Why have seed oils become a target of so much ire?

In the last few years, and especially the last few months, we’ve heard a lot of chatter, both online and in real life, about seed oils. Why have seed oils become a target of so much ire? What do we know about their impact on human health, and how should this guide our choices about what we eat? We decided to ask Professor Christopher Gardner, a professor of medicine and the director of nutrition studies at Stanford University’s Prevention Research Center. For the last two decades, most of his research has been focused on the potential health benefits of various dietary components, and in January of this year, he wrote an op-ed for MSNBC urging people to continue consuming seed oils in moderation.

Evan Kleiman: I’m so grateful to have you here, because, boy, is this a miasma. So I understand that you do a fair bit of research on human health. To what extent have you studied seed oils and their health impacts on humans?

Dr. Christopher Gardner: So I do a lot of whole food studies. So I get people to eat Mediterranean or vegan or vegetarian and oils, cooking oils, salad oils, and making stir fry woks are always part of my studies. I haven’t actually studied one seed oil versus another type of seed oil, or butter versus lard, but I will say that I just served on the Dietary Guidelines Advisory Committee which happens every five years as they try to update the Dietary Guidelines for Americans and one of our very specific questions was butter versus plant oils, and many of those plant oils are seed oils, and the plant oils won over butter, and that’s part of our 421-page report to the incoming Secretary of Health and Human Services.

Do you think it will make a difference?

 I don’t know that he’ll read the 421 pages, but it’s there for him if he does.

So, let’s start by having you explain to us what seed oils are. I know for some people, it’s hard to imagine a seed expressing oil.

Right. And actually, I do think there’s some simple confusion that I could help clarify here. So picture sunflower seeds or safflower seeds. Canola oil is made from a seed called rapeseed oil. That’s not the same as grape seed oil. Flaxseed oil, sesame seed oil. So a lot of nuts and seeds together are actually good sources of unsaturated fat, and they’ve been promoted in the heart disease literature for decades and decades. And it is true, you’d have to squeeze them a lot to get the oil out, and there’d be some processing involved. You can’t just step on them or squeeze them in a garlic press. There’d be a lot more involved in that. But those seeds have oils, so that when you plant the seeds and they grow there’s going to be some nutrients in there, including the oils that will be responsible for them growing into plants. But if they’re not going to grow into plants, you can eat them, and they’re healthy for you as seeds.

And that includes corn. And of course, we’re not talking about fresh corn on the cob. We’re talking about field corn, dry corn.

Field corn, vegetable oil that, you know, corn that was actually never grown to be eaten on the cob by humans, but was grown to be used for its components. Sure, yes, that’s one of them. 

So, you’ve talked about studying and concentrating on whole foods, but to what extent do seed oils make up the average American diet? I know they’re in a lot of things like baked goods, salad dressings, potato chips, but also in a lot more high-processed food.

Well, and that’s a really important distinction, right there. So a lot of the data that suggests Americans have been consuming higher rates of seed oils is really because Americans have been consuming higher rates of ultra-processed foods. So the food industry continues to make more and more variety to tempt our stomachs and our appetite. And I want to say that quite a few of those ultra-processed foods are typically high in added sugars, sodium and lots of other ingredients. And so herein lies some of the confusion for me. If that’s really the main reason for the increase in seed oil consumption in the US, it’s kind of hard to pin it on the seed oils, and not the added sugar, high sodium or other ingredients that come with those foods. We’ve been asking people to cut down on those foods, those ultra-processed foods, junk foods, for decades in America. Kids don’t really listen. I think it would be kind of amusing to me if suddenly I said, “Oh, not only do I have all the other things that I wanted you to avoid, but now we know they have seed oils.” If people suddenly stopped eating them because they found out there were seed oils in them, as a scientist, I wouldn’t be able to attribute the adverse health-conscious consequences to the seed oils, but I would certainly smile that they were not eating as many anymore.

So when did we first start seeing the current backlash against seed oils? Who or what has been fueling it?

Hard to pin that down. I have seen rumors of it. I’ve seen podcasts of it going back four or five years. I really didn’t pay that much attention to it. I hope we can get to it. There’s an immense body of evidence for their benefit, the way that they were traditionally used and traditionally studied. But it really came to the forefront when RFK Jr.’s nomination came up for Health and Human Services Secretary, and he was very opposed to them, which led me to listen to more podcasts and listen to more social influencers berate them and even call them “The Hateful Eight.” I’m curious if you have heard that name?

Yes, I have. It’s like the Dirty Dozen. Can you go into that? I would love that.

 Let me talk about “The Hateful Eight” for a minute because this is really fun for me to look into. I’m gonna have to do this from memory. But it’s certainly corn, sunflower, and safflower. It’s cotton seed, it’s grape seed, for some reason, it’s also rice bran oil, which I don’t see very much, and soybean oil. And what’s really odd to me is those aren’t all seeds. Soybeans are beans and rice bran, rice isn’t really a seed. And importantly, not included in the Hateful Eight are flaxseed and sesame seed. I don’t know how those somehow avoided being defamed or berated, but those were left out. So it starts out as being seed oil, and it moves over to the Hateful Eight, and not all the Hateful Eight are seed oils, and not all the seed oils are in the Hateful Eight. So I think something that’s being conflated here is omega-6 and omega-3 fats. I’m guessing those are terms you’ve heard, and many of your listeners have heard, if they’re interested in nutrition, omega-3 and omega-6 fats is a topic that’s been around for decades. Have you heard of that?

Yeah, definitely. I had a question for you about them. We hear a lot of talk about the ratio, that the ideal ratio we’re supposed to eat of these two different kinds of fats. Can you explain the difference between these fats and where we find them, and then how that plays into the seed oil conversation?

