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Some wellness influencers warn against consuming seed oils, blaming them for a range of health problems and characterizing them as toxic. Scientific studies consistently show otherwise.

“There is abundant evidence suggesting that seed oils are not bad for you. If anything, they are good for you,” says Matti Marklund, PhD, MSE, an assistant professor in International Health. 

As a nutrition scientist, Marklund researches how different fats can affect chronic disease. “The fatty acids typical in seed oils—like linoleic acid—are associated with lower risk of chronic diseases like cardiovascular disease, heart attack, strokes and diabetes,” he says.

According to Marklund and other nutrition researchers, seed oils have been demonized based on misunderstandings of how they’re made and how the human body uses them, as well as their ubiquity in ultraprocessed foods.

Seed oils and the “hateful eight”

The discourse around seed oils focuses on eight particular oils: canola, corn, cottonseed, grapeseed, rice bran, safflower, soybean, and sunflower. Products sold as “vegetable oil” generally contain one or more of these oils. As the name implies, seed oils come from the seeds of plants—unlike olive oil or avocado oil, for example, which are made from the fruit.

Cold-pressed (or expeller-pressed) oils—created by pressing the seeds to manually extract the oils—retain much of their odor and flavor. But they also have a low smoke point, meaning they degrade when cooked at the high heat used for things like sautéing or frying.

Refined oils—including many seed oils—are processed further using chemical solvents to extract even more oil, filter it, and remove strong flavors and colors. The solvents, like hexane, that are used in refinement are not present in the final product that reaches shelves and do not pose health risks to consumers, says Marklund. Because of their affordability, shelf life, neutral flavor, and high smoke points, refined seed oils like canola and soybean have become staples in many home and commercial kitchens.

Not all fats are bad for you

Dietary fats fall into two categories: good fats (mono- and polyunsaturated) and bad fats (saturated fat, trans fat, and cholesterol).

“The fatty acids typical in seed oils—like linoleic acid—are associated with lower risk of chronic diseases like cardiovascular disease, heart attack, strokes and diabetes.”

These fats are broken down by the body and primarily used for energy. However, eating too much saturated fat—found in animal products and tropical oils like coconut and palm—can raise your cholesterol (LDL) and . Unsaturated fats, on the other hand, can have positive health effects when consumed in moderation as part of a balanced diet.

According to Marklund, the health benefits of seed oils come mainly from the linoleic and alpha-linoleic essential fatty acids they contain. “Linoleic acid is the major polyunsaturated fat in our diet,” Marklund explains. “It's present in a lot of seeds and nuts, and thereby it's present in a lot of seed oils as well, like soybean and canola oil.”

The evidence behind the health benefits of linoleic acid

In , Marklund and colleagues measured levels of linoleic acid in the blood and adipose tissue of over 68,000 participants, across 30 studies in 13 countries. Each study then followed their participants—some for as short as 2.5 years, others for more than 30 years—to track incidence of heart disease and stroke. 

The study showed that people with the highest levels of linoleic acid in their blood had a lower risk of developing cardiovascular diseases. “The association of higher linoleic acid levels and lower risk was especially strong for cardiovascular mortality and incident stroke,” Marklund says.

He emphasizes that this study showed a strong association—that those with the highest levels of linoleic acid had the lowest risk of cardiovascular disease, but not that the lower risk was caused by the higher levels; that’s where other study types come in. For example, controlled trials in which participants were given a specific amount of linoleic acid  that linoleic acid reduces bad cholesterol (LDL cholesterol), increases good cholesterol (HDL cholesterol), and may even lower blood pressure.

Research also shows that  and even prevent a person from developing type 2 diabetes, “which is a well-known risk factor for cardiovascular disease,” Marklund says. His research team found that participants with the highest levels of linoleic acid had a  compared to those with the lowest levels.

Do seed oils promote inflammation?

Seed oils do not cause inflammation, according to nutrition scientists. The concern that they do is based on a misunderstanding of the omega-3 and omega-6 essential fatty acids they contain—essential meaning that humans cannot produce these on their own, so we have to get them from food.

Omega-3 and omega-6, the main classes of polyunsaturated fatty acids, exist in high amounts in many seeds, nuts, tofu, fatty fish, seaweed, and eggs, and they play .

Christopher Gardner, director of nutrition studies at the Stanford Prevention Research Center, explains in  that in addition to providing energy, omega-3 fatty acids are also anti-inflammatory, help lower triglycerides, and help with blood vessel constriction and dilation. “Omega-6s do many of the same things,” just not as effectively as omega-3s, he says. “Somewhere along the line, this got flipped into a misunderstanding that … [omega-6s] do the opposite of omega-3s.”

Clarifying the “ratio” and finding a balance of omega-3 and omega-6 fatty acids

A lot of discussion about seed oils focuses on a purported imbalance of omega-3s and omega-6s in most modern diets, which are heavier in grains and seeds compared to those of early humans. Some influencers claim that our consumption of omega-6s far outweighs that of omega-3s and that we should aim for a 1:1 ratio. The evidence does not bear this out, Marklund says. In their study of linoleic acid and cardiovascular disease, researchers also looked at participants’ omega-3 levels. They found that the association between linoleic acid and cardiovascular risk was similar among participants with high or low levels of omega-3.

Marklund warns against focusing on ratios and instead on eating a healthy diet. “Omega-3 and omega-6 are necessary and are important, and we should probably eat more of both,” he says. “If people want to get the ratio closer to 1:1, the recommendation should not be to reduce omega-6, but rather to increase your omega-3 intake. Eat more walnuts or fatty fish.” Another food that contains a lot of omega-3, Marklund points out: canola oil.

Animal-based fats vs. seed oils

Many arguments against consuming seed oils include the claim that it’s healthier to cook with lard, beef tallow, and butter, despite decades of evidence that saturated fats raise cholesterol and risk of heart disease and stroke. “Those data go back to the 1950s,” says Gardner, who was part of the USDA’s Dietary Guidelines Advisory Committee in its latest review of the . 

The 2020–2025 edition of Dietary Guidelines for Americans maintains its recommendation to limit intake of saturated fats. “We reaffirmed the evidence that we've seen again and again, of swapping out the saturated fat from animal foods for cooking with plant oils, including canola, sunflower, and safflower,” he says. Seed oils “lower LDL cholesterol compared to butter, lard, and beef tallow.”

Seed oils and ultraprocessed foods

In addition to being sold on their own for cooking, seed oils are ubiquitous in packaged food products ranging from salad dressings to potato chips and frozen dinners. Part of why seed oils have gotten such a bad reputation, Marklund and Gardner say, is that their effects are conflated with the unhealthy foods they are so commonly used in.

“I've gone back to some of the social influencer podcasts … and what I typically hear is, seed oil consumption has doubled. And in the same time it's doubled, obesity rates have risen, inflammation has risen, [and] chronic diseases are a problem,” Gardner says. “This is an association, not causation.” Indeed, processed foods make up an increasing share of the American diet. In December, Bloomberg School researchers published findings that more than half of calories that U.S. adults consume at home  come from ultraprocessed foods.

“We know that ultraprocessed foods generally are not good for your health. They are usually high in sodium or salt, added sugars, unhealthy fats, and additives,” Marklund says. “That's why it's bad for you, not the inclusion of seed oils.” 

Seed oils can be part of both healthy and unhealthy diets. Instead of cutting out all foods containing seed oils, Marklund says, “consider eating less ultraprocessed food and more whole foods, fruit, and vegetables—and then use seed oils together with those.”