← What's That Rash?
What's That Rash?
Why you don't need to avoid seed oils
00:17:44
It can be hard to keep up with food fads and diet trends (and spoiler: you don’t need to). But an intriguing assumption that has gained traction recently is that seed oils – think canola, sunflower, grapeseed – are terrible for you. Norman and Tegan unpack how that assumption has spread, and whether there’s any solid evidence to back it up. References: Biomarkers of Dietary Omega-6 Fatty Acids and Incident Cardiovascular Disease and Mortality Serum n-6 polyunsaturated fatty acids and risk of death: the Kuopio Ischaemic Heart Disease Risk Factor Study Omega-6 fats to prevent and treat heart and circulatory diseases Polyunsaturated fatty acids intake and risk of all-cause mortality, cardiovascular disease, breast cancer, mental health, and type 2 diabetes: A systematic review and meta-analysis of prospective cohort studies Perspective on the health effects of unsaturated fatty acids and commonly consumed plant oils high in unsaturated fat If you’re worried about inflammation, stop...
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- [00:00]
Norman Swan
ABC Listen, podcasts, radio, news, music and more.
- [00:08]
Podcast Narrator
Australia's always been the lucky country. Sunshine, beaches, and that one magpie that always seems to know where you live.
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Norman Swan
Yeah, get away from my chip, please. Luck might not cut it anymore.
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Podcast Narrator
So can we make our own luck and turn this complicated world to our advantage?
- [00:25]
Norman Swan
That's our global roaming summer season. Can Australia surf the world's chaos without.
- [00:30]
Podcast Narrator
Wiping out fresh new episodes all summer? Search for global roaming on the ABC Listen app or wherever you get your podcasts.
- [00:37]
Dr. Sarah Berry
Norman, it pains me to ask you this because I have forgotten my Mediterranean diet Bell today.
- [00:43]
Norman Swan
Ting.
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Dr. Sarah Berry
That's it. I was gonna ask you what your favourite oil is to cook with.
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Norman Swan
Well, you kinda know what it is already. It's olive oil.
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Dr. Sarah Berry
Exactly. I know.
- [00:52]
Norman Swan
Ding ding, but only at low. Only at low temperature following that sort of moderate heat type recipe. If it's high heat, it's a different story.
- [00:59]
Dr. Sarah Berry
What do you go for?
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Norman Swan
I go for canola.
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Dr. Sarah Berry
Interesting.
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Norman Swan
Which in fact leads into today's episode of what's that Rash? Where we answer your questions.
- [01:07]
Dr. Sarah Berry
Let's get into it. So Peter has written in saying RFK I. E. Robert F. Kennedy Jr. Who's Trump's pick for health secretary in the US has stated that people are being poisoned by seed oils and has implied animal fats would be a preferable alternative. There are people in my life who have expressed similar views. I know that over the last few decades, production of seed oils has increased dramatically and our consumption must now be much higher than in traditional. This is what Peter writes. Ding Diet based around olive oil. Peter personally loves olive oil, uses it whenever he can. But on the other hand, he's not worried if seed oils are called for in a recipe or in the ingredients list. Should I be? He asks, and he finishes by saying, to preempt the obvious pun, could you give us the good oil on this, please?
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Norman Swan
You must be disappointed in that because somebody else has stolen your pun.
- [02:00]
Dr. Sarah Berry
Well, yes, and you know, I do love a pun, but I'm going to give this one to Peter because it was clever. So it'd be good to first start with a bit of a definition of what we're talking about when we're talking about seed oils.
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Norman Swan
We're talking about oils which are pressed from or manufactured from seeds. So sunflower seeds, flax seeds, sesame seeds, peanuts. Some people would even say olive oil might even be considered a seed oil, but it's not really. It's the oil of the fruit. You're not really getting the seed in the middle. So it's oils made from those seeds.
- [02:33]
Dr. Sarah Berry
And canola is the big one. Or at least in Australia, we're big manufacturer of canola oil.
- [02:38]
Norman Swan
Yeah, canola is a big one internationally, but peanut's pretty big, as is rice bran oil. So when you go into the supermarket, there's a lot of seed oils there. And those are the. That are being, if you like, condemned by Robert F Kennedy Jr and some others for various reasons.
