Seed Oils: Should You Switch to Butter?

Summary

Science Vs: "Seed Oils: Should You Switch to Butter?"

Host: Wendy Zuckerman (Spotify Studios)
Date: November 6, 2025

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Overview

This episode of Science Vs explores the rising controversy over vegetable (seed) oils and saturated fats. Host Wendy Zuckerman investigates the scientific evidence behind the new trend demonizing seed oils (canola, soybean, sunflower, etc.) and promoting butter and other saturated fats as healthful, guided by claims from Dr. Kate Shanahan and viral social media narratives. The core questions: Are seed oils really dangerous? Is butter back on the menu as a healthy choice? With expert interviews and deep dives into recent research, Wendy seeks clear answers rooted in science, not fads.

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Key Discussion Points & Insights

1. Seed Oils Under Fire: The "Hateful Eight"

• Dr. Kate Shanahan's Claims (00:57–04:08):
  • Shanahan vehemently opposes mainstream nutrition, arguing that eight highly refined seed oils (soy, safflower, sunflower, corn, cottonseed, canola, rice bran, grapeseed) are extremely harmful.
    • “Avoiding vegetable oils is the most important action you can take to improve your health.” (02:17)
  • She attributes a wide array of diseases (from heart disease to cancer) to seed oils, claiming personal and patient experiences of miraculous recoveries when swapping seed oils for saturated fats.
    • Describes effects: “People who've done it feel better than ever... I had diabetes and I got off my diabetes medications in a weekend. I had heart failure. I no longer have heart failure.” (03:49)
• Social Buzz: The demonization is bolstered by online influencers who call seed oils “inflammatory”, “poisons,” and “of the devil.” (04:22–04:45)

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2. Revisiting Saturated Fat: Is Butter Really Bad?

• Historical Sidelining of Saturated Fat (06:44–08:29):

  • The show flashes back to the 1980s-90s diet culture: saturated fat (in butter, bacon, cream) was universally maligned due to its role in raising cholesterol.
  • “Saturated fat can clog this pipe. Imagine what it’s doing to yours.” (UK health ad, 08:01)

• Expert View: Jason Wu, Nutrition Scientist (08:29–13:10):

  • Wu describes how evidence linking saturated fat to heart disease emerged from 1950s epidemiology, but more recent studies complicate that story.
    • “The story is not as simple as what it seemed.” (09:24)
  • Wu’s large meta-analysis (600,000+ people, 10,000 heart disease cases):
    • Eating butter daily slightly increases premature death risk (by just 1%)—a “barely statistically significant” result.
    • “Absolutely no relationship between eating more butter and heart disease risk.” (11:38)
    • Slightly lower risk of type 2 diabetes (by 4%) for butter eaters, but much smaller than risks from sugary drinks.
  • Conclusion: Butter is not a health food—but not a “big killer” either.

• Nuanced View:

  • While some reviews show cutting back on saturated fat slightly reduces heart disease risk, the overall effect is modest.
    • “Saturated fat is not the big killer that the 80s led us to believe.” (12:55)
  • Wu cautions: “We basically found a somewhat neutral to marginal effect of butter.” (21:47)
  • Saturated fat may increase LDL ('bad') cholesterol, but many other factors (genes, nutrients in butter, type of cholesterol) matter.

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3. Cholesterol: Villain or Vital? (14:34–21:39)

• David Shade, Endocrinology Professor:

  • “Cholesterol is absolutely critical... Otherwise we’d all be a pile of Jello.” (15:33)
  • Explains cholesterol’s essentials (cell structure, hormone synthesis) and why excess LDL is problematic: small LDL particles sneak into artery linings, leading to dangerous build-ups ("plaque") and possible heart attacks.

• The LDL/Saturated Fat Puzzle:

  • Diets high in saturated fat do raise LDL cholesterol (18:07). Even Dr. Shanahan’s cholesterol “went through the roof” on such a diet (18:07).
    • “My cholesterol levels have gone through the roof since I started this.” – Dr. Shanahan (18:07)
  • Yet, if LDL and saturated fat are up, why isn’t heart disease risk clear-cut? Shade explains LDL is just “about a 1% player out of the whole 100% field”—other factors (genes, smoking, blood pressure) are much more significant (18:52).
  • Saturated fat tends to increase less harmful, larger LDL particles; minor nutrient benefits may offset some risk.

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4. Seed Oils and Disease: Is There Evidence? (25:14–39:11)

• Dr. Shanahan’s Theory:

  • Increasing seed oil consumption in the US correlates with rising chronic diseases. She believes biochemistry and animal studies suggest seed oils cause inflammation via “dangerous particles” and free radicals (26:26–28:08).
    • Lists diseases she links to seed oils: “skin conditions like acne and eczema...cancer, dementia, Parkinson’s, heart attacks...there’s nothing that won’t get better when you stop eating seed oils.” (26:52)

• Testing the Claims: Experimental Evidence

  • David Egman’s Muffin Studies (29:07–30:28):

    • Ran randomized trials feeding people muffins baked with either palm oil (saturated fat) or sunflower oil (seed oil). After eight weeks, “no increases in inflammation” found in the seed oil group (30:25–30:28).
    • Large systematic reviews echo: “virtually no evidence that adding seed oils to your diet bumps up your inflammatory markers.” (30:28)

  • Critiques from Dr. Shanahan:

    • She argues studies are too short and only measure “markers,” not real clinical disease (30:44–31:12).

