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  • Hello and welcome to Zoe Shorts, the Bite Size podcast where we discuss one topic around

  • science and nutrition.

  • I'm Jonathan Wolf, and as usual, I'm joined by Dr. Sarah Barry.

  • And today's subject is cooking oils

  • From sunflower to soya bean to olive and coconut oil.

  • There are loads of oils out there.

  • But it's tricky to know which ones are best to cook with.

  • Plus, more and more people are searching 'cooking oil bad' on Google.

  • So, wait Sarah, are you saying cooking oils are bad for us?

  • It's a bit more complicated than that, Jonathan.

  • Okay, I'm intrigued.

  • Let's get into it.

  • Let's imagine a typical home kitchen.

  • You might picture some vegetables roasting in the oven, or maybe a stir fry sizzling

  • in a hot pan.

  • It sounds yummy.

  • So what oils would they typically be used to make this feast?

  • So chances are it's gonna be vegetable oil and the most common vegetable oil is rapeseed

  • oil, as it's called in the UK, or canola oil as it's called in the US.

  • Otherwise, it's often a blend of vegetable oil such as sunflowers, soybeans, and other

  • oils.

  • And we did some research with a friend of Sarah's who is a world expert on this, and

  • there are a lot of other popular oils.

  • So there's sunflower oil, there's olive oil, coconut peanut, and sesame.

  • And in case you are wondering, apparently the french fries at McDonald's are cooked

  • in a blend of rapeseed and sunflower oil at ratios to make the oil as stable as possible.

  • And hopefully Sarah you will explain that a bit more in a minute.

  • I will, but that ratio is top secret, so I can't divulge that information, what I can

  • divulge is that all the fats and oils that we cook with and that we consume are made

  • up of a mixture of saturated and unsaturated fats and different oils have different proportions

  • of these types of fats.

  • For example, most vegetable oils such as rapeseed which is also like I said called canola oil

  • and sunflower have a lot of these healthy unsaturated fats.

  • Whilst tropical oils such as palm oil and coconut oil tend to have an equal proportion

  • of saturated fats and unsaturated fats, and depending on the type of saturated fat in

  • these tropical oils, these oils tend to be less healthy for us.

  • But Jonathan, it's really important to think about what happens to the oil when we cook

  • with it.

  • And I think one thing that people often ask about is this thing called the oilsmoke

  • point’, right Sarah?

  • I understand that's the point when an oil begins to burn and smoke, as I have definitely

  • experienced when cooking, getting distracted and you look back and you know the smoke is

  • pouring towards the fan.

  • So if you heat the oil near to or past that point, the taste of the oil can change and

  • I think some of the other nutrients in the oil can also be degraded.

  • Yeah, that's correct, Jonathan.

  • And I think that the way I often think about this is according to three important factors

  • that affect an oil when you cook with it, which change its taste, but also change potentially

  • some of the health effects.

  • And these three factors are moisture, air, and temperature, These can change the structure

  • of the oil as well as oxidize the oil.

  • And it's these changes in structure and these changes in oxidation that can have potentially

  • unfavorable health effects.

  • But how much fat changes during cooking is dependent on your cooking method.

  • For example, the temperature at which you're cooking, how long you're cooking it for, and

  • also really, really importantly, whether you are repeat frying.

  • So reusing the oil as well.

  • As a general rule of thumb, it's good to pick oils that have a higher smoke point.

  • It's good to avoid heating above 170 degrees centigrade or also 340 degrees Fahrenheit

  • and avoid this repeated use of the same oil for frying as you might use, for example,

  • in deep frying.

  • So oils that have a high smoke point and therefore meet those criteria.

  • Include rapeseed, canola, and sunflower blends.

  • What about virgin olive oil?

  • So that doesn't have such a high smoke point, and so I think various people have said that

  • you shouldn't cook with it, but I think it's more complex than that.

  • Yeah, it's a real balancing act because oils like extra virgin olive oil have more of these

  • bioactive nutrients such as polyphenols.

