Life Kit - Are seed oils really bad for you? Researchers unpack RFK Jr.'s claims

Episode Date: July 31, 2025

Health Secretary Robert F. Kennedy Jr. and others have said that seed oils, like soybean, corn and sunflower oils, are poisoning Americans. But what does the research say? NPR health correspondent Maria Godoy speaks with nutrition and fatty acids scientists about the most common concerns with seed oils. Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy

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Today, we're talking about seed oils. Health Secretary Robert F. Kennedy Jr. has said that seed oils, like canola oil, sunflower oil, and soybean oil, are poisoning Americans and can have dangerous health effects. These oils are used a lot, especially in restaurants and in food. packaged foods. So on this episode of Life Kit, seed oils. What does the research say? And what can you do if you're concerned? NPR health correspondent Maria Godoy has been digging into this topic. I talk to her after the break. Hey, Maria. Hey. All right, let's start off with the basics. What is a seed oil?

Like, are we just talking about cooking oils? Yeah, I mean, like basically what you think of as vegetable oils like canola oil or corn oil. These are oils extracted from the seeds of plants. And when you get oil out of a seed, you can press it out like you do with cold-pressed olive oil. But it's not the most efficient process. So seed oils are typically refined, which means that producers use a chemical solvent, usually something called hexane. And you use that to extract the maximum amount. amount of oil from the seed. It's sort of cheaper and more efficient than just like squeezing

it mechanically. And critics tend to target eight of these refined seed oils, and they actually call them the hateful eight. And besides canola and corn, it's safflower, soybean, cotton seeds, sunflower, rice bran, and grape seed oil. And just to be clear, sometimes non-seed oils are also refined in the same way, which means they can contain that chemical hexane. You'll see the word refined on the package. So for example, extra virgin olive oil is not refined. But if you buy something called pumice olive oil, that is refined, often with hexane. And what are some commonly used cooking or dressing oils that are not seed oils? I mean, olive oil is probably the best known. There's avocado oil. There's coconut oil, which is the saturated fat. Oh, you know, it's interesting

because avocado oil is getting really popular. But there was a study done back in 2020 that that found the majority of what is being sold as avocado oil was either rancid or mixed with other oils. And there were a couple of samples that probably didn't have any avocado oil in them, but that's an aside. It just goes to show how careful we need to be about what we're buying. I mean, yeah, the complicated world of cooking oils. So what do people say they're concerned about when it comes to seed oils? Yeah, there are three main criticisms you hear, and the first has to do with how the seed oil. oils are refined. So manufacturers often use hexane, as I mentioned, to pull more oil out of a seed,

and hexane is hazardous, but it's removed during the processing of the oil. Even so, you can end up with very small amounts left in some seed oils. So toxicologists from the federal government have looked at this, and in a report published earlier this year, they concluded that the trace amounts of hexane residue in the seed oils we eat are, quote, toxicologically insignificant. again. I talked to one researcher who studies the health effects of fats and oils, and he told me any residual hexane that remains should evaporate during cooking. But, you know, even though it's trace levels left in seed oil that are considered too low to be toxic, some people worry about the potential health effects of even these small amounts. Yeah, what health risks

are they worried about specifically? Well, you know, I think it's the cumulative effect of hexane exposure, even in these trace amounts, over a long time is relatively unknown. The European Food Safety Authority right now is working on an updated assessment of Hexane to better understand these potential risks. I think it's the fact that we don't know that worries people. But, you know, I also spoke with Caitlin Dow. She's a nutrition scientist with the Center for Science in the public interest. She told me she's not personally concerned about Hexane and Herseed oils, but she did have this tip for folks who might be worried. If you buy or Organic oils, even organic seed oils that have been processed, they can't contain hexane.

So that's one option to avoid hexane is to buy organic. Okay. That's good to know. What are the other concerns about seed oils? So the second argument you often hear is that, you know, seed oils promote inflammation. It's probably the argument that gets the most traction in social media and other circles. What do you mean by inflammation? So inflammation is a physiological response that helps the body heal from infection or injuries.