  • The "Buttock Fat" Study (31:12–33:47):

    • Egman's team examined long-term fat stores in the body (“buttock fat”) of Swedish men:
      • Those with more polyunsaturated fats from seed oils stored in body fat had a lower risk of dying.
      • “If you have more of this in your buttock fat...then you lived longer.” (33:14)
    • Dr. Shanahan: “That doesn’t make any sense...that does contradict my theory.” (33:49–33:56)

  • Wider Context:

    • Most large reviews (inc. a 24,000-person meta-analysis) suggest swapping saturated fat for seed oils reduces heart disease risk. (34:20–36:02)
      • “The evidence are pretty consistent…replacement of saturated fat with polyunsaturated fat does reduce the risk of cardiovascular disease.” – Jason Wu (35:58)
    • Dr. Shanahan dismisses the bulk of evidence, focusing on a minority of studies that support her view.

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5. Summing Up: Seed Oil Theory vs. Mainstream Science

• Host’s Reflection (38:19–39:15):

  • Shanahan trusts a “few” studies showing harm, dismisses many showing safety/benefit.
  • Personal anecdotes (e.g., celebrity deaths) used as support are not evidence.
  • Junk food is unhealthy regardless of fat type; removing seed oils and eating more whole foods may help, but not necessarily because of seed oils.

• Final Verdict (David Shade):

  • “Every year, there are crazy diets that people put out without any scientific justification, and that’s one of them. It’s all crapola.” (40:23)
  • “Crapola is how you say crapola.” – Wendy Zuckerman (40:33)

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Notable Quotes & Memorable Moments

• On Dogma vs. Evidence:
  • “Medical science is messed up when it comes to nutrition.” – Dr. Kate Shanahan (00:57)
• On Butter & Disease:
  • “Absolutely no relationship between eating more butter and heart disease risk.” – Jason Wu (11:38)
  • “We basically found a somewhat neutral to marginal effect of butter.” – Jason Wu (21:47)
• On Biochemistry & Paradigm Shifts:
  • “Really, what’s needed for any paradigm shift is a wholesale restructuring of the way we approach a problem...Paradigm shifts are difficult.” – Dr. Kate Shanahan (37:43)
• On the State of Seed Oil Science:
  • “Replacement of saturated fat with polyunsaturated fat does reduce the risk of cardiovascular disease.” – Jason Wu (35:58)
• On Fads and Science:
  • “It’s all crapola. Crapola is how you say crapola.” – David Shade, Wendy Zuckerman (40:23–40:35)

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Timestamps by Key Segments

| Timestamp | Segment / Discussion | |-----------|------------------------------------------------------------------------------------------------------------| | 00:00 | Introduction and rise of the anti-seed oil trend; Dr. Kate Shanahan interview | | 04:45 | Explosive social media rhetoric against seed oils | | 06:44 | History of saturated fat guidelines in the 80s-90s | | 08:29 | Jason Wu: reassessing evidence on saturated fat and butter | | 11:38 | “No relationship between eating more butter and heart disease risk” – Jason Wu | | 14:34 | Conversation with David Shade: What is cholesterol? | | 18:07 | Case studies of skyrocketing LDL cholesterol on high saturated fat diets | | 21:47 | “Neutral to marginal effect of butter” – nuanced message around saturated fat | | 25:14 | Focus shifts to seed oils; Dr. Shanahan’s theory on disease rise | | 29:07 | Muffin study: randomized trial on inflammation and seed oils | | 33:14 | Buttock fat study: higher seed oil consumption linked to longer life | | 34:20 | Big-picture review: evidence consistently shows seed oils reduce risk vs. saturated fats | | 38:19 | Dr. Shanahan on why she ignores most of the evidence | | 40:23 | David Shade’s “crapola” dismissal of fad diets |

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Tone & Style

Wendy Zuckerman’s tone is witty, playful, and scientifically rigorous. She brings both skepticism and openness as she explores claims, pokes fun at diet dogmas, and persistently chases down evidence.

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Conclusion

Science Vs concludes that the mainstream, evidence-based view still holds:

• Saturated fat (like butter) is not the dietary villain it was once made out to be, but also not a health elixir.
• Seed oils do not show evidence of being intrinsically harmful or more “inflammatory” than other fats, and large studies suggest that substituting them for saturated fats generally improves cardiovascular health.
• The anti-seed oil movement relies more on theory and anecdote than robust evidence.
• As always, context, overall diet quality, and moderation matter most—ignore the fads, trust the weight of the evidence, and pass (or keep) the butter if you like, but no need to fear your canola oil bottle.

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For citations, in-depth studies, and further reading, see the episode’s show notes and transcript links.

Transcript

[Wendy Zuckerman]

Wendy. Hi, I'm Wendy Zuckerman, and you're listening to Science Verses. And today on the show, we are pitting facts against fats. For years, the top dogs in nutrition have been howling about how foods like butter and bacon are bad for us because they are packed with saturated fats. And instead they say we should be eating vegetable oils. These oils are filled with a different combination of fats that experts have told us are good for us. But there's a trend that's popping off right now that says that these top dogs are barking up the wrong tree. And in fact, butter is healthy. And those vegetable oils which are probably sitting on your kitchen countertop right now, are actually incredibly dangerous and might even be killing you.

[Dr. Kate Shanahan]

Medical science is messed up when it comes to nutrition.

[Wendy Zuckerman]

This is Dr. Kate Shanahan. She's a family physician who's been raging against the nutrition science machine.

[Dr. Kate Shanahan]

It's just so wrong. It's morally wrong. It's ethically wrong. It's shocking. And I just. After 20 years, I still haven't gotten over it.