  • Which are special because they have antioxidant properties.

  • It means that they reduce the impact of free radicals caused by oxidation.

  • But the flip side of this is that they're more sensitive to heat because of their lower

  • smoke point.

  • And what happens is when you heat an oil, like extra virgin oil, it can lose some of

  • its benefits.

  • And so what can happen is if it's exposed to light and air for a long time and heated,

  • you lose some of these healthy polyphenols.

  • Now, refined oils usually have higher smoke points, as you pointed out, but they often

  • have less of the beneficial plant chemicals that we find in olive oils.

  • And I think one of the things you've already mentioned is generally if you're just cooking

  • at home for yourself, you don't cook these things for very long, right?

  • And so there's sort of focus around smoke point.

  • Very different from being at home versus thinking about some sort of restaurant, which is cooking

  • things over and over.

  • Is that right?

  • That's correct.

  • I think when we need to think about the health effects of cooking with oils, we need to separate

  • what happens in a more commercial or in the food industry versus what we actually do at

  • home.

  • So I think it'd be good to dig into the potential health risks, Jonathan, of cooking oils a

  • bit more because there are a lot of myths out there.

  • I think that sounds like a great idea.

  • And so people talk about what about the compounds sort of reduced during, you use this word

  • oxidation, right?

  • This is basically where oil is going past this smoke point and it's, it's changing.

  • So there's this talk about this can potentially increase blood pressure and cholesterol and

  • cause vascular inflammation and this all sounds terrible.

  • Yeah, and I think it's really important to pick up on this, Jonathan, because this is

  • where I think there's a lot of myths out there.

  • So a couple of points I want to mention is, firstly, most of the evidence around what

  • you've just pointed out about all of these dangerous effects of cooked oils is actually

  • from animal studies.

  • Secondly, and even more importantly, the harmful effects of cooking oil generally only happen

  • when oil is used over and over again at really high temperatures.

  • For example, in the old-fashioned home deep fat fryer where the oil might be used repeatedly

  • over a month.

  • So bear in mind, very few people use deep fryers now at home and the general way in

  • which we cook our food now at home using oils doesn't generate most of these unfavorable

  • and harmful compounds.

  • Got it.

  • So we are talking about restaurants and fast food chains and places like this where oil

  • is going to be used repeatedly for long periods of time at these high temperatures.

  • Now, I think there are laws right in the US or in Western Europe about having to change

  • their oil regularly and sort of legal limits on the level of these unfavorable compounds.

  • Is that right?

  • the UK, and in America regarding, the levels of particular compounds that are allowed to

  • be in commercial oils.

  • I do think certainly many of the big food companies adhere to this very well.

  • And we

  • had a lot of questions on this, so I'm gonna ask you about a few other oils that some people

  • were incredibly excited or confused about.

  • What about avocado oil?

  • Yeah, Jonathan avocado oil is an interesting one.

  • It came, only about a couple of years ago to be, sold commercially.

  • If I'm honest with you, I think it's a load of nonsense.

  • I think it's a ripoff.

  • Basically.

  • It's sold as having, these wonderful properties cuz it's high in unsaturated fats.

  • Actually, in my opinion, it's almost no different to rapeseed oil.

  • The only difference is you'll pay about 50 times more per liter for it.

  • What about coconut oil?

  • Isn't that supposed to have some sort of super healthy properties, it's all-natural, et cetera?

  • It's actually a really controversial area, Coconut oil, even in nutritional research.

  • And firstly, something just to say about cooking, I don't think it's a good choice.

  • It's got a really low smoke point, so it's oxidized easily, in terms of its health effects,

  • I think that there is some suggestion that coconut oil when consumed as part of the coconut

  • can be healthy, but when it's extracted from the coconut and the other properties in the

  • coconut, I don't think that there's much evidence to say that it's a healthy option.

  • There are some studies published that have shown that there are some health benefits,

  • but I would question those studies and I certainly wouldn't consume it myself in large amounts.

