This BBC podcast is supported by ads outside the UK. Hello, I'm Greg Foote and welcome to the show that investigates the Wonder products promising to make you happier, healthier or greener. Each episode I run one of your suggested Wonder products through the evidence mill to find out if it is indeed the best thing since sliced bread or marketing BS.
And today I'm joined in the studio by Sarah Powell from Hyde in Greater Manchester. Hello, Sarah. Hi, Greg. Welcome along. Tell us the wonder product that you would like us to investigate today and why.
I'm interested to know if it's worth spending extra money on expensive cooking oils compared to the cheaper vegetable sunflower oils available in the supermarkets. Do they have more health benefits? And is butter, ghee, lard, is that still bad for your health?
I tell you what Sarah, we have had an absolute wokload of emails sent to sliced.bread at bbc.co.uk asking about cooking oils. A listener, Alistair in Middle-Othean, wrote that, for years, we were told to cook with polyunsaturated oils like sunflower oil. But now, all the YouTube doctor experts are telling us seed oils are harmful. They advocate consuming extra virgin olive oil, but as I understand it, that's not suitable for frying a fish.
Also, I hear that over a certain temperature, olive oil turns harmful. What the heck do I use for frying and roasting? And listener Kamal sent this voice note to our WhatsApp number, which is 07543 306 807. Hi Greg, how are you? I cook enough curries with grape seed oil, which is vegetable oil. And I hear coconut oil is a wonderful and avocado oil is also cooking oil that you should be using more often.
There's also butter and also ghee, which has a higher smoking point. So I'm a bit confused as to what oil should I be cooking in my curries. Bye. To help us serve up the sizzling science, let me introduce today's expert, Professor of Population Health and Nutrition at the University of Cambridge, Nita Faroohe. Hi, Nita. Hi, great to be here.
Nita, we've just heard how many different types of oils there are, so there's so much we need to explore today, but I think we should start with what is actually in these oils, fats. The understanding of fat has evolved, hasn't it, over the past decades? We now know that fat isn't just fat, there are different types of fat. Can you walk us through them?
So there are some very bad fats that we should completely cut out from the diet, some bad fats that we should reduce, and some good fats that we should eat more of because we don't get enough of them. So the really bad type of fats are what we call hydrogenated or trans.
those we should really minimize and cut out as much as possible. And that would be in things like baked goods and fried products. These trumpets come from industrial processes, which convert oils into solids that can then have a longer shelf life. It's about saving money. It's about prolonging shelf life.
Then we come to the not so good fats, and that is saturated fats in things like butter, dairy products. But don't forget, meat and meat products are also relatively high in saturated fat.
And then the third type and the fact that we know from a lot of research that are actually good for us are the unsaturated fats and they come in two types, monounsaturated or polyunsaturated type. And the fact is we do need some fat in our diet, don't we?
We do because actually fat is pretty essential for human living and for human functioning. That is needed for ourselves to function, for us to absorb vitamins and for energy intake. And lots of other important uses, but fats are pretty essential to health. OK, we do need some fat, but not all fats are made equal. So what are the current guidelines on how much of these different types of fat we should eat?
previously, which used to be thought that all fat is bad if consumed in large amounts. It was about limit the amount. So there was a concern, firstly, that if you have too much fat, then obesity and increasing weight would be a problem.
And the other one was that there was emerging evidence more than 50, 60 years ago now that fat intake is related with artifacts, then the more nuanced understanding came. That is not all fat. Some fat should be cut out altogether because trans fats, there is very strong, very consistent evidence that
higher trans fats increase your bad cholesterol level, which is called LDL cholesterol, and the rates of heart attack and stroke are massively increased with beta trans fats. Whereas for polyunsaturated fats, they're actually protective for the same conditions. So higher levels would help to reduce your LDL or bad cholesterol, raise your good cholesterol, and reduce the risk of heart attack and stroke and so on. What are the concerns if we eat too much saturated fat?
So we shouldn't demonize saturated fat to the extent that they were before. The government guidelines consistently have said to keep that under 10% of our energy intake or calorie intake per day. That comes from, again, good quality evidence that having high amounts of saturated fat has similar effects that I described as before for trans fats, which is it raises the bad cholesterol and it raises heart attack and cardiovascular disease risk.