[Wendy Zuckerman]

Kate has a big problem with vegetable oils that are extracted from seeds, the so called seed oils. What exactly are the seed oils?

[Dr. Kate Shanahan]

The problematic seed oils are a collection of eight highly refined, industrially processed vegetable oils, specifically soy, safflower, sunflower corn, cottonseed, canola, and rice bran and grapeseed oil.

[Wendy Zuckerman]

Kate calls these oils the hateful eight. You might have noticed your olive oil is still fine, but canola oil and soybean oil, they are in the bad books. It's the vegetable oils that are often yellow and come in those giant plastic bottles. And you'll find them in lots of different foods.

[Dr. Kate Shanahan]

So they are in salad dressing, your canned tuna, preserved veggies are in, even olives these days. They're often in soy oil, frozen dinners, tater tots, microwave popcorn, granola, you know, supposedly healthy granola.

[Wendy Zuckerman]

In a book that Kate wrote on this topic, which really helped kick off this new seed oils trend, she wrote that quote, avoiding vegetable oils is the most important action you can take to improve your health. End quote. Because according to Kate, eating a lot of seed oils produces a ton of inflammation in your body, increasing your risk of an array of diseases from heart disease to cancer.

[Dr. Kate Shanahan]

If I were to list all of the diseases you can get by eating seed oils, this podcast would be going on for until tomorrow. There's too many. It's every single one they contribute to.

[Wendy Zuckerman]

And so instead of eating these seed oils, Kate wants you to be chowing down on something else. Saturated fat, the Very facts that doctors.

[Dr. Kate Shanahan]

Will tell you to avoid. We're talking about, you know, fatty cuts of meat like steak and, you know, pork and bacon and dairy fat like butter and cheese and cream and eggs.

[Wendy Zuckerman]

This is really the list of, like, the demonized list for this is really like a. No, no, no, no, no, no, no, no, no. I know.

[Dr. Kate Shanahan]

And, you know, dietitians listening to this are probably thinking, she's a loon.

[Wendy Zuckerman]

But Kate went on this diet herself. Seed oils out, saturated fat in. And she said she felt great. She even started putting her patients on this diet. And she told me that she's seen some miraculous things.

[Dr. Kate Shanahan]

People who've done it feel better, and they feel better than ever. They feel younger in their 60s than I did in my 30s. They say that I had diabetes, and I got off my diabetes medications in a weekend. I had heart failure. I no longer have heart failure. My kidneys were failing.

[Wendy Zuckerman]

They're better now. And it's not just Kate who's saying this kind of thing. This idea has blown up. People all over socials and podcasts are swearing by this diet, and they're saying that you need to stop eating seed oils.

[Jason Wu]

Seed oils are some of the worst things your body can consume.

[David Shade]

These oils are inflammatory. They've been linked to heart disease, cancer. They are poisons, plain and simple. Seed oils are of the devil. Seed oils are one of the most unhealthy ingredients that we have in foods.

[Wendy Zuckerman]

So today on the show, we are finding out what is going on here. Is your canola oil really killing you? And is butter now healthy? It's the ultimate clash of the titans. In one corner, seed oils, and in the other, your bacony, buttery saturated fat. Who will win? And I gotta tell you, chewing the fat on this one, I haven't worked on an episode of Science Versus that has upended so many of my views about food. When it comes to this diet, there's a lot of seed oils are of the devil. But then there's science. Science versus seed oils is coming up just after the break. This episode is sponsored by Anthropic, the team behind Claude. Good science means understanding what studies actually show. How are participants selected? How do findings connect across research? Claude is an AI that works through these questions with you, helping you explore scientific methodology and build richer understanding of evidence. For minds that love discovering how we know what we know, try Claude for free at Claude AI scienceverses and see why the world's best problem solvers choose Claude as their thinking partner. That's Claude AI scienceverses.

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[Wendy Zuckerman]

Welcome back. Today it's seed oils versus saturated fat. Should you ditch your canola oil like Kate Shanahan says and fill your belly with butter and bacon instead? To get to the bottom of this, let's leave Kate for now and go on an adventure to simpler times where the shoulder pads are sky high. And the messages that we got about saturated fat were crystal clear. Back in the 80s and 90s, we were told that eating foods high in saturated fats. So think meats, butter, cream was one of the worst things you could do for your health. Why? Because these foods raise your cholesterol and increase your risk of heart disease. If you eat too much of this, then over time fatty deposits could build up in your arteries and this increases your risk of heart. Here's this grim ad from the UK in the 90s, you can see a glass jug filled with fat that someone is slowly pouring down their kitchen sink. The saturated fat can clog this pipe. Imagine what it's doing to yours. In the US this was the vibe. 10 doll looking fellas were mansplaining dietary advice to their ladies. Gee, hope that's not full of saturated fat.

[Dr. Kate Shanahan]

Of course not. See, made with sunflower oil. No cholesterol, low in saturated fat.

[Wendy Zuckerman]

Oh, and in Australia, fat, fat, fat, fat. We'll show you some ways straight from the book to cut down on the fat in the food that you cook. Are you ready? But song or no song, the message was clear. Saturated fat is bad. So is this true? To find out, we need to meet a new guest, so please introduce yourself.

[David Egman]

Yeah, sure.

[Jason Wu]

My name is Jason Wu. I'm a professor and head of the nutrition science team at the George Institute for Global Health, based in Sydney, Australia. I'm on the land of the Gadigal people of the urination.

