Fats and Oils: What's the Real Story? | Dr Sarah Berry

[Music] 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 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 low-fat offerings tasted unappealing so they loaded them with sugar with sugar so cheap their profitability increased seeing an opportunity they did everything they could to influence the debate funding research that downplayed the risk of sugar and highlighted the dangers of fat only now so many decades later has the impact of this lobbying began 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 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 uh that we have is what's healthier for most people a poached egg or an egg fried in olive oil uh egg fried in olive oil okay i think that's gonna 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 will surprise a lot of people and we can we can talk a bit more about it another question we had uh come up a lot is olive oil safe if you fry or roast with it so that the oil gets hot um absolutely it's safe just to 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 um i think the jewelry is 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 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 eating like can fat ever be healthy i think we've we've had this view i think you know saturated fats have a bad unsaturated good so can this be healthy and is it as simple as sort of saturated versus unsaturated or how does you know 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 child 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 um 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 it's dependent on the type of fatty acid within these groups but it's also very dependent in terms of that 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 whether 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 um for example the 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 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 that's great but i actually want this this practical advice so i think we'll come back and really talk about um specific fats um towards the end um we already already touched a little bit on this question about um weight and i think um 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 you know 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 of 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 we can do that so obviously that's it's an essential thing um but i'm storing fat so can you explain you know how is it possible for people to put on weight if they're eating low-fat diets because they're not actually putting any 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 um as fat got it and this is why it doesn't really matter you know 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 you know my fat for uh you know let's say coca-cola actually you're saying it's just the same thing right my body has this ability to to swap this backwards and and forwards yeah our bodies are really clever adapting to what nutrients um are available to us and it it's an area of huge contention in the nutrition world that 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 at loggerheads with the low-fat zealots about which is the best approach to lose weight and i think that you know 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 um around around this you know 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 you know 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 to my house without getting up from my seat so um is that sort of what you're talking about about this sort of um this environment that we're in yeah so the fact that it's highly accessible to you um but also or for most individuals it's highly accessible but also um 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 bioaccessible 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 you know given how clever our bodies are at maintaining this set point in our weight in maintaining and preserving energy we're we're kind of fighting a losing battle to a certain extent because we have this highly accessible food we have this highly bioaccessible 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'll 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 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 and 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 life long and this is why on the long term many diets do fail regardless of the nutrients and so um with that context one would think that fats were still a bad uh thing and you think they were a bad thing because they have um more calories than carbs for the same weight right sarah and maybe you can tell us exactly what that that difference is but it would sort of seem um 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 um going to put on more weight therefore um eating 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 um what seems logical yeah and this is why the whole low-fat um 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 you know 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 added 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 to pick up our 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 assessed 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 lost between the high carb people and the high fat people but when he went and looked on average 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 you 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 or 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 we switch another topic i i think we're interested to talk about sort of like the behavioral impact on this and how it makes us feel so um you know one of the things that people often ask me is well how has your diet changed since you you started zoe and um and the answers 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 um uh five years ago my 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 obviously we of course ate lots of carbohydrates because that's what you do to fill it in and and of course lots of refined carbohydrates pasta and bread and things like this so um i then did these zoe tests and it turned out that actually my blood sugar control was really quite bad and actually my blood fat control was much better um and so that's sort of you know what the advice is pushing but i still feel really guilty when i eat cheese like it's even though i've you know seen this and i also have noticed the way that actually my hunger is is lower when i'm eating these um high-fat foods like i still have this basic feeling that it's it's a bit naughty isn't it like it's not the right thing to do um you know 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 uh perspective that lots of people have around how do i reduce my cholesterol levels well let's consume low 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 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 um 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 um 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 increasing good cholesterol alongside an increase in bad cholesterol and saturated fatty acids increase our bad cholesterol but they do some of them do also increase our good