How Worried Should You Be About Seed Oils? Nutrition Experts Reveal The Truth

Yahoo

30-01-2025

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If you're following the latest health headlines—or certain social media influencers—you've likely heard rumblings about 'The Hateful Eight.' No, these aren't belated reviews of the 2015 Quentin Tarantino Western movie. They're concerns over the health effects of eight types of seed oils—canola, corn, cottonseed, grapeseed, rice bran, safflower, soy, and sunflower.
On TikTok, words like 'toxic,' 'dangerous,' and even 'rancid' are often bandied about in regards to these oils. And the conversation is even reaching the halls of Congress, as Robert F. Kennedy Jr.—a vocal opponent of seed oils—testifies in confirmation hearings for the role of Health and Human Services secretary.
'Americans should have every right to eat out at a restaurant without being unknowingly poisoned by heavily subsidized seed oils. It's time to Make Frying Oil Tallow Again,' he wrote in a post on X (formerly Twitter) in October 2024.
While the discussion around seed oils seems to be reaching a fever pitch, it's not exactly a new one. Questions and concerns around these oils—and their ratio of omega-3 and omega-6 fatty acids—have been around for a while, though not with such fervor, says Kristen Lorenz, RD, who specializes in longevity and metabolic health. When it comes to the discourse around the ratio of omega-3s to omega-6s, research suggests that there is a sweet spot for keeping inflammation at bay—as omega-3s are anti-inflammatory and omega-6s are thought to be pro-inflammatory.
'I've been a dietitian for 18 years, and even then we were learning about an ideal ratio of omega-3 to omega-6,' Lorenz says. 'But it was teaching about it and teaching how to work around it and work with it—it wasn't this demonization of food.'
Which raises the question: Is all of the disdain around seed oils deserved? Or are they getting an undeservedly bad rap? Here's what you need to know before you consider flinging that brand-new bottle of canola oil into the trash bin.
Meet the experts: Kristen Lorenz, RD, is a nutritionist based in Grand Rapids, Michigan, and specializes in longevity and metabolic health. Sander Kersten, PhD, is the director of the Division of Nutritional Sciences and the Schleifer Family Professor at Cornell University in New York.
As the name would suggest, seed oils are derived by extracting oil from the seed, rather than the fruit, of a plant. In addition to the 'Hateful Eight' mentioned above, other common types of seed oils (also known as vegetable oils) include pumpkin, sesame, chia, and peanut, according to the Mayo Clinic.
Seed oils, such as canola and corn oil, are often preferred for cooking and frying, because they have a higher smoke point than other oils, like olive oil. Seed oils are also heavily used in processed and ultra-processed foods (more on that in a bit) because they are mild in taste and don't impart much flavor to the finished product.
Canola
Corn
Cottonseed
Grapeseed
Rice bran
Safflower
Soy
Sunflower
Pumpkin
Sesame
Chia
Peanut
There are two methods by which seed oils may be extracted and produced, according to Sander Kersten, PhD, director of the Division of Nutritional Sciences at Cornell University. One is mechanical and the other is chemical. The mechanical method entails pressing the oils out, whereas the chemical method entails using a solvent to dissolve the fats into an oil. The latter method is the most commonly used process for seed oils.
'The seed oils you buy in the grocery store are almost always produced through chemical extraction,' says Kersten. 'I'm sure sunflower oil and corn oil exist as a pressed oil, but they would probably only be available in specialty shops as an expensive luxury product.'
Chemical processing is one component of seed oils that often draws criticism: Not only does the solvent strip away some of the plant's nutrients (such as antioxidants), says Kersten, but the solvent itself, typically hexane, can remain in residual amounts. While toxic to humans in its gas form, researchers have historically said that consumers shouldn't be concerned about these trace levels found in seed oil. But research is ongoing on the topic.
