Social media says seed oils are "toxic." Science says...it's a lot more complicated.

For the past few years, seed oils have become one of the most controversial topics in nutrition. Scroll through social media and you'll see claims that soybean oil, sunflower oil, corn oil, and other vegetable oils are responsible for everything from chronic inflammation to obesity and heart disease.

But when researchers actually put these claims to the test in controlled human studies, the results tell a very different story.

A new randomized clinical trial published in Current Developments in Nutrition (2026) examined whether consuming a diet high in soybean oil, a seed oil rich in the omega-6 fatty acid linoleic acid, actually increased inflammation.

The short answer?

It didn't.

In fact, researchers found no increase in inflammatory markers and even observed signs that inflammation may have slightly decreased.

Let's break down what the science actually shows.

What Are Seed Oils?

Seed oils are oils extracted from plants such as:

• Soybean
• Sunflower
• Safflower
• Corn
• Cottonseed
• Grapeseed

These oils are naturally rich in linoleic acid (LA), an essential omega-6 fatty acid.

Essential means exactly what it sounds like:

Your body cannot make it; you must get it from food.

Linoleic acid plays important roles in:

• Maintaining healthy cell membranes
• Supporting skin health
• Normal immune function
• Cardiovascular health
• Brain function

Most dietary guidelines around the world recommend consuming adequate amounts of linoleic acid because of its well-established health benefits.

Why Do People Think Seed Oils Cause Inflammation?

The argument usually goes something like this:

1. Seed oils contain omega-6 fats.
2. Omega-6 fats can be converted into arachidonic acid.
3. Arachidonic acid can produce inflammatory molecules.
4. Therefore, eating seed oils causes chronic inflammation.

It sounds logical.

The problem?

Human biology doesn't work that simply.

The body tightly regulates how much linoleic acid becomes arachidonic acid.

Research estimates that only about 0.2% of dietary linoleic acid is converted into arachidonic acid, making the idea that eating soybean oil floods your body with inflammatory compounds scientifically inaccurate.

Even more importantly:

Arachidonic acid isn't just involved in starting inflammation; it also helps resolve inflammation by producing specialized molecules called lipoxins.

Inflammation is a normal biological process. The body needs both "on" and "off" switches.

The New Study

Researchers at The Ohio State University recruited adults with overweight or obesity and compared two diets.

Participants consumed foods containing either:

• 30 grams per day of soybean oil
• 30 grams per day of palm oil

Each diet lasted four weeks in a randomized crossover design, meaning every participant tried both diets.

Researchers then measured several biomarkers associated with inflammation, including:

• IL-6
• C-reactive protein (CRP)
• Soluble CD14
• Lipopolysaccharide-binding protein (LBP)
• Oxidized LDL

These are among the most commonly used laboratory markers for assessing systemic inflammation.

What Did They Find?

The biggest takeaway?

Nothing got worse.

Despite consuming approximately 16 grams of additional linoleic acid per day, participants experienced:

• No increase in CRP
• No increase in oxidized LDL
• No increase in LBP
• No increase in soluble CD14

Researchers also observed a trend toward lower IL-6, one of the body's major inflammatory signaling molecules, in the soybean oil group.

That doesn't support the claim that seed oils trigger inflammation.

If anything, it points in the opposite direction.

What About Arachidonic Acid?

This is where things get even more interesting.

Many internet claims suggest eating more linoleic acid should increase arachidonic acid levels.

That's not what happened.

Researchers found that arachidonic acid actually decreased in red blood cells after soybean oil consumption.

This finding aligns with numerous previous studies showing that increasing dietary linoleic acid does not meaningfully increase arachidonic acid in healthy adults.

This Isn't Just One Study

One study alone never settles a scientific debate.

Fortunately, this isn't the only evidence we have.

Several systematic reviews and meta-analyses have reached remarkably similar conclusions.

