This is a transcript of the Gastropod episode, Seed Oil Scare: The Curious Case of Canola, first released on April 8, 2025. It is provided as a courtesy and may contain errors.

BROADCASTER: We’re hearing a lot about seed oils. Why should people be worried about these kind of products?

ROBERT F. KENNEDY JR: Seed oils are one of the… most unhealthy ingredients that we have in foods. And seed oils… the reason they’re in the foods is because they’re heavily subsidized. They’re very very cheap, but they—they are associated with all kinds of very very serious illnesses. Including body wide inflammation.

CYNTHIA GRABER: That is Robert F. Kennedy Jr., and we’re sorry to start the episode with him because we’re also sorry that he is currently the secretary of Health and Human Services.

NICOLA TWILLEY: There are so many reasons we’re sorry about this. But nonetheless, we started the show with his voice because he is far from alone in saying that seed oils are dangerous. It’s quite a common belief these days.

JOE ROGAN: Seed oils are some of the worst fucking things your body can consume. There’s some sort of a correlation between seed oils and macular degeneration. Like, it causes inflammation, and inflammation is fucking terrible for you, no matter what.

GRABER: Yes, again, sorry, that’s Joe Rogan, host of a truly shockingly popular podcast, and we of course are also hosts of a popular podcast. This is indeed Gastropod, the podcast that looks at food through the lens of science and history. I’m Cynthia Graber.

TWILLEY: And I’m Nicola Twilley, and we, like many of you, have been hearing this anti-seed oil propaganda for a while now. But then, a listener got in touch with an intriguing question that made us want to dive a little deeper.

AMY MACLEOD: Hi, my name is Amy MacLeod. I’m from Vancouver, British Columbia. And I’m curious about canola oil. My grandfather was a farmer in Saskatchewan and he grew canola on his farm, in addition to other things. And—I always use canola oil in my cooking. I feel like it’s a great way to support Canadian farmers. But now with all the buzz around canola oil being really processed, I’m not sure if it’s the healthiest choice. And I’m wondering sort of what the history of canola oil is, and if there’s something that’s a better choice or if it’s still fine to use.

GRABER: Amy, we are on the case. What is canola oil, and why is it so popular in Canada?

TWILLEY: And is it, and all its seed oil brethren so extremely terrible for you? What is so bad about how it’s processed? We’ve got all the answers, coming right up.

GRABER: This episode is sponsored in part by the Alfred P. Sloan Foundation for the public understanding of science, technology, and economics, and by the Burroughs Wellcome Fund for our coverage of biomedical research. Gastropod is part of the Vox Media Podcast Network, in partnership with Eater.

[MUSIC]

DUNCAN FARRINGTON: So originally the, the Romans brought rapeseed over to the UK when they invaded it. So that’s sort of two or 3000 years ago.

TWILLEY: This is Duncan Farrington, he’s a British farmer, and you might not have realized but he is talking about canola. He just called it rapeseed because that’s what we call it in the UK because that’s what it started out as. We’re old school like that.

GRABER: We’ll get back to where the name canola comes from, but rapeseed, that sounds unpleasant, but it’s related to the plant’s Latin name. Rapeseed is a brassica like kale and broccoli and cabbage, and the oil plant comes from a subspecies called brassica napa or brassica rapa, rapa for turnip, but then rapa became rape, like the vegetable rapini or like rapeseed.

TWILLEY: And rapeseed—or rape as it is sometimes called just to make matters worse—it goes way back. Botanists think it may have originated in India, there’s records of it being cultivated there as much as six thousand ago, but it’s definitely been used for thousands of years everywhere from China to the Mediterranean.

GRABER: The Romans, as Duncan said, they grew rapeseed to press for oil, but they may not have been using it for food.

FARRINGTON: They probably could have eaten it, but naturally, rapeseed is more of a—has more of a bitter flavor oil. The Romans probably most likely used it for oil lamps and candles. And also Roman baths to put on the body as a—you know, when the, the guys and girls went to the baths and had a massage oil.

TWILLEY: Back home in what’s now Italy, Romans had access to lots of lovely olive oil, that was their fave. But as they colonized northern Europe, where the weather is crap and olive trees don’t grow, they needed a new oil source. Rapeseed did the trick.

GRABER: It grows really well in cold climates. And so while it was kind of bitter, probably Northern Europeans did eat it occasionally if they didn’t have their favorite butter or lard around. It was definitely used for animal fodder, and apparently by the 1500s it was Europe’s major source of lamp oil.

TWILLEY: Then, once the Industrial Revolution got going in Britain, this lamp oil found a new role as an engine lubricant.

GRABER: Steam engines were a foundational technology that powered the industrial revolution, and it turns out that rapeseed oil is a great lubricant for steam engines. Water and steam don’t wash it off, it stays oily and lube-y where it’s supposed to be.

TWILLEY: Once our petrochemical era really got going, and steam engines were replaced by diesel engines that didn’t need rapeseed lube anymore, our unfortunately-named oily friend kind of fell out of favor.