However, when you cut down on one, what do you replace it with? As we say, reduce saturated fat to under 10% of your calorie intake per day, we have to save the same breast and replace it with the unsaturated fats. Brilliant. That's the message I'd like to get out. Okay, one final question on fat, and then we'll get to picking oil, Sarah, don't you worry. Can I eat as much of these good unsaturated fats as I like then?
No, we still have to keep them within limits because if you just consume it in unlimited amounts, it's going to give you a disproportionate amount of calories. And there is an opportunity cost because you're then not eating the other good stuff which has health benefits. So if you fill yourself up with a whole load of fatty stuff, where are you going to fit in your fiber intake? Where are you going to fit in your fruit and vegetable intake and legumes intake? So it's all about imbalance.
Thank you so much. So yeah, they're good for us, but Sarah, we can't eat unlimited amounts of nuts and avocados, sadly. Unfortunately. Let's move on to cooking oils because that's what you've asked about Sarah's. So any particular cooking oil, if you look at it and the nutritional information on the bottle, it will say it contains a mixture of saturated, mono unsaturated and polyunsaturated fats in different proportions.
Nita, let's go through the types of cooking oil one by one. Let's start with vegetable oils. It is a huge catch all name that covers any oil from seeds, fruits, nuts and grains. And your commonly known vegetable oils are sunflower and rapeseed or canola, which is a variation of rapeseed, palm oil too. There's also saff
flour, soybean oil, corn oil, cottonseed oil, grape oil, rice bran oil, avocado oil, coconut oil, which we heard about as well of course, that's a lot. Technically olive oil is a vegetable oil too, but let's start with some flour and canola or rapeseed because those are the cheapest.
bottles labelled vegetable or sunflower looked to cost around two pound a litre at most supermarkets. The ones that are labelled vegetable oil actually tend to ordinarily be just rapeseed oil. Bottles labelled specifically as rapeseed oil, they come at a little more expensive, normally two to three pounds a litre. And if you're after an organic rapeseed oil, then the price jumps to close to five pounds a litre. Neater in terms of the fats in sunflower and canola or rapeseed.
They looked to both be around 5-10% saturated fat. Is that good news? And when it comes to rapeseed or canola oil, the biggest size of that fatty pie appears to be mono unsaturated fats. They can be around 70-80%. Is that good news?
It is because we want to keep the saturated fat intakes overall on the lower side, 10% of calories per day. And we also want to increase the unsaturated fats because they are good for health. So it's a win. If we look at some flour, oil, the biggest proportion of the fats there are polyunsaturated fats around two thirds. The fact that these vegetable oils have a lot of mono or have a lot of polyunsaturated fats
Are they actually healthier than we think that they deserve the stigma that they get so you make a really good point why is there news out that that they're not good for us actually that is false news or fake news these oils are absolutely good for us.
And this is not just an opinion. There is a huge amount of research that shows that when saturated fat is cut down and replaced with these types of oils instead to provide the mono and the polyunsaturated fat, that there are benefits for human health, reduced heart attack rates and so on. Sarah, is that a surprise?
That was quite unexpected. A lot of the information out online that I've read tends to disagree with that, saying that the alternative, more expensive oils are much better for you.
You raise a really good point about when you read online, it looks like oils like the canola oil or rapeseed oil or sunflower oil. They aren't good for you, but I've just said, actually, they are healthy alternatives to the saturated fat. So all lines of evidence stack up in the same direction. When saturated fat is reduced and replaced with these oils, which are rich in the mono and the polyunsaturated fats, we get a reduction in disease risk.
Now something I have seen talked about a lot when people are claiming how healthy a cooking oil is. Amiga 3, Amiga 3 and Amiga 6. Can you introduce us to those please, Nita?
Okay. Polyunsaturated fat is also not just one entity. Broadly speaking, there are two types of polyunsaturated fat. One is called the omega-3 polyunsaturated, and the other is called the omega-6 polyunsaturated fat. Don't worry about why they're called omega-3 and omega-6, but if you're really curious, basically, it's to do with the chemical structure. We know about omega-3, because you get that in fish oil, don't you? And that's recommended.
So omega-3 largely comes from fish and marine sources, fish and seafood, but a lot of people don't know this. You can also get omega-3 from plant sources, such as from some of the nuts like walnuts and black seed.
