Simon Hill on The Truth About Seed Oils & What’s Actually Making Us Sick

This whole debate about seed oils, why is it such a boogeyman word?

Where a lot of the confusion comes from is that Simon Hill is a nutrition scientist and physiotherapist best known for cutting through wellness hype with science and his mission to help you make evidence based choices to live better and longer.

Our consumption of soybean oil has increased a thousand fold since 1900.

When I look at the increase in chronic disease, to me the most obvious explanation for that is not an increase in the consumption of seed oils. It's an increase in the consumption of hyperpop palatable, ultra processed foods. The goal should be to create an environment where the convenient and affordable option just happens to be the healthy option as well. The food industry doesn't want to hear.

That protein is the latest darling of the nutrition world. And what do we know about protein?

You do not see a difference in muscle size or strength, regardless if it's animal or plant, regardless of the two diets.

I asked you about protein, we end up talking about strength training. Well, I think that's really important.

It's intentional.

Summarize the bottom line for people like what should they do, what should they be eating?

But what' really the problem is that.

Simon, welcome to the podcast. It's so good to have you here.

Mark, thank you very much. It's been a little while coming and it's a big honor to be with you.

We've been talking about it. Yeah. You know, Simon, for those of you don't know him, is a very measured, deeply thoughtful, non ideological nutrition scientist and there aren't very many of those around, which is why I love him. And he also started his career as a physical therapist studying muscle mass and has a lot to say about nutrition, longevity, how we age. And one of the things that we're going to talk about a lot of stuff today, but one of the things that's this hot topic and you've recently done a couple of podcasts on it, but I want to talk about on the show is this whole debate about seed oils. And personally I've been very focused on this for a long time because I was confused and when I usually am confused about something, I write a book.

I've seen that, I've observed that.

So I wanted to know more about fat because I was just, there was so much noise in the field. And so I wrote a book, 20, I think 16, called Eat Fat, Get Thin. And the idea was, you know, are all our thinking about fat was wrong and we villainize saturated fat and we've not. Not really well understood the role of fats in our diet. We're supposed to be low fat. Is that really we should be doing? So there was the whole low fat craze that ended up causing a huge catastrophe. And so I sort of mapped out the whole historical context and the science behind it, and I. And I really wanted to understand this whole controversy about Omega 6 oils, otherwise known as plant oils, otherwise known as seed oils. And with the whole Maha movement, it's become a lightning rod. And I'm like, well, wait a minute. You guys are talking about the wrong thing here. I mean, sugar. It's the sugar and the starch in our diet and the ultra processed food. And. And that's a vehicle for carrying a lot of these refined plant oils or vegetable oils or. I don't even know what you mean by vegetable oil, because that's exact. Broccoli oil. No, it's like, Julie, seeds or beans, like soybean oil, corn, canola, safflower, sunflower, and all these oils that are used in industrial food, but also been used, you know, throughout history, sesame oil and cooking and different cultures. And. And so I really dove into the literature and I read every study and I tried to figure it out, and I looked at the methodologies and, you know, and I think I'd like to sort of dive in at a high level with you, like, why do you think this becomes such a lightning rod topic? Why is everybody glommed onto it? And. And why is it. Is seed oil such a boogeyman word?

Yeah, it's become a bit of the whipping boy. Yeah. And, yeah, it's. I. I think you're trying to throw me under the bus here.

No, no, no, no. We're gonna have a good conversation. I don't have all the answers, but I really want to. Want to dive into this.

Yeah.

So as I start out, you're a thoughtful scientist.

Yeah. Why has this become, you know, a bit of the whipping boy and I guess a target from Maha movement? You know, I think we're all looking for an explanation to why our population's so unhealthy. And deep down, we're experiencing people around us suffering unnecessarily. And so we are passionate about finding a reason for that. Right. You know, you and I and everyone else in this space is really about. It's more than just trying to get people to be healthy. But why do we want to be healthy? We want to be healthy to increase our life fulfillment. And so we're about increasing fulfillment for. For People and at the end of the day, we're, we're all trying our best to look through the new science and find out what is it that is increasing our risk of these chronic diseases, causing us to increase our body fatness levels over time and driving metabolic disease. So I think the intention piece is generally pretty good. Yeah, I think that where a lot of the confusion comes from is the context and missing some of the nuance in the, in the research. So when I look at, you know, the increase in chronic disease over the last 50 or 70 years, to me the most obvious explanation for that is not an increase in the consumption of vegetable oils or seed oils. It's an increase in the consumption of hyper palatable ultra processed foods, which we.

Used to call fast food and junk food.

