The Facts About Seed Oils and Your Health

From salad dressings and fast food to protein bars and even baby formula, seed oils are almost impossible to avoid.

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Every decade has a new food enemy. First, it was fat. Then, it was sugar. Now, seed oils are under fire—blamed for causing obesity and chronic disease.

Nearly impossible to avoid, seed oils are in everything from salad dressings and fast food to protein bars and even baby formula. Critics claim that they’re harmful, while supporters argue that they’re safe, affordable, and even good for you.

However, the truth is more nuanced. The debate is often oversimplified. Even the term “seed oil” is misleading, lumping together oils that have been part of traditional diets for centuries with those created for large-scale food production.

At its core, the controversy isn’t just about whether seed oils are inherently good or bad—it’s about how they’re processed and consumed.

What Are Seed Oils, Really?

If you’ve been following health trends, you’ve probably heard claims that seed oils are toxic and should be avoided. What exactly are seed oils, and why do some people consider them harmful?

At the most basic level, seed oils are oils extracted from seeds. This might seem harmless—after all, olive oil comes from olives, and coconut oil from coconuts.

But not all seed oils are the same. Some, such as sesame and flaxseed, have been integral to traditional diets for centuries and are extracted through natural, cold-press methods that preserve their nutrients and antioxidants.

However, others are highly processed. Industrial seed oils—such as soybean, corn, canola, sunflower, safflower, cottonseed, grapeseed, and rice bran—are mass-produced through high-heat extraction and chemical refining.

Manufacturers frequently use solvents such as hexane to extract the maximum amount of oil. These oils are refined, bleached, and deodorized, earning them the label “RBD” oils. This process makes them neutral in taste and more shelf-stable, but it also removes beneficial compounds such as vitamin E and antioxidants.

Many industrial seed oils were never intended for human consumption. Canola oil began as rapeseed oil, primarily used as a machine lubricant until Canadian scientists modified it in the 1970s to remove toxic compounds. The name itself—a blend of “Canada” and “oil”—was a marketing invention. “Vegetable oil” is another misleading term—it’s often a blend of industrial seed oils marketed to sound healthier than it is.

Dr. Cate Shanahan, a physician and scientist specializing in dietary fats, explained that industrial seed oils were not developed with nutrition in mind.

“The crude oil from these seeds is inedible,” she told The Epoch Times. “Soy and canola weren’t bred for nutrition—they were bred for high yields and industrial durability.”

Most soy grown in the United States isn’t intended for human consumption at all. According to the Department of Agriculture, more than 70 percent of U.S. soybeans are used for animal feed, while another 5 percent is processed into biodiesel. What remains is primarily refined into soybean oil—a product stripped of much of the soy plant’s original nutritional value.

Additionally, more than 90 percent of U.S. soy is genetically modified to withstand herbicides such as glyphosate, allowing farmers to spray entire fields without harming crops. This high-intensity farming, combined with heavy industrial processing, results in oil far removed from its original form.

Unlike traditional oils such as olive or sesame, which retain their natural antioxidants, industrial seed oils require extensive refining to become shelf-stable. Shanahan argued that this process removes beneficial compounds, making them more prone to oxidation and degradation.

“What works for machines doesn’t always work for humans,” Shanahan said.

Are Seed Oils Good or Bad for Your Health?

Seed oils’ health effects are hotly debated. Some experts say they’re a heart-healthy alternative to butter and other animal fats, while others believe that they might contribute to inflammation and disease.

The Case for Seed Oils as a Heart-Healthy Alternative 

For decades, scientists have debated the role of different fats in heart health. Research suggests that replacing saturated fats—found in butter and red meat—with polyunsaturated fats (PUFAs) from seed oils may offer cardiovascular benefits.

Advocates argue that the science is well-established.

“The research on seed oils is consistently positive,” Matthew Nagra, a naturopathic doctor, told The Epoch Times. “Numerous meta-analyses of randomized controlled trials have demonstrated that replacing saturated fat with seed oils rich in polyunsaturated fats can lower the risk of cardiovascular disease, America’s top killer, without any clear detriment.”

Large-scale studies support this claim. A 2021 study of more than 500,000 people found that those who replaced saturated fats with oils such as canola, corn, and olive had a lower risk of heart disease and early death.

“Our findings support shifting the intake from solid fats to non-hydrogenated vegetable oils for cardiometabolic health and longevity,” the authors wrote. Examples of solid fats include butter and lard.

A 2025 study published in JAMA Internal Medicine reinforced these findings, showing that people who ate more plant-based oils—such as olive, soybean, and canola—lived longer and had lower heart disease and cancer rates. Meanwhile, those who ate more butter had a higher risk of early death. The researchers estimated that swapping butter for plant oils could reduce overall mortality risk by 17 percent, including a 17 percent drop in cancer-related deaths.

Because of this growing evidence, the American Heart Association continues to recommend seed oils as part of a heart-healthy diet.

The Case Against Seed Oils: Oxidation and Inflammation

Not everyone agrees with the association’s endorsement of seed oils, and some experts question the research behind it.

“This study is of low quality,” Dr. Vinay Prasad, a hematologist-oncologist and professor of epidemiology and biostatistics at the University of California, San Francisco, told The Epoch Times in an email. “It lumps extra-virgin olive oil with soybean and safflower oil, which is ridiculous.”

He also criticized the study’s methodology, arguing that it fails to accurately measure butter consumption and instead relies on an imprecise estimation method.

“This kind of nutritional epidemiology fuels dogma rather than providing clarity,” he said.

Beyond concerns about research methods, critics argue that the real issue with seed oils is oxidation.