GRABER: But then, in the 1930s, a farmer from Poland was living in Canada—

MICHAEL ESKIN: And, a friend of his sent him a few seeds of rapeseed. And, he found it grew very well. And, when the Second World War broke out, there was a, a need for a lubricant for marine engines. And the oil from rapeseed was a perfect lubricator for marine engines.

TWILLEY: This is Michael Eskin, he’s a distinguished professor in the Department of Food and Human Nutritional Sciences at the University of Manitoba in Winnipeg, Canada. And he is a key player in the rapeseed slash canola story. Which really heated up, like Michael said, during World War II.

GRABER: There was a huge shortage of oil in Europe at the time, they were using anything they could get their hands on: whale blubber, cottonseed oil, anything. And they really needed lubricants for the engines that powered their ships. So Canadian farmers quickly picked up the slack, grew a lot of rapeseed, and sent it over.

ESKIN: Thankfully, the war ended and there was no need for a, a lubricating oil. And so the question was, someone raised in Agriculture Canada, has this oil any potential? It smelled bad, and it had a bad color.

TWILLEY: It was greenish and stinky, Canada was growing a lot of it, and the engine lube market had disappeared. Meanwhile, as the Canadian government had noticed, the country was also importing 90 percent of all its edible oils. So a couple of plant breeders, one in Saskatoon and one in Winnipeg, got to work to see if they could make it a little more palatable.

GRABER: The reason the rapeseed oil was stinky and kind of bitter was because of a couple of particular components.

ESKIN: There were two, two things they were interested in reducing. They were interested in changing the fatty acids. But they were also interested in reducing what we call the glucosinolates.

TWILLEY: The fatty acid in question was erucic acid. This is a pretty common fatty acid in plants, but it’s found at especially high levels in rapeseed. It was the erucic acid in particular that made rapeseed so great for machine lubrication, but It tastes quite bitter, which makes it harder to love as an edible oil. Plus it had a bad rap for health reasons.

FARRINGTON: There was some research done a long, long time ago, shown that—and the research was done on rats. Showing that high levels of erucic acid in rats can actually cause heart lesions. It can cause a weakening of the heart wall.

GRABER: There was a bunch of research on rats showing various negative health outcomes of consuming erucic acid. So, people assumed it was also toxic to humans, although that has never been shown in human studies. But in any case, the breeders wanted to take the erucic acid out.

TWILLEY: The other target for elimination was the glucosinolates. These are also found in all brassicas, they give brussels sprouts and cabbage and mustard their pungent, slightly sulphury brassica flavor, which I like. But that was considered off-putting in a wannabe edible oil too.

GRABER: Another big issue with glucosinolates was that after the seeds were pressed for oil, the leftover seed residue was fed to animals, and they seem to not love that brassica flavor. So for it to be useful as high protein animal feed, which was a major goal, getting rid of glucosinolates was important.

ESKIN: This was in ’45. So a process started, and it took until the ’60s, until two breeders, and there are a lot of others involved in that, but two breeders. One was a fellow called Baldur Steffanson.

TWILLEY: He was in Saskatoon and there was another scientist called Keith Downey in Winnipeg, and to this day both provinces like to claim credit for the resulting breakthrough.

ESKIN: So I guess there was a little competition, but it was friendly. And they worked together. And, what they did, it was the old fashioned type of plant breeders, where they crossed plants and they analyzed.

GRABER: As Michael said, this took more than 20 years of crossbreeding, and a bunch of other people got involved too. One of the things they needed to do as they were doing all this breeding, they had to come up with a name that didn’t involve the word “rape.”

ESKIN: We were happy to change the name. The name was going to be Canbra, but a company had already established that name. So they had to look for another name.

TWILLEY: Can-bra is short for Canadian brassica. But in lieu of that, they decided to go with can-ola.

ESKIN: Canadian oil, canola.

GRABER: So the breeding was successful: there was almost no erucic acid or glucosinolates in the new variety. There was a new name that didn’t include rape at all. And then they had to do nutrition studies to demonstrate that this new variety of rapeseed, now called canola, was what’s known as GRAS: generally recognized as safe. Meaning anyone and everyone could cook with it and make products with it and eat it.

TWILLEY: The room where they first fed canola to humans to make sure it was safe is still right there at the University of Manitoba.

[ECHOEY FOOTSTEPS]

[KEY FIDDLING IN LOCK]

CARLA TAYLOR: So, right now we’re entering the room where the original studies were conducted for feeding humans, university students, the first canola oil that was available for testing.

GRABER: Carla Taylor is a professor in food and human nutritional sciences at the University of Manitoba, and one of the things she studies is canola oil.

TAYLOR: The students would come up for all their meals. And they were taking blood samples so that they could look at how the fatty acid composition in their plasma was changing over the time that they were on the study.

TWILLEY: Michael was part of the team back then, his colleagues were doing that nutrition research and he was studying the basic chemistry.

ESKIN: They looked after feeding the stuff to students and analyzing the urine and feces. We always knew when they were analyzing feces, because you came into the department that day and you need to put a peg on your nose. And, and we looked at the composition, the stability, the performance, the—a whole range of activities.

GRABER: After all the research was done, in the ’70s and ’80s, the Canadian government recognized canola oil as safe, then the American government did too, and farmers in both countries started to grow it.