- [02:55]
Dr. Sarah Berry
So oils, by definition, are really high in calories, like they're very high in energy, sort of no matter where they're coming from. What is it about seed oils specifically that seems to be the problem? Is it a paleo diet thing? Cause if it is, I've got ammunition.
- [03:11]
Norman Swan
Well, let's do the paleo diet first. Cause there's a lot of misconception about the paleo diet. I mean, seed oils are not really new.
- [03:19]
Dr. Sarah Berry
No. And a few years ago, some years ago now, I interviewed an academic from the University of Minnesota who had a wonderful term she called paleo fantasy. And this idea that we kind of romanticise this period in human history where humans sort of were one with nature and we were eating what our bodies were evolved to eat, and that since then, with the agricultural revolution, the Industrial revolution, all that sort of stuff, we're now not living in harmony with nature. And she pushes back against that, she's an evolutionary biologist, by basically saying humans have never lived in harmony with nature, we're constantly adapting to it. That's what evolution means. And in addition to that, that sense that perhaps we're not living the way we were, quote, unquote, evolved to eat, is the fact that seeds have been part of human diets for, well, hominid diets for millions of years. There's evidence that even before sapiens existed as a species, that seeds were part of the diets of early human ancestors. So maybe not in the volumes, definitely not in the volumes that we eat them today, but they're not new to human diets like you say.
- [04:23]
Norman Swan
No, indeed. And it's not just the oils, it's the carbohydrates as well. And they were processing carbohydrates. Really interesting recent study on hominids suggesting that they were processing quite complex carbohydrates to eat, and seeds would have been part of that. So the debate about this is about the fats in the seed oils.
- [04:43]
Dr. Sarah Berry
Okay, so breaking down different types of fat, then. So what are we looking at?
- [04:47]
Norman Swan
Well, let's just talk about the fats that we eat in oils and use terms that you've probably that people have heard before. So there's monounsaturated fats, there's polyunsaturated fats, and there's saturated fats.
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Dr. Sarah Berry
Saturated fat's bad, right? I know that one.
- [05:01]
Norman Swan
Saturated fats generally bad, depending on what food it comes in. But by and large, saturated fats are bad for you. Monounsaturated fats, which are the dominant fat. So these are not fats as much as fatty. And this is an important part of the story to understand what's going on here is that we're talking about fatty acids, which in the same way as amino acids, are the building blocks for proteins, fatty acids are the building blocks for fats in our bodies. And we do need fats to survive. We've got fats surrounding ourselves to keep the integrity of our cells together and.
- [05:34]
Dr. Sarah Berry
Our brains, really importantly.
- [05:36]
Norman Swan
And communication between cells involves fats as well. So fats are important, and fatty acids are what they're made from. And fatty acids in this definition are defined chemically. I know I'm going to blind you with science here, but I'll blind the audience with science here. But when you talk about omega 3s, omega 6s, these are different variations on the polyunsaturated fat. So saturated fats, the bonds that attach carbon to these fatty acid molecules, if it's just a single bond throughout the whole molecule, that's called a saturated fat. Sometimes there's a double bond there, and depending on whereabouts in the molecule, it is near the beginning or near the end, it can be called an N3. In other words, an omega 3 fatty acid. Or towards the end, it could be an omega 6 fatty acid.
- [06:25]
Dr. Sarah Berry
Is that what the omegas mean?
- [06:27]
Norman Swan
Yeah, it's the place on the molecule. And people have got it into their head that omega 6 fatty acids are bad for you and omega 3 fatty acids are good for you.
- [06:41]
Dr. Sarah Berry
Okay, so what I've heard a lot about in this space of people who are sort of quoting research, quoting science, with concerns around seed oils, is about the ratio of omega 3, which I think a lot of people have heard of, because it's in fish. And it's good for you, it's good for your brain. That's sort of the narrative around Omega 3 and Omega 6 and that perhaps we're eating a lot more Omega 6 compared to Omega 3 than we did in more traditional diets.
- [07:07]
Norman Swan
Yeah. In many of these seed oils, not all of them, but in many of these seed oils, there's more Omega 6 than Omega 3. So you're talking about substance, for example, like linoleic acid as an omega 6, where alpha linoleic acid is an omega 3.