Absolutely. So I do think this is the main issue, and even this part is being confused, so let’s clarify. So a lot of the fat you eat, most of it, you just store in your body and use it later for energy in it. Most of the fats we eat come in long carbon chains. It could be anywhere from four carbons to 26 carbons, but usually it’s 16 or 18. That’s sort of the typical kind of fat source that we eat. 

And in these long carbon chains, they’re saturated, monounsaturated and polyunsaturated, and that’s how many double bonds are between the carbons. And that probably sounds a little more geeky than you wanted, and you don’t need to know that part, other than if it’s a monounsaturated fat with one double bond that makes the straight chain of carbons bend a little bit, and it makes it so it won’t be solid at room temperature. Butter is saturated. Lard and beef tallow are saturated. They’re totally straight, and it has to do with their melting point, and that’s why they’re solid at room temperature. Olive oil and canola oil are both monounsaturated fats. They have one double bond. I you actually put those in the refrigerator instead of just on your counter, they might go a little cloudy on you. They might solidify a little in the cold temperature of a refrigerator. But the polyunsaturated fats that have two double bonds or more, that would be your sunflower, safflower, those won’t actually go cloudy in the fridge. They have two double bonds. That means their strings of carbons are super bent. They don’t like to be solid at any temperature, so they’re always going to be liquid. And the six and the three parts, the omega-six and omega-three, get ready, drum roll please –There’s actually a starting and an ending carbon. If you went into organic chemistry and figured out how to do that. And if you count six carbons back from the end to get to your first double bond, it’s omega-6. And if you start at the end and you count back and the first double bond is three carbons back, it’s omega-3. Now that probably sounds pretty pointless. Who cares where the heck the double bond is, but in our bodies, it actually has a metabolic role. 

So even though most of the fat we eat is just used for energy, the particular polyunsaturated fats that have those omega-6 or omega-3 configurations, some of them, not all, but some of them actually act like hormones and help regulate our metabolism. And this is where I think the public and the influencers are getting mixed up. So omega-3s  became very popular when we figured out the Mediterranean diet and we were looking at fish oil, which is way different than cooking oil. Fish have omega-3 fats in them, and fish have been promoted for a long time for heart health, because an omega-3 compared to an omega-6  helps you be a little more anti-inflammatory, helps you lower some triglycerides in your blood, helps your blood vessels dilate. So the key is the omega-3 versus omega-6 are a little better. But here’s what’s happened that I don’t understand and people have shifted that to meaning, “Oh, so that means the omega-6s are proinflammatory, triglyceride raising, pro blood constricting,” and that’s wrong. Omega-6s  are good, omega-3 are a little bit better, but that doesn’t make omega-6 bad. And then here’s the real twist of this. If you were to look for those omega-3s, you brought up the issue of the ratio. So if you were trying to get a better ratio, a higher omega-3 to omega-6 ratio, and we’re not talking fish, not talking about eating fish. We’re just talking about cooking oils to use. What would you turn to? So it turns out the only plant oil that people cook with, or bake or do anything with, that has more omega-3 than 6 is flax oil. I don’t know about you, and I have no flax oil in my kitchen. I asked a lot of people, they don’t either.Do you have any flax oil to cook with or make salad dressings with?

I used to, but it went rancid too quickly, so I stopped having it. 

Okay, so, yeah, that’s one of the potential downsides of the polyunsaturated fats, is they can go rancid. So soybean has a little, but that’s on the Hateful Eight list. Canola has a little, that’s on the Hateful Eight list, but both soybean and canola have more omega-6 than omega-3. So if you’re trying to get the flax and the canola and the soy together, you wouldn’t improve your ratio. You’d have to be all flax. That’s the only way you do it, because the other ones are mostly omega-6. So when people talk about that ratio, unless they’re talking about eating cold water fish that has sort of even extra special omega-3 fats, it would be really hard to change your ratio to this better ratio. And what I’m most interested in is, what do you use those oils for? So I have sunflower and safflower that I make salad dressings with, and what do I put on vegetables? I’m eating more vegetables. Could I put olive oil into my salad dressing? Absolutely. But once in a while for people, either olive oil is too expensive or it has a stronger taste, and somebody’s looking for something more neutral, like a canola or a sunflower or a safflower, or it could be baking. Do you really want olive oil in your corn muffins? I think I would put corn oil in my corn muffins. I don’t want them to taste like olive oil or if you were cooking in high heat. So if you were stir frying some veggies, you would probably want to use a plant based oil, and even in that case, one that has been processed to withstand high heat without going rancid and meeting the smoke point. So quite odd to me that people are pushing for this shift to a higher omega-3 omega-6  ratio when there aren’t many omega-3s out there. And I’m more concerned that you do eat stir fry, your veggie stir fry, that you do have salads, and I think more people will do that if they have this set of options of oils to choose from.

So bottom line, in an ideal world, how much seed oil, or can you even quantify how much seed oil you think the average person could should consume? And if most of our diet comes from whole foods, as you described at the beginning of our conversation, is this a non-issue?

Yeah, from whole foods, it’s a non-issue. Boy, I know if somebody gave me, you know, a head of raw broccoli and said, “Eat this,” versus a sauteed head of broccoli… I can only eat, like one floret of raw broccoli before I gag, but I can eat almost a whole head of broccoli if you were to saute it, put some herbs on it. Yeah, you’d be getting a couple tablespoons of oil a day, and that would be fine. Now, really to regardless almost of which kind of oil it was, preferably the less processed, preferably the cold pressed, preferably you were just cooking nice things, sauteing vegetables, making veggie stir fries, and using it in a very reasonable way, in modest amounts, would be fine. It would make our food taste better.