TWILLEY: And Michael told us its success exceeded everyone’s expectations.

ESKIN: Canada has 43,000 canola farmers. And they generate around $30 billion annually into the economy. So it is, it is the largest—yields the largest return of any agricultural product. And in fact changed the agriculture landscape of Canada.

TAYLOR: It’s a big deal. [LAUGH] If you were here in… end of June, beginning of July, when canola is blooming. You would think that about half the fields are yellow.

GRABER: And because things need to be explicitly pointed out these days, government research that took decades is now worth billions of dollars every year in North America. But so Carla comes from a farming family, and her family owned one of the farms that happily switched over and ended up enjoying wide swaths of yellow flowers each summer.

TAYLOR: Yeah, so, I grew up on a farm. And my brother still runs the family farm. And, canola is one of the main crops. And actually, I can remember when I was young growing up, there weren’t any yellow fields in front of the house. I know the time that there was kind of the switch, that canola was suddenly this crop that became available. It could be grown here, in this climate. Before it would be wheat, barley, and some oats, and now it’s switched to mostly canola and wheat.

GRABER: The resulting oil—the final end point of thousands of years of growing and decades of breeding—the final product is that clear, flavorless cooking oil available basically everywhere these days.

TAYLOR: For quite a long time now, I mean, that’s just the main vegetable oil that’s in the grocery stores here.

TWILLEY: But in my home country, England, that innocuous multipurpose cooking oil is not the only kind of rapeseed oil on the shelves. In fact, these days canola—or as we still call it, rapeseed oil—is taking extra virgin olive oil on at its own game, and sometimes winning. How rapeseed got fancy, after the break.

[BREAK]

GRABER: Duncan Farrington is a fourth generation farmer in England, and he remembers when his dad started growing rapeseed for oil.

FARRINGTON: We started growing it here—my father started growing it in 1984. But there were other neighbors around that were growing it five or so years, maybe even 10 years before that.

TWILLEY: What happened was, in the 1970s, French plant breeders started looking at old-fashioned rapeseed again. They’d seen what their Canadian colleagues had done, and they had good reason to be interested in an edible oil that could be grown in the milder, wetter climates of northern Europe.

GRABER: One of those reasons was that in the 1970s, America suffered an intense drought and we didn’t want to send our soy to Europe, even though they had been depending on it for animal feed. We put an embargo on shipping it over. Remember, the rapeseed leftovers after oil pressings are great for animals.

TWILLEY: These were uncertain times. Food imports in general were threatened by the oil crisis in the Middle East. Meanwhile, another edible oil source, the peanut—that was having a little crisis of its own, also drought related. US supermarket shelves were stripped of peanut butter. So oils were in short supply all around.

FARRINGTON: The EEC, European Economic Community got together. And one of the things they looked at doing, which was very important, was making sure Europe wouldn’t starve again, and Europe would have food security.

GRABER: And so those French breeders did what the Canadian breeders had done: they created a rapeseed plant that had low levels of erucic acid and glucosinolates, but that was better suited to European climates, where you can get two harvests a year. This solved both the edible oil issue and the animal feed crisis.

TWILLEY: And just like in Canada, this new and improved version of rapeseed caught on right away.

FARRINGTON: There was a high demand for it. And the prices originally were very, very high. And I remember when I was a boy, farmers would call it black gold because it was worth a lot of money.

TWILLEY: This European rapeseed oil 2.0 was pretty much identical to the Canadian version, except it wasn’t called canola. It wasn’t fancy, to be sure.

FARRINGTON: Back in the day, you’d go into the supermarkets and there’d be an array of plastic bottles, and it was called vegetable oil. It’d often have a nice little pretty picture of a yellow flower on there. But, it wasn’t called rapeseed oil. It was just called vegetable oil.

GRABER: Duncan went off to university and studied the family business, he studied agriculture.

FARRINGTON: And I thought rapeseed sounded pretty interesting. So I did a literature review on rapeseed and rapeseed oil. And while I was doing it, I just came across the fact that there’s a crop that we grow in Britain. It’s considered, as we’ve been talking about, it is a cheap commodity crop found in a supermarket, in a plastic bottle, highly refined, no character, no one knows anything about it. It’s got an awful name, of “rape.” So no one cared about it.

TWILLEY: Duncan didn’t think that was fair. He felt like it deserved better.

FARRINGTON: I researched it at university and found out how wonderful it was and thought, why on earth are we not making something about this in Britain? And actually one of the researchers was a chap called Dr. Kerr Walker, who was a researcher from Scotland. And I was talking to him one day. And he had done a lot of nutritional research on the effects of rapeseed oil. And, he was known globally. And I said, why don’t we talk about it and make something of it in Britain? And he said, Duncan, it will never work. With the word rape, it’s never going to work.

GRABER: We’re going to get back to the nutritional research on rapeseed oil—obviously that’s something contentious these days—but Duncan wasn’t put off by the problematic name. He needed a high value crop to help keep his family farm afloat. At the time what they were growing, which included rapeseed for boring vegetable oil and animal feed, it wasn’t enough.