- [07:21]
Dr. Sarah Berry
I'm saying these as if they're household names, Norman. Where would I be finding linoleic acid?
- [07:27]
Norman Swan
So you'll be finding linoleic acid in grapeseed oil in quite large amounts, canola, sunflower oil, in peanut oil, rice bran oil. They're all there. And it's much lower in olive oil, for example, although that's not a seed oil. So a scientist a few years ago decided that there was an important issue around the ratio in our diet of omega 6 to omega 3, and that somehow if the ratio was high, in other words, you had Too much Omega 6 versus Omega 3, that was bad for you, caused an imbalance to your production of fats. So therefore, potentially increasing cholesterol, increasing inflammation, increasing oxidative stress in your body, and largely that's been debunked, is that the ratio of omega 6 to omega 3 fatty acids is really largely fallacious. Because what's known now is that omega 6 fatty acids are good for you. It's related to lower rates of heart disease, lower rates of inflammation, has not got an adverse effect on oxidative stress. And omega 3 fatty acids are good for you, too. And one critic of this ratio issue saying is that you're dividing the good, in other words, omega 6, by the good omega 3, and it's really spurious and that omega 6 fatty acids have been wrongly labeled as bad for you. They're not bad for you. There's almost no evidence for that. When you look at the large studies, omega 6 fatty acids are pretty good for you.
- [08:55]
Dr. Sarah Berry
So if they're good for you, then why are people like RFK saying that they're causing health harms?
- [09:01]
Norman Swan
Because there are some writers, based on not very much evidence, suggesting that these are poison and that they're causing major nutritional problems, in his case, in the American population, but elsewhere as well, and they're talking about the return to animal fats, which are high in saturated fats and are associated, amongst other things, with increasing inflammation, increase in oxidative stress, whereas these fatty acids aren't.
- [09:24]
Dr. Sarah Berry
I do want to talk about that because, yeah, I see a lot of make oil tallow. Again, they're really big on beef tallow and lard, which are rendered form of animal fats, which for sure have absolutely been part of human diets for a really, really long time. But as you say, we do know that those animal fats are really high saturated fats, and we absolutely don't live other parts of our lives like cave people did either.
- [09:48]
Norman Swan
So you can't take this in isolation. So often they'll talk about the Amish. And I think you and I have spoken about the Amish before in North America. So a group of people who, for religious reasons and cultural reasons, live a very traditional, pre industrial lifestyle. And when you analyze their diet, it's very high in animal fat. But they're living a pre industrial lifestyle. They're burning thousands of calories a day.
- [10:14]
Dr. Sarah Berry
Yeah, I can't remember the last time I built a barn. They seem to do it every day. It doesn't feel like a fair comparison.
- [10:20]
Norman Swan
That's right. And when you're burning a large number of calories a day, your body is actually quite forgiving of what you eat. Second thing is, which is partly this paleo fantasy, just remember life expectancy in the paleolithic was about 28. So just be careful what you wish for here.
- [10:37]
Dr. Sarah Berry
Yes.
- [10:37]
Norman Swan
So when you take a monounsaturated fat, so lots of us are having olive oil, and olive oil, particularly extra virgin olive oil, is great for you. It's got polyphenols in it, it's got antioxidants, it's got bioactive substances, and it's got monounsaturated fats. In other words, there's only one bond that's double in these fats. And the story with olive oil and coronary heart disease is not so much that monounsaturated fats are fantastic for you, it's that they're neutral when it comes to your cholesterol. What you do when you cook with olive oil and have it in your food is that you're replacing saturated fat with olive oil. And it's that replacement that gives you most of the benefit when you're eating monounsaturated fats. On the other hand, when you take polyunsaturated fats like Omega 6 and Omega 3, remember, these are also what are called essential fatty acids. We don't make these fatty acids in our body, we need to take them in our diet. And by the way, if you don't take enough linoleic acid in your diet, you can actually suffer a linoleic acid deficiency, which can be a dermatological condition like itchy, scaly skin. So we need these substances in our diet. But what these polyunsaturated fatty acids do is they interfere with cholesterol metabolism and reduce the production particularly of LDL cholesterol, the nasty form of cholesterol. So they intervene in, in a healthy way in the cholesterol metabolism in our body, which monounsaturated fats don't, which means they have potentially added benefit.