You can also get from meat, but the large focus of omega-6 comes from nuts and seeds and avocados and those type of plant-based foods largely. The confusion out there has been about whether omega-6 are, in fact, healthy. That's been the biggest debate out there. But the research conclusion is that over the 6 fatty acids should not be demonized. They are actually good for human health.
Okay, so it's actually good to go for a vegetable oil we're talking about at the moment that has both omega-3s and omega-6. Yes, that's correct. And in fact, all oils do have a mix of those. It's not as if you can get some oils that are pretty much omega-6 or only pretty much omega-3.
There is a type of vegetable oil that I feel we should very briefly discuss and that's partially hydrogenated vegetable oil. Now, this is oil that's been processed to increase its shelf life. But as a result, it usually contains high proportions of trans fats, potentially around 25 to 40%. Now, you can't buy a bottle of it in the UK because recent legislation limits the proportion of trans fats in food to know more than 2% of the total fat.
But it is worth checking the ingredients list on things like margarines, for example, for hydrogenated vegetable oils, isn't it, Nita? Yes, that is absolutely right. So in the past, the margarines used to be a source of these partially hydrogenated oils. But now the modern day margarines can have close to zero amount of trans fats. So does that mean we need to remove the demonization of margarine, potentially not a bad guy?
Yes, that is absolutely right. So, margerines, when they do not contain partially hydrogenated oils, do not contain trans fatty acids, they can be part of a healthy diet, they can be part of a management of reducing the bad cholesterol. Let's move on to another type of vegetable oil, a specific type, olive oil. Do you find this one in your cupboard, Sarah?
Yes, I've got it at home. Recently I've started just using it for dressings on salads and I've stopped cooking with it and now I'm not so sure. So you used to cook with it? I used to cook with it after reading stuff online about smoke points, the temperature you should take it to. I've just started using it as a dressing. But I think maybe it should be okay for cooking. Let's get into olive oil.
Now these do come out much more expensive at supermarkets than sunflower or rapeseed oil. We saw that olive oil is usually between seven to eight pounds a liter. An extra virgin olive oil is normally a pound or so more. First things first need to what is the difference between olive oil, virgin olive oil and extra virgin olive oil.
It's to do with the degree of processing or refining of the oil. If you take olives and you have a pressing machine and you just squish it out, you'll get a lovely extra virgin, extra fresh, brimming with all the goodies olive oil. Now, no matter how extra virgin it is that you buy it from the supermarket shelves, it's not going to be equivalent to you having squeezed it in your home and consuming it within a day or two of doing that.
However, extra virgin overall just means it is as close to the natural state as possible. It hasn't been refined. It hasn't been processed. So the virgin olive oil is just a lesser degree of the sort of, if you will, the purity or close to the natural state.
Whereas the standard olive oil, you can be pretty sure that means that it's been refined and processed and that it takes out some of those small solids and things that are part of that pressing down from the fresh stuff. There's also a fourth type light olive oil. What's going on there?
It depends, different supermarkets and also different countries use the word light in different ways. It could either mean that it's a blend, but different proportion of the degree of pressed nests. It could also mean that it's a blend of olive oil with potentially some other oils added in.
Yeah, some brands, for example, Olivia are a blender vegetable oil with 15% pure olive oil. Sticking with the pure olive oil though, looking at the back of the bottles, we've seen that that is very high in mono unsaturated fats, but it's also higher in saturated fats than sunflower oil and rapeseed or canola oil.
So is olive oil the healthier option that we're being told it is? We have pretty good evidence that olive oil, particularly extra virgin olive oil, that it is good for health in a multitude of ways. The question about whether the fact that it has slightly more saturated fat than some of the other plant oil, seed oils, like canola or sunflower, is that a problem? No, it doesn't seem to be a problem because even the olive oil is not just about its fat content.
We've got all sorts of other things other than the fats. So within oil, that would be things like antioxidants and polyphenols and vitamins. So it's the totality of the product. So olive oil, in relation to health, it's certainly the good guy. So even though it's got that slightly high proportion of saturated fats, the evidence suggests it is still a healthier option.
it absolutely is, because it's completely dominated with the very high amount of the oleic acid, which is in it, which is the monounsaturated fat, plus all the other goodies that go with extra virgin olive oil.
