The Forgotten History (and Slippery Science) of Canola Oil

If you’ve been hearing that canola is a killer, you’re not alone. It’s one of the so-called “hateful eight” seed oils: Robert F. Kennedy, Jr. says it’s among the most deadly things you can eat, and Joe Rogan agrees. But is it true?

In a recent episode of Eater podcast, Gastropod, co-hosts Cynthia Graber and Nicola Twilley get to the bottom of the debate over the plant formerly (and still, in some places) known as rapeseed. Why does it have such an unfortunate name, and how did it transform into canola, at least in North America? Is it really engine oil? Does it actually contain a poisonous solvent? And why on earth are Brits buying up a fancy cold-pressed version by the gallon, as the new, home-grown olive oil? Are they roasting their potatoes with an inflammation- and disease-causing disaster?

Listen to the episode for the forgotten history and slippery science of this much discussed, little understood oil. And read on for an edited excerpt from the episode, in which Carla Taylor, professor in food and human nutritional sciences at the University of Manitoba, Matti Marklund, nutrition scientist at Johns Hopkins University, and Darriush Mozaffarian, cardiologist and director of the Food is Medicine Institute at Tufts University, share the most rigorous and up-to-date scientific consensus on canola oil and health — and the evidence behind it.

Robert F. Kennedy Jr., Fox News: Seed oils are one of the… most unhealthy ingredients that we have in foods. […] They’re very very cheap, but they — they are associated with all kinds of very very serious illnesses. Including body wide inflammation.

Joe Rogan, The Joe Rogan Experience: 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.

Nicola Twilley, Gastropod co-host: We, like many of you, have been hearing this anti-seed oil propaganda for a while now. Thanks to all the haters out there, a lot of people are now cutting out canola along with its fellow seed oils. So what’s the truth?

Cynthia Graber, Gastropod co-host: 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.

Carla Taylor, University of Manitoba: 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.

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, Johns Hopkins University: Another omega-6 fatty acid. Which can be turned into pro-inflammatory metabolites.

Graber: Matti Marklund 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 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 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, Tufts University: 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 and Joe Rogan, 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-6s 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.