cholesterol so again it's a little bit more complicated i'm sorry to say um depending on the type of saturated fatty acid but what what we do now know which i don't think we were so aware of you know 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 loot 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 effect on our health as butter does and the reason is is because of this matrix which i mentioned earlier the kind of special structure in which the fatty acids sit within the dairy products with that are fermented within the cheese and the yogurt so you could feed you know people a high motor 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 fat composition and despite the fact that actually basically the cheese comes from the butter right sarah so that's like even more surprising um you know i haven't done this at home but i uh you know tim talks a lot about you know sort of that you can ferment this is how you end up so um help us because help us unpack that a little bit it sounds a bit magical um it is because going back to my favorite word i think now is because food is really complicated and you know it's magical because how we process food has a huge impact on its health outcomes so how we process dairy whether it's us butter or whether it's as cheese or whether it's this 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 foods or consuming pureed fruit or consuming whole almonds or consuming ground almonds where you're changing the matrix it has a huge impact on this by accessibility 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 you know a vast effort uh are put onto all of these foods um and which you know in many countries right there's 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 is that is that what you're saying sarah yes in my opinion i 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 food it's in and this is because you're lumping all of these different things together so you're saying like well somebody's eating lots of animal fats and i think you're you still think animal fats are not um 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 huge impact and so that i do think that whilst labeling can be um 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 uh being preoccupied by labeling can actually be potentially even make us you know select more unfavorable health choices so if we consume um if we were to consume whole almonds we almonds have a very special matrix they have a very rigid cell structure so what happens is that remains intact largely as we chew them and they pass through our digestive tract and we only absorb about 60 percent 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 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 you know 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 that's that's um i think really powerful advice right that in general um thinking more about this is a food rather than as these sort of set of numbers on the back is actually um and of course all of this labeling you know i think it was it's all been done with good intent right um but actually um isn't very helpful and of course if it had been really helpful then um we would have seen all these wonderful health outcomes over the last 30 or 40 years which you know 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 um 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 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 those categories so you put at the sort of at the top so so olive oil you would need to use a higher layer type of sunflower oil and rapeseed oil is still a pretty good oil to use now in the u.s one of the main oils that they use for cooking on one of their main oleic acid so monounsaturated rich oils is soybean oil that's one of the most commonly consumed oil in the u.s it's home-grown so it's also good in terms of environmental impact because of it being a home-grown oil so i would say olive oil would be the best one and then in the u.s soybean oil and in the uk high-elect sunflower 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 you fry with olive oil yourself jonathan a lot then that's great it is a healthier option yeah and i 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 actually you know i love it so i would also say that it's like a lot of um it's like a lot of things right when you're making a change in um nutrition the hardest bit is making a shift because you're in the patterns that you're you're used to um 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 um and and so i i i at least you know as a speaking for one i i now 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 i think that it is an important point right that um you talked a lot about about this you know we food for pleasure and it's really important you don't think oh i can never have and anything else this is all about finding the right balance yeah and something else to mention is that um domestically so how we would cook at home frying an egg 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 and 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 you know uncooked foods it's not as it's not a good ingredient functionally for the food industry but also for us because all of the fa me most of the favorable uh benefits um 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 differences is in how many uh processing steps it goes through so extra virgin olive oil is the least processed and has the most amount of these you know great polyphenols that are so good for heart health they'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 um just straight olive oil nearly all of these favorable 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 of soybean oil and that's really helpful sarah and i think you talked already about sort of olive oils sort of you know magical properties as seen in this this big study um we did get a lot of questions around the dangers of cooking with it why um where does that come from and you said right the beginning you know very confidently it's fine and can you just elaborate just just briefly on why we can all just be relaxed and put it in the frying pan okay because i think there's a lot of scaremongering some time ago about um compounds such as peroxides polar compounds three mcpds if i've got that correct um 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 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 you know 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 scare mongering 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 uh repeat frying every day um i think you're pretty safe to fry and use this at home that that's really helpful i think um and i think also that that point that comes up a lot right about the difference between some sort of animal study in um 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 um you see you know there was that really you know either negative impact or really promising impact in this animal study and then it gets rolled out to you know humans and you've done uh you know i think more than 30 of these randomized controlled trials right and then you're like oh well that doesn't actually happen in in real life with real um real people is