[Wendy Zuckerman]

I've always just known that saturated fats are bad. When did you first get the message that saturated fats are bad for us?

[Jason Wu]

Certainly it was from a pretty young age as well. You know, I was born in the 80s and my family, my parents, you know just about every person when they think about nutrition around oh, if I want to be healthy, I just got to stay away from it. So it's a message that has been around for a long time.

[Wendy Zuckerman]

Yeah. That message partly dates back to some controversial research from the 1950s suggesting that some countries where people eat a lot of saturated fat, like the U.S. canada and Australia, also have higher rates of heart disease compared to countries where people don't eat that much of it.

[Jason Wu]

And since then, we've had a whole lot more evidence, which I'm happy to go into, that sort of suggested that the story is not as simple as what it seemed.

[Wendy Zuckerman]

So let's get into this evidence. Saturated fat is a type of fat that's generally solid at room temperature. So think of chunks of lard, coconut oil, palm oil, and, of course, butter.

[Jason Wu]

Butter is sort of what's traditionally held up as the poster child of what to avoid.

[David Egman]

Right.

[Wendy Zuckerman]

It is a big chunk of saturated fat. Right.

[Jason Wu]

That is butter of animal based. Right?

[David Egman]

Right.

[Jason Wu]

Saturated fat.

[Wendy Zuckerman]

If you imagine a stick of butter, half of that is literally saturated fat. And several years ago, Jason and his colleagues wanted to see if butter was really that bad for us. So they scoured through the literature, grabbing all these studies that had looked at whether people who ate a lot of butter had higher rates of things like heart disease, stroke, diabetes, and even premature death.

[Jason Wu]

We don't just cherry pick one study, two studies. We pull these kinds of studies together and say, if you look at them all together, what does it tell us?

[Wendy Zuckerman]

They found nine studies that included more than 600,000 people who'd been followed for many years, and every now and then quizzed about what kinds of foods they were eating, and particularly how much butter they were popping in their pie hole. By the end of the study, nearly 10,000 people had heart disease, and more than 28,000 had died. So did the butter boys fare worse? Well, let's start with the worst possible thing here. Premature death.

[Jason Wu]

People who reported eating more butter had an ever so slightly elevated risk of total mortality.

[Wendy Zuckerman]

Okay.

[Jason Wu]

Per average serve, so about 14 grams of butter per day, it's about a 1%, barely statistically significant elevated risk of premature death.

[Wendy Zuckerman]

Got that? Eating a bit of butter every day increased your risk of dying prematurely by 1%. So it's clearly not arsenic here. And then when we zoom in on heart disease, what was the link between getting a heart attack or stroke and eating butter?

[Jason Wu]

Zero. Absolutely no relationship between eating more butter and heart disease risk.

[Wendy Zuckerman]

Oh, wow. With diabetes, eating a little butter actually lowered your risk of getting it by around 4%, which I couldn't believe lower risk of type 2 diabetes.

[Jason Wu]

You heard that correctly. So it's a very, very small amount. Just to give you something in comparison, in similar kinds of analysis, looking at things like sugary drinks, right? Coca Cola, Pepsi, every one serve per day of, say, a can of Coke is related to nearly 20% higher risk of type 2 diabetes. So just to give you a sense of.

[Wendy Zuckerman]

Just to say. And this was like in the 1%, 2% in either direction.

[David Shade]

Yeah, yeah.

[Wendy Zuckerman]

In 2016, Jason and his team published this study and gave it the title Is Butter Back? And some scientists couldn't believe it when.

[Jason Wu]

It first came out. It was very controversial. A lot of people sort of took us to task and said, oh, look, you know, this is. I mean, butter, it's clearly bad for you. And we said, well, we've just shown you the evidence, and if you've got other evidence you would like to present to us and say how terrible it is, you know, like, on the realm of sugary drinks, I'm all for it. Please show us that data. Please show us that evidence. And none were really particularly forthcoming.

[Wendy Zuckerman]

So that is butter. Now, when you zoom out to all kinds of foods that are rich in saturated fat. So not just butter, but also stuff like cream, lard, bacon, beef, pork, sausages, the research is a little more mixed. Like, one big review did find that overall, shoving less saturated fat down your gob could cut your risk of heart disease by a bit. But still, the message coming out of science right now is that saturated fat is not the big killer that the 80s led us to believe. Turns out it was the shoulder pads all along. But this did make me wonder, what does this mean for that whole story that we've been told about why saturated fat is bad? Like, you know, that foods like butter and bacon clog our arteries with dangerous cholesterol, and then, bam, heart attack. Like, is that whole story a lie? Because some headlines seem to be suggesting, yeah, high cholesterol may not mean heart disease in your future. After all, most Americans believe heart attacks happen when cholesterol clogs your arteries. In reality, cholesterol is actually not the main culprit. Some are even saying that cholesterol is healthy for us. So what is going on here? To find out, I called up David Shade, a professor of endocrinology at the University of New Mexico Health Sciences center on the other side of the globe.

[David Shade]

Are you still in Australia?

[Wendy Zuckerman]

I am still in Australia.

[David Shade]

Wow. We're doing this across the world. This is amazing.

[Wendy Zuckerman]

It's good, right?

[David Shade]

I've Never done it that far. So this is exciting to me.

[Wendy Zuckerman]

And it was exciting for me to chat to David because I wanted to know, is it possible that cholesterol is good for us? And David was like, well, duh, yeah. Cholesterol is super important.