Now, we have had loads of emails from listeners asking whether they should actually be drinking their extra virgin olive oil. We did very briefly mention that in our longevity episode, in our 100th episode. This could be a whole separate discussion for sliced bread, I can see in the future. We're not going to get into that today, but sticking with cooking oils, which we're talking about, this is where it gets interesting.
Olive oil products say they are great for frying, stir frying, baking and roasting. But extra virgin olive oil products say they should be used for sources, dips and dressings and for drizzling over salads or pasta. Some even say using this oil for high cooking temperatures is not recommended. Listener Alistair said that he'd heard that over 165 degrees C olive oil actually turns into trans fats like the hydrogenated oils.
Is that true? To my knowledge, that is not true because the temperature that your listener has mentioned seems to be about the smoke point. And a smoke point is basically where when an oil is heated, it starts to break down and its chemical structure or molecular structure changes and it starts to release bad things. So there has been some concern, a legitimate concern that if that was to happen by heating at very high temperatures,
then over time there could be bad health problems. However, I would question the 165 degrees that were mentioned. The temperature tends to be quite a bit higher at which the smoke point of olive oil is reached. Secondly,
It's not so much that hydrogenation takes place and therefore trans fats are produced. It's more that some other things are released bad chemicals, which are things like aldehydes and heterocyclic amines or polycyclic amines. That's the concern.
As part of researching this episode, we were chatting to a chemist called Martin Groodveld, who writes about how polyunsaturated fats in particular seem to release what are called toxic byproducts when they react with oxygen, when they're heated to a high temperature. For example, he did some testing for the show Trust Me I'm a Doctor and found that sunflower oil and corn oil produced toxic aldehydes at levels 20 times higher than recommended by the World Health Organization. What's your view here, Nita?
Yeah, so I would agree with the science that when you heat temperatures to very high levels and exceed the smoke point, you will get breakdown of the oils and release some nasty chemicals, including aldehydes and hydrocyclic amines.
But that type of cooking in the home is not very common. And one has to distinguish between where that type of cooking happens in commercial kitchens. If you're taking takeaways a lot, then you have to question. And if you're doing home cooking, that's a different issue.
And studies also need to be then correlated back to long-term human health issues. And what I would say is the studies that have looked at different types of oils, from plants, from seeds, from olive oil, without exception, are related with better outcomes for chronic diseases.
Martin also said that oils high in monounsaturated fats like olive oil or rapeseed or canola oil produce fewer toxic compounds than polyunsaturated fats like sunflower oil. So would that actually therefore suggest, would you advise people based on that to cook with olive or canola over sunflower if it's going to potentially produce fewer toxic compounds?
It is right that when the oil has more of the monounsaturated fat, that it adds to the stability and slightly higher smoke point, and therefore you get fewer of the nasty chemicals released. But it's not to a degree that when you link it back to human health, that it necessarily makes a difference there. So what I would recommend is go with what tastes and costs
considerations you have, and use a mix of the different types of oils. Sarah, there's a lot of information here. What do you make of these thoughts about olive oil versus sunflower or canola?
I would like to know if the manufacturing process has much to do with the amount of nutrients you've got left in your oils. Is it worth buying the cold pressed oils, which are a bit more expensive as opposed to the more refined vegetable and some flour oils? Great question, Sarah. The defining process, there's been a lot of discussion and debate whether that materially changes it.
So the hard-grade evidence isn't really out there to really say definitively that you should always have the cold-pressed variety only. But the cold-pressed more close to the natural state oils do have helpful benefits because the proportion of the fatty acids or the fats doesn't change by the refining, but some of those other components that would protect you from inflammation
that have polyphenols and that are generally good for health and have the good vitamins like vitamin E and all that are in there. Remember, you can get those goodies, the polyphenols and the vitamins and the antioxidants from a whole host of foods other than oils. The humble fruit and vegetables are a great source of polyphenols and a whole lot of antioxidants as well.
and they bring you other benefits. You need fiber in your diet and so on. So legumes, fruits and vegetables. So I always go back to the overall diet rather than a focus only on oils. Thanks, that makes a lot of sense. I've got a bit of a treat for us now. We're talking about cooking oils. We got in touch with someone who was brilliant on our previous pots and pans episode of sliced bread, Tim Haywood. He is a regular on Radio 4's kitchen cabinet. He headed into his kitchen to fry up some lunch and talk us through his favorite oils.
