork that we eat. So there's this kind of inefficiency that comes in when you put human edible food through an animal. So that's the main issue. Got it. So basically, it's incredibly inefficient. I could have eaten all these carrots myself. I feed them to the chicken. And ultimately, I'm having to give the chicken seven times as much carrots in order to give me the same amount of energy as I would have had directly. Exactly. And obviously, with a cow, for example, I might be eating grass. So it's a bit more complicated there if it's eating grass. And

of course, we might be feeding food that couldn't be eaten by humans to pigs, for example. So there's a lot of interesting research on how can we try and make that not just the human edible food, but ultimately, the majority of farmland is used for producing food to feed to animals. And so that's 80% of global agricultural land is used to produce food that's fed to animals. And so part of what you're saying is if you reduced the amount that we were eating of animal products, then actually you'd suddenly really reduce the amount of demand just for growing food of any sort and that reduces the sort of total climate impact. Yeah. So land is such a premium right now. We can't really afford to deforest more land. So we've got to use that

land as wisely as we can. And actually, most of the climate solutions use land. So this is why it's really important to then think, well, actually to produce one calorie of animal product on average is 16 times as much land as producing one calorie of plant-based products. So we've got this big factor which is in there. So in this very extreme case, if the whole world went vegan, and we look back at that 80% of farmland being used to produce food to feed to animals, if we factor in that factor of 16, it turns out if in the extreme case, everybody went vegan, we'd free up 75% of agricultural land globally for other uses, for example, climate solutions. So

just gives you a sense of the power of that kind of angle. What about byproducts of animals? So what about things like dairy and so milks and cheeses and all the rest of it? How much do we have to worry about those? Yeah, so the calculations that have been done will calculate the climate impact of those things as well. And so we find actually that chicken meat and eggs cause fairly similar amounts of climate change because we still have to feed those chickens. And that's the main thing that's causing the climate change from the meat. And it's also the main thing that's causing the climate change from the eggs. But it's still relatively low for all animal animal products it's at the low end there if we talk about something like dairy then obviously we've got the cows and we've got the burping of the methane again but if we look at milk a lot of that's water so per gram it looks relatively okay but actually if you then turn that into cheese for example then cheese per gram comes out similar to something like pork so So it's still quite a significant contribution. And that's even after you've taken into account the fact that we also produce meat from some of those animals. So that doesn't really make the problem go away. And from a carbon footprint,

would milk alternatives, in fact, look much better? Or because they're so processed, does that actually mean that in the end, they're as bad? How should people think about this if they are thinking about, at this point, this lens about trying to reduce our footprint on the planet? Yeah, so there have been a number of studies done on plant alternative milks. And obviously, it depends a lot on the details, as you say, of how that's processed, for example. But overall, there's not really an overlap. It's about a factor of two or more better for the climate to be having those plant milk alternatives compared to dairy milk again you know other issues about nutrition not as nutritious for example so

many other issues to factor in in terms of people often ask me you know about different types of plant milk which is the best one for climate change but there's not really a clear-cut answer to that because it depends on how you're producing, for example, oats or soy or whatever. If it's coming from a deforested region, then that would be bad. But on the other hand, soy is a very efficient way of producing plants and it's a legume, so it's fixing nitrogen. So in detail, it's not a clear cut answer because it often depends on the processing and the packaging and the way that's dealt with as well. But actually, there's still a big difference between dairy and non-dairy. And I think the other thing I guess I'm taking from this is the quantity that you eat is quite

important as well. So, you know, if you're having a small amount of milk because you're just having it with your coffee through the week, then total impact on your footprint in the week might be quite low. If I'm having cereal every day and all the rest of this thing, and so I'm going through many, many pints of it, then potentially this is quite significant. Is that also sort of part of the way that you should be thinking about this, Sarah? Definitely, definitely. And so, for example, as a calculation, I was quite surprised that when I looked at, for example, a large latte, if you're having a pint of milk in a large latte, which, you know, in a large coffee, which is mostly milk, then that can blow

a large fraction, like two thirds of your daily budget for your climate impact already just in that one drink. So on the other hand, if you've got a tablespoon and a cup of tea, it's almost no difference at all. Okay. So you've already depressed half the listeners at this point. I'm sorry. I'm sorry. I think if they put down, they're literally, they have the latte in their hand because people tend to listen to the podcast while they're walking around, right? They have the latte in their hand because people tend to listen to the podcast while they're walking around, right? They have the latte in their hand, you know, the dog in the other hand. They feel like they're doing everything right.