[David Shade]

So we're all made up of billions of cells, right? Skin cells, heart cells, muscle cells, and something has to keep those cells together. Otherwise we'd all be a pile of Jello, right? But we're not a pile of Jello.

[Wendy Zuckerman]

The reason we are not a pile of Jello is partly thanks to cholesterol, which is this waxy, yellowish fat that hangs out in the lining of our cells, giving them structure. We also use cholesterol to make a bunch of hormones like cortisol and testosterone.

[David Shade]

So cholesterol is absolutely critical.

[Wendy Zuckerman]

And so then tell me, how did cholesterol get such a bad name?

[David Shade]

Okay, so a little bit is great, but too much is bad.

[Wendy Zuckerman]

So David tells me, here's the deal. To travel around your body doing all of its important things, cholesterol travels in these little balls of fat via the highway that is your blood. But when you have too much of this particular kind of cholesterol, called LDL cholesterol, swimming around in your blood vessels, some of it can get trapped in these teeny, tiny holes in the lining of your arteries, and this becomes an issue. Now, we used to think that cholesterol literally clogged up your arteries, but now we know that's not entirely true. It's actually that your body tries to get rid of that nasty cholesterol with the help of these immune cells called macrophages.

[David Shade]

Okay? Those cells are really scavenger cells. They take up any bits of old cells around dead things. They're scavengers. And if they see little droplets of cholesterol, they take it up.

[Wendy Zuckerman]

They're like little Pacman, like Pacman, like.

[David Shade]

Exactly, exactly. And they eat cholesterol, but they eat so much that they die, basically.

[Wendy Zuckerman]

And what can happen is that if you have more and more bad cholesterol in your blood, you end up with this big, gross pylon.

[David Shade]

That's exactly what happens. They pile up. You can see these yellow streaks in the arteries, and those are macrophages, just practically dead, just full of cholesterol. That's bad news.

[Wendy Zuckerman]

Eventually, that big globby mess of pac men, cholesterol and other stuff builds up and up and up, forming what we call a plaque, and that can rupture or explode into your blood vessels, causing a heart attack. So having too Much LDL cholesterol or bad cholesterol does up your risk of getting heart disease. And science has shown this again and again and again. And the thing is, eating a diet that's high in saturated fat, the kind of diet that Dr. Kate Shanahan, who we met at the start of the show, is promoting, on average, that kind of diet, it actually increases the amount of LDL cholesterol swimming in your blood. And in fact, on this diet, Kate's bad cholesterol went up.

[Dr. Kate Shanahan]

My cholesterol levels have gone through the roof since I started this.

[David Shade]

Yeah, I have a patient like that.

[Wendy Zuckerman]

And David has seen this as well. So, according to the CDC, a healthy LDL level is roughly 100.

[David Shade]

And we're talking about their LDL cholesterol went from 110 to 430.

[Wendy Zuckerman]

Whoa.

[David Shade]

Yeah, she went on that kind of diet.

[Sponsor/Advertisement Voice]

Really?

[David Shade]

And it zoomed way up to 430. Yeah. That's terrible.

[Wendy Zuckerman]

The big question is, if eating saturated fat ups your bad cholesterol and. And bad cholesterol ups your risk of heart disease, then why aren't we finding that butter and even saturated fat more generally are that bad? Well, here's how David sees it.

[David Shade]

You know, on the field of heart disease, there's a bunch of players. There's smoking is a player, Hypertension is a player, and then there's saturated fat. Well, it's about a 1% player out of the whole 100% field. In other, it's not an important player.

[Wendy Zuckerman]

And there's a couple of reasons why saturated fat isn't an important player here. One is that what makes up your bad LDL cholesterol isn't just how much saturated fat you eat. In fact, a huge chunk of your LDL cholesterol is actually produced by your own body. And some people, thanks to their genes, just naturally have very high LDL levels. And then there is this super interesting idea that I actually had no idea about until I started researching for this episode. So do you remember how this bad cholesterol gets into the little holes in the lining of your arteries? And that kicks off the process with the Pac man and the big globby mess that can eventually lead to a heart attack. Well, what we are learning is that there are different kinds of bad cholesterol that come in different sizes.

[David Shade]

As with everything else, there are different sizes of people. There are different sizes of dogs. There are different sizes of. Of cholesterol particles that circulate around in you. Okay, now, it turns out, since the cholesterol has to go through these pores, the little ones go through much easier than the big ones. So the little ones are much more dangerous than the big ones.

[Wendy Zuckerman]

You can think about it like this. The smaller the dog, the rattier it tends to be, the smaller the cholesterol, the more dangerous it tends to be. And research is suggesting that the kind of cholesterol that saturated fat ups in your blood is kind of like a pug sized cholesterol. So it's not great, but it's not some shitty chihuahua. And then finally, there's something else going on here. When you eat foods with saturated fat, you're not just eating fat. Like, if you think of a stick of butter, there's other stuff in it, like omega 3 fatty acids, calcium, and vitamin D, all of which might play a role in reducing your risk of heart disease. So maybe when you eat some of these saturated fatty foods, you might up your bad cholesterol, which increases your risk of heart disease, but then you might end up with some more nutrients, which lowers your risk of heart disease. So at the end of the day, when it comes to butter, here's how Jason sees it.

[Jason Wu]

And I think this is a really important point. At no point in time do we say that therefore go and knock yourself out. Eat as much butter as you like.

[Wendy Zuckerman]

Right?

[Jason Wu]

Because that clearly also isn't what we found. We basically found a somewhat neutral to marginal effect of butter.

