ZOE Science & Nutrition - Fats and oils: What’s the real story?

Episode Date: April 14, 2022

Today we’re talking about fat, a delicious component of our food with a terrible reputation.   Fats have been broadly associated with weight gain and heart disease until recently. A mountain of new scientific evidence suggests this is wrong and that it's not as simple as ‘all fat is bad’. Indeed, eating more healthy fat might actually reduce heart disease for many people.   In today’s episode, Jonathan speaks to Dr Sarah Berry to learn about what science tells us today, whether it is possible to lose weight on a high-fat diet, what oils we should be cooking with, and the different types of fats. Dr. Sarah Berry is one of the world's leading experts on human nutrition, who has personally run over 20 randomised clinical trials looking at how humans respond to different fats. Download our FREE guide — Top 10 Tips to Live Healthier: https://zoe.com/freeguide Timecodes: 00:00 - Intro 02:50 - Episode Start 03:08 - Quickfire round 04:54 - Can fat ever be healthy? 08:53 - Is it possible to put on weight if you’re on a low-fat diet? 10:50 - Food accessibility & bioaccessibility 13:22 - Understanding the caloric data of fats 19:25 - Fats’ relationship with cholesterol 23:40 - Food labels aren't necessarily helpful 27:45 - What are the best oils to cook with? 33:04 - Are there any dangers of cooking with oil? 37:43 - Are eggs safe? 38:56 - Is fish good for you? 42:26 - Summary 45:59 - Goodbyes  46:28 - Outro Episode transcripts are available here. Follow Sarah: https://twitter.com/saraheeberry 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. Today we're talking about fat, a delicious component of our food with a terrible reputation. Fat can be found in many different forms, from olive oil and avocados to bacon and butter. But until recently, all fats have been linked to weight gain and heart disease. We now know this to be wrong, but the fallout from the smear campaign against fats remains. So how on earth did we get here? Let's look back.

America 1940. Bring to our people's contribution to America and freedom. In a host of laboratories across the country, scientists are working feverishly to identify the cause of heart disease, which is killing over a million Americans each year. A number of these scientists uncover similar findings, a correlation between high cholesterol and diets high in saturated fats. With cholesterol linked to heart complications, their hypothesis is that a low-fat diet could benefit those at risk.

Fast forward to the 1980s and things have got rather confused. Low-fat diets were being recommended to everyone, not just those at risk of heart disease. Governments, doctors and food manufacturers the world over were touting the low-fat diet as the route to better health and weight loss. Unfortunately, there was little evidence that a low-fat diet was helping anyone. During the same decades that the low-fat approach took hold in the developed world, their populations were putting on weight fast. Food manufacturers knew new low-fat offerings

tasted unappealing, so they loaded them with sugar. With sugar so cheap, their profitability increased. New Kellogg's toppers for the big kid in you. Seeing an opportunity, they did everything they could to influence the debate, funding biased research that downplayed the risks of sugar and highlighted the dangers of fat. Only now, so many decades later, has the impact of this lobbying begun to fade. A mountain of new scientific evidence suggests that it's not as

simple as fat is bad. Indeed, eating more healthy fat might actually reduce heart disease for many people. In this episode, we'll be finding out what science tells us today. We'll learn if it's possible to lose weight on a high fat diet, what oils we should be cooking with, and the different types of fats. I'm joined by my good friend, Dr. Sarah Berry, one of the world's leading experts on human nutrition, who has personally run over 20 randomized clinical trials looking at how humans respond to different fats. Sarah, it's always such a pleasure to discuss food with you. We had an enormous number of questions about fats and about cooking with

oils today, and I hope we're going to manage to address a lot of those. Why don't we start with a quick fire round of questions from our listeners. And so the first question that we have is what's healthier for most people, a poached egg or an egg fried in olive oil? Egg fried in olive oil. Okay. I think that's going to be a surprise for many people. Okay. Can you eat a high fat diet and still lose weight? Yes, but it's hugely variable between people. So I guess the following question is, can you eat a low-fat diet and lose weight? Yes, but it's hugely variable between people, but it's harder for most people actually to lose weight on a low-fat than a high-fat diet. I think we'll surprise a lot of people and we can talk a bit more about it. Another question

we had come up a lot is olive oil safe if you fry or roast with it so that the oil gets hot? Absolutely, it's safe. Just a note that the levels of all these wonderful antioxidants, these polyphenols that are in olive oil will actually reduce though if you do heat it excessively. So it might not be as healthy, but it's still absolutely safe. And what about coconut oil? Is that something we should all be eating more of? I think the jury's still out. So based on current evidence, no. Can eating fats reduce blood sugar spikes? Yep. Yes. Can too much fat lead to inflammation?

