A Look at the Science, the Statistics, and Why Your Great-Grandmother Probably Cooked with Butter

At the beginning of the 20th century, heart disease was relatively rare. Historical mortality records show that around 1900 less than 10% of deaths in the United States were caused by heart disease. Today it is the leading cause of death worldwide, responsible for roughly 20% of all deaths globally according to international public health data.

Something clearly changed.

Smoking increased and then decreased. Sugar intake rose. People moved less and sat more. Ultra-processed foods flooded grocery stores.

But one of the largest dietary shifts in human history quietly happened at the same time: the dramatic rise of industrial seed oils.

Before the early 1900s, oils extracted from soybeans, corn, cottonseed, sunflower seeds, and safflower seeds were essentially nonexistent in the human diet. Extracting oil from tiny seeds required industrial presses, high heat, and chemical extraction, technologies that did not exist at scale before the industrial food era.

Today these oils make up a massive portion of the modern diet.

Let’s take a look at what research has found.

1 Seed Oil Consumption Skyrocketed in the 20th Century

In 1909, Americans consumed roughly 2 pounds of soybean oil per person per year.

Today the average American consumes over 60 pounds of vegetable oils annually, most of it coming from seed oils like soybean, corn, sunflower, safflower, and canola oil.

One of the main fatty acids in these oils is linoleic acid, an omega-6 polyunsaturated fat.

Analysis of human fat tissue samples from the past century shows that linoleic acid levels in human body fat have increased by more than 2 to 3 times since the early 1900s. In other words, the oils we eat literally become part of our tissues.

2 Linoleic Acid Can Remain Stored in the Body for Years

Unlike carbohydrates that are burned quickly for energy, linoleic acid tends to accumulate in fat cells and cell membranes.

Research examining fatty acid turnover suggests linoleic acid stored in body fat may have a half-life of about 600 to 680 days.

That means the seed oil you ate two years ago might still be hanging out inside your cells.

So if your body had a refrigerator, linoleic acid would basically be the leftover container in the back that no one remembers putting there.

3 Polyunsaturated Oils Are Chemically Unstable

Polyunsaturated fats contain multiple double bonds, which makes them far more prone to oxidation compared with saturated fats.

When exposed to heat, light, or oxygen, these oils can break down into lipid oxidation products such as aldehydes.

Laboratory studies show some of these oxidation products can damage cellular proteins and DNA and contribute to oxidative stress.

High-temperature cooking — especially deep frying — dramatically accelerates this process.

And let’s be honest… restaurant fryers are not exactly known for their spa-like treatment of cooking oils.

4 Oxidized LDL Plays a Major Role in Artery Plaque

Heart disease is not simply about cholesterol levels.

What researchers often focus on is oxidized LDL cholesterol.

Oxidized LDL is strongly associated with the development of atherosclerosis, the process that leads to plaque buildup in arteries.

Because linoleic acid is highly susceptible to oxidation, some scientists have questioned whether high tissue levels may increase the likelihood of LDL oxidation under certain conditions.

5 Modern Diets Are Extremely High in Omega-6 Fatty Acids

Human diets historically contained a relatively balanced ratio of omega-6 to omega-3 fatty acids, estimated to be around 1:1 to 4:1.

Today the Western diet often reaches ratios of 15:1 or even 20:1 due largely to seed oils and processed foods.

Omega-6 fats are essential nutrients, but excessive intake may stimulate pro-inflammatory signaling pathways, especially when omega-3 intake is low.

Chronic inflammation is widely recognized as a major contributor to cardiovascular disease.

6 Ultra-Processed Foods Contain Huge Amounts of Seed Oils

Seed oils are inexpensive, shelf-stable, and neutral tasting.

For the processed food industry, that makes them perfect.

Walk through a grocery store and you will find them in:

Chips
Crackers
Frozen meals
Fast food
Protein bars
Salad dressings
Bread products
Snack foods

Large population studies involving hundreds of thousands of people consistently show that diets high in ultra-processed foods are linked to higher risks of cardiovascular disease, obesity, and metabolic disorders.

Seed oils are rarely the only ingredient involved, but they are almost always part of the package.

7 Industrial Processing Is Extensive

Unlike olive oil, which can be produced simply by crushing olives, many seed oils require a complex industrial refining process.

Typical processing steps include:

High-heat mechanical pressing
Chemical solvent extraction
Bleaching
Deodorizing
Refining at high temperatures

The result is a stable, neutral oil that works well in packaged foods.

But it is also very different from the fats humans consumed for thousands of years.

Your great-grandmother probably churned butter or saved bacon grease.

She probably did not deodorize cottonseed oil in a factory.

8 Repeated Frying Produces Harmful Compounds

When oils high in polyunsaturated fats are repeatedly heated, they produce compounds including aldehydes and lipid peroxides.

Researchers studying cooking oils have found that repeated heating can dramatically increase these oxidation products.

Some of these compounds have been studied for their potential roles in oxidative stress and cellular damage.

If you have ever smelled the inside of a fast-food kitchen, you already know those fryers have seen things.

Things they probably should not talk about.

9 Heart Disease Rose During the Same Era Seed Oils Took Over

Again, correlation does not equal causation.

But the historical timeline is interesting.

The explosion in vegetable oil consumption during the 20th century occurred alongside rising rates of heart disease, obesity, metabolic syndrome, and type 2 diabetes in industrialized nations.

Of course many other factors changed during this period — including sugar intake, smoking rates, sedentary lifestyles, and environmental toxins.

But when a food ingredient increases tenfold or more, scientists tend to pay attention.

10 Traditional Whole-Food Diets Remain the Health Champions

Despite endless debates about saturated fats versus polyunsaturated fats, nutrition science repeatedly arrives at the same conclusion.

Diets built around whole, minimally processed foods consistently produce the best health outcomes.

Vegetables
Fruits
Fish
Nuts
Naturally occurring fats
Unprocessed meats

Populations eating traditional diets rich in real food show far lower rates of cardiovascular disease and metabolic illness than populations consuming heavily industrialized diets.

Which leads to a surprisingly simple rule.

If a food requires a refinery, a chemistry lab, and a deodorizing chamber before it reaches your plate… it might deserve a second look.

And if your great-grandmother would not recognize it as food, there is a decent chance your arteries might not either.

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