Research consistently shows that higher linoleic acid intake is associated with:

• Lower risk of cardiovascular disease
• Lower risk of type 2 diabetes
• Better insulin sensitivity
• No increase in inflammatory biomarkers
• Lower levels of C-reactive protein in some populations

The authors of the new study specifically note that their findings agree with previous randomized controlled trials and systematic reviews showing no evidence that dietary linoleic acid increases inflammation.

Why Does the Myth Persist?

Much of the confusion comes from laboratory experiments.

Some cell culture studies expose isolated cells to extremely high concentrations of linoleic acid that would never occur in humans eating a normal diet.

Those experiments can provide useful mechanistic information.

But they don't necessarily predict what happens inside a living person consuming real foods.

Human physiology includes:

• Hormonal regulation
• Enzyme control
• Antioxidant systems
• Immune regulation
• Multiple metabolic pathways

That's why human randomized controlled trials carry far more weight than isolated laboratory studies when evaluating dietary recommendations.

Are All Seed Oil Foods Healthy?

This is where nuance matters.

Many ultra-processed foods contain seed oils.

Examples include:

• Potato chips
• Fast food
• Packaged desserts
• Fried snack foods
• Frozen convenience meals

But that doesn't mean the seed oil itself is causing health problems.

Those foods are also often high in:

• Refined carbohydrates
• Added sugars
• Sodium
• Calories
• Low fiber
• Low protein

Blaming seed oils alone ignores the bigger picture.

It's entirely possible to eat a nutritious diet that includes soybean or sunflower oil.

Likewise, it's possible to eat an unhealthy diet that avoids seed oils altogether.

Should You Avoid Seed Oils?

Based on the best available evidence, there isn't strong scientific support for avoiding seed oils simply because they contain omega-6 fats.

Instead, focus on dietary patterns that consistently improve long-term health:

• Eat plenty of fruits and vegetables.
• Choose whole grains when possible.
• Include lean protein sources.
• Consume nuts and seeds regularly.
• Eat fatty fish rich in omega-3s.
• Minimize highly processed foods.
• Maintain a healthy body weight.
• Exercise consistently.

These habits have far stronger evidence than worrying about whether your salad dressing contains soybean oil.

The Bottom Line

Despite their reputation online, seed oils continue to perform well when tested in carefully controlled human studies.

The newest randomized clinical trial found that consuming soybean oil:

• Did not increase inflammation
• Did not increase oxidized LDL
• Did not increase CRP
• Did not increase other inflammatory biomarkers
• May even modestly reduce IL-6

Nutrition science is rarely black and white, but the current body of evidence suggests that seed oils themselves are unlikely to be the inflammatory villains they're often made out to be.

Instead of fearing one ingredient, you'll likely gain far more by focusing on the overall quality of your diet.

References

1. Yang CT, Cole RM, Colombo E, et al. Foods Fortified with Soybean or Palm Oil Show No Effect on Inflammation or Oxidized Low-Density Lipoprotein in Adults with Overweight or Obesity: A Secondary Analysis of a Randomized Placebo-Controlled Crossover Trial. Current Developments in Nutrition. 2026.
2. Johnson GH, Fritsche K. Effect of dietary linoleic acid on markers of inflammation in healthy persons: A systematic review of randomized controlled trials. Journal of the Academy of Nutrition and Dietetics. 2012.
3. Jackson KH, Harris WS, Belury MA, Kris-Etherton PM, Calder PC. Beneficial effects of linoleic acid on cardiometabolic health: An update. Lipids in Health and Disease. 2024.
4. Farvid MS, Ding M, Pan A, et al. Dietary linoleic acid and risk of coronary heart disease: A systematic review and meta-analysis of prospective cohort studies. Circulation. 2014.
5. Djuricic I, Calder PC. Beneficial outcomes of omega-6 and omega-3 polyunsaturated fatty acids on human health: An update for 2021. Nutrients. 2021.