FARRINGTON: And if I wanted to stay on the farm, which I was absolutely—you know, I wanted to be a farmer. But if I wanted to stay on the farm, the only way I could, economically do that was look at diversifying in some way or another. So I went back to my university research, a little germ of a—or an embryo of an idea of a business. And I went and I spent 18 months actually doing a business plan.

GRABER: His idea was to produce a high quality, higher price rapeseed oil, like extra virgin olive oil versus the cheap industrial stuff.

FARRINGTON: And eventually, in 2005, we set up Britain’s first cold crush business. We were the first company in the UK to grow press and bottle rapeseed oil on farm. And, we’ve not looked back since.

TWILLEY: The growing part doesn’t involve anything revolutionary. Duncan grows rapeseed pretty much the same way his father did. He plants it in late summer and it takes a while to get going.

FARRINGTON: So over the winter it lays dormant and looks like lots of very small cabbages. And then as the weather starts warming up and the day length lane lengthens, from the end of February it starts really growing. And what happens then? It turns more away from looking like a cabbage to a tall plant with lots of branches on it. And it has these tiny little pods which look like… more like, runner bean pods or pea pods. And inside those pods, when they are mature, are little black seeds, and inside the black seeds is a yellow kernel. And we squeeze that. And that’s where the lovely, delicious yellow oil comes from.

GRABER: Squeezing it, that’s the real difference between Duncan’s oil and the industrial product. For industrial rapeseed oil manufacturing, the seeds are all first heated to 185 degrees Fahrenheit. Not quite boiling but very hot.

FARRINGTON: Because the higher the temperature, the more efficient the oil extraction. And then it’s, refined using often, a hexane solvent. ‘Cause it dissolves the oil.

TWILLEY: The oil is trapped in solid plant matter, and hexane pulls it out.

GRABER: And the hexane and oil liquid mix is separated out from the solids, then the hexane is boiled off.

FARRINGTON: And then it’s bleached, and it’s deodorized. And you end up with a very bland looking oil. And a tasteless oil.

TWILLEY: There’s a couple of good economic reasons to make rapeseed oil this way. One, mass market edible oil suppliers actually want an end product that’s anonymous and undistinguished, it allows them to hedge their bets.

FARRINGTON: If rapeseed harvest fails one year, or the price of rapeseed is high, soya oil, sunflower oil, olive oil, other oils can be substituted. And if it’s all put in a bottle and it’s all a clear, tasteless product, it doesn’t matter what’s in it. And it’s called vegetable oil.

GRABER: But also this industrial process is really efficient. It works so well that the seed residue only has about 1 percent oil left in it.

FARRINGTON: Compared to ours on a cold day at 18%. And in the summer we might have 10% oil in it. So, what, what we are doing, it is, it is very, very inefficient compared to a great big factory doing it more in a commercial way.

TWILLEY: Duncan’s oil is, like he said, cold pressed, which means all the flavors and antioxidants in the oil aren’t cooked out. Again, it’s like extra virgin olive oil compared to industrial olive oil.

FARRINGTON: It’s very simple. We, we call it the process of no process. All we do, we take our rapeseeds and we squeeze them. I started with one press. I’ve now got 18 of them. And they are squeezing the seeds without any added heat.

GRABER: Duncan showed us some those seeds his presses squeeze, they look like the tiny round little balls of mustard seeds you might buy at the store to cook with.

FARRINGTON: But mustard seeds have a brown or yellow coating, rapeseed has a black coating. And if you actually squeeze one of those seeds between your fingernails, inside, there’s this yellow kernel, and that is where the oil-bearing cells are. Now, if you have a mortar and pestle and you bash those seeds, it takes an awful long time to get oil out of it. But our little presses, they’re going 24 hours a day, seven days a week, and it’s just gently squeezing the seed. The oil comes out—and the oil comes out with bits of seed husk and material. So then we pass it through a filter, which is like a great big tea strainer, and then we put it in a bottle. And it is as simple as that. And what we are doing, we are just capturing all of the natural nutrition and character of that oil. We aren’t removing anything. We aren’t adding anything. So it is, it is what it is.

GRABER: Of course the final product is more expensive than plain vegetable oil but it’s cheaper than extra virgin olive oil.

TWILLEY: So far, so great, but like Duncan’s scientist friend Kerr Walker, at this point in the story, I confess that I am feeling a little scepticism about whether the great British public was really going to embrace an artisanal cold pressed rapeseed oil.

GRABER: That is just what Duncan found himself up against when he first launched his company more than 20 years ago.

FARRINGTON: So when I first started, if you’re really posh, you know, everyone consumed olive oil. If you weren’t quite so posh, sunflower oil sounds nice. It’s nice and sunny and has a good feeling about it. And, you know, if you’re a, a common garden person like myself, you’d probably have rapeseed oil from the local supermarket and, that was what you had. And rapeseed, or vegetable oil, as it is known, was seen as the cheap, cheerful commodity product.

TWILLEY: What that meant is that he didn’t just have to make oil, he also had to change people’s attitudes.