  • Definitely no coconut oil then and the final one, which is controversial for several reasons.

  • What about Palm oil?

  • so palm oil is used a lot commercially in cooking by the food industry because it has

  • fantastic functional properties.

  • You'll find that not many people cook with it at home, but you will find that in nearly

  • all processed foods.

  • Palm oil is on the back of the pack labeling.

  • It’s a tricky one because you've got the environmental concerns regarding palm oil.

  • And also we know that palm oil isn't the best oil for us in terms of our health.

  • You remember at the beginning I mentioned to you these tropical oils have high amounts

  • of saturated fat, and the particular type of saturated fat in palm oil isn't great for

  • our health.

  • So Sarah, What's the overall verdict then?

  • Are cooking oils bad for you?

  • So my opinion is using cooking oils in the way that we typically use them in the home.

  • There is no evidence to show that they're bad for our health unless we repeat deep frying

  • them over several weeks.

  • Got it.

  • And then maybe let's just talk for a minute about what people will use and I would say

  • from my own side as a result of many conversations with you, Sarah, I end up using extra virgin

  • olive oil for almost everything that I cook with.

  • So I fry with it.

  • I also use it a lot where I would've used butter because, of all of these properties

  • should I feel comfortable about that If I'm stir-frying something or I'm frying an egg

  • does that feel good from a health perspective?

  • Yeah, I think so, Jonathan, because you are not reusing the fat.

  • You're not reheating it.

  • Also, you are not heating it to an excessive temperature.

  • So remember I said at the beginning, an ideal temperature is around 170 degrees centigrade

  • or 340 degrees Fahrenheit.

  • So if you were to fry your egg, generally your pan would heat the oil to about 160 or

  • 170.

  • And so I think given the applications that we use at home, a light olive oil would be

  • a really good option, but I do also think a very standard vegetable oil that you can

  • get from the supermarket that has rapeseed or canola oil is also a good option.

  • And what about you, Sarah, as one of the world's experts on fats?

  • What do you use at home?

  • Well, Jonathan, I don't do the cooking at home.

  • My husband does all the cooking, so it depends on what he likes.

  • I think Jonathan, a really important point though to mention is there are a lot of people

  • that will be listening to this.

  • I might have also listened to many other podcasts that talk about seed oils being the evil of

  • our diet and cooking with seed oils causes cancer or causes heart disease.

  • And so I think it's important to say that we are not necessarily saying cooking with

  • rapeseed oil is especially healthy, but what I do believe is that it's not unhealthy to

  • cook with.

  • And I think there are probably a lot of people listening to this who are still saying, Well,

  • hang on, I use one of these sprays that's gonna put like one calorie of some sort of

  • chemical to cook with because I don't want to fry my food because it's unhealthy.

  • What would you be saying to them?

  • So I'm a real advocate of people consuming a decent amount of fat in their diet.

  • A decent amount of healthy fats so I think that trying to reduce the amount of fat that

  • you put on the pan is not a good way to either improve your health or improve your weight

  • if they're the two reasons that you are doing this.

  • And I'm sure that we can do maybe another podcast on this, Jonathan, all around the

  • effects of fat and it’s association with weight but also it's the association with

  • health and dispelling hopefully many of the myths there are around low-fat diets.

  • I think that sounds like a, a brilliant idea and a great place to wrap up.

  • If you'd like to understand more about the facts that are right for you, then by all

  • means do come and try Zoe's personalized nutrition program to improve your health and manage

  • your weight.

  • and you can get 10% off by going to join zoe.com/podcast.

  • I'm Jonathan Wolf.

  • And I'm Sarah Barry.

  • Join us next week for another Zoe Podcast.

Hello and welcome to Zoe Shorts, the Bite Size podcast where we discuss one topic around

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Cooking Oils: what to use and when | Dr Sarah Berry

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    林宜悉 發佈於 2022 年 11 月 08 日
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