Norman Swan (1:56)

You must be disappointed in that because somebody else has stolen your pun.

Dr. Sarah Berry (1:59)

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.

Norman Swan (2:11)

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.

Dr. Sarah Berry (2:33)

And canola is the big one. Or at least in Australia, we're big manufacturer of canola oil.

Norman Swan (2:37)

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.

Dr. Sarah Berry (2:54)

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.

Norman Swan (3:11)

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.

Dr. Sarah Berry (3:18)

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.

Norman Swan (4:22)

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.

Dr. Sarah Berry (4:42)

Okay, so breaking down different types of fat, then. So what are we looking at?

Norman Swan (4:47)

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.

Dr. Sarah Berry (4:58)

Saturated fat's bad, right? I know that one.

Norman Swan (5:00)

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.

Dr. Sarah Berry (5:34)

Our brains, really importantly.

Norman Swan (5:36)

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.

Dr. Sarah Berry (6:25)

Is that what the omegas mean?

Norman Swan (6:26)

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.

Dr. Sarah Berry (6:41)

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.

Norman Swan (7:07)

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.

Dr. Sarah Berry (7:20)

I'm saying these as if they're household names, Norman. Where would I be finding linoleic acid?

Norman Swan (7:27)

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.

Dr. Sarah Berry (8:55)

So if they're good for you, then why are people like RFK saying that they're causing health harms?

Norman Swan (9:01)

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.

Dr. Sarah Berry (9:23)

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.

Norman Swan (9:48)

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.

Dr. Sarah Berry (10:13)

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.

Norman Swan (10:19)

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.

Dr. Sarah Berry (10:36)

Yes.

Norman Swan (10:37)

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.

Dr. Sarah Berry (12:09)

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.

Norman Swan (12:33)

And they're also heat stable, which means if you need heat to make those foods, they're going to be stable.

Dr. Sarah Berry (12:38)

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?

Norman Swan (12:46)

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.

Dr. Sarah Berry (13:42)

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?

Norman Swan (13:54)

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.

Dr. Sarah Berry (14:24)

Bring a ding ding.

Norman Swan (14:26)

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.

Dr. Sarah Berry (15:01)

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?

Norman Swan (15:13)

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.

Dr. Sarah Berry (15:52)

Oh, my God.

Norman Swan (15:54)

Don't grow up in Glasgow.

Dr. Sarah Berry (15:56)

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.

Norman Swan (16:06)

Yeah, but just show me a. Just show me a French fry and I go back, I regress immediately.

Dr. Sarah Berry (16:14)

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.