Yes, but depends on the type of fat, the food it's in and the amount you're having. Final short question, as we age, does our ability to metabolize high fat foods change? Absolutely, yes. Brilliant. Thank you, Sarah. Well, I think we're going to dive in more detail onto one of those questions. Hi, I want to take a quick break here and tell you about something new we've created, a free guide that will kickstart your journey to better gut health. Now, if you're a regular listener of this podcast, you're no doubt already aware of how important the gut microbiome is. It's responsible for so much, from digestion to immune support and even

our mental well-being. As we've heard many times on this show, and as our members know through using Zoe, we feed our gut microbiome through the variety of foods that we eat. And in return, our microbes give us this wealth of health benefits. So how can you nurture your gut in the best way? Which food swaps can you try to nourish those good bacteria? What does a high fiber shopping list look like? Our free gut health guide shares it all. Emails and actionable tips that are designed to put you in control of your gut health. To get yours for free, simply go to zoe.com slash gut guide.

I think a lot of us were brought up to feel that fat was fundamentally unhealthy if we put aside those sort of special magic fats that we need to live and think about them you know the majority of things are routine like can fat ever be healthy I think we've had this view I think you know saturated fats are bad unsaturated good so can this be healthy and is it as simple as sort of saturated versus unsaturated help us to understand how we can figure this out. Yeah, so firstly, can fat be healthy? Absolutely. It's a really important component of our diet. And I think, you know, a lot of us are living with the remnants of this surgence of low fat diets, low fat products in the 80s and 90s. You know, I was a teenager growing up in the 90s, everything on the shelves was, you know, proclaiming to be healthy because it's low fat. And, you know,

we really need to move beyond this. The evidence in terms of not just obesity, but in terms of many different health outcomes ranging from cardiovascular disease, type 2 diabetes does not support any favorable effect of having a low fat diet over having a moderate fat diet and so I think that's really important to remember and we can pick up on this later as well maybe around how you know it's actually damaging I think people trying to lose weight by having these very high refined carbohydrate diets in this effort to stick to this low-fat diet that supposedly will be wonderful for weight loss. I think we've taken in nutritional research generally quite a reductionist view in how we've considered the health effects of foods in that we have traditionally looked at

nutrients. And this same quite reductionist view has also been taken when it comes to fat. So typically in the past, we've just bagged all saturated fats into one bag of saturated fats, MUFA, which are monounsaturated fats into one group and polyunsaturated into another group. But it's a lot more nuanced than this and dependent on the type of fatty acid within these groups. But it's also very dependent in terms of the health effect that the fatty acid has on what other fatty acids there are in the diet, but also the food that it's delivered in. And I often think a really simple way to try and think about how healthy

or unhealthy a fat is, is to think about whether it's intrinsic or an extrinsic fat. And this is a term that isn't really used much. It's a term that I like to use when I'm explaining this to people, because I think it's a way that most people can understand a bit more easily. So when I say an extrinsic fat, I'm talking about a fat that's added to food. So I'm talking about a fat that might be added during cooking at home or a fat that might be added to a highly processed or any kind of processed food. And so therefore, when we think about the health effect of that fat, that's an extrinsic fat added to the food, we can think about it a little bit more simply about it based on what kind of fatty

acid it is. Now, if we think about the health effects of a fat that's intrinsic, so it's already in a food, so this could be, for example, a fat that's in an avocado or the fat that is already in a piece of meat, then it's really important we consider the other components of the food that it's actually found within. And so it is nuanced and it is difficult. And therefore, I think actually the simplest way to consider the health effects of a fat is to consider it is difficult and therefore I think actually the simplest way to consider the health effects of a fat is to consider it in the context of the meal that you're eating and your overall dietary pattern. Got it and we can talk a bit I think about specific examples I think lots of people will be saying yeah that's great but I actually want this practical advice

I think we'll come back and really talk about specific fats towards the end. You already touched a little bit on this question about weight and I think I'd love to understand that a bit more because, you know, if I put on weight, it's because I'm storing fat in my cells, right? That's how my body is doing that. And we know that we do that because when we evolved, you're like, wow, I really need that, right? I might not be able to find any food tomorrow on the savannah. And thankfully, I've got all those fat stores. And this is why, in fact, we can live for a long time without any food right and why people can fast you know as long as we've got water we can do that so obviously that's an essential thing but i'm storing fat so can you explain how is it possible for people to put on weight if they're eating low-fat diets because

