Recap: The truth about seed oils | Prof. Sarah Berry

0:00Hello, and welcome to Zoe Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health. Today we're talking about seed oils. From Instagram reels to viral tweets, seed oils have become one of the latest nutrition villains. And the theme is getting real. People are emptying their cupboards, terrified these everyday oils are silently wreaking havoc on their health. So is this panic justified? Or does the science require further scrutiny? Well, scrutiny is Professor Sarah Berry's middle name. She's going to cut through the confusion, dig into the data, and tell you whether it's time to rethink your next stir fry.

0:46What is a seed oil, and how is that different from some other sort of oil? So we get many different sources of dietary fat. in our diet. So you have animal fats and oils that come from animal products, and dairy is a great example, dairy fat. You have other vegetable oils. So for example, you have olive oil, but the largest source of oil in our diet comes from seed oils. And these are very simply put oil that's extracted from a seed, whether it's sunflower or safflower or corn, you know, the seeds of these plants can be crushed and the oil can be extracted. That sounds pretty straightforward. And you're saying that actually most of the oils that I would find in the grocery store have been extracted from these seeds?

1:34Yeah. So the largest contributor of fat in our diet comes from palm oil. Now that isn't a seed oil, but then nearly all of the rest of the oils that we consume come from these seed oils. So one of the most common is soya bean oil, which is very, very common in the US and constitutes the majority of the oil that's consumed there. In the UK, the most common oil is rapeseed oil. That's actually called canola oil in the US and in North America. It's the same thing, just with different labels across different countries. It's exactly the same thing, but just with different labels. And then we, in both countries and in many countries, we also have a high amount of sunflower oil, but to a lesser extent than soybean and rapeseed oil.

2:19And then we have minor amounts in our diet of some of these other seed oils like sesame seed oil, corn seed oil, and so forth. And Sarah, how are they actually made? And part of the reason I'm asking that is like one of the things that's been eye-opening for me over the last couple of years is that some of the things that like I buy turn out to go through like this extraordinary industrial process. And those are things we've tended to, you know, turn out to be calling ultra-processed foods and other things are incredibly straightforward. What's the situation with these seed oils? So it is actually, I think, relatively straightforward.

2:51And I think this, again, is one of the arguments that some of the people that claim seed oils to be toxic use that, oh, it's really refined. It's got all of these terrible chemicals in it. And there are different types of ways you can process oils. And I think it's important we briefly cover these. So all oil has to firstly be extracted from the seed. OK, and you can do this a couple of different ways. One way you can do it is what you call cold pressed seed oil. This is literally just, in simple terms, squeezing the seeds so that the oil comes out. Now, that's all very well, but actually it's not the most efficient process because what happens is lots of the oil gets kept inside the seed.

3:33And obviously, we always want to maximize production, don't we? Particularly in the food industry, seed and oil industry. So what you can do is you can either heat that seed or in addition to that, you can add in a particular solvent. and typically we use hexane as a solvent and basically that allows us to extract all of the oil so it becomes a more efficient way of extracting the oil at that point it can no longer be called cold pressed and it started to go through what many people would say is a more refined process what can also happen and most of the oils that are used additive foods and most of the oils that you buy off the shelf unless they say they're cold pressed go through further stages of processing and this is to remove many minor components that you might find in the oil and these terms that you might hear that are used as a processing techniques are things like bleaching and deodorization now they do sound quite scary people are thinking probably bleaching peroxide it's not as scary as it sounds what happens is the end oil is therefore very stable there are no harmful chemicals left in that end stage oil the only potential downside of this is that in that process of where the oil might have been heated or had these additional chemicals added occasionally you might remove some of the other favorable elements and seed oils so they tend to be very high in vitamin e which is a natural antioxidant they also tend to be high in other phytonutrients like phytosterols, for example.