So you need some inflammation. But when you have too much over long periods of time, that's chronic inflammation. And that can lead to a lot of health problems like out of immune diseases, heart disease, and some cancers over time. So the idea or criticism that seed oils promote inflammation is rooted in the kinds of fats found in these oils. Seed oils tend to have high levels of essential fatty acids called omega-6s, and then they have lower amounts of other essential fatty acids called omega-3s, and both are important to good health. That's why they're called essential. You need to get them from your diet.

Our bodies don't make them. Both play important roles in different processes in the body, and that includes regulating inflammation. I spoke to Sarah Berry. She's a professor of nutrition at King's College, London. And, you know, she explains that our bodies tend to convert omega-3s into chemicals that fight inflammation. And meanwhile, omega-6s can be converted into chemicals that promote inflammation. Now, critics say if you consume too much omega-6, you're going to end up with chronic inflammation, which can lead to chronic diseases. Barry says that makes sense in theory, but it's not what happens in real life.

Now, that all looks beautiful on a piece of paper, but it doesn't play out in the human body. and there's randomized control trials consistently to support this. Yeah. So she says for one thing, omega-6s can also have a neutral effect on inflammation, so they don't always promote it. And in fact, omega-6s can also be converted into chemicals

that have an anti-inflammatory effect. And randomized controlled trials have found that when people eat more seedals, they don't show signs of too many compounds that promote inflammation in their tissues, and they don't have more markers of inflammation. So it's not like we can say, that omega-6 fatty acids are just bad for us and we should avoid them? No, so don't avoid them altogether because you need them for good health. If you didn't have any, you'd get really sick.

So these fatty acids do different things in our body. Like if you didn't have any omega-6s in your body and you cut your finger, that wound wouldn't heal as efficiently because wound healing is an inflammatory response. So you need that, right? And that's just one example. And there's actually strong evidence that omega-6 has helped lower levels of bad cholesterol, which can reduce the risk of heart disease. That's why the American Heart Association supports eating omega-6s as part of a healthy diet. Okay. So Tom Brenna is another person I spoke with. Brenna is a fatty acids researcher at the University of Texas at Austin. And you could say he's a person who thinks we eat too many omega-6s in our diet, but even he stresses that you can't cut them out altogether or

you'd get really sick. Some of the influencers are talking about getting rid of all the omega-6 in the diet. That would be a terrible idea. So make sure you say some omega-6 is absolutely required. The question is how much? Brenna says you can't cut out omega-6s. He's actually one of those people who worries that some people may have too much omega-6s. And there's emerging research from him and other people that suggest that some people

have a genetic variation that when their bodies bring up. break down omega-6s, they might be more prone to have inflammatory effects. And, you know, most of us aren't going to get tested to see what kind of genetic variations we have. And so he sticks with olive oil, but there's actually not enough olive oil in the world, like for all of Americans to switch to olive oil and replace seed oils entirely. But if you are worried, you could also just buy high olake seed oils. And these are seed oils that have fatty acid profiles very similar to olive oil. So they have lower mega-6s, lower mega-3s, and they have, like, a lot of of something called omega-9s, which is what olive oil has.

Okay. So in general, it sounds like we don't need to fear seed oils. Yeah. You know, I spoke with Christopher Gardner. He's a nutrition researcher and professor of medicine at Stanford. And he says for decades, studies have consistently shown that when you replace saturated fats like lard or beef tallow with fats from plant oils, including seed oils, that leads to better health outcomes.

This is one of the more studied topics in nutrition. So it's sort of extra bewildering to quite a few of us in the field that this is coming up. So are we meant to be keeping track of how many omega-3s and omega-6s were eating every day? I don't even know how you could do that. Like I, as I've probably said on Life Kit before, I'm kind of strangely obsessed with tracking everything I eat for fun. But I don't even know how I would go about tracking my omegas. Nutrition researchers I spoke with agree that for good health, you want to have a good balance of omega-6s and omega-3s.