they're not actually putting any fat into their body so any excess energy is converted into fat. So if we consume excess carbohydrates, if we have a diet devoid of fat, any excess energy from carbohydrates is converted into fat and stored in our body in fat. So regardless of the source of the excess calories, whether it's from carbohydrate or fat, the excess calories is deposited as fat. Got it. And this is why this idea, well, I mustn't eat fat because, you know, I'm going to put on weight doesn't really make any sense because basically, well, if I just swap my fat for Coca-Cola, actually, you're saying it's just the same thing, right? My body has this ability to swap this backwards and forwards. Yeah, our bodies are really clever at adapting to what

nutrients are available to us. And it's an area of huge contention in the nutrition world, the area of whether you should be consuming a high fat or a high carb diet. So you have these low fat zealots promoting the low fat diets and many low carb zealots who are loggerheads with the low-fat zealots about which is the best approach to lose weight. And I think that we're going to see more evidence emerging around this in the future, but there's lots of studies already out there. And I think there's no clear consensus around this. It's tough to lose weight regardless of where your energy source is coming from. The odds are stacked against us, unfortunately. And this is because like you said, Jonathan, evolutionary, we have been primed to be able to conserve energy, to conserve body weight so that we can survive in periods of fasting.

And so that was fine prior to the environment we live in, but we now live in this obesogenic environment. We live in this environment, or most of us do, of highly processed foods with highly bioavailable nutrients. And I can just pick up my phone now, right, and order. It's amazing how much food I can now order to my house without getting up from my seat. Is that sort of what you're talking about, about this environment that we're in? Yeah. So the fact that for most individuals, it's highly accessible, but also an interesting concept that's been evolving over the last 10 years is this area around accessibility in terms of the bio-accessibility. So yes, you can pick up your phone and in 10 minutes, you could probably have something

delivered on a bike to your house with goodness knows what kind of food in it. But another area that we're becoming aware of is the importance of how food is processed and we know that by processing food you make food some more bio-accessible and what that means is the food is in a format that it's really more easily digested you're absorbing more calories you're absorbing the energy more quickly you're processing it more quickly. And we know that this is detrimental for lots of different reasons. And given how clever our bodies are at maintaining this set point in our weight, in maintaining and preserving energy, we're kind of fighting a losing battle to a certain extent because we have this highly accessible food, we have this highly bio-accessible nutrients. And then our body and the feedback

loops that we have between our gut and our adipose tissue, so our fat tissues where we're storing the energy and our brain is so powerful. And a lovely example that I heard recently that I think really brings home just how challenging this is, is that this feedback loop works in such a way that if you or I were to reduce our energy intake by 200 calories a day, so if we were to go try and go on a lower calorie diet, forget what nutrient this is coming from for the moment, but we would reduce our energy by 200 calories a day, the hunger feedback loop that would occur in response to this stimulating areas in our brain related to hunger and fullness would actually drive an increased energy intake of about 750 calories. So we're only having a deficit, so a loss of 200 calories, but the drive in our brain to consume more is actually for about 750 calories. Now, when we're highly motivated in those first few months or first few weeks to lose weight, then our motivation can

overpower this to a certain extent, but we cannot keep that up lifelong. And this is why on the long term, many diets do fail regardless of the nutrients. And so with that context, one would think that fats were still a bad thing. And you think they were a bad thing because they have more calories than carbs for the same weight, right, Sarah? And maybe you can tell us exactly what that difference is. But it would sort of seem logical. And lots of people have talked about this. Well, you wouldn't want to eat fats because they're very energy dense. And it sort of seems obvious that actually you're going to put on more weight, therefore eating them them than carbs and so you said right at the beginning actually it's not true but can you help us to unpick that because it seems like totally in

conflict with what seems logical yeah and this is why the whole low-fat diets and low-fat products have been such a success because it is in conflict with what seems logical because per gram of fat there's nine calories per gram of carbohydrate there's four calories so if i was to consume 50 grams of fat yeah it's more than half a difference in terms of the calories per the amount of food but what that doesn't consider is that when we consume this food what actually happens during the digestion process and this feedback process, how it affects different hormones, not just the hormones in our brain feeding back to us about how hungry or full we feel,

but also hormones that affect how we deposit fat and how we release fat. And there's something called the carbohydrate insulin hypothesis that is advocated by the proponents of the high fat, low carb diets. And this is based on the principle that if you consume lots of carbohydrates, you're increasing your insulin secretion by increasing your insulin secretion in that immediate period after consuming high carbohydrate foods, what that does is it stops the fat being released from your adipose tissue, so from your fat tissue in your body, and it also causes more deposition of fat that's circulating back into the adipose tissue. So if you were to go on a low carb diet and consume a high fat diet, you produce very

little insulin. So what that means is that means that you're not having that blockage of preventing the fat coming out from the adipose tissue. So you would have more fat being released from the adipose tissue and you wouldn't have the fat being pushed back in the adipose tissue. Now mechanistically, that's great, but the evidence doesn't necessarily support this when we translate this to clinical trials. And I think a really important note to pick up on this is because I think it's different

for everyone. What works for one person doesn't necessarily work for another person. There's a great study that illustrates this called the Diet Fit Study that one of our colleagues, Jonathan, that you know very well, Christopher Gardner led. And he allocated people randomly to either consume for a period of time, either a very high carbohydrate, low fat diet, or a very high fat, low carbohydrate diet. And he then followed them up over a period of time and assess their change in weight. Now, he found that everyone lost a little bit of weight, but he found that there was absolutely no difference in the amount of weight loss between the high carb people and the high fat people. On average, right?