FARRINGTON: Originally, my mother and myself did our first day’s bottling, And we spilled oil everywhere, and we were trying to work the machinery, and then eventually we knew how to do it. But I had a few bottles at the end of the day and I put them in the back of, in the boot of my car. And I literally drove around. I got a speeding ticket on the way ’cause I was in a hurry. I think on that first day. I drove around nine potential customers. I came back with eight customers.

GRABER: Duncan didn’t want to do the farmers market route, he wanted to go to shops and have them displaying his oil alongside all their other beautiful products. One of the nine shops he visited was the local butcher.

FARRINGTON: And he said, okay. And he, it is probably just trying to shut me up and get me to disappear. But we did this deal and I said, look, if you buy a case off me, if it doesn’t sell, give me a call in a couple of weeks time or whenever and I’ll come and I’ll give you your money back. And we’ll say at least we gave it a try. And Mr. Johnson was his name. He said, that sounds like a good idea, Duncan. So we did that. And then two weeks later the phone rings and it’s Mr. Johnson. I thought, oh no, here we go. And he said, Duncan, you know that oil you bought, can I have two more cases please?

TWILLEY: Pretty much everyone who tried Duncan’s cold pressed rapeseed oil became a convert, even the non human consumers.

FARRINGTON: Put it this way, when, when we first started the company, we had a a here, My wife and I, Ellie and I, we had a German pointed dog, called Ollie. We named him after the oil company. Ollie. Ollie the dog. And he was the company mascot for a long time. And he absolutely loved—if he, if he’d get the chance to go and lick up a bit of oil off the floor anywhere. he, he absolutely loved it and he had a very shiny coat because of it.

GRABER: That sounds lovely, I’d love a shiny coat myself. And Duncan said his oil really is totally different from industrial vegetable oil, the clear canola or rapeseed oil in the see-through plastic bottle.

FARRINGTON: It’s as difference as chalk and cheese. First of all, you can see the lovely yellow color. Well that yellow color, it’s the carotenoids in there. So, refined oil, they would bleach it. So the color goes straight away. And when the color goes, it takes away some of the nutrition.

TWILLEY: Having got a hold of a bottle ourselves, we can confirm that it is in fact extremely yellow

TWILLEY: Here we are at the inaugural canola tasting.

GEOFF MANAUGH: Thank you for having me. I can’t wait.

TWILLEY: Once again, I roped my long-suffering husband Geoff into another glamorous Gastropod tasting. I toasted some bread and put out extra virgin olive oil, Duncan’s cold pressed rapeseed oil, and some regular canola oil in three little saucers.

MANAUGH: They all have liquid in them. One is, what I suspect to be olive oil. Another one is very, almost clear? And doesn’t look… particularly good. And then another one is a very deep yellow. It’s a pretty unappetizing color of yellow, frankly. It looks like someone has kidney problems. And. Or like somebody just had a massive molten butter incident at a movie theater.

GRABER: My partner Tim and I did a similar tasting, we were going to compare the cold-pressed rapeseed to normal canola oil, to olive oil, and to sunflower oil from Maine, not too far from me. Unlike Geoff, I thought the color was delightful.

GRABER: Now I’m going to open for the first time this rapeseed oil that was delivered all the way from the UK.

[BOTTLE OPENING]

GRABER: Okay. Very pretty color. I’m going to pour it out. Just a little bit. It is the brightest yellow of the bunch.

GRABER: Tim cut us some bread he’d just made that day—[CUTTING BREAD] and we took it over to the four white saucers that had the oil. Tim and I started with the plain canola oil.

TIM BUNTEL: It really has a zero color. [QUIET SNIFF] No real smell. [CHEWING] Doesn’t change the taste of the bread at all, but it changes the texture. Because you’ve got the little… kind of oily mouthfeel.

GRABER: Oh, it’s weird. To just dunk in plain. Because it’s like you get the fat but no flavor. It’s not like butter. Or olive oil.

BUNTEL: Not a winner.

TWILLEY: Yeah, same verdict in our household.

MANAUGH: Hmm. Well. I don’t know, but I’d go as far as to say that it doesn’t have a taste.

TWILLEY: Hmm. [CHEWING] It has no flavor. It has… fat. Like my, my tongue has a… like a fat texture on it now.

GRABER: Okay for cooking, not for dunking. Unsurprisingly, all four of us totally loved dunking our bread in olive oil.

TWILLEY: Honestly I could drink good olive oil by the glass, it is pure bliss.

GRABER: I wanted to love my local sunflower oil, but I’m not a huge fan.

BUNTEL: [CHEWING] It’s kind of weird. It’s almost a little smoky. Or burnt tasting, maybe. I don’t know.

GRABER: It just tastes so intensely of sunflower seeds to me? That. even when I cook with it, I want to really like it, because I like supporting local oil. And it’s okay with like, cabbage. But it keeps a very strong flavor of sunflower.

TWILLEY: And then it was on to the main event: the bright yellow cold pressed rapeseed oil.

TWILLEY: All right. I’ve soaked up a lot of it just to make sure. [BITE, CHEWING] It definitely has a flavor. And I, I want, I want to say it’s a, it’s a little cabbagey, honestly. Not—I mean, I like cabbage, but. It’s savory and cabbage- y.