Hi Sarah. So here we've got cheap yellow olive oil. That's good for shallow frying. If you want a Mediterranean kind of Spanish flavor, then there's extra virgin olive oil. That's just for dressings or to pour over cooked food like grilled fish, maybe pasta. Raped seed oil is my standard flavorless oil. It's got a good high smoke point. I use it for shallow frying only. It's okay for frying sweet things, but it's expensive. Too expensive to use for any deep frying.
I use sunflower oil for deep frying, it's cheaper and there's got a higher smoke point. Every oil, depending on how refined it is usually, how much of the original organic material it's got left in it, has a smoke point. The smoke point is the temperature at which the oil starts to break down and nasty compounds are released. Things that make the oil taste bitter or burnt or unpleasant. You don't want those things in your food.
For frying something like chips or something in batter, you really want the oil to be around 185, maybe 175 degrees centigrade. To deep fat fry, you need to pick an oil that has a smoke point above that point. And that would be a good vegetable oil, like a grander oil or a corn oil, perhaps. Weirdly, in the old days, they used to use lard for this because obviously that has quite a high smoke point that works well.
If you start trying to fry with a high temperature underneath the oil and you use an oil like for example extra virgin olive oil which has quite a low smoke point because it's got all that green stuff is provided by organic compounds that are in the oil. That will break down at a lower temperature and you'll never get it high enough before it tastes horrible to actually do the frying.
Then these little bottles are walnut oil, argan oil, hazelnut oil, all just for salad dressings. They don't heat well at all. So there are two bottles of sesame oil, one cheap one that I can use it a walk, but I keep a separate, better quality one just for dressings.
It sounds like he's following your advice, Nito, and he has a whole host of oils in his kitchen. Absolutely. And I think that's the advantage of mixing and matching. I think we should look at a couple of the oils that Listener Kamal has introduced before we turn to butter and ghee and maybe lard that Tim just mentioned there. So Listener Kamal asked about avocado oil. Products claim that this is ideal for high heat cooking.
as well as drizzling over salads, fruits and smoothies, and they boast how high it is in mono-unsaturated fat. It does look to be one of the most expensive type of oils you can get, generally at least 12 pounds a liter. So Kamala asked if it's a wonder food. What do you think, Nita? What might justify the price tag?
Certainly avocado oil is good for all the reasons mentioned, but is it worth justifying the cost? If you're a particular connoisseur of the taste it brings and you'd prefer it and you have the money, then knock yourself out. But there's lots of myths around these superfoods and wonder oils and wonder this and that, and it's just all, I'm afraid, hogwash.
Kamal also asked about coconut oil. The price there looks to be up around olive oil's price, around seven pounds a litre depending on where you buy it from. Products say it's best used to fry, bake, roast and spread, also that it's great in smoothies, marinades and stir fries. It sounds pretty versatile, but it looks to be very high in saturated fat.
Yes, so coconut oil and its health effects have been round the block a few times. Some culture used coconut oil as part of their normal cuisine. But the concern is it's very high amount of saturated fat. But fat is not simple. And saturated fat, sorry to break the bad news, is also not just one entity, saturated. There's more to this.
There is more to saturated fat as well. Now, coconut oil does proportionately have more of a particular type of saturated fat within it, which is called loric acid. And there is some evidence that loric acid is actually not as bad as the other saturated fatty acids, which raise the bad cholesterol.
We ourselves have done a small clinical trial on this. And what we found was that butter raises the LDL cholesterol more compared to coconut oil. But I'd be very cautious going from one study that we or anyone else might have done to saying now the public can take that as evidence to eat more coconut oil.
So what the public health bodies say is that because overall of its high saturated fat content, coconut oil should stay be used sparingly if you particularly enjoy using it, keep it within the overall saturated fat intake per day. So no more than 10% of your energy calories in a day should come from saturated fat, but don't use it for everything.
Sarah, have you used it? I've used it more on my skin than anything else. I don't really cook with it. I wasn't really sure whether it was good or bad for you. I do use butter occasionally, but not all the time, but I think it's a good idea. What you're saying to use a range of cooking oils, and I think I'll keep the most expensive ones to use as a salad dressing or keeping them cold.