Yes. So this is on average. So traditionally in nutritional research, what we do is we take the average response. When we put someone on a diet, let's say we have 50 people going into a dietary trial. At the end of it, we look on average, what's the change? So when he looked at the two different diets on average, there was no difference. But then he went and looked at the individuals. So he looked at all of the different individuals consuming the high fat and all of the individuals consuming the high carb. And he found that there was a hugely variable response.

He found that for some individuals, the high fat diet worked really well in promoting weight loss. Whilst in others, it was terrible. It caused weight increase. And then the same for the high carb. He found that for some people, this was a really effective means, but for other people, it was really ineffective. And it really highlights something that I'm very passionate about is this whole area of

personalized nutrition, which is at the heart of all of the research I'm doing together with Zoe and yourself on the Predict program of research. And I think it really highlights that, yes, we can talk about these lovely fancy mechanisms to do with how we metabolize fat or carbohydrate and the carbohydrate insulin theory. But actually, it boils down to what works for you. And the diet fit study, I think, is a great illustration of that, as well as our own predict research. And that we need to move beyond this one size fits all approach. We need to be thinking at a very personalized level. Maybe just before we switch another topic, I think I'd be interested to talk about sort of like the behavioral impact on this and how it

makes us feel. So one of the things that people often ask me is, well, how has your diet changed since you started Zoe? And the answer is it's changed a lot. And one of the biggest ways it's changed is that I now eat a lot more fat than I did. I was absolutely sure that fat was bad for me five years ago. My dad was basically put on very low fat diet because he was told he had very high cholesterol in his 30s. So this is now, you know, sort of 40, 45 years ago. And so that means that at home, you know, we ate this very low fat diet. As a result, we, of course, ate lots of carbohydrates because that's what you do to fill it in. And of course, lots of refined carbohydrates, pasta and bread and things like this. So I then did these Zoe tests and it turns out that actually my blood sugar control was really quite bad.

And actually my blood fat control was much better. And so that's what the advice is pushing. But I still feel really guilty when I eat cheese. Like it's even though I've seen this and I also have noticed the way that actually my hunger is lower when I'm eating these high fat foods. Like I still have this basic feeling that it's a bit naughty, isn't it? Like it's not the right thing to do. What are your thoughts on that, Sarah? I've got loads of thoughts. I'll just touch on a few that I think might resonate with people. So you mentioned about your father, for example, being put on a low fat diet because he had high

cholesterol. And this is still a common perspective that lots of people have around how do I reduce my cholesterol levels? Well, let's consume low fat diets because it contains cholesterol, because it will increase my cholesterol levels. The first thing just to mention that I hope most people now are aware of, but in case they're not, is that if you consume dietary cholesterol, which is contained from some foods, dietary cholesterol doesn't increase your circulating cholesterol. So it doesn't actually increase your blood cholesterol levels, or it does only to a minimum. It's the type of fats that you're consuming that increase your cholesterol levels. So yes, we know that some saturated fatty acids might increase your

cholesterol levels. And can you say what sort of foods those are, Sarah, just for those of us who don't think about things in this chemical way? Yeah. So we know that the kind of saturated fatty acids that are in butter, in palm oil, in animal fats, for example, can increase our cholesterol. Now, cholesterol is made up of good and bad cholesterol. And what we particularly don't want is an increase in good cholesterol alongside an increase in bad cholesterol. And saturated fatty acids increase our bad cholesterol. Some of them do also increase our good cholesterol. So again, it's a little bit more complicated, I'm sorry to say, depending on the type of saturated

fatty acid. But what we do now know, which I don't think we were so aware of 30, 40 years ago, is that carbohydrates can have a really big impact also on our cholesterol levels and also on our circulating triglyceride levels, which we also know is an independent risk factor for cardiovascular disease. So if you consume a diet high in refined carbohydrates, and by refined carbohydrates, I mean bread, I mean pasta, I mean rice, I mean also a lot of the processed carbohydrates like snack bars, crisps that you might consume. What this does is at the level of our liver, it promotes the production of lipids. So this is another word for the kind of fats that are produced in our body. And that increases our cholesterol levels and increases