[Wendy Zuckerman]

Neutral to marginal effect. Perhaps a Jurassic park analogy might help us here. Saturated fat is no T. Rex. It's not a big killer. But it's not Laura Dern either. It's more of a Jeff Goldplum, you know, like a bit creepy, but also kind of fun. And, you know, if you personally have a high risk of heart disease, then cutting back on saturated fats is something that you can do to reduce your risk. But bottom line, I think Dr. Kate Shanahan, who we met at the start of the show, she has a point when she says that these foods aren't as bad as we've been told they are. But to Kate, the real velociraptor in the kitchen are seed oils. She says that it's these oils that are causing an array of diseases inside your body. And with the help of thousands of muffins and a whole lot of butt fat, we're gonna find out if she's right after the break.

[Dr. Kate Shanahan]

So good, so good, so good.

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[Wendy Zuckerman]

Welcome back. Today on the show, we're looking into this new diet that wants you to throw out your seed oils. So think canola oil, corn oil, that giant bottle of yellow stuff in your kitchen. Get rid of it. People are saying, why? Because they are toxic. And if that's true, it's troubling because in the US Consumption of seed oils has more than doubled since the 1960s. Dr. Kate Shanahan, who's the queen of this new diet, says that as we've been eating more and more seed oils, our rates of certain diseases have gone up and up. There's this graph that she uses on her website and book, and it's flown around the Internet that shows seed oil consumption skyrocketing. Alongside various diseases like obesity and cancer.

[Dr. Kate Shanahan]

We have the entire population of the United States consuming more seed oils than ever Every year. How can you explain that if seed oils are healthy, how do you explain that everyone's asking us to ignore this? It's like the man behind the curtain on the wizard of Oz. Don't pay any attention to what you see with your own eyes.

[Wendy Zuckerman]

Now, this is, of course, just a correlation. And, you know, one big reason why cancer rates are going up is because our population has been getting older and older. And Kate told me that she knows correlation doesn't equal causation, but she's also pretty convinced that seed oils are mucking up our bodies. And so what diseases do you think eating seed oils are linked to? Can you list them off for us?

[Dr. Kate Shanahan]

So just to list some diseases that are common, that I see a lot. Well, actually, let's start with the good news. Let's give some little good news here. Things that go away really quickly when you stop eating seed oils are skin conditions like acne, inflammatory skin conditions like acne and eczema and recurring hives, Inflammatory digestive systems get a lot better. And even irritable bowel, even celiac disease, you know, I think brain cancer, dementia and Parkinson's, heart attacks, they cause heart attacks. So there's nothing that they don't cause. And that means there's nothing that won't get better, at least a little bit and maybe a whole lot when you stop eating seed oils.

[Wendy Zuckerman]

So in Kate's mind, this long list of diseases are connected by one thing. Inflammation. And based on quite a lot of theory, Kate reckons that by looking at the biochemistry, you know, examining what makes up these seed oils at a molecular level, she thinks that when we burn these seed oils for fuel in our body, it releases free radicals that she says are bad for us and can.

[Dr. Kate Shanahan]

Release very dangerous particles into our bodies after we've eaten these things in large amounts.

[Wendy Zuckerman]

And this, she says, can lead to inflammation. Now, when we asked Kate for her best evidence that seed oils are linked to all those different diseases, a bunch of the papers that she sent us weren't actually about seed oils, but studies connecting oxidative stress, inflammation, and certain illnesses. But if you look in the literature, there have been other theories about whether the fats in these seed oils might cause inflammation. And all over the Internet, people are saying that the way that we refine and make these oils puts a bunch of toxins in them that then are dangerous when we eat them. So what we've got is a lot of theory, but now it's time to put it to the test. To meet David Egman, he's A doctor and researcher at Uppsala University in Sweden. And he has gone to heaven and earth to find out what is up with these fats. Or at least his team did a lot of baking.

[David Egman]

We made a lot of muffins, like thousands and thousands of muffins, but we changed the flavor like every week. We had some chocolate, some vanilla, some cinnamon.

[Wendy Zuckerman]

David and his team baked all of these muffins because he's done a series of studies to find out if you feed people muffins that are packed with either seed oils or saturated fat, what happens? Does inflammation in their body go up or not? So for example, in one study he got around 60 people to eat muffins, some which were made with palm oil, which is a saturated fat, and others were made with sunflower oil, which is a big no no according to Kate.

[David Egman]

So they were like very similar in all aspects, except just what kind of f we put into them.

[Wendy Zuckerman]

So people ate these muffins for eight weeks. And throughout the experiment, David and his team would then test a bunch of things in their body, including markers of inflammation. Now, if seed oils are indeed bad for us and cause inflammation, then you'd expect that the sunflower oil group would see a bump in their inflammatory markers. Right? In your study, what did you find? Did the sunflower oil eating group have more oxidative stress?

[David Egman]

No, we measured no increases in inflammation.

[Wendy Zuckerman]

This markers and in fact, a big review paper on this topic said that there was, quote, virtually no evidence that adding seed oils to your diet bumps up your inflammatory markers. I talked to Kate about the muffin.

[Dr. Kate Shanahan]

Study, so there's a lot there to unpack. So for one thing, it was an eight week study. That's not long enough. It takes years before the body composition will change. And secondly, we're not talking about real endpoints when we're talking about inflammatory markers. Inflammatory markers are blood tests. We don't treat blood tests in medicine. We treat human beings who have real physical feelings.