TWILLEY: Geoff thought it was more like a string bean thing than a cabbage vibe, but both of us liked it.

MANAUGH: And I’m just spitballing here, but like if it was on a salad. Maybe I wouldn’t notice that it wasn’t olive oil. And it would just continue the taste of a salad. Because it has that kind of leafy, string bean-y. You said it was cabbagey. But it tastes, you know, a little- it tastes like a dressing that has already been on a salad and now it’s at the bottom of the bowl.

GRABER: At first I think I was influenced by knowing that it’s related to broccoli.

GRABER: I get like a little vegetal… little vegetal like brassica thing going on.

GRABER: Then I just took a little sip of the oil straight.

GRABER: So tasting it on its own, I’d actually say it almost, it almost has a little nuttiness to it. I’m not—like, even maybe more than this, like, cabbage-y thing. It’s like a vegetal, slight nuttiness, not intense nuttiness, like sesame. It’s really interesting.

TWILLEY: Also, it was not nearly as bold as the olive oil, which for me made it better for cooking or dressing a salad rather than dipping, but that’s part of its charm.

FARRINGTON: It is, as the name says, it’s yellow in color and mellow in flavor. There’s no bitterness at all.

GRABER: And that’s the origin of the name: Duncan’s oil is called Mellow Yellow. After our tasting, Nicky used it to make roasted potatoes, which sounded delicious, and I made some cabbage with it at high heat, it was great. I’m a fan.

TWILLEY: Rapeseed slash canola has a higher smoke point than olive oil, which basically means you can heat it to a higher temperature before it breaks down and starts to smoke. So it’s good for anytime you want to cook at a really hot temperature.

FARRINGTON: And because it’s light in flavor, and not overpowering, that’s why you can use it in a salad dressing or you can use it right through to baking cakes. And it’s not going to overpower the cake you bake with it.

GRABER: When Duncan started, as we’ve said, nobody was making cold pressed rapeseed oil. But his oil got so popular, so quickly—Michelin starred chefs started using it, too—anyway, he basically invented a new food sector in the UK.

FARRINGTON: I think within the first five years there were probably, I dunno, say, 50 growers around the country starting doing their own brands.

TWILLEY: So what we have established here is that rapeseed oil can taste great. But—and I hate to mention it: isn’t it supposed to be killing us?

GRABER: That’s coming up, after the break.

[BREAK]

MEGYN KELLY: They are the hateful eight. Canola, soybean, corn, sunflower, safflower, grapeseed, red bran, and cottonseed oils.

GRABER: Megyn Kelly used to be on Fox news and she now hosts her own Sirius radio show called the Megyn Kelly show, and she was speaking with someone named Casey Means who calls herself a functional medicine slash holistic medicine doctor. She is a doctor.

TWILLEY: Which does not make her advice any more scientifically sound, unfortunately. Casey told Megyn that if you eat canola you’re basically eating engine lubricant, which if you’ve been listening, you’ll know is really stretching the truth. Rapeseed oil was indeed a lubricant, and then its entire fatty acid composition was transformed through breeding. But that’s not the only criticism of canola out there.

FARRINGTON: The funniest one I heard was—or read—was that, rapeseed is related to mustard. And, mustard was used in the second World war as mustard gas, so it kills you. So you shouldn’t eat rapeseed oil. Well, excuse me, people are quite happy to put mustard on their hot dog, and yet they thought that, it’s the same thing as mustard gas. So there is a lot of nonsense out there.

TWILLEY: In case you’re worried, mustard gas the weapon is a human made chemical, it’s not chemically related to mustard or other brassicas. It just got its name because it smells a little sulphur-y at room temperature and turns yellow-brown when it’s mixed with other chemicals to form a weapon.

GRABER: Casey didn’t mention mustard gas, but she did also go hard on the industrial process for turning canola seeds into oil.

CASEY MEANS: I think if you really want to lose your lunch, you should Google a video of how canola oil is made.

KELLY: For the listening audience, it looks like they put that through a car engine. That’s really what it reminded me of. Putting it through a car engine and then feeding it to you.

MEANS: I don’t want that in my body.

TWILLEY: Duncan described this process to us earlier. It’s the standard process for all industrial oils including non-extra virgin olive oil. And like most industrial food production processes, it does look a little, well, industrial—it’s not what we like to picture when we’re thinking about how our food gets made, but welcome to reality, folks.

GRABER: Also, the hexane residues in edible oil processing don’t seem to be a health issue. Look, we don’t love the sound of hexane, which is a petroleum product, and we haven’t studied the impact of its entire lifecycle. But it’s been used to extract oil since the 1930s, it’s been extensively researched. High exposures do cause health effects, but there’s a vanishingly small amount of hexane left after the processing is done. And so you get more exposure to hexane from the fumes when you fuel up your car than by eating industrial canola oil.

TWILLEY: Still, thanks to all the social media misinformation out there, a lot of people are now cutting out canola along with its fellow seed oils.

YOUTUBER: Sweetgreen just announced they are removing [BLEEP] oils from their cooking oil, and phasing it out from their salad dressings. This is amazing, guys.

TWILLEY: And some are even replacing it with good old fashioned beef tallow.

