Seed Oils and the Science Behind the Fear

Seed oils get blamed for a lot online, but most of the common claims don’t line up with actual nutrition science.

One of the biggest myths is that seed oils “oxidize at high heat,” but all fats oxidize at high temperatures, including butter, coconut oil, and tallow. Normal home cooking doesn’t reach the levels needed to create harmful oxidation products, and the kinds of oxidation people worry about typically occur only in industrial, repeated high temperature frying conditions, not in a home kitchen. Human studies do not show negative health outcomes from using seed oils for everyday cooking.

Linoleic Acid and Inflammation

Another common claim is that seed oils are dangerous because they’re high in linoleic acid. Linoleic acid is simply an omega-6 fatty acid, and omega-6 fats are essential. Your body cannot produce them on its own, so you must get them from food.

The real issue isn’t the presence of omega-6, but overall balance with omega-3s. If you regularly include fish, chia, flax, walnuts, or other omega-3 sources in your diet, your ratio is naturally supported. Research also shows that increasing omega-6 intake does not meaningfully raise arachidonic acid levels in the body or increase inflammation, which is one of the biggest misconceptions pushed online.

What Human Studies Actually Show

Seed oils are often accused of causing inflammation, but large meta-analyses show the opposite. When people replace saturated fats with unsaturated fats such as canola, soybean, sunflower, safflower, or other plant oils, inflammatory markers decrease and cholesterol profiles improve.

Cardiovascular outcomes consistently favor diets that include unsaturated fats over diets high in saturated fats. Human clinical trials and large population studies repeatedly show better heart health, improved LDL and HDL levels, and reduced all-cause mortality when unsaturated fats are included.

Metabolism and Insulin Sensitivity

A newer fear-based claim is that omega-6 fats “cause metabolic damage” or “block fat burning,” but human evidence does not support this. Higher linoleic acid intake is actually associated with improved insulin sensitivity and a lower risk of cardiovascular disease.

Processing Myths

The “they’re too processed” argument is misleading. Processing does not automatically make a food unhealthy. In the case of seed oils, the final product is purified, filtered, and tested so that only the oil and its fat-soluble vitamins remain.

All commercial oils, including olive, avocado, coconut, and seed oils, go through some form of processing. Health outcomes depend on the nutrient profile and overall dietary pattern, not the extraction method. Claims about “solvents” or “chemical residues” ignore the fact that final purified oils do not contain these compounds in meaningful amounts, and they are required to meet strict safety standards across major health agencies worldwide.

Rancidity and Toxicity Fears

Some people worry about rancidity or toxicity, but properly stored oils do not spontaneously become dangerous. Rancid oils may taste unpleasant, and you will notice it, but they are not inherently harmful in the tiny amounts someone would accidentally consume.

The idea that seed oils “gum up your cells” or “damage mitochondria” comes entirely from influencer marketing, not peer-reviewed human research.

Calories and Weight Gain

A lot of people worry about calories, but seed oils are not uniquely high in calories. All dietary fats contain nine calories per gram, while carbohydrates and protein contain four calories per gram.

Olive oil, avocado oil, butter, coconut oil, and seed oils all provide the same calorie density. This means portion control matters for any oil you use. Oils are easy to over-pour, so measuring or using a spray can help keep overall fat intake aligned with your goals. Weight gain does not come from a specific oil, it comes from an overall calorie surplus.

Putting It All Together

The overarching theme is that human data does not support seed oil fear. When unsaturated plant oils replace saturated fats, health outcomes improve across LDL, HDL, inflammation markers, heart disease risk, and long-term mortality.

These findings come from randomized trials and large population studies, not isolated rodent studies, cell culture experiments, or influencer content taken out of context.

It is also worth noticing that many of the loudest anti-seed-oil voices online are selling something, including supplements, detox kits, blood tests, cookbooks, “anti-seed-oil” snacks, or their own “safer” oils. The carnivore and “ancestral” diet communities in particular use seed oil fear as a marketing tool, despite the fact that the claims are not supported by human evidence. Much of the fear persists because it keeps people buying products.

Seed oils are not toxic. They are simply fats. You can use olive oil, avocado oil, canola oil, sunflower oil, butter, or whatever you prefer. What matters most is overall dietary pattern, fiber intake, fruit and vegetable consumption, omega-3 intake, and total food balance. Those factors influence long-term health far more than the type of oil used for sautéing.

References

https://publichealth.jhu.edu/2025/the-evidence-behind-seed-oils-health-effects

https://www.heart.org/en/news/2024/08/20/theres-no-reason-to-avoid-seed-oils-and-plenty-of-reasons-to-eat-them

https://www.health.harvard.edu/heart-health/seeding-doubt-the-truth-about-cooking-oils

https://www.eufic.org/en/misinformation/article/does-the-processing-of-seed-oils-pose-a-health-risk

https://med.stanford.edu/news/insights/2025/03/5-things-to-know-about-the-effects-of-seed-oils-on-health.html

https://www.aarp.org/health/healthy-living/are-seed-oils-actually-bad-for-you/

https://pmc.ncbi.nlm.nih.gov/articles/PMC6121943/