[Wendy Zuckerman]

And this brings us to a completely different study that David was a part of. I asked him about it. So what did you do? You took samples of butt fat from these elderly men?

[David Egman]

Yeah, yeah, it was buttock.

[Wendy Zuckerman]

So in this study, David's team analysed these fat samples which had been taken from the buttocks of more than 800 older Swedish men and then stored for around 15 years. Were you excited when you found out there were these samples in the fridge? Like that's a good.

[David Egman]

We just found this fridge lying around with all these buttock fat samples. And that's not Quite how it happened. But yeah, it's a cool study. I mean, it's very impressive that we have all this data.

[Wendy Zuckerman]

And to understand what David is doing with all of this data, you need to know that seed oils have a bunch of these particular kind of fats in them called polyunsaturated fats. So on a very basic level, you can think about it like this. Butter and bacon equal saturated fat. Seed oils equal polyunsaturated fat. Although in reality, life is always more confusing. But basically, whichever fat you're eating more of, if you don't burn it right away as energy, it'll get stored in your body as that kind of fat. And this means that David and his team could look at the makeup of the butt fat in all of their samples and say, well, if you ate a ton of seed oils 15 years ago, are you now more likely to have something like heart disease or to die prematurely? Which, if Kate's right, should be crystal clear in their data. Right, but it wasn't. In fact, having tons of those fats that come in seed oils was connected.

[David Egman]

To lower risk of dying.

[Wendy Zuckerman]

Oh, so people lived longer.

[David Egman]

Yeah. If you have more of this in your buttock fat and if you're a 71 year old man in Sweden, then you lived longer.

[Wendy Zuckerman]

Now, it wasn't by much. And one big review paper found that it probably doesn't make too much of a difference to your lifespan if you eat seed oils or not. But bottom line, they're not finding that seed oils are dangerous. Here David concluded that having more of these seed oil fats, then your buttock.

[David Egman]

Fat does not seem to be harmful in any way. It may be the opposite.

[Wendy Zuckerman]

I talked to Kate about this study.

[Dr. Kate Shanahan]

Oh, okay. Well, that doesn't make any sense.

[Wendy Zuckerman]

When you say doesn't make any sense, what do you mean?

[Dr. Kate Shanahan]

That's not what I would predict. And you're right, that does contradict my theory.

[Wendy Zuckerman]

It is the opposite of the theory. Right, that's the opposite of the seed oil theory. That's just suggesting that.

[Dr. Kate Shanahan]

Yeah, yeah, correct. But it sounds like the opposite. But if you drill down into the details of these studies, which I have done, I usually find that they're missing something very, very important which makes them misinterpret the finding.

[Wendy Zuckerman]

Kate took a close look at David's paper and in an email afterwards, she sent me a few criticisms. One was that she said his study actually did find a link between one of the fats in seed oils and death. But once he adjusted for other risk factors, that link Disappeared. I sent these criticisms to David and he wrote back to me saying, among other things, well, you need to adjust for risk factors. These are things like smoking and high blood pressure. And these things can affect your likelihood of getting heart disease or dying. So if you don't control for this stuff, you can come up with the wrong conclusion and say, blame these fats for something that smoking is doing. And zooming out, there are other kinds of studies that don't use fridges full of buttock fat and God help me, I'll say buttock as many times as I like. And in these studies, you can find a couple that suggest seed oils up your risk of heart disease. But the vast majority of the research here doesn't. And in fact, one review looking at almost 50 randomised controlled trials involving more than 24,000 people, found that, on average, these oils are probably good for your heart. And that, generally speaking, swapping out saturated fat for seed oils, you know, completely contrary to Kate's advice, is actually the healthier thing to do. Here's how Jason sees it. You know, our. But a researcher replacement of saturated fat.

[Jason Wu]

With the polyunsaturated fat does reduce the risk of cardiovascular disease.

[Wendy Zuckerman]

The exact opposite of what this trend is suggesting.

[Jason Wu]

Yeah. So the evidence are pretty consistent, really.

[Wendy Zuckerman]

So eating these, even like highly refined chemical, as chemically canola as you can get, eating those instead of saturated fat, we're actually seeing better health outcomes.

[David Egman]

Absolutely.

[Wendy Zuckerman]

I asked Kate about the science on this.

[Dr. Kate Shanahan]

I have looked at these studies and I have found a flaw in all of them. After the first, I don't know, 300 studies, I kind of lost interest in, you know, what is the latest way that they're misinterpreting it?

[Wendy Zuckerman]

You know, if the seed oils theory was as strong as perhaps you'd like it to be, you would expect all these studies, even with their flaws, would find that people who have seed oils that have polyunsaturated fats in their fat in their blood are doing worse. Like, even despite the flaws in the studies. Right. You would expect.

[Dr. Kate Shanahan]

I think you do find that. When I look. I do find that.

[Wendy Zuckerman]

Right. I mean. Oh, interesting, because the researchers who did the studies are telling me, like, the ones who did, the ones who were getting the fat samples and making the muffins and crunching the numbers, they're telling me they still think polyunsaturated fats and these oils are the healthier ones. That's when they look at the data. That's what they say.

[Dr. Kate Shanahan]

It's too large of a leap to make all in one study.

[Wendy Zuckerman]

Right.

[Dr. Kate Shanahan]

You can't.

[Wendy Zuckerman]

But even when they look at the picture, they look at all these different. The muffin, the fat samples, the blood samples, there's so many others.