Fast food, junk food.

Now it's called ultra processed food.

Right. That drives increased energy consumption and calorie surplus and weight gain. And from there you get a whole lot of metabolic consequences. And if you pair that with being sedentary and you lose muscle mass and muscle quality, well, now you're just spelling sort of metabolic disaster.

Double whammy.

The double whammy. And we're seeing that and put very simply that that can be distilled into consuming too many calories and not moving enough.

Not that simple.

It's not that simple. And I find what's interesting is double clicking on that, looking at all of those details. But when it comes to, to say vegetable oils or just fat in general, the context piece that, that I'm pointing to, that I think is often missed is when we're evaluating a food or nutrient in nutrition science to determine is it increasing risk of some disease or is it neutral or reducing risk? We have to consider dose. We have to consider compared to what? Because very, very infrequently when you make food choices, does it happen in isolation. You usually remove something when you add something. We have to also consider, particularly in this, this conversation of fats, because you mentioned saturated fat. Saturated fat is an umbrella term, but as you know, there are many different.

Types of saturated fat, types of plant oils or.

Right, many types of plant oils. So when we're talking about say reducing saturated fats for wholly unsaturated fats, what saturated fats are we talking about? Are we talking about butter, are we talking about cheese, yogurt, Are we talking about the saturated fats in red meat? Are we talking about stearic acid, the most predominant saturated that in chocolate or cacao? That really doesn't seem to affect blood lipids. And so I think hopefully I'm painting a picture to the listeners that, that this context matters.

Yeah.

And if you oversimplify it, what can happen is you can point to one study where it's like, oh, that reduction saturated fat didn't lead to a favorable outcome, but then this one did, and it starts to get very confusing. And it looks like the science all over the place.

It is, yeah.

And the outcome of that. And I was in this position before I did a master's in nutrition science. What compelled me to go back to university was that I was confused by all of this stuff and the changing headlines.

Imagine how the average person feels.

What I will say is that in academia there is far less confusion. Although, although there is some disagreement among academics and scientists. They generally agree on 80, 90% of the these big, big topics. And that's because they understand the context. And when you understand the context, these conflicting or seemingly conflicting results become explainable. And if I was to kind of just double click a little bit more because I feel like you want to kind of hear my position on vegetable oils and seed oils, what do I find? I'll explain my thought process here.

I would. I just want to set the context for the audience just first, because, you know, when I began to look into this, I was like, okay, well, what's, what's our evolutionary diet? And I have a, a bias, which is that if we haven't been eating it for hundreds of thousands of years, maybe it's something we should take a look at. If some one component of our diet has increased dramatically, what is the effect from an evolutionary point of view and what our needs are? And when I began to look at this in 1900, heart attacks were super rare. If you had a heart attack, everybody would rush in. And at that time, we were eating 40% of our fats as butter, cream, whole milk, eggs, and heart attacks were almost unknown. And. And then at the same time, we started to refine these vegetable oils, we call them seed oils, whatever you want to call them, plant oils. And we developed Frisco, which was basically hydrogenated plant oils, trans fats, which really was a problem. And then our consumption of soybean oil has increased a thousand fold since 1900. And so when I think, well, there's something that's increased that much, what, what's it doing to the population? And how do you fit in the context of all your knowledge? We know. So it's like I had an initial bias around it, and there were some studies that were early done in the 70s that tried to answer these questions. The Minnesota coronary experiment, the Sydney heart trial, which were randomized control trials, which are really hard to do in nutrition, where you randomize people different diets and you follow them and you control them. And, and, and they seem to find that people who had the omega 6 diets actually.

Did worse. Like in the Minnesota corn experiment, the ones who had corn oil versus butter, even though their cholesterol dropped, LDL dropped by 30 points. For every 30 point drop in cholesterol of LDL cholesterol, the risk of heart attack went up by 22%. Yeah, but it's kind of murky because you kind of look below the surface. At that time, they thought margarine was fine. I grew up on Fleischmann's corn margarine when I was a kid. And so the corn oil they used was margarine, which we know is deadly.

Yeah. So they like in those interventions. Because I agree with you. I think I agree with you intuitively what you stated.

Yeah. Also makes sense, but the data doesn't really.

Also makes sense to me that as this increase in this food group that we didn't consume, we see an increase in cardiovascular mortality.

Yeah.

So that's worth. That's, that's definitely worth questioning and researching because I agree with you. It makes sense. It's like, hang on, let's. Let's. That's a red flag. Let's look into that. Those two studies, I think at a high level, you know, in 1960s, were really elegant studies for their time. There are some issues, at least from what I found, that I'm happy to walk through.