our levels of circulating triglycerides. But to loop back to what you mentioned about cheese i think that's a really good example of how we need to move beyond this simplistic approach of thinking about the types of fat so i just said that actually the type of saturated fat you have in butter is bad for us now dairy cheese so fermented dairy such as cheese and yogurt, has a really similar fatty acid composition to butter. But actually, it doesn't have the same unfavorable effects on our health as butter does. And the reason is, is because of this matrix, the kind of special structure in which the fatty acids sit within the dairy products that are fermented within the cheese and the

yogurt. So you could feed people a moderate cheese diet and moderate butter diet. The cheese wouldn't have any unfavorable effects, yet actually the butter would have an unfavorable effect despite having a similar fat composition. And despite the fact that actually basically the cheese comes from the butter, right, Sarah? So that's like even more surprising. Help us to unpack that a little bit. It sounds a bit magical. It is because food is really complicated and it's magical because how we process food has a huge impact on its health outcomes. So how we process dairy, whether it's as butter or whether it's as

cheese or whether it's as yogurt can hugely impact how our body responds to it. And the same applies for how we process other foods, whether it's consuming whole fruits or consuming pureed fruits or consuming whole almonds or consuming ground almonds where you're changing the matrix. It has a huge impact on this bioaccessibility that I mentioned earlier, so the release of nutrients and how our body processes them. And I think dairy is a really nice example of how we need to look beyond the nutrients and we need to think about the food that it's actually contained within. So basically, the food labels, which a vast effort are put onto all of these foods,

and which, you know, in many countries, right, the States or the UK included, talk about sort of saturated or unsaturated, are not necessarily really giving you any information that is helpful. Is that what you're saying, Sarah? Yes, in my opinion, I think it's worth mentioning that broadly speaking, epidemiological studies, so these big studies that will be following people over a number of years or looking at one point in time in thousands of people and then looking at certain health outcomes and looking at dietary intakes, they do consistently show that a high saturated fatty acid diet is less favorable than a high mono or polyunsaturated fatty acid diet at the population level. But when we do clinical trials, what we know is once we

start to tease this apart, it becomes really apparent that that's too simplistic. And at an individual level and at a food level, it's again, far too simplistic that we need to consider the type of fatty acids. But more importantly, we need to consider the type of fatty acids. But more importantly, we need to consider the food it's in. And this is because you're lumping all of these different things together. So you're saying like, well, somebody who's eating lots of animal fats, and I think you're you still think animal fats are not particularly healthy. Is that right, Sarah? Yeah. So I would say that you could have foods that contain the same fatty acid composition. So an animal fat and some

particular other tropical oils, for example, that contain the same fatty acid composition, but could have different impacts on health outcomes because of the source, because of the matrix that they're in has a huge impact. And so I do think that whilst labeling can be useful, broadly speaking, I think we need to be very, very careful to not be too caught up on labeling. And there's an example I often use to do with almonds. Now, this isn't related to the fatty acid composition, but it's related to how I think being preoccupied by labeling can actually potentially even make us select more unfavorable health choices. So if we were to consume whole almonds, almonds have a very special matrix. They have a very rigid cell structure. So what happens is, is that remains intact

largely as we chew them and they pass through our digestive tract and we only absorb about 60% of the energy. So about 40, 30% of the energy and fat is excreted. So it reaches our large intestine where it's great food for our microbiome, which is fabulous, but also it's a lot lower energy. Now, if we were to grind those almonds up, so we break this magic matrix, we break the cell walls, we release all the fat, we're going to absorb everything. And so that you suddenly have a food that has about a 30 to 40% higher energy content in terms of what we're absorbing than the whole almonds. However, if I was to go into a supermarket and look at a bag that had whole almonds intact, as we typically would consume for a snack versus the whole almonds ground, as we typically would consume for a snack, versus the whole almonds ground up, like we might use as an ingredient, the back-of-pack

labeling would show that they had identical energy values. They wouldn't show that per 100 grams, you had this huge difference of several hundred calorie difference. And so I think that's a really nice example of how we need to think about the food. Is it in its original matrix? Is it unprocessed? Does it contain healthy other nutrients like fiber and mono and polyunsaturated fatty acids rather than looking at that back-of-pack labeling? 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, well, 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. That's really powerful advice, right? That in general, thinking more about this as a food rather than as the set of numbers on the back. And of course, all of this labeling, you know, I think it was all being done with good intent, right? But actually isn't very helpful. And of course, if it had been really helpful, then we would have seen all these wonderful health outcomes over the last 30 or 40 years which we haven't seen either we've been teasing our listeners for ages let's get down

to the bit that they probably have been like oh this is the bit i care about so the number one question that we had is what are the best oils to cook with so let's start with that so i'm going to say it's complicated seeing as though we've already started on that theme. I feel I'm allowed to say that. It depends on what you're cooking, how you're cooking it and what temperatures and for how long. As a rule of thumb, an oil that has a lot of monounsaturated fatty acids. So this is, for example, oleic acid that is particularly high in some types of sunflower oil and olive oil, tends to be a very good oil to cook with. And the reason for that is because it's a very stable oil.