And seeds, let's just sum up the seed oil point because listener Alistair asked about that. He said that he'd seen all the YouTube doctor experts telling us that seed oils are harmful. Where's that coming from, Nita? And is it something we should be concerned about? We should ignore the YouTube videos.
that don't give a balanced evidence review. The totality of the evidence is absolutely clear that the omega-6 rich seed oils are part of the solution to help reduce the heart of the epidemic that we have in the world. They help us to reduce saturated fat and replace it with the polyunsaturated fats.
Sarah, you mentioned butter earlier. We heard Tim mentioned lard. There's also ghee, a clarified butter, butter that's essentially had its water and its milk solids removed, so it's essentially just butter fat. These are all non-vegetable paste. What are your thoughts on these, Anita?
Butter, it's yo-yo-ed. There was that classic headline of butter is back, et cetera, based on some research that showed that perhaps it's not as bad as previously thought, but it's all about relative comparisons. So if you have more of butter because you're partial to its taste, you get more saturated fat and you lose out on the opportunity of having the good fats.
My advice is if you love butter, for instance on your toast, by all means have it there, but for cooking experiment with different types of oil that will bring you some health benefits as well. Overall, keep the saturated fat intake.
to below 10% of calories, that's roughly 30 grams for a man on a 2000 kilo calorie diet per day and 20 grams for women. So that's not hard to achieve. 30 and 20 is reached very rapidly if you start having things with butter or ghee.
Wow, I've learned a lot today. Thank you so much, Nita. Sarah, it's time for us to put that big final question to Nita. Nita, do you think more expensive cooking oils are the best things since sliced bread? Are they SB or are they marketing BS? Definitely not worth it. Marketing.
Is that what you expected to hear Sarah? Wow, no, I wasn't expecting that at all. And it's been so interesting. I've learned so much today as well. I'm going to stock up on a few different oils. I'm going to try different ones. And I'm going to stop going down those rabbit holes on YouTube and Instagram. You're going to go home, start cooking.
Yeah, making choreography. Coming round. Sounds great. Well, with that, I shall wrap up today's Slice Bread. Next time, I'll be investigating the most requested wonder product in Slice Bread history, grounding sheets. They promise to reduce pain and help with sleep by connecting you to the Earth's own electrical field, just like a grounding wire in a plug. But does the science match the marketing hype? I'll be finding out.
Hello, Greg Jenner here. I am the host of You're Dead to Me from BBC Radio 4. We are the comedy show that takes history seriously, and then laughs at it. And we're back for a brand new series, series 9, where we're covering all sorts of things, from Aristotle, to the legends of King Arthur, to the history of coffee, to the reign of Catherine Abadichie of France. We are looking at the Arts and Craft movement and the life of Sir Journer Truth, and how cuneiform writing systems work in the Bronze Age. Loads of different stuff.
It's a fantastic series. It's funny. We get great historians. We get great comedians. So if you want to listen to your Dead To Me, listen first on BBC Sounds.
Yoga is more than just exercise. It's the spiritual practice that millions swear by. And in 2017, Miranda, a university tutor from London, joins a yoga school that promises profound transformation. It felt a really safe and welcoming space. After the yoga classes, I felt amazing.
But soon, that calm, welcoming atmosphere leads to something far darker, a journey that leads to allegations of grooming, trafficking and exploitation across international borders. I don't have my passport, I don't have my phone, I don't have my bank cards, I have nothing. The passport being taken, being in a house and not feeling like they can leave.
World of Secrets is where untold stories are unveiled and hidden realities are exposed. In this new series, we're confronting the dark side of the wellness industry with the hope of a spiritual breakthrough gives way to disturbing accusations. You just get sucked in so gradually.
and it's done so skillfully that you don't realise. And it's like this, the secret that's there. I wanted to believe that, you know, that
Whatever they were doing, even if it seemed gross to me, was for some spiritual reason that I couldn't yet understand. Revealing the hidden secrets of a global yoga network, I feel that I have no other choice. The only thing I can do is to speak about this and to put my reputation and everything else on the line. I want truth and justice.
and further people to not be hurt for things to be different in the future. To bring it into the light and almost alchemise some of that evil stuff that went on and take back the power. World of Secrets Season 6, the Bad Guru. Listen wherever you get your podcasts.