5:10And what we know is that as you go through the refinement process, some of these can be removed and some polyphenols as well. These phytonutrients are typically quite well preserved, but you might get some losses. And again, this is one of the arguments that's often used for why you should buy cold pressed rather than refined. What you're saying, I think, is that the end product of this, you're saying is actually still sort of the oil itself rather than a whole bunch of added chemicals that aren't there otherwise. And the downside is actually that you're losing some of these phytonutrients, polyphenols you're mentioning that you would keep with a cold press.

5:51So it's losing some of those benefits, but it's not like this ultra processed food, which is full of things that we've never normally digested. Absolutely. And I know this for many people will be considered a controversial statement to make, but I actually believe based on current evidence and based on the kind of techniques the seed and oil industry use, that these refined oils actually are very similar to the cold pressed oils and the loss that you get is quite minor. But I think it's important to say, yes, there is a little bit of loss, but I don't think it's enough to constitute for people who maybe are finding cold pressed oils very expensive because they are a lot more costly to say, okay, they are really, really this much healthier.

6:35Got it. So you're saying there is this industrial extraction process, but your research and the research of other people are suggesting that the end product actually basically looks like the sunflower oil, the canola oil that you would have got if you just squeezed the seed in the first place. Yeah. And interestingly, there's been a couple of randomized control trials that have actually compared cold press versus the refined oil. And they actually don't show any difference in many of the different outcomes that we would think might be impacted by the loss of some of these phytochemicals like inflammation, like oxygen stress.

7:07There hasn't been many. And as I know, I always like to caveat, Jonathan, I'm making a statement based on the current evidence. In five years, 10 years, as I always tell my students, there might be more evidence to say otherwise. But based on current evidence, I don't think there's any harm from the processing techniques that are used to create processed seed oils. So why are 99 % of YouTube videos saying that these seed oils are bad for us? What are people worried about? Because in my experience, often there's some reason that comes from somewhere, what are they worrying about gosh if only i could get on my soapbox now jonathan honestly it's it drives me insane when i see this and in preparation for this i did google on on i went on to podcast app and i had a look at cedars and these alarms like cedars are toxic cedars are going to kill you it's absolute nonsense you've been studying this for what 25 years you've been interested in sort of how fats interact with our body and our health.

8:11Is that right? Yeah, 25 years. You're spot on, actually. Overall, we're all eating vastly more seed oil than we were in the past. And we know that we are seeing an explosion of health issues, right? Whether that's living with obesity or diabetes or just this whole host, right, of health issues. Yeah. So one of the first things that people claiming seed oils to be toxic use. There's beautiful infographics, beautiful figures that show a nice chart where you see on one axis of this figure increase in seed oil intake and on the other axis you see increase in cardiovascular disease, cancer, type 2 diabetes.

8:52Think of all of these chronic related diseases that are increasing over the last 50 years. And you see this almost linear relationship as we call it. So as your intake of seed oil increases, so does the level of all of these different diseases over the years. So that sounds pretty bad. Yes, it does. But that's association. It doesn't mean causation. And what is really alarming here is that it's ignoring everything else that's happening over the last 50 years. the fact that actually these seed oils are typically now eaten as part of these very heavily processed unhealthy foods. So actually the majority of our intake of seed oils comes from these cereal-based foods, so pastries from cakes and these kinds of foods.

9:41And so it's not the seed oils themselves that are causing this, it's the ingredients that all of the other ingredients in these foods, but also what else has been happening over the last 50 years. So, you know, our increase in being sedentary, so lack of physical activity, or increase in stress, or increase in sleep problems, et cetera, et cetera, et cetera, all of these other issues. So just because in the same timeframe that CEDAWS are increasing, these other diseases are increasing, doesn't mean one causes the other. And so I know that often in science, the way that nutritional scientists try to unpick this, is this thing called epidemiology, right?