- [12:09]
Dr. Sarah Berry
Okay, so I feel like one of the big pieces of the puzzle with why people don't like seed oil is its role in manufactured food. So ultra processed foods specifically, often really high in calories, and often those calories are coming from seed oils because they're cheap to produce and they don't really have strong flavour a lot of the time. So they end up being the source of fat in those foods.
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Norman Swan
And they're also heat stable, which means if you need heat to make those foods, they're going to be stable.
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Dr. Sarah Berry
So how much of the bad rap that seed oils are getting are actually because they're in ultra processed foods rather than the seed oils themselves as being the villain?
- [12:46]
Norman Swan
Well, the people who are complaining about seed oils and saying that they are poison are actually arguing from a metabolic point of view. They're saying they're bad wherever you get them from. And at least my reading of it, they're not really that focused on ultra processed foods. They're focused on these fatty acids themselves. I mean, to give you an example of how misleading it is, they're worried about this substance called arachidonic acid. And arachidonic acid is actually known to increase inflammation to some extent. And so they say, well, because linoleic acid is turned into arachidonic acid, that's why you get a problem with inflammation. But in fact, the proportion of linoleic acid that's turned into arachidonic acid is 0.12%. So it's insignificant compared to everything else linic acid does, or the other polyunsaturated fats do in your body. So they do argue in quite a sophisticated way against it, but using misleading biochemistry.
- [13:43]
Dr. Sarah Berry
Okay, so I feel like we've said a lot of really long names, we've talked about chemical bonds and whatnot. I haven't really heard any strong evidence against seed oils. Norman, is there something that I've missed here?
- [13:54]
Norman Swan
Not that I can find. If you just look at the literature of large group of people, there haven't been very many clinical trials. But when you look at the epidemiological studies, when you look at the metabolic studies, the biochemistry studies in the lab, they all point in the same direction in terms of a beneficial effect on blood fats, on cholesterol, LDL, maybe even with some seed oils, on type 2 diabetes. And that may be an effect on LDL. Cholesterol. It's a fascinating study. So we have a bell for the Mediterranean diet.
- [14:25]
Dr. Sarah Berry
Bring a ding ding.
- [14:26]
Norman Swan
But we also, over the last year or so on what's that rash, have been talking about another phenomenon, pleiotropy, where genes have two kind of roles in the body. And there's a recent study which suggests that the genes for type 2 diabetes and LDL cholesterol might be linked. And when you reduce LDL, you also reduce the risk of type 2 diabetes. And it's a genetic effect which could be. The link here is that these substances, these polyunsaturated concentrated fatty acids, reduce LDL and therefore reduce the risk of type 2 diabetes.
- [15:01]
Dr. Sarah Berry
So to come back to Peter's question, the claim that he's heard from RFK and others is that people are being poisoned by seed oils. Animal fats would be a preferable alternative. Is this something that he should be worried about?
- [15:14]
Norman Swan
No, if he's using seed oils responsibly, in other words, if he's using them for frying and frying judiciously and not going mad and filling up his calorie allowance with fried foods, and it's fine. So it's the fried foods and the calories that you should be worried about far more. But you should not be reusing seed oils more than once. In other words, once you've cooked with them at high heat, you have to get rid of them responsibly because they can change chemically from repeated heated use. Which makes me concerned because when I was a child, my mother had a chip pan on the stove the whole time and that oil was never changed.
- [15:52]
Dr. Sarah Berry
Oh, my God.
- [15:54]
Norman Swan
Don't grow up in Glasgow.
- [15:57]
Dr. Sarah Berry
I do love the rebrand that you've managed to pull off here, Norman, by being a boy eating chips in Glasgow to being the ding ding diet toting health guru that you are today.
- [16:07]
Norman Swan
Yeah, but just show me a. Just show me a French fry and I go back, I regress immediately.
- [16:14]
Dr. Sarah Berry
Oh, well, Peter, thank you so much for sending in your question. If you have a question, we love answering them, you can email us that rash@abc.netau See you next time. See you then.