There's a lot of issues I'm happy to walk through.

Like what. How I see them and, and why. Why I don't look at those as evidence that reducing saturated fats for polyunsaturated fats doesn't improve cardiovascular risk at a high level. So Minnesota coronary experiment, and that was an Ancel Keys study, who. A lot of people will be hit.

Buried it. They buried that study. And I met Joe Hiblin, who uncovered the data and actually reanalyzed the study because he found the son of one of the original researchers with Ansel Keys, and he said, this never was published. It was funded by the nih, but it was never published. You know what happened to your dad's data? He's like, yeah, it's in the basement in his house. And so he then reanalyzed it. But it was problematic.

Yeah, it was. There was. There was problems with it. And I mean, there's some different opposing views on that and whether it was buried or whether it was incomplete. So 75% of the subjects appear to drop out in the first year. So it may well have been that the research team were like, this is completely underpowered for us to even publish and understand, like, do we have a significant finding here or do we have enough power to detect difference?

And power in a study means are there enough people in the study to be able to prove a hypothesis one way or the other? And if you don't have enough people, it's not powered enough.

And these. This was in the setting of a psychiatric ward. And so the way they had it set up was that which is really a neat part of this study was that they were, it was randomized. People didn't know what fat they were getting. So when they make the food in the, in the kind of cafeteria setting, they can just give it to them without them knowing. And it's either coming from saturated fats or from margarine. And, and not only was there a huge dropout, but the participants were allowed to go out home and sometimes stay at home for multiple days and then come back. And so there's all these kind of little issues that we look at now and we're like, oh, that probably wasn't controlled enough. And then Sydney diet, heart study. Without going into too much details, pretty good study. But also, as you said, the intervention group was contained a margarine that we believe probably contained trans fats. At the time being in the 1960s, it was before trans fats were really reduced in the food supply. And. But what I would say is overall there are other studies when you, when you put them into a meta analysis, which is not perfect, right? Because meta analysis really depends on the quality of studies going in. But when you do that and when you look at the trials that are longest in duration with the least dropout with a good intervention that's probably doesn't have this confounding variable of trans fats, you do see a, a reduction in risk of cardiovascular events in the short term kind of RCTs. And we're probably never going to have those kind of trials again.

So population studies, you also see the same.

And then in population studies you see a similar thing. My. And then further to that, if you go and look at population studies of, and you look at linoleic acid, which is the primary omega 6 fat in vegetable oils or seed oils, and about 40% of linoleic acid in America comes from soybean Oil alone. And when you look at just dietary surveys, which are a starting point, they're not perfect, they have issues. When you look at that and you sort of, you quantify how much linoleic acid are in people's diets, they have lower risk of coronary heart disease compared to people with higher amounts of linoleic acid compared to those with lower. You can go a step further. Some of these kind of more modern, more thorough observational studies also have biomarker blood biomarker assays where they look at red blood cell content, like the function health test that looks at how much linoleic acid do you have in your red blood cells. And also some of them have looked at how much linoleic acid you have in adipose tissue. And so that's like a step further.

Instead of asking people what they can actually biopsy, validate blood tests and see what it is.

Yeah. It's because that fat we don't make. Yeah. The only way it ends up in your red blood cells or in your fat tissue is from consuming it.

Yeah.

And you can then look and see is there an association between higher fat stores, higher red blood cell linoleic acid and a risk of coronary heart disease, for example, or total mortality, dying of anything during whatever the follow up period was. And you see again here you see lower risk of coronary heart disease, lower risk of total mortality with higher levels in both red blood cell or adipose tissue. And so when you, when you look at all of that evidence and then you look at the mechanisms. So what is the, probably the mechanism that would explain this? And I don't think it's all of it, but it is probably the LDL cholesterol reduction that you get with that, that swap and then that's supported in and of itself through genetic Mendelian randomization studies, population studies where you consistently see lower LDL cholesterol, you know, reduced risk of coronary heart disease. And so that's how I think about all of that. That said, do I think it's healthy to consume vegetable oils and seed oils in the within these ultra processed foods? No, I think they're driving an excess of calorie consumption.

Okay. To eat if you have a bottle in your kitchen, but not when you stick it in ultra processed food and.

Even in your kitchen. Right. Do I think it's good to be having tablespoons and tablespoons of this stuff? No, it's super calorie dense. What I do think though is the consumption of vegetable oil at home, like a Tablespoon on vegetables. Cooking them is very different to having them in ultra processed foods or deep frying them and reheating them.

Oh yeah, that's the worst. Oh my God.