And now they're looking at it and feeling bad. All right. So as little milkers in one latte is already a pretty big climate impact is what you're saying. Yeah, sorry. Well, it's at least good to have the information. So I want to come back to that question I had right at the beginning about the baked potato. So a baked potato sounds like it should be good, right? Like it's a vegetable. We know if anyone's ever grown potato, like the number of potatoes you grow in a really small

area is really high. It can be bought locally almost anywhere in the world. So it sounds fantastic. And then I think you described right at the beginning, well, actually a baked potato might be much worse than these other things. Can you help us to understand, I guess, you explained the first part of this story about what's happening to make the food. So why could a baked potato not just be great from a climate perspective? Yeah. So in terms of producing the potato, you're completely right that it's really quite low climate impact to produce that potato that you take out of the fridge or cupboard, but it really comes down to the cooking. So if you're then putting the oven on for two hours to put your one potato in there, then the climate impact of putting the oven on, if it's fossil fuelled oven, is going to be,

you know, again, sort of a significant fraction of your daily budget will be used up on just putting that oven on. And if you then put the air conditioning on to cool the house down, then that's even worse. On the other hand, if you've turned down your heating because you've got the oven on heating up your house, then it's not such a big difference. So it's really the energy that it takes to cook that potato. Got it. And so does that mean if you are in a country where renewables have become a really big source of energy and this was an electric oven, then actually you might be just fine. Whereas if I had put it on the gas-fired barbecue, for example, you're saying it's completely different. Is that what you're saying? Yeah, you can actually see the fossil fuel there and the gas-fired barbecue burning away. Yeah, I guess we could get into discussions about whether

you've just caused somebody to burn more fossil fuels to produce more electricity for somebody else, even though you're happily using your renewable electricity. There's a whole philosophical question there we could get into, but yeah. I think maybe that's a rabbit hole we won't get. We're going to get to that. So what else is really important as I'm trying to figure out how I might change what I'm eating? Yeah. Okay. So I would say the oven is problematic in terms of climate change, partly because you're heating up a big metal box for potentially a significant amount of time. So I'd say focus on the oven. If it's not in the oven, it's not a big significant fraction. A microwave would be more efficient, pressure cooker, slow cooker, more efficient. Again, it's not a huge thing compared to all

the other components that add up. So I'd say focus on oven usage would be the main thing to look at there in terms of cooking. And then in terms of other things, we talked about the type of food, I would say then about air freighting. So if you're bringing something by air, then it causes about 100 times as much climate impact as bringing the same type of food by boat. And there's a great book actually by Mike Berners-Lee called How Bad Are Bananas? I don't want to spoil the answer to everybody, but the answer is not very bad. So this is particularly, I guess, thinking about bananas that have come a long distance by boat, maybe from another continent by boat. A lot of people might think, oh, that's really bad. It's come a long way. The actual climate impact of producing those bananas, which is already relatively small, is still bigger than the climate impact of that

transportation. So you're saying, you know, there'll be some listeners right now in Central America who are like, well, I get the banana right next door, that's fine. But you're saying, interestingly, if your banana is being shipped, be it across the ocean to Europe, or I guess also trucked across America to a listener in Chicago, actually, even though it's clearly not local, you're actually saying you don't need to worry too much? Exactly. Yeah. It's not really the big thing. So I'd say looking at air freighted foods and thinking about, you know, do you really need to have those strawberries in the middle of winter, for example, you know, that's the thing to look next, maybe. So it's not really food miles then, which is something that people definitely talk about.

It's really air miles, is it? Is that really the issue? Absolutely. Yeah. And in fact, the person who coined that term food miles is really sort of not happy about the way it's taken off in the public consciousness as being the main thing. But yeah, if we could get air miles maybe a bit more on the agenda, that would be good. Well, I think possibly because it overlaps with something that we're also very interested in at Zoe, right, which is around this idea of food that is less processed, less ultra processed. And so I think that tends to push this idea of, you know, if you're eating food that is perhaps more locally available, all the rest of these things, and I guess those two have overlap, but it's really interesting.