[Dr. Kate Shanahan]

Even just one study did not convince me. Right. It took me many, many, many studies, and it took me knowing biochemistry to become convinced. So a researcher who's doing one study on seed oils in many other studies that they've done, it's a small part of their brain devoted to it. Really, what's needed for any paradigm shift is a wholesale restructuring of the way we approach a problem. Right. I mean, that's. Paradigm shifts are difficult.

[Wendy Zuckerman]

Going back and forth with Kate on this, I think it's just that she trusts the few studies out there showing that seed oils are harmful and doesn't trust the many, many studies that show that these oils are fine for you and possibly even healthier.

[Dr. Kate Shanahan]

I would talk to my patients and ask them if somebody came out of the hospital. What did you eat before you went into the hospital? Fish. What'd you fry it in? Canola oil. You know, time and time again, I heard things like that. James Gandolfini, what was his last meal? Do you know?

[Wendy Zuckerman]

I'm not familiar.

[Dr. Kate Shanahan]

He had shrimp deep fried, double serving of it, dipped in mayonnaise, which is made out of seed oils. That was. He had like two portions of that. That's like. See, the worst form of seed oil. He had a heart attack that. That night and died.

[Wendy Zuckerman]

Right. And that. You think that's what killed him?

[Dr. Kate Shanahan]

No, it was a lifetime of seed oils. And that was the fatal blow.

[Wendy Zuckerman]

Right. So that's where Kate stands. But there is one final point to make here. Even though on the average, the research tells us that the fats in seed oils are healthier, they're not so healthy that if you're eating a diet full of junk food that happens to have seed oils in it, like chips and tater tots and fast food, that that diet will be good for you. So, you know, if you go on this new seed oil diet and you bin your seed oils and end up eating a bunch more fruit and veggies and home cooked meals, you could end up on top. But it probably wasn't avoiding the seed oils that did it. They're more like an innocent bystander here. And so when it comes to this idea that seed oils are the devil and saturated fat is our savior, well, perhaps let's give David Shade, our cholesterol researcher, the final word here.

[David Shade]

You know, every. Every year, there are crazy Diets that people put out without any scientific justification, and that's one of them. It's all crapola.

[Wendy Zuckerman]

Crapola is how you say crapola.

[David Shade]

Crapola, yeah. That's what it is. That's a technical term.

[Wendy Zuckerman]

That's Science Versus.

[David Shade]

Hey, Wendy.

[Wendy Zuckerman]

Hey. Joel Wenner, supervising producer at Science Versus.

[David Shade]

Are you excited that Seed Oils is now we finished the episode. That's it.

[Wendy Zuckerman]

That's right. Congratulations to the audience.

[David Shade]

So how many, how many citations were there in the episode today?

[Wendy Zuckerman]

There were 102 citations. Yes.

[David Shade]

And how can people find these citations?

[Wendy Zuckerman]

I'm just, like, looking at them now and my head is spinning, even though I'm the one that put the vast majority of them in there. If people want to see these citations and read more about anything that we talked about today, then head to our show notes and click on the link to the transcript and you'll see all the citations to basically every word that came out of my mouth today. And we have a podcast recommendation for you. It is called Heavyweight. It's not a new podcast, but they have a new season out. And this podcast is phenomenal. Right?

[David Shade]

Heavyweights, like, I don't know, I feel like it's the podcast that podcasters rave about. Like, people who make podcasts notoriously don't have time to listen as much as they want to. And, you know, we're too busy kind of making the thing to listen to the thing. But Heavyweight is the one show that everyone I know who works in audio never misses an episode of. It's an absolute classic.

[Wendy Zuckerman]

Yeah. Yeah. So go check it out, Heavyweight. It's available on all of your podcast catches just like we are. So, yeah, so go enjoy it. New season. It's going to make you laugh and cry and do both at the same time. All right, thanks, Joel.

[David Shade]

Thanks, Wendy. Bye.

[Wendy Zuckerman]

This episode was produced by me, Wendy Zuckerman, with help from Joel Werner, Rose Rimler, Nick Delrose and Michelle Dang were edited by Blythe Terrell. Fact checking by Carmen Dral Mix and sound design by Bumi Hidaka. Music written by Bobby Lord, Emma Munger, Peter Leonard and Bumi Hidaka. Thank you to all of the researchers that I spoke to. I really went back and forth with a bunch of researchers and I just so much appreciate your time and explaining the science to me. So thank you to everyone I spoke to, including Dr. Loretta Pacheco, Dr. Chi San, Dr. Tetsumori Yamileth, Dr. Idris Mughal, Professor Rashika Ahmed, Dr. Atem Taleema, Dr. Heidi Silva, Professor Ronald Krauss, Dr. Yutang Wang, Dr. David Sullivan, Professor Peter Clifton, Dr. Lee Hooper and others. A big thank you to Morgan Ruckel, Jen Mortimer who put me on this whole seed oils adventure. Thank you Jen, the Zuckerman family and Joseph Lavelle Wilson. Science Versus is a Spotify Studios original. You can listen to us for free on Spotify or wherever you get your podcasts. You can find us everywhere. If you are listening on Spotify, follow us and tap the bell icon for episode notifications. And if you like the show, give us a five star review. Come on, do it. And plus if you want to come say hello, I am on TikTok so I'm Wendy Zuckerman. W E N D Yes Z UK E R M A N Ross on Instagram Science Underscore Vs. I'm Wendy Zuckerman. Back to you next time. You know the words dominating today's headlines. Private equity, generative capital gains.

[Dr. Kate Shanahan]

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[Wendy Zuckerman]

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[David Shade]

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[Wendy Zuckerman]

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