Are Seed Oils Inflammatory? What the Research Actually Says

Medically Reviewed by Ian Nathan, MBChB, on 9th February 2026

Seed oils - from soybean oil to sunflower, canola, and corn oil — have become a highly debated topic in nutrition and health circles. Critics claim these oils are pro-inflammatory and harmful, while many health organizations and scientists say the evidence doesn't support that notion. So which view is correct?

This article breaks down what the research actually says, with scientific studies, clinical trials, systematic reviews, and expert guidance — plus links to the original sources.

Introduction: The Debate Around Seed Oils

Seed oils are used in kitchens worldwide and are a common ingredient in packaged and prepared foods. However, in the last several years, blogs, influencers, and even some public figures have claimed that these oils cause inflammation, obesity, heart disease, and other chronic illnesses.

Much of this concern is based on the fact that seed oils are high in omega-6 fatty acids, particularly linoleic acid (LA) — an essential fat the body must get from food because it cannot synthesize on its own. Some argue that high omega-6 intake tips the balance toward inflammation by increasing pro-inflammatory molecules in the body.

But does science back this up? To separate fact from speculation, this article reviews randomized controlled trials, systematic reviews, meta-analyses, and large observational studies.

What Are Seed Oils?

Seed oils are liquid vegetable oils extracted from the seeds of plants. Common examples include:

• Soybean oil
• Corn oil
• Sunflower oil
• Safflower oil
• Canola (rapeseed) oil

These oils are rich in polyunsaturated fatty acids (PUFAs), especially omega-6 fatty acids such as linoleic acid.

Linoleic acid is an essential fatty acid, meaning the human body cannot synthesize it and must obtain it through diet.

Seed oils also provide vitamin E and other antioxidant compounds.

Why Do Some People Believe Seed Oils Cause Inflammation?

The claim that seed oils are inflammatory stems from biochemical theory. Linoleic acid can be converted into arachidonic acid, a fatty acid involved in producing inflammatory signaling molecules known as eicosanoids.

Critics also point to the omega-6 to omega-3 fatty acid ratio, suggesting that excessive omega-6 intake promotes inflammation. However, biochemical potential does not always translate into clinical outcomes in humans.

Evidence from Human Clinical Trials

a) Systematic Reviews of Randomized Controlled Trials

A systematic review published in the Journal of the Academy of Nutrition and Dietetics analyzed 15 randomized controlled trials examining dietary linoleic acid and inflammatory markers in healthy adults.

The authors found no consistent evidence that increased linoleic acid intake raised inflammatory biomarkers such as C-reactive protein (CRP), interleukins, or tumor necrosis factor-alpha.

Study link: https://pubmed.ncbi.nlm.nih.gov/22889633/

b) Meta-Analyses of Multiple Trials

A 2017 meta-analysis pooled data from 30 randomized controlled trials involving over 1,300 participants.

The analysis showed no significant association between increased dietary linoleic acid and markers of inflammation.

Study link: https://pubmed.ncbi.nlm.nih.gov/28752873/

Observational and Biomarker Studies

Large observational studies measuring blood fatty acid levels provide additional insight. Research involving nearly 1,900 adults found that higher blood linoleic acid levels were associated with lower inflammatory biomarkers and better metabolic health.

Summary: https://www.sciencedaily.com/releases/2025/06/250621103446.htm

Why Biochemical Theory Does Not Equal Real-World Outcomes

Although linoleic acid can be converted to arachidonic acid, human metabolism tightly regulates this process. Increasing dietary linoleic acid does not significantly raise tissue arachidonic acid levels in most individuals.

Furthermore, arachidonic acid also plays roles in immune regulation and resolution of inflammation, highlighting the complexity of fatty acid metabolism.

Seed Oils in the Context of Overall Diet

Diet quality matters more than any single nutrient. Many ultra-processed foods containing seed oils are also high in refined carbohydrates, sugars, and excess calories, which are known contributors to inflammation.

Replacing saturated fats with unsaturated fats, including seed oils, has been consistently associated with improved cardiovascular outcomes.

Practical Guidance for Consumers

• Use seed oils appropriately for high-heat cooking due to their higher smoke points.
• Balance omega-6 intake with omega-3 sources such as fish, flaxseed, and walnuts.
• Prioritize whole foods and minimize ultra-processed foods.

Common Myths and Facts

Myth: Seed oils cause chronic inflammation.
Fact: High-quality human studies do not support this claim.

Myth: Omega-6 fats are harmful.
Fact: Omega-6 fatty acids are essential and not inherently inflammatory.

Conclusion

The claim that seed oils are inherently inflammatory is not supported by robust scientific evidence. Randomized controlled trials, meta-analyses, and observational studies consistently show neutral or beneficial effects on inflammatory markers when seed oils are consumed as part of a balanced diet.

Rather than eliminating seed oils, a more evidence-based approach is to focus on overall dietary patterns, adequate omega-3 intake, and minimizing ultra-processed foods.

References

1. Johnson GH, Fritsche KL. Effect of dietary linoleic acid on markers of inflammation. PubMed
2. Su H et al. Dietary linoleic acid intake and inflammatory markers. PubMed
3. American Society for Nutrition. Seed oils and inflammation. ScienceDaily
4. European Food Information Council. Do seed oils cause inflammation? EUFIC