So for listeners who are in the UK, you know, one of the things that you often see in a supermarket might be lamb that has come from the other side of the world, from New Zealand or lamb that has come, you know, from the United Kingdom. I would have naturally assumed that the lamb from New Zealand is far, far worse for the environment because I mean because it's literally come about as far as it can be. Is that wrong, Sarah? Yeah, absolutely wrong. I hate it when you say that. Okay. Yeah. There's a study about 10 years ago, which looked into this. And I mean, it was quite a while ago

now, but that study was specific looking at that question. And it found that because of a particular way that they were producing the lamb at that time in And it found that because of a particular way that they were producing the lamb at that time in New Zealand, that actually the greenhouse gas emissions of that lamb was slightly lower off the farm than it was in the UK at that time. And so the climate impact of bringing it by boat was anyway such a small fraction of that whole thing that it actually was better at that time with this particular study to get the lamb from New Zealand and bring it to the UK than it was to get it from the UK. I think things have changed a bit since then. If I'm sitting in the States right now, then a lot of food, again, I might be in Chicago,

this food has come from Florida. And so I'm not having to necessarily fly something, but this has been trucked a long way in order to deliver me something in March that I can eat. Is that still actually not a big problem because it hasn't gone on a plane? Yeah, it's not nearly as big a problem. And actually, if you release greenhouse gas emissions, you burn fossil fuels at altitude, then that actually causes about three times as much global warming as burning exactly the same amount of fossil fuels down on the ground. So there's these kind of factors to consider. Got it. So really, this is this idea that I'm eating this food and it's been flown from, for example, the Southern Hemisphere, if you're in the Northern Hemisphere, this is really bad, is it? I see my asparagus and it's

come from Peru or Chile. I have to accept that there might be health benefits from this, but the climate impact is pretty bad. Yeah. I mean, if we can quantify that a little bit. So I mean, it's certainly a very large, it's the majority of the greenhouse gas emissions of that asparagus, if it's been flown in, majority of the climate impact of that asparagus is coming from the flight itself rather than the production of the asparagus. The climate impact of that portion of asparagus is going to be comparable to a similar amount of a low impact meat like chicken. So it's not as bad as having a similar quantity of beef, for example, in terms of climate impact. But on the other hand, it's up there with lower impact animal products.

So we had a whole bunch of listeners asking, are avocados killing the planet? And it's particularly relevant because this is a food that we think has very strong health benefits for most people. So in generally, when we're just thinking about health, it tends to score very highly for almost everybody who's going through these sort of personalized results. However, if we're thinking about this from the climate, what's the story? So avocados are a tree fruit. If we've got a tree which is long lived, it's producing these avocados. It's also sequestering carbon in the soil because it's producing roots under the soil. It's building trunk and branches above the soil. That's taking carbon dioxide from the atmosphere and storing it away in that tree and under the soil. So that is actually a good thing. The big question comes as

to, you know, have you just cut down lots of rainforest to plant avocado trees, in which case that's really bad. Numerically, that comes out as a big problem for climate change. On the other hand, if that avocado tree has been there a very long time and it's going to be there for a very long time, then it's actually a net positive in terms of climate impacts relative to annual crops that are grown in a field, for example. So it really depends on how it's produced. And if we have a global kind of explosion in interest in eating avocado and we need to clear land to produce those avocado trees, then that would be a problem. It really depends. Just before I go on, I just want to finish on the avocados because I think one of the reasons that people often talk about this is

about water consumption. You talked about the tree growing, but what about the impact of all this water? There's often a lot of talk about the very negative impact on the planet there. Yes. Yeah. So if we're having to water that, and if it's, for example, being water that's being pumped out of underground aquifers, which is depleting that water, or if it's taking out of rivers, which is actually being used for lots of other things further downstream, and we've just taken the water out, that'd be a big big problem if it's being grown somewhere where there's plenty of water then it's not an issue so yeah it can be an issue but again depends on whether it's water that's falling anyway or whether it's water that has to be gone and got from somewhere can we talk about

packaging for a minute because it's one of those things that really stresses me out so i'm quite into my recycling so i like i wash out the plastic pot for the yogurt. And every time I do it, I'm wondering whether I'm actually making everything worse by using this clean water and like washing it out and putting it away than if I didn't do that and it went in to be burnt. And then I see these things that are glass pots that's starting to increase now and things are getting glass pots or, know beans and aluminium and i'm really unsure because is that actually better or is it just all a trick you know for me on a consumer because it feels like it's recyclable

because you know we've used glass things so packaging am i unnecessarily stressed out how do i think about this yeah i think it is really interesting, isn't it? Because when you've eaten something, it's a really tangible kind of thing you've still got in your hand after you've eaten it. You're like, oh, this is the main issue here when it comes to climate change, because I've got this thing left over in my hand and I've got to figure out what to do with it. And you've forgotten already about the climate impact of the thing you've eaten because you've already eaten it.

So I think it is very easy to get obsessed about the packaging. In terms of something like milk, for example, if we think about a pint of milk in a plastic bottle, then actually the milk inside the bottle causes 20 times as much climate impact as the plastic that the milk's inside. So in terms of climate change, it's very much what's in that bottle rather than what sort of packaging is it if it's an animal product like milk. So although I have to admit that it's something absurdly satisfying about having milk in a glass bottle. I mean, I feel very proud as I take my glass bottles out of the fridge. So there's maybe some childhood memories there or something. But yeah, it turns out that what's in it is much more important.

