Are Seed Oils Really That Bad? Let's Break It Down

Seed oils have quietly taken over our food supply, slipping into everything from salad dressings to protein bars. But are they silently contributing to the rising rates of chronic disease? 

A century ago, the fats in our diets looked very different. People cooked with stable animal fats like butter, lard, and beef tallow. That changed in the early 1900s when industrial seed oils—like soybean, canola, and corn oil—entered the food scene.

Products made from hydrogenated seed oils became popular as a cheaper alternative to animal fats. 

By the 1990s, economic incentives and government subsidies made seed oils even more appealing to food manufacturers.

Fast food chains swapped out beef tallow for seed oils, and the American Heart Association (AHA) began recommending oils like canola and soybean as "heart-healthy" alternatives. However, this endorsement was not without controversy.

The AHA had received significant funding from key players in the seed oil business—raising questions about the objectivity of their guidelines.

Seed oils are highly unstable when heated

Seed oils like soybean, corn, and sunflower oil are rich in omega-6 polyunsaturated fats, particularly linoleic acid. These fats are highly sensitive to heat and light, causing them to break down and form harmful compounds1 during processing and cooking.

Formation of toxic compounds

When seed oils are heated, they produce lipid oxidation products (LOPs), such as aldehydes and peroxides. One of the most harmful byproducts is 4-hydroxy-2-nonenal (4-HNE), a toxic compound linked to inflammation, diabetes, Alzheimer's disease, heart disease, and cancer2.

Connection to heart disease & cancer

Ironically, the oils marketed as heart-healthy might be harming our hearts. The rise in seed oil consumption parallels the increase in chronic diseases like obesity, diabetes, and coronary artery disease. 

A 2020 study3 found that corn oil heated for long periods produced a 70- to 80-fold increase in 4-HNE levels, raising concerns about its impact on heart health and cancer risk. 

Another study discovered that french fries cooked in omega-6-rich seed oils contained more 4-HNE than those fried in more stable oils, suggesting a higher risk of developing chronic diseases.

Disrupted fatty acid balance

Omega-6 fats, like those in seed oils, aren't inherently bad. They're essential fats our bodies need, just like omega-3s found in fish, flaxseeds, and walnuts. The problem is that most modern diets provide far too many omega-6s and not enough omega-3s.

Historically, humans consumed omega-6 and omega-3 fats in a balanced ratio. Today, the typical Western diet contains five to 15 times more omega-6s than omega-3s, contributing to inflammation and chronic disease.

Increased risk of chronic diseases

A recent study found that people with the highest omega-6-to-omega-3 ratio were 26% more likely to die from any cause—including heart disease and cancer—compared to those with a more balanced fat intake. While both fats are beneficial in moderation, omega-3s offer stronger protection against disease.

But when omega-6 intake is too high, it takes over these enzymes, leaving less room for omega-3s to do their job. As a result, fewer anti-inflammatory compounds are made, and more pro-inflammatory ones build up.

Impact on migraines 

Interestingly, a 2021 study showed that migraine sufferers who increased omega-3 intake while lowering omega-6 intake reduced their headache frequency by 30–40%4.

Seed oils are a modern addition to our diet, introduced through industrial processing and driven by economic incentives—not health benefits. Their high omega-6 content, instability under heat, and potential to trigger inflammation make them a questionable choice for long-term health. Experts like Robert Lufkin, M.D., argue that avoiding seed oils could be a crucial step in preventing chronic disease.