10:16Where you study tens of thousands or hundreds of thousands of people over decades, and you look at what they've recorded they've eaten and you see the difference. And I know that we've seen that for many foods, there is a really strong link between eating more of those foods and worse health outcomes because you and others talk to me about this all the time. You don't see that link with the CDAWS? So if you adjust for all of these other confounders that I've just mentioned, no, you don't. What you see is consistently, there is a favorable effect from increasing omega-6, which is a good marker of seed oil intake, with a reduction in coronary heart disease.

10:56We know that omega-6, which is this polyunsaturated fatty acid, so one of the main fatty acids in these seed oils, we know that it reduces our bad cholesterol. It has a very potent effect in reducing our bad cholesterol, which we call our LDL cholesterol. You're saying that what the science is showing is if you have more of this omega-6 inside you, which you said is one of the mono-ons? So omega-6 is one of the polyunsaturated fatty acids. There's two types of polyunsaturated fatty acids that we eat. One is called omega-6 and one is called omega-3. And omega-6 is found in particularly high amounts in most seed oils.

11:36And it is also found in quite high amounts in these other oils like soybean and canola oil. So it's the main polyunsaturated fatty acid that's in these oils. What we see is that an increase in omega-6 intake from these population epidemiological studies is actually associated with favorable effects on all-cause mortality. So I know we refer to that as how likely is people going to die. It's associated with huge reductions in LDL cholesterol, or bad cholesterol, and it's associated with reductions in cardiovascular disease. And it's this omega-6 level that's often used as an argument to why seed oils are bad.

12:14and why you get this association. There's a study that's often referred to as well. It's called the Sydney Heart Study. And this is a key study that people use as a way of saying, actually, even in a randomized control trial, that seed oils are bad for us. And this is a study that was conducted quite some time ago, back in the 1960s. And this is where they asked men who had already had some sort of cardiovascular event to increase the amount of omega-6 through seed oils in their diet. And what they found was that there was an increased risk in those people who increased their seed oil intake. However, a really important caveat here is that a large proportion of the seed oil that they ate was in margarine spreads, which back in the 1960s was in the form of trans fatty acids, which we've done a previous podcast on, which we know, yes, are bad for us if they're industrially produced.

13:12They're not bad for us now because we're not eating them now. And so it was heavily confounded. And this study is used a lot to say, okay, well, the Sydney heart study shows you eat seed oils and it's worse for your health. And what you're saying is actually tells you that if you eat trans fats, it's bad for you and it's a 60 year old study. What do all the more recent studies say about this omega-6 you're talking about? Is it bad for you? So all the recent studies, the epidemiological research shows that as you increase your polyunsaturated fat intake, you reduce your risk of ill health from cardiovascular disease and so forth.

13:48There's also many, many randomized control trials that show that if you increase your polyunsaturated fatty acid intake, you reduce your LDL cholesterol significantly and it results in a 32 % reduction in cardiovascular disease. So you're saying that actually if you have more of this omega-6, you reduce your risk of things like heart attacks by... So up to, some of the data shows up to about 30%. Now, obviously it depends on the length of exposure, i.e. it's not going to happen overnight. But the evidence, apart from this one study, which we know is flawed, the overall totality of the evidence is that omega-6 is beneficial for health.

14:34I do need to caveat that, Jonathan, though, that there are a very small proportion of the population that have a particular genetic variant that means that they are susceptible to high intakes of omega-6. And it's always important to say, look, I'm talking about averages here. Everyone responds differently. But overall, the majority of people will actually benefit from increasing their polyunsaturated fatty acid intake. As you can imagine, hosting this podcast, running Zoe, juggling family life, it all keeps me pretty busy. So I try as best I can to stay energized and show up well in all those parts of my life by fueling my body with the right food, by exercising, and by adding a scoop of Daily 30 to my meals every day.

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15:58By the way, whenever we talk about Daily 30 as a good source of fiber, we're required to say that it contains four grams of total fat per serving. Obviously, that's all amazing healthy fats from plants. So order yours today at zoe.com slash daily 30. Thanks for listening and see you next time.

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