Refining makes seed oils more resistant to spoilage, allowing them to last longer on store shelves. However, once exposed to heat, air, or light—especially during cooking—their chemical structure begins to break down.

Unlike traditional oils such as olive or sesame, which naturally contain antioxidants that help prevent degradation, industrial seed oils lose these stabilizing compounds during processing. As a result, they are more vulnerable to oxidation, a process that creates byproducts such as aldehydes and free radicals. These compounds can damage cells, promote inflammation, and contribute to chronic disease.

Heat accelerates this process. Studies show that repeatedly heating vegetable oils—such as those used in restaurant fryers—can generate oxidative byproducts linked to tissue damage and increased cholesterol levels in lab animals. Some research has also found oxidized linoleic acid, a degraded form of omega-6 fat, accumulating in human fat tissue and artery plaques, raising concerns about long-term health effects.

Not all experts agree that oxidation is a major threat.

“These processes have pros and cons,” Christopher Gardner, a nutrition professor at Stanford University, said. “They help prevent oils from breaking down but also strip away some beneficial components.”

A review in The Scientific World Journal found that while refining removes antioxidants such as vitamin E and polyphenols (compounds that help protect cells), it also eliminates impurities, making the oils more stable and less likely to spoil.

Still, oxidation happens faster in seed oils than in other fats. Research shows that PUFAs degrade more quickly when exposed to heat, light, and air, whereas monounsaturated fats (found in olive oil) and saturated fats (found in butter and beef tallow) remain more stable.

The Processed Food Connection

If there’s one thing both critics and defenders of seed oils agree on, it’s that they’re everywhere. And that’s no accident.

Cheap, abundant, and heavily subsidized seed oils are a pillar of the modern food industry. The U.S. government pours billions of dollars into supporting crops such as soybeans, corn, and cottonseed, making their oils far more affordable than alternatives such as olive or avocado.

Soybeans dominate the market, accounting for about 90 percent of U.S. oilseed production. In 2016, the soybean industry alone received $1.6 billion in subsidies—helping to keep production high and costs low.

Government support doesn’t just make seed oils cheap for home cooks—it makes them the backbone of ultra-processed foods (UPFs), which now make up nearly 60 percent of the U.S. diet. Along with refined grains and added sugars, seed oils form the foundation of modern processed foods, used to enhance texture, extend shelf life, and boost flavor at a low cost. These ingredients appear in everything from breakfast cereals to frozen dinners, making them nearly impossible to avoid in a typical supermarket.

A 32-ounce bottle of canola oil costs about $5.79, while the same amount of extra-virgin olive oil can cost $13.99 or more. For food manufacturers trying to keep costs down, the choice is obvious. Because they’re inexpensive, neutral in flavor, and relatively shelf-stable, seed oils are a food manufacturer’s dream—allowing processed foods to last longer, taste better, and remain profitable.

Shanahan estimated that seed oils account for 20 percent to 30 percent of the average American’s daily calorie intake. This figure wasn’t easy to calculate, as seed oils aren’t tracked as a category. Shanahan analyzed decades of production data from crops such as soybeans and canola, using government and industry reports to uncover the extent of seed oils’ presence in modern diets.

“Humans have never consumed polyunsaturates at this level before,” she said. “Historically, diets relied mainly on animal fats, not oils rich in PUFAs. If you don’t know to avoid them, you’re eating vast quantities.”

Gardner agreed, but said the issue isn’t just seed oils. The rise in seed oil consumption isn’t because more people are making homemade salad dressings, he said. It’s because UPFs—in which these oils are used heavily—now dominate the U.S. diet.

Gardner argued that even if seed oils were removed from the food supply tomorrow, UPFs wouldn’t disappear—they would just be reformulated.

“If the same UPFs were made with another oil like butter, beef tallow, lard, or coconut fat, those foods would not suddenly become health foods,” he said.

At its core, the debate over seed oils is about more than just the oils themselves. It’s about the processed foods they’re in—and whether we should be eating so many of them in the first place.

What Should You Cook With?

Rather than fixating on eliminating seed oils altogether, experts say the bigger issue is reducing UPFs and choosing high-quality, stable fats when cooking at home.

“If you want to improve your health by cutting back on seed oils, the best way to do that is by eating fewer ultra-processed foods,” Gardner said. “That would be a win in several ways—less sugar, less refined grain, and less sodium.”

For those looking to make better choices in their kitchens, experts recommend using stable, minimally processed oils that are less prone to oxidation:

Better Options for Cooking

• Avocado: High in monounsaturated fats, stable for high heat
• Extra-Virgin Olive: Rich in antioxidants, ideal for drizzling or light cooking
• Butter and Ghee: Naturally stable for high-heat cooking
• Coconut: High in saturated fat, making it oxidation-resistant

Oils Best Used Cold

• Flaxseed: High in omega-3s, best for dressings
• Walnut: Antioxidant-rich, flavorful in salads
• Sesame: Aromatic and moderately heat-stable

Industrially Refined Oils 

• Soybean
• Corn
• Canola
• Cottonseed
• Sunflower
• Safflower
• Grapeseed
• Rice bran

While some specialty versions of these oils exist in cold-pressed forms, they are far less common than their mass-produced, highly processed counterparts.

The Bottom Line

The debate over seed oils is far from finished, but one thing is clear: How you consume them matters.

A drizzle of canola oil on a homemade salad is not the same as eating french fries fried in old restaurant oil. Relying on UPFs filled with cheap oils, sugar, and additives is where the larger problem lies.

For most people, the best way to improve their diet isn’t to worry about every drop of seed oil—it’s to eat more fresh, unprocessed foods, Gardner said.