Once you start adding polyunsaturated fatty acids, and remember, these are the ones that have more double bonds, and these double bonds are very easily oxidized, then what can happen is when you cook with an oil that has a lot of polyunsaturated fatty acids, and an example of this is rapeseed oil or some other variety of sunflower oil, what happens is those double bonds can become oxidized. And so you get that rancid taste and it's quite obvious. And I don't know whether you've ever tasted that, Jonathan, if you've used something that's highly polyunsaturated or even fish oil if it's left out in the air or heated you can taste it quite easily that it's got some kind of rancid off taste.

So from a taste perspective it's best to use a monounsaturated oil. So olive oil, sunflower oil which I think is not used as much in the States, right? As it tends to be in Europe. Is there anything else that fits into those categories that you put it at the top? So olive oil, you would need to use a hyalaic type of sunflower oil and rapeseed oil is still a pretty good oil to use. Now in the US, one of the main oils that they use for cooking and one of their main oleic acids, so monounsaturated rich oils, is soybean oil. That's one of the most commonly consumed oil in the US.

It's homegrown, so it's also good in terms of environmental impact because of it being a homegrown oil. So I would say olive oil would be the best one. And then in the US, soybean oil, and in the UK, high-leck sunflower oil. Now, something to bear in mind, though, is as with all fats, it's all about the taste, the functionality. And I personally don't like to cook with olive oil because I find it too fragrant. I find the taste too strong. And what's giving it this taste is all of these great polyphenols. So I would choose to have an oil that works for me in terms of taste. Now, if you like

the taste then, and I know you fry with olive oil yourself, Jonathan, a lot, then that's great. It is a healthier option. Yeah. And I would say when I first started, I really noticed it and seemed a bit strange. And actually now I cook with it all the time and I actually love it. So I would also say that it's like a lot of things, right? When you're making a change in nutrition, the hardest bit is making a shift because you're in the patterns that you're used to. And, you know, it's a bit like when, you know, you're giving up drinking sugary drinks, right? And to start with, it's really hard.

You're really just so used to that. And so I, at least speaking for one, I now think, think of course that's what I would fry my eggs with because not only has Sarah explained to me how good it is but actually I really like it but I think that it is an important point right that you talk a lot about about weak food for pleasure and it's really important that you don't think oh I can never have anything else this is all about finding the right balance yeah and something else to mention is that domestically so how we would cook at home frying an baking, olive oil will retain most of its favorable compounds. So these polyphenols, the antioxidant compounds. Industrially, it would be very difficult to use olive oil because

particularly when there's very high temperature cooking, it would destroy these compounds. And also because there is a reasonable amount of polyunsaturated fatty acids in olive oil, which again, if it's used as an added ingredient industrially, would mean that the food would or the oil would go rancid and the food would have a shorter shelf life. So whilst I think it's great for home cooking, home use, and particularly adding to salads, so in uncooked foods, it's not a good ingredient functionally for the food industry, but also for us because most of the favorable benefits will have gone. And actually that brings me on quite nicely to

thinking about olive oil in terms of the type of olive oil there is. So on the market, there's extra virgin olive oil, virgin olive oil, and then just standard olive oil. And the difference is in how many processing steps it goes through. So extra virgin olive oil is the least processed and has the most amount of these great polyphenols that are so good for heart health. I've got microbiome and many more favorable health effects. Once you get to the next level of processing, the virgin olive oil and the following one, the just straight olive oil, nearly all of these favourable compounds have gone. And actually, it's no different to sunflower oil and no different to rapeseed oil. So if you are going to buy olive oil because of its health benefits, you need to get the extra

virgin olive oil. Otherwise, you might as well buy the far cheaper sunflower rapeseed or in the States, the soybean oil. And that's really helpful, Sarah. And I think you talked already about sort of olive oil's sort of magical properties as seen in this big study. We did get a lot of questions around the dangers of cooking with it. Where does that come from? And you said right at the beginning, you know, very confidently, it's fine. And can you just elaborate briefly on why we can all just be relaxed and put it in the frying pan? Okay, because I think there was a lot of scaremongering some time ago about compounds such as peroxides, polar compounds, three MCPDs, if I've got that correct, which I'm not even going to try and give you the full name for that.