FOX NEWS: Steak ‘n Shake says, all locations will be quote “RFK’d” as they swap vegetable oil for a healthier beef tallow to cook their iconic shoestring fries.

GRABER: Bad news for vegetarians who like their fries, or people who care about industrial animal agriculture and its welfare and environmental implications. But also, Carla says that beef tallow isn’t so great for us.

TAYLOR: There is plenty of evidence out there to say that a high saturated fat diet is not beneficial. Certainly not beneficial in terms of cardiovascular disease, and perhaps certain types of cancers.

TWILLEY: So beef tallow definitely has issues. Meanwhile the hexane and mustard gas and engine oil issues with canola are not really real. But for critics of canola, those are all side issues. The real problem with canola is that it supposedly causes inflammation.

GRABER: Inflammation is blamed for just about every health problem these days, but the science of it is definitely more nuanced. Inflammation can be bad, but also a little inflammation can sometimes help you heal. That’s part of why this immune system response exists.

TWILLEY: The problem with canola—again, according to the critics—is to do with the particular fatty acids it contains.

TAYLOR: Canola oil is known for its high monounsaturated fatty acid content.

GRABER: The term monounsaturated has to do with its structure. Monounsaturated fatty acids are the kinds of fatty acids you find a lot of in vegetable oils like olive oils. Our bodies can make monounsaturated fatty acids, but it’s also important that we get them from food.

TWILLEY: Saturated fatty acids are fats like in meat, cheese, coconut oil, and palm oil, and science has shown pretty clearly that these aren’t as great in large amounts for most of us for our overall health. Canola oil has very little saturated fat.

GRABER: And then there’s what’s known as polyunsaturated fatty acids. These are the omega fats—omega-3 and omega-6 are the main ones. We did a whole episode on these types of fatty acids called omega 1-2-3, you should check it out.

TWILLEY: Guess what, canola oil has those, too.

TAYLOR: It also has a fairly good level of omega-3 as ALA, alpha linolenic acid. And the other polyunsaturated fatty acid there, besides the ALA, is primarily what we abbreviate as LA or linoleic acid, which is an omega-6 fatty acid. If we get those in our diet, then we can convert them to all these other fatty acids that we need in our body.

GRABER: Omega-3 and omega-6 are called essential fatty acids because our bodies need them, and we can’t make them ourselves. We have to get them in food.

TWILLEY: So great, canola has both of these essential polyunsaturated fatty acids. But then the argument goes, the linoleic acid, the LA, which is the omega-6—in our bodies, that becomes something called arachidonic acid.

MATTI MARKLUND: Another omega-6 fatty acid. Which can be turned into pro-inflammatory metabolites.

GRABER: Matti Marklund is a nutrition scientist at Johns Hopkins, and he and a team of researchers around the world tried to figure out whether eating linoleic acid was connected to arachidonic acid and to bad health outcomes. And, as we discussed in our recent episode about nutrition science, it’s hard to get good information on what people eat, so they found a way to measure it that was much more scientific.

MARKLUND: Instead of asking people what they are eating, can we take a blood sample and measure the fatty acid concentration in the blood?

TWILLEY: Matti and his colleagues analyzed the data from more than 30 different studies involving more than 70,000 people from different countries. Some of them were short term studies, some ran for more than thirty years.

MARKLUND: And during that follow up time, we are looking at how many people are developing cardiovascular disease. We also looked at cardiovascular mortality as an outcome. And what we found was that those with the highest levels of linoleic acid in their blood had the lowest risk of developing cardiovascular diseases.

TWILLEY: So that’s good, right? Lower risk of cardiovascular disease sounds like a win to me.

GRABER: But what about this idea that linoleic acid or omega 6 turns into arachidonic acid and that’s where the problem lies? Well, Matti told us that first of all arachidonic acid turns into different chemicals in the body, some cause inflammation and some actually are anti-inflammatory. But even more importantly, it seems as though, inside our bodies, linoleic acid doesn’t turn into much arachidonic acid at all.

MARKLUND: Studies using a stable isotope. So they can actually look at the specific molecules. They have found that there is very limited conversion of linoleic acid to arachidonic acid in the human body.

TWILLEY: So that whole mechanism that’s supposed to be behind the omega-6s in canola and other seed oils causing inflammation—it turns out that’s not what’s actually going on. In fact, Matti told us, the evidence suggests that linoleic acid—the supposedly bad stuff in canola oil—it not only doesn’t increase inflammation, it also seems to have some real health benefits, and not just for lowering the risk of heart attacks and strokes.

MARKLUND: We also found that linoleic acid was strongly associated with lower risk of type two diabetes. So linoleic acid, we know, can, can also improve glucose metabolism. And there are other data suggesting that linoleic acid reduces inflammation, it can also reduce blood pressure.

GRABER: But another thing that seed oil haters claim is that it’s the ratio, that we have way too much omega-6 compared to omega-3 in our diets today, and that’s what’s making us sick. Matti checked for that, too.