Yeah. So I think we can all agree that we need to completely try and avoid those types of foods as much as possible. But it is different to again, cooking with some vegetable oil in your pan at home where you're not deep frying and reheating.

And I think the other issue is, you know, it's like, it's, you know, I often talk about like, you know, cafo meat versus regeneratively raised meat and the differences and the, the, it's not the cow, it's the house. The same thing is true with the oils. And it's like where they come from, what are you eating them with, what else are you not eating? What are you eating more of, what are you eating less of? And you know, the, that sort of reminds me of this, this bigger context is that the science, when you look at the science of essential fatty acids and fatty acid metabolism, omega 3s flow down a pathway that creates all these anti inflammatory compounds in the body. Whereas LA or linoleic acid, which we're talking about, the omega 6s go down a pathway that creates inflammatory molecules. So theoretically these omega 6s should be inflammatory, but it all depends on context. And everybody needs an anti inflammatory system and inflammatory system. It's not that they're good or bad, it's just they have to be in balance. And the other big thing that's changed, aside from our dramatic drop in saturated fat content and our increase in these refined oils, is the difference in our omega 3 content. And omega 3s. And the 6 ratios seem to be pretty important. When you look at the data at a high level and analyze it all, it seems as though a lot of people who don't have the Omega 3s, if they have a lot of these Omega 6s, they get into trouble potentially. Whereas if you have a ratio that's, you know, two to one, one to one, four to one, five to one, it's okay. But most Americans are like 20 to one of the Omega 6 to Omega 3s. And that I think that's another big issue. We're all, we're all not eating wild food, we're not eating wild fish, we're not getting omega 3 fatty acids. 90% of us are deficient in it. So you've got a really complex matrix of a problem that makes people think seed oils are bad. But I don't think they necessarily are.

Because all of that data that you presented there is that the facts, that's what you'll come across. It's how you explain those. Yeah, that so for me I think the omega 3:6 ratio is generally a proxy of like overall diet quality. Usually the higher that ratio the more ultra processed foods. And like you said, not getting enough omega 3s. I don't actually think it's inherently the omega 6 that that's causing the issue there. And I say that because there are clinical trials where you overfeed people Omega 6s and linoleic acid and you measure the amount of arachidonic acid, which is the, the next Omega 6 that's produces.

And which is inflammatory.

Yeah. And it doesn't go up. So the body seems to buffer it and hold it at a pretty steady state. So where I think though that this, this is an issue is that if you're not consuming enough direct DHA and epa. Right. Because these two pathways you mentioned, they share the enzymes. So if you have a whole lot of Omega 6 running through that pathway and using a lot of these enzymes.

Like trying to get it through a highway, it's a very narrow highway and if you have a lot of one type of vehicles going through, you can't get another.

So if you're only consuming like plant based Omega 3s Ala. Yeah.

From Flax Chia, you rely on the.

Conversion to DHA and epa. But if you have a lot of omega sixes in the diet, that conversion's even lower. And so this is where I think then people see increased inflammation. So I think I completely agree with you in terms of what you're putting forward there. And I, I, it sounds like we agree that a big part of that problem is under consumption of omega 3s, particularly the direct DHA and EPA.

Yeah.

Whether you go out and eat fatty fish two or three times a week, which a lot of people don't, and.

In sardines three times a week. I, I prob.

And or having a good DHA EPA supplement to make sure that you're getting enough of those long chain omega 3s.

So at the end of the day we've got this whole controversy. Seed oils are the boogeyman of 2025. Secretary Kennedy's called them out, I think not correctly at the highest level. How would you kind of guide people on how to understand this complexity between saturated fat is plant oils and omega 3 oils. Because those are the three buckets. And as you said earlier, they're not homogeneous. There's many types of saturated fat. There's many types of omega 6 fats, there's many types of omega 3 fats. Right. So they're not like monolithic. But it's important to understand that overall diet matrix and complex that you're eating of these things determines the impact on your health, which is, end of the day, what we're talking about here.

Yeah, it's the key. And then also your personal genetics.

Oh, that. Oh, that.

Yeah, yeah, that's.

That's very true. But that's humbling as a doctor, because when you hear people say these categorical things and you go, well, wait a minute, I've seen thousands of people and the same thing will cause one person's cholesterol to spike and another person's to drop like a stone. And like, how do you explain that? It's genetics.

Yeah, it's genetics. And it's also, again, that a lot of the time the change doesn't occur in a vacuum. So I've mentioned off air to you that when I increase coconut oil in my diet, that I see my LDL cholesterol and APOB go up a lot. 30% in fact, on my latest function test, your metabolically fit and.