But the general advice to do this is just make sure you eat plenty of omega-3s, and that means eating plenty of things like fatty fish, like salmon, mackerel, nuts and seeds, like walnuts, flax seeds, chia seeds, which are good for you for fiber, too, and other things. And so the reason you want to focus on eating omega-3s is because we already get a lot of omega-6 is in our diet, and that's mostly because they're used in ultra-processed foods, and ultra-process foods dominated our diet. So if you really wanted to cut back on omega-6s, what you should really be doing is cutting back on ultra-processed foods, because that's really what we're getting too much of, and there's lots of health evidence showing that when we eat too many

ultra-process foods, we get poor health outcomes. And that's for a lot of reasons. That's for a lot of reasons, because if you look at, you know, ultra-process foods, I said, dominate our diet. They also are often high in salt, sugar, and unhealthy fats and low and good things for us like fiber. They also have things like additives, you know, artificial dyes, et cetera. And we know that like eating too much sugar, for instance, is not good for health over time. So, you know, this actually leads us to like another common criticism against seed oils. Because the reason we get so much seed oils in our diet is because they're used in ultra-processed foods because seed oils are cheap and plentiful. But nutrition researcher Sarah Berry says

the health effects of ultra-processed foods tend to get unfairly tangled up in the discussion around seed oils. So is it the seed oils or is it the ultra-processed food? Many of the seed oil haters show these beautiful graphs showing how as intakes of seed oils have increased over the years, so have our rates of all of these awful chronic diseases, cancer, cardiovascular disease, type 2 diabetes, obesity. But look, what else has changed? Our food landscape is almost unrecognizable now compared to how it was 50 years ago. You know, Chris Gardner of Stanford University agrees, he says you can't blame seed oils for these correlations when ultra-process foods are high in other ingredients that we know for sure drive bad health. So is it the junk food that's

causing these health issues, or is it the seed oils? And I have always thought it's the junk foods. It sounds like the advice here is, as always, eat less ultra-processed food. Yeah, yeah, I have, like, all roads lead to that, I think. You know, if nothing else, I really hope that's what listeners take away from this. Eating more fruits and vegetables, lean proteins, beans, nuts, seeds, fatty fish like salmon, et cetera, that's what you should really focus on. You know, don't worry about your omega-6s and omega-3s and trying to track those. And then if you use a seed oil to make a dressing for your salad or stir-fry veggies, and that gets you to eat more vegetables, nutrition researchers like Christopher Gardner would argue that's a win for health.

Okay, thanks so much, Maria. Thanks for digging into this. It's a lot. Yeah, I think I got a PhD in biochemistry from this process. Or just a minor, just a minor in biochem. All right, time for a recap. One concern about seed oils is that they may contain trace residues of a chemical called hexane. It's introduced as part of the refining process. Toxicologists from the federal government have said the amount of hexane and seed oils is toxicologically insignificant. And the experts we spoke to aren't concerned about the long-term health effects. But if you are, opt for organic seed oils or cold-pressed seed oils, which don't contain hexane.

Another concern critics cite about seed oils is that they contain a higher ratio of omega-6 fatty acids compared to other options. We need omega-6s to function, and they play important roles in our bodies. One thing they do is help lower what's known as bad cholesterol. But they can also produce chemicals that promote inflammation in the body. Although trials in humans have found that that doesn't really bear out in practice, then that eating more seed oils doesn't lead to more of these inflammation. inflammatory chemicals in people's bodies. But the overall advice here is we already get plenty of omega-6s in our diets, so make

sure to eat foods high in omega-3s as well, like fatty fish and walnuts and chia seeds to balance things out. And if you want to get fewer omega-6s from seed oils, opt for what are called high oleic seed oils, which have a similar fatty acid profile to olive oil. Also, cut down on how much ultra-processed food you eat, which is a good tip. in general. For more Life Kit, check out our other episodes. We've got one on how to meal prep and another on how to eat intuitively.

You can find those at npr.org slash life kit. And if you love LifeKit and want even more, subscribe to our newsletter at npr.org slash life kit newsletter. Also, if you have episode ideas or feedback you want to share, email us at LifeKit at npr.org. This episode of Life Kit was produced by Margaret Serino and Andy Tagle. Our visuals editor is Beck Harlan and our digital editor is Malika Gereeb. Megan Kane is our senior supervising editor and Beth Donovan is our executive producer. Our production team also includes Claire Marie Schneider and Sylvie Douglas.

Engineering support comes from Stacey Abbott. Fact-checking by Tyler Jones. I'm Mary El Cigarra. Thanks for listening. You know,