While neither Lorenz nor Kersten can exactly pinpoint the origin of suspicions around seed oils, it's likely due, at least in part, to their levels of omega-6—a polyunsaturated fat that the body needs but doesn't produce on its own. While omega-6s help reduce bad cholesterol levels, lowering the risk of heart attack and stroke, according to the American Heart Association, they've also been linked to higher levels of inflammation in the body. But that's when they're consumed in excess of omega-3s (i.e., eating too many omega-6s while not also eating enough omega-3s), explains Lorenz.
Omega-3s are another type of polyunsaturated fat that may be found in seed oils (though at a much lower percentage than omega-6s). Their benefits to the body are greater than those of omega-6s: They're important to the cells, as well as the cardiovascular and endocrine systems, according to the Cleveland Clinic—and studies have linked them with better brain function. Good sources of omega-3s include fish, nuts, seeds, and fruits.
So, what should a diet with balanced omega fatty acid levels look like? 'The optimal range, as far as omega-6 to omega-3, is 1:1 to 4:1,' Lorenz says. Simply put, the goal is to emphasize the consumption of omega-3s over omega-6s.
However, as the Western diet has evolved over the years, that ratio has crept up to 20:1, according to a study in Missouri Medicine. And with that higher ratio in favor of omega-6s comes a higher likelihood of inflammation.
One of the main reasons for the recent controversy surrounding seed oils is their inclusion in ultra-processed foods, Kersten says.
'Seed oils are important ingredients in ultra-processed foods, so they're basically guilty by association,' Kersten says, 'But it would be too simple to say, 'Seed oils are part of ultra-processed foods. Ultra-processed foods are bad, so seed oils are bad.' '
When judging seed oils on their own merit—divorced from the whole ultra-processed foods debate—the average American shouldn't worry too much about the inclusion of seed oils in their diet, within moderation, says Kersten. In fact, the dietary guidelines set forth by the government in MyPlate (formerly the Food Pyramid), recommend the inclusion of unsaturated fats, such as canola oil.
As for the concern over the inflammatory properties of seed oil, Lorenz says that is also likely overblown—and research seems to back her up on this. A systemic review of randomized control trials found no evidence of 'increases [in] the concentration of inflammatory markers' when linoleic acid—an omega-6 found in seed oil—was added to the diets of healthy adults.
'The inflammation you get from the stress of worrying about seed oils is probably worse than the actual seed oils,' she says.
There are no hard and fast rules about how much seed oil one should consume. Guidelines do exist around the intake of linoleic acid, which places it at 1–1 ½ tablespoons of seed oil per day, Lorenz says.
But without widely agreed upon intake recommendations, it all boils down to moderation—ensuring your omega-6 intake doesn't vastly surpass your omega-3 intake—and making smart swaps.
Olive oil—which is higher in healthy omega-3s—is a good alternative to seed oils in cold preparations, such as salad dressings. If you're grilling or cooking at high-heat and need an oil with an adequate smoke point, Lorenz recommends avocado oil as an alternative.
But there will be occasions when a seed oil is the better option. For instance, if you're frying up chicken for Sunday dinner, canola oil is going to be a better option than olive oil—first, because it has a higher smoke point; second, because a whole vat of olive oil would simply not be economically feasible; and third, because olive oil (specifically extra-virgin olive oil) is cold-pressed preserving much of its natural essence, it may impart a flavor you're not looking to add to your fried chicken.
Experts agree that seed oils are also preferable to animal-based fats (think: beef tallow, lard), as seed oils contain unsaturated fats rather than the saturated fats found in animal products. 'For decades, people have been encouraged to move away from butter or animal-based fats towards plant-based fats by the dietary guidelines,' Kersten notes.
Seed oils are not only the healthier option for people—but potentially for the planet as well, says Kersten of sustainability issues surrounding animal-based fats. 'If we all start relying on animal-based food sources, we can't feed the world,' he says. 'Let's be clear about this. There's no way. We're going to be in trouble.'
In that case, we'll have a lot more to worry about than The Hateful Eight.
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