On the other hand, if you're having a bottle of water, obviously, the climate impact of producing that water is very, very small and the plastic is a large fraction of it. But yeah, for something like milk, it's very much about what sort of milk you've got there. What about glass? Is it better? Like if I have the chance, should I be trying to get something that's in glass or aluminium versus something that's in plastic? Yeah, so I did look into this. So there's a lot of issues, obviously, with plastic versus glass versus aluminium, unrelated to climate change. So for example, you know, plastic, has that really been recycled properly? Or is it just being thrown into

the sea? We don't always know that with your council. That's nothing to do with climate change, but it's still to do with the environment. So just focusing in on the climate change aspect of it, they're actually not that different. So if you have glass, for example, then that can be then melted down and then remade back into glass, which is good. The raw materials to make glass are not super difficult to get hold of in the first place. So it's not a huge thing. Also, if you have glass, it's heavier. So that actually causes more transport emissions because you're transporting a heavier thing. So it all tends to balance itself out, really. Got it. emissions because you're transporting a heavier thing. So it all tends to balance itself out, really.

Got it. And what you're saying, I guess, is important is I'm tending to think about climate change and all these other environmental things together. But actually, I think sometimes these might be intention. Is that right? So you're saying that plastic might be really bad because if it ultimately gets thrown into the environment, you get microplastics and ends up in the sea. That's really bad for the environment and for the fish and maybe ultimately even for us as we eat it later. But the carbon footprint might even be better than a glass alternative. Is that right? Yeah, they're fairly similar in terms of the climate impact. So yeah,

obviously, yeah, let's not throw this stuff in the sea. But yeah, if it's managed properly, then it's very similar in terms of climate impact. And one of the surprising things that comes out of that is something like food in tins. I'd be curious from a sort of health perspective, your thoughts on that. But, you know, one of the things I started doing was, you know, cooking all these beans and pulses from scratch and, you know, trying to be very careful about how much energy I was using for that, thinking it was making a big difference compared to opening a tin. But actually, the climate impact of producing that tin of beans or tin of lentils, for example, is still very small compared to the climate impact of an animal

alternative that you might be having. So I think that was a really epiphany moment when I worked that out because I was like, okay, this is great because boiling all this stuff up from scratch and soaking things overnight, that's a massive hassle. But actually opening a tin is really easy. So sometimes there's steps that people can take that they might have thought was worse because they're producing, got all these tin cans left over at the end. But actually, it does actually add up to be better for climate change anyway. So I think the answer in terms of our view actually is that surprising when you speak to a lot of nutritional scientists, canned food tends to come out really well because these foods actually can almost immediately after they're picked fresh.

So very surprisingly, this tends to mean that many of the vitamins and everything that's in them are actually in better shape than if you buy them sort of fresh from the grocer. So it's nice to hear the alignment we're thinking about this from climate impact. And could we mention frozen foods in this as well? You know, you think, oh, we need to eat more fruit and vegetables and more plant-based foods. And then you immediately think of the fresh foods and there's lots of issues with accessing that on a sort of daily basis, but also in terms of food waste, if that isn't all eaten at the supermarket or is left in the bottom of our fridge or whatever. But yeah, so many ways to consume more plant-based foods that aren't fresh. So the tins that we're talking about now, but also frozen. That was something that I was really curious to look at the numbers for because yeah,

if you freeze those vegetables, for example, those peas, for example, you put them in the freezer, you've got to cool them down. That takes energy. And then maybe you've got to heat them up again when you're cooking them. But it turns out that those climate impacts of that freezing and the extra cooking, it's not a huge deal. And actually you have less food waste because, for example, those things in the supermarket, you're not going to end up with a whole load of food that's on the shelf that's past its date because it's in the frozen compartment in the supermarket. So you can end up having less food waste as well. And how big a deal is food waste? Massive. Yeah, massive. So I mean, globally, about one third of all food is lost or wasted.

And so that's bad because we've produced that food and we've caused that climate impact from producing that food and then that was not needed. And so if we're thinking, we just do that calculation of like one third of all climate change caused by food, one third of all food lost or wasted, 10% of all climate change roughly is just food that's wasted. So does that mean that if we didn't waste our food, we could all still fly somewhere nicer on holiday?