MARKLUND: Yeah, we, we did. So we did statistically adjust for omega-3 fatty acid levels, and we also did kind of stratified analysis where we look specifically in those with low omega-3 and those with high omega-3 acid levels. And we didn’t see any difference in this association between linoleic acid and cardiovascular disease. So, our study and other studies does not really suggest that the ratio itself should be changed by reducing omega-6 fatty acids. It’s more, probably that you should increase omega 3 fatty acids to improve the ratio.

TWILLEY: In other words, cutting out seed oils is not going to help boost your omega-3 levels. For that, you have to eat more omega-3s. And, outside of oily fish, which are delicious but which most Americans consume very little of—and outside of tofu and chia seeds and flaxseed, which are also pretty underrepresented in the standard Western diet, canola is actually a bit of a omega-3 superstar.

TAYLOR: It is at a level that is, a little bit higher than soybean oil. Definitely much higher than the omega-3 found in, something like corn oil or the traditional sunflower, safflower oils and so forth. And also compared to olive oil. Canola oil has a much higher level of omega-3.

GRABER: Darriush Mozaffarian is director of the Tufts University Food is Medicine Institute, he was on our nutrition science episode, and he’s one of the co-authors of Matti’s study. He says basically there’s no reason to avoid canola or any other seed oil.

DARRIUSH MOZAFFARIAN: This is, you know, one of the great Internet myths that’s out there, that seed oils are harmful. Canola oil has been studied in well over a hundred randomized control trials. And overwhelmingly been shown to improve every risk factor that has been looked at. And never been shown to be pro inflammatory, which is kind of the theory. We have all the science, like—we don’t need any more studies on canola oil. This is one of the most well established areas of science there is, is the health effects of plant oils.

TWILLEY: So long story short: RFK, Joe Rogan, Megyn Kelly and her guest, and a whole bunch of other online influencer types are, to put it politely, completely and utterly incorrect on this issue, as well as many others.

GRABER: Now, just saying that a processed junk food like cookies or chips has canola oil won’t give it magical health-promoting properties, of course. And we certainly can’t say that there won’t ever be research linking omega-6’s to increased risk of any disease. Still, Matti and Darriush and Carla and everyone else who studies it say that canola and other seed oils are fine. The industrial ones are fine for you. But Matti agrees with Duncan that the Mellow Yellow cold-pressed stuff is likely even better.

MARKLUND: Perhaps with cold-pressed oils, you can retain more antioxidants and other things that could be destroyed during high heat treatment. So, yeah, in that sense, it might be a good idea to use more cold pressed oils.

TWILLEY: Mellow Yellow is not on the shelves here in the US. but you can find a little less processed canola oil in grocery stores—it’s organic and expeller pressed rather than being the more heavily refined stuff. But it is not at all the same as Duncan’s cold pressed. Carla says she knows of a small company in Canada that tried to do the same thing as Duncan, but it didn’t really catch on.

TAYLOR: I think the biggest roadblock right now is the consumer perception. Because here in North America, we’re, you know, kind of are growing up around, our vegetable oil is, you know, a nice clear light colored. And yeah, it, maybe it just wasn’t the right timing to take off to say, here’s an alternative for what we can do with something that’s grown here.

TWILLEY: That point, about canola being local—that’s also important. Matti is originally from Sweden, and he said that for northern countries like Sweden, or England, or Canada, where olive oil is not grown, canola-slash-rapeseed has even more value as part of a healthy diet.

MARKLUND: So in Sweden and in Scandinavia, we have worked on developing a healthy Nordic diet, since we might not always have the foods that are typical for the Mediterranean diet, like fresh fruits. So, then, you should look into the healthy Nordic diet. And one component is to consume more canola oil, instead of other fats.

GRABER: Carla says she doesn’t just study canola oil, she eats it too.

TAYLOR: I mean, yeah, I do research on it and I, I use myself. [LAUGHS] I do have some olive oil for some particular uses. But my everyday go-to happens to be canola oil.

TWILLEY: Carla’s talking about regular canola. But if you’re lucky enough to get your hands on some of Duncan’s Mellow Yellow, he has some tips for peak enjoyment.

FARRINGTON: Do whatever you want to do. There’s no particular rules on this. If your thing is stir fries, you know, use it as a stir fry oil. Or if you like roast potatoes and you’re very traditional on a Sunday, especially in Britain, do your roast potatoes in Mellow Yellow. It is a high temperature oil. And you get the most lovely crispy potatoes. They’ve got this lovely golden color because the, the color of the oil on there. And they’re fantastic.

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GRABER: Thanks this episode to Duncan Farrington, Michael Eskin, Carla Taylor, Matti Marklund, and Darriush Mozafarrian. And of course to listener Amy McLeod who sent us down this rabbit hole. We have links to their research, companies, and rapeseed oil on our website, gastropod.com.

TWILLEY: Thanks also to our superstar producer Claudia Geib. We wanted to leave you this episode with a special treat—turns out Michael Eskin is not just a distinguished professor, he’s also a rapper.

ESKIN: [RAPPING] Without lipids, we can’t survive; they help the cells in our bodies stay alive. They control what enters and what leaves, by the way the phosphor lipids in the membranes enter weaves. Adipose tissue comes from lipids we eat; it covers our bodies and regulates heat. Without it…

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