something i think for our listeners always to um to be aware of because it's part of why there's so much um sort of confusing different stories or even contradictory stories right it's not that anybody each of the pieces of science is correct but it it doesn't necessarily flow through in the way that maybe the media has put on its um 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 um you know corner street kebab shop um you know 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 you're still even in that scenario you're not going to produce enough of these that are even that you'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 in at home so the quality of those kind of oils will be determined on the functionality and this is something that we 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 blender 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 acid so this is an example where food 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 a completely different um food let's talk about eggs for 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 they're certainly i think a healthy uh 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 they're 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 it's boring a message i know that is everyone wants a you know cure or 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 you know the evidence would point to you know three to five eggs a week it is a good component of a healthy diet brilliant and maybe the last food because i know we could talk for ages but we're we're definitely over time um can we talk about fish for a minute so um tim who's not on right now is a bit negative on on fish despite you know many of the things that have been said about you know omega-3 and omega-6 um love to get your perspective sarah okay so um to give it some context i think we should separate fish into two categories so you've got your oily fish and or 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 um you know none of the unfavorable refined carbohydrates etc in it so it is a really good component of the diet oily fish are fish such as tuna not tin tuna though fresh tuna a 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 omega 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 um 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 favorable 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 is quite um 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 you know in the first place um why can't we just use the plant-based ones um 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 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 oily fish 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 alkal 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 um summary for that we always like to um to summarize at the end so let me try and um play back a bit some of this this journey and and correct me if i've i've got any of this wrong so um we started by can they ever be healthy and the starting point is fats are really complicated and you started to help to to explain why with chemistry but i slightly lost the thread which i suspect other people will as well um but the key message i think is that um you can't just think about it as saturated fats are bad unsaturated fats are are good actually you 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 um our bodies just have this amazing ability to basically swap between sugars and and fats and so you know you can eat no fats but um your body doesn't care it's going if you're eating uh all of these refined carbohydrates or whatever you can swap back and forth um and that um even though fats have much many more calories per um [Music] per gram than carbohydrates and so it would seem obvious that if you want to lose weight you need to reduce fats actually you know there is this wonderful study you mentioned the diet fit study that shows that on average people lose the same amount of weight on a low fat or a low carbohydrate diet so actually the whole thing about energy density you know definitely doesn't matter because there was a big difference we talked a little bit about cholesterol i told about you know that i i'm one of many people who still finds this idea well you know is it really all right to eat fats is difficult and that there are some foods i think you said that there's some animal fats and and foods like butter that can increase our cholesterol but actually so can carbohydrates we discussed a little bit about labels um and that um they may not sort of give you the the answers that um uh that you're looking for because you can have saturated fats like an animal fat or you could have a saturated fat like a a cheese uh and similarly i think it's a great example where you know the label says almonds have certain number of calories but actually you're probably only consuming sort of 60 of those so again a big difference between what the label says versus what you're actually going to to feel um and then we talked about well okay practically you know what should we um what should we cook with what what should we eat i wrote down you know olive oil is pretty magical so you know that's where that's where uh you start yeah and only extra virgin as well and only extra virgin absolutely that it's really important to get that um that distinction and that sunflower oil and soy bean oil uh were also um two oils that had um strong healthy properties so definitely alternatives to look at and that people can generally relax about um the temperatures they're getting their oils to at home despite a lot of scary things that they may have read that there's a huge difference between what might happen in an animal study and what really happens you know with with human beings um and that also there's a huge difference between the cooking that we have at home and something that's happening in a restaurant where they're cooking over and over again and even then there are regulations if you're in in the u.s or in in europe so you know it's not going to um have sort of these these deadly compounds and at the same time they're very unlikely to have used as high quality fats as um we would use um use at home and uh so they probably will be lower quality oils and finally we touched on a few other foods you said uh i am allowed to eat my eggs um but i'm not allowed to eat three a day so you know sort of moderation um in all things including moderation um and then we talked a bit about early fish and i think on balance your view is that you know there's a benefit to many people you know if you are a vegetarian or vegan there are um alternatives for getting these fats that um 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 um 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'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 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 wolf zoe science and nutrition is produced by fascinate productions with support from sharon feder and megan mcpherson here at zoe see you next time [Music] you

Channel: ZOE

Views: 178,903

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Id: qUQnf_ok63w

Length: 51min 58sec (3118 seconds)

Published: Mon Apr 25 2022