And these are compounds that are produced when you heat fats, when you repeatedly heat fats, and you heat them to a very high temperature, especially in the presence of small amounts of water. We know that these compounds firstly are horrible because they make the fat taste horrible. But we also know that some of these have been shown to be carcinogenic at high levels in animal models, not in humans, but in animal models. The reality is the way that we cook at home will not produce these compounds. You will not produce these polar and peroxide compounds in the way that typically we consume fats at home. Now, some people might still have the deep fat fryers for frying chips. I don't think many people do this now at home.

And if you were to use the same oil for many months and many repeated fries and hundreds of repeat fries, then eventually, yes, you would produce these compounds, but it's just not relevant to us. And this is the problem where there's so much scaremongering about dietary links with cancer or other diseases that are based on situations and scenarios that just aren't relevant to how we as humans actually consume food. So if you are not deep fat frying your olive oil over six months using the same oil with chips, repeat frying every day, I think you're pretty safe to fry and use this at home. That's really helpful, I think. And I think also that point that comes up a lot, right, about the difference between some sort of animal study in a very controlled sort of laboratory and then the reality of what happens when you do a human study over time

and that I think all the time, right? You see either negative impact or really promising impact in this animal study and then it gets rolled out to humans and you've done, I think, more than 30 of these randomized controlled trials, right? And then you're like, oh, well, that doesn't actually really happen

in real life with real people is something I think for our listeners always to be aware of because it's part of why there's so much confusing different stories or even contradictory stories, right? It's not that anybody, each of the pieces of science is correct, but it doesn't necessarily flow through in the way that maybe the media has put on its front page. Yeah. And Jonathan, can I pick up on something as well that people often ask me? And so I think anyone listening might be interested in this. People often say okay it's fine saying it's safe at home but what about takeaways? What about your McDonald's fries?

What about your corner street kebab shop that might or chip shop that might be using the same oil day in day out? Well firstly there's very strict regulations across all of Europe and the US about the level of these compounds allowed and all food outlets are randomly checked. But as long as you're changing your fat about every week, still, even in that scenario, you're not going to produce enough of these that it'd be hardly detectable and certainly wouldn't have any unfavorable health outcomes. So even getting your repeat deep fried chips from your local corner shop in most instances are still going to be okay and still going to be safe for consumption.

Got it. Now they'll be safe. I imagine that you're going to tell me the quality of those oils is not as good as the oils that I'm going to be using at home. So the quality of those kinds of oils will be determined on the functionality. And this is something that we haven't picked up on and might not have time to, and I'd love to come back and spend a whole hour talking about the importance of functionality. But those kind of oils will have a slightly higher saturated fat content. So the kind of oils that are often used commercially in food outlets will have a higher proportion of fats such as palm oil actually together with a rapeseed oil blended together. This makes the fat a lot more stable. It means it lasts longer

and it means it doesn't again produce these compounds that are produced mainly because of the polyunsaturated fatty acids. So this is an example where food industry has to think of two things. They have to think of the health effects, but industry has to think of two things. They have to think of the health effects, but they also must think of the functionality as well of the fat. Does it function for the purpose? That's fantastic, Sarah. So switching to completely different food, let's talk about eggs for a minute. Are eggs safe or are they deadly?

Well, I've never heard anyone say they're deadly. So I'm surprised you're using that word. Are they safe? Like with anything, it's up to a certain cutoff of intakes. I think a healthy part of our diet, they contain some really valuable micronutrients, vitamins, minerals. And, you know, it's something I make sure that my children are getting a regular intake of eggs in their diet, because I know there's such a dense source of nutrients, good source of proteins. You know, like with any kind of food, it's all about moderation. You know, and it's boring a message, I know that is. Everyone wants a, you know, cure all food to have or one food to demonize. Well, I think in moderation, eggs are a really important and good component of our diet. I wouldn't encourage someone to be having three eggs a day,

but I think the evidence would point to three to five eggs a week is a good component and healthy diet. Brilliant. And maybe the last food, because I know we could talk for ages, but we're definitely over time. Can we talk about fish for a minute? So Tim, who's not on right now, is a bit negative on fish, despite many of the things that have been said about omega-3 and omega-6. Love to get your perspective, Sarah. Okay. So to give it some context, I think we should separate fish into two categories. So you've got your oily fish and your non-oily fish. So your non-oily fish is your typical kind of white fish, like cod, for example, which is a great source of protein, none of the unfavorable refined carbohydrates, etc. in it. So

it's a really good component of the diet. Oily fish are fish such as tuna, not tinned tuna though, fresh tuna, salmon, mackerel. Oily fish contain high amounts of the very long chain omega-3 fatty acids. And these are the fatty acids I mentioned at the beginning that are essential fatty acids. So they're essential polyunsaturated fatty acids that we cannot make. They're also the fatty acids that produce these pharmacological-like compounds that I mentioned earlier that have so many therapeutic effects. Now, there's two factors to consider in this. One is, can we get these very long-chain omega-3 fatty acids from plant-based sources? Yes, we can. But can we convert them in adequate amounts to the very long chain fatty acids?

