Seed oils are blamed for inflammation across social media. What does the scientific evidence actually show?

The real concern is not the oil. It is how you cook with it.

There is one nuance worth taking seriously. When you heat any oil to high temperatures repeatedly (think commercial deep-fryers that go days between oil changes),it breaks down and forms, lipid peroxides and other oxidation products^[14] that are linked to inflammation and chronic disease. Fried food themselves also develop advanced glycation end products (AGEs) when carbohydrates and proteins react to high heat, adding another layer of health risk.

This applies to seed oils, but it also applies to coconut oil, lard and even olive oil if you push them past their smoke points. The cooking technique matters more than the oil category.

Practical takeaway: consider avoiding foods cooked in repeatedly reused frying oil (commercial fryers, certain takeaways), and try to avoid smoking your own pan at home. Using a few tablespoons of canola or sunflower oil to sauté vegetables, or in a salad dressing, is, according to the assessment from many major institution's assessment, generally considered a fine and healthy choice.

If you consume seed oils mainly through ultra-processed snack foods (chips, crackers, fast food), the inflammation risk attributed to the oils is more likely attributed to the foods themselves^[15]:their refined carbohydrates, added sugar, sodium and calorie density. As we have argued in our other coverage, no single ingredient is the problem when the underlying food category is the problem.

Frequently asked questions

Which oils are considered seed oils?

The most common are canola (rapeseed), sunflower, soybean, corn, safflower, cottonseed, grapeseed and rice bran oil. Olive oil, avocado oil and coconut oil are not seed oils. They are extracted from fruit pulp or nut flesh, not seeds.

Is olive oil a seed oil?

No. Olive oil is pressed from the fruit pulp of olives. It is the most extensively studied cooking oil globally and is consistently associated with better cardiovascular health outcomes in large scale research^[16].

Are seed oils worse than butter or beef tallow?

Most evidence points the other way. Randomised trials show that replacing saturated fats (butter, lard, tallow) with unsaturated fats (including seed oils) lowers LDL cholesterol. Reviews^[17] synthesising evidence^[18] from these trials, indicate that this lipid change is associated with reduced cardiovascular risk. This is the basis of long-standing guidance from the American Heart Association^[19] and the British Heart Foundation^[20] which recommend replacing saturated fat with unsaturated fats to reduce cardiovascular risk.

What is the healthiest cooking oil?

For most everyday cooking, olive oil (especially for low-to-medium heat), canola oil (neutral flavour, high smoke point) and avocado oil (high smoke point) are good choices^[21]. The healthiest oil is the one used in modest amounts as part of a diet rich in vegetables, fruits, whole grains, legumes and fish.

Do seed oils cause heart disease?

No. The American Heart Association^[7] and the British Heart Foundation^[13] both suggest that replacing saturated fats with unsaturated fats from seed oils can reduces cardiovascular risk. Anti-seed-oil influencers often invert this finding.

Why are seed oils controversial then?

Three reasons. First, they are cheap and ubiquitous in ultra-processed foods (chips, crackers, fast food). Those foods are genuinely less healthy^[15], but for reasons (sugar, refined carbs, sodium, calorie density) that have little to do with the oil itself. Second, the linoleic-acid-causes-inflammation hypothesis sounds intuitive even though human studies^[13] generally do not support it. Third, the issue has been amplified by wellness influencers and political figures, which keeps it in the algorithmic spotlight regardless of what new research shows.

Should I throw out my vegetable oil?

No. The advice from major health organisations we cited above is consistent: there is no need to avoid seed oils. Use them in moderation as part of an overall diet rich in vegetables, fruits, whole grains, fish and legumes.

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The bottom line

The strongest evidence available (controlled trials, systematic reviews, pooled cohort analyses, and statements from major health institutions