I have to do the calculation and get back to you. All right, all right. Thank you, Sarah. That's extraordinary. So I did have one question that came through quite a few times, which was, can a sustainable diet be affordable? And obviously, there's a cost of living crisis, and it's for people who've got lots of money. Can this be affordable? Absolutely. Yeah, there have been some studies on that, which show that actually, if we look at what people are having typically, then that often is cheaper. I think the confusion comes in because in a supermarket, if you go in and you find some of the packets which are labelled vegan, maybe it's the

plant burgers or some things which have been specially made to try and look like animal products and they've got the big vegan branding on, sometimes people feel those are quite expensive. But actually, if we're looking at things which are you know plant-based anyway for example tins of beans or even bags of beans that you can then cook at home in a slow cooker or pressure cooker we use with little energy then those things themselves are not particularly expensive obviously it depends on what you're going to eat there. The ratio you were describing right of going from plants to meat helps to explain why meat in general is more expensive than plants.

So logically, this seems like it's the right answer. So Sarah, we've covered a lot of stuff. And I think in a lot of cases, because you're a serious scientist and you've done all the math, the answer is, hey, this is quite complicated. And we're weighing up this on one side and one on the other.

I'd like to come to conclusion with sort of firm guidance for somebody who's listened to this and said, like, I'd like to do something with my diet so that I feel that I can sort of contribute to solving this problem. So if you were going to say, you know, there are three things that you should do in order to reduce your impact on climate change, what are the three things? Okay, so if we think about quantity, so finding out what are the foods that you eat that cause the most climate change, and then reducing the quantity of those things. And for a lot of people

in say the US and UK, then that's on average is going to be animal based products. So really, what's the quantity? What's the frequency of the things you regularly consume? Maybe focus on those first rather than things you have on feasts or irregularly. So quantity, and then I would say food waste. So reducing food waste is a bit of a no-brainer really for everybody in terms of reducing costs as well as climate impact. And then the third thing I would say is actually sometimes people come to me and they say, I'm doing this, I'm doing that, I'm doing the other. I've got quite a low climate impact of my diet already, what more can I do? And actually, if you do the maths again, the answer often is going to be talk to somebody else about their diet and try to get systemic change rather than individual change. So individuals can have a surprisingly large impact because supermarkets, for example,

respond to a small subsection of the population demanding, for example, plant-based foods. That's had a big impact over the last few years. So individuals can make a difference, but actually, we need some sort of systemic change. And we have a big problem at the moment that if a policymaker, for example, wants to make a new policy, which is going to help reduce the climate impact of food, That's not popular. And so we actually need to get to a place where if we think about plastics, I say five years ago, it's changed a lot in terms of people demanding less plastic in what they're buying. And that is now getting supermarkets, governments, policymakers falling over themselves to come up with these plastic free policies and ways of doing things.

I'd love to see that same kind of change in attitudes to the climate impacts of food and policies around that and see people trying to tout the benefits of their wonderful new climate-friendly foods. Brilliant. Sarah, thank you so much. I think we covered lots of different areas here. And I think one thing that is really clear is the complexity of the topic and that there's not one very simple answer to everything. We always try and do a quick summary at the end of what we covered. So let me have a go and correct me if I've got any of this wrong.

So the first thing is, amazingly, the food that we eat is a huge part of what contributes to climate change. I think you said a third of the total impact, which I think is a huge surprise for me and many other people. We don't all have to go vegan to stop climate. That's a very extreme call. However, what we do need to do is probably reduce significantly the amount of animal products that we're eating. If you leave the oven on for hours, that's probably also more of an issue than you might've thought. On the other hand, things like frozen and tinned goods that you might've thought there was some heavy element from actually you're very supportive. And that is

because the value of reducing waste is so important. I think you said that food waste was like a third of this entire impact. And so for us, actually, maybe one of the biggest things is, well, how much are you throwing away at the end of the week? And how could you change all of this? And I think the final thing you talked about is think about reducing air miles. I think you're also saying this really matters. And so just as we think about what we do and what we tell our children elsewhere about the sort of world we want to live in, then actually these are food choices where we can make a difference, and not only by doing

this for ourselves, but by trying to communicate to other people. Brilliant. Sarah, thank you so much. I think it's food for thought, and today we don't have this advice built into the ZOE guidance, for example. It's something we talk a lot about, as you're aware, because we've been talking to you about this, and I think you see this complexity and you can see how we need to make that available. So thank you for taking the time. Thank you for spending the hours, months, and years trying to calculate all of this and sharing it with the rest of us. Thank you so much for having me. It was a real pleasure. Bye-bye. Bye. Thank you to Professor Sarah Bridle for joining me on Zoe's Science and Nutrition today. We hope you enjoyed today's episode. If you did, please be sure to subscribe Thank you to Professor Sarah Bridle for joining me on Zoe's Science and Nutrition today.

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