It depends. So you can get omega-3 fatty acids from plant-based sources such as flax seeds, walnuts, but these aren't the very, very long chain ones, the ones that we need to produce these pharmacological like chemicals. Now our body can convert some of these plant-based ones to these very long-chain favourable ones, but the conversion rate is quite low. Generally, we only convert about 10%. So that is why generally as nutritionists and dietitians, we have recommended that people consume the very long-chain omega-3 from fish oil sources,

because we know that our body's quite inferior or inadequate in terms of how it converts the plant-based sources. Now, more recently, there's been much questioning as to, do we actually need these very long chain omega-3s from fish oils in the first place? Why can't we just use the plant-based ones? And this is because the evidence has been quite inconsistent. So there's been a lot of randomized controlled trials looking at the effects of these fish oil sourced omega-3s on different health outcomes. Now, the best way to describe why it's been inconsistent is because most of these studies have recruited people that have different baseline

levels of intake of oily fish. If you're having an intake that's adequate, then there's no further benefit of increasing your intake of the omega-3 from oily fish. If however, your intake is low, so if you have a low omega-3 status, then the evidence I think is quite clear of a benefit. So again, this takes us back to, it depends on who you are. So it's very individualized. So we can't say, yes, everyone will get a benefit. It depends if you're already getting a decent amount, there's no point having a further increase. So my recommendation is that people do try and have one portion of oily fish in their diet. If you are vegan or vegetarian, you can use algal sources and you can buy now quite affordable

algal sources of these very long chain omega-3. Brilliant, Sarah. I think that's a wonderful summary for that. We started by, can they ever be healthy? And the starting point is fats are really complicated. But the key message I think is that you can't just think about it as saturated fats are bad unsaturated fats are good actually need to think about the food we then talked a bit about is it possible to put on weight if you eat low-fat diets and the answer is absolutely yes

and this is because our bodies just have this amazing ability to basically swap between sugars and fats and so you know you know, you can eat no fat, but your body doesn't care if you're eating all of these refined carbohydrates or whatever you can swap back or forth. We talked a little bit about cholesterol. I told about that I'm one of many people who still finds this idea, is it really all right to eat fats? It's difficult.

And that there are some foods, I think you said that there's some animal fats and foods like butter that can increase our cholesterol, but actually so can carbohydrates. We discussed a little bit about labels and that they may not sort of give you the answers that you're looking for, because you can have a big difference between what the label says versus what you're actually going to feel. And then we talked about what should we cook with? What should we eat? I wrote down, you know, olive oil is pretty magical. So, you know, that's where you start.

Yeah. And only extra virgin as well. And only extra virgin. Absolutely. That it's really important to get that distinction. And that sunflower oil and soybean oil were also two oils that had strong, healthy properties. So definitely alternatives to look at and finally we touched on a few other foods you said i am allowed to eat my eggs but i'm not allowed to

eat three a day so you know sort of moderation in all things including moderation and then we talked a bit about oily fish and i think on balance your view is that you know there's a benefit to many people if you are a vegetarian or vegan there are alternatives for getting these fats that you can't get otherwise uh fantastic summary jonathan i think everyone can just skip right to this but it just shows what a lot of ground we've covered i think lots of things that we didn't have time to sarah thank you so much for taking the time and i know that you feel i constantly try and simplify something which is very complicated to the like okay but so what should people do so thank you for bearing with me not just in this podcast but over the last five years I think that's amazing because this is stuff that I think everybody can

just go and go and implement it at home and I hope you will come back again soon I will thank you it's been fun talking about my favorite topic it It's been brilliant. Thank you, Sarah. Bye-bye. Thanks, Jonathan. Thank you to my good friend, Sarah Berry, for joining me on Zoe Science and Nutrition today. We hope you enjoyed today's episode. If you did, please be sure to leave us a review and subscribe. If you're interested in learning more about Zoe

and the best foods for your body, you can head to joinzoe.com slash podcast and get 10% off your personalized program. Finally, if this episode left you with any questions, please send them in on Instagram or Facebook, and we will try to answer them in a future episode. As always, I'm your host, Jonathan Wolfe. Zoe Science and Nutrition is produced by Fascinate Productions with support from Sharon Federer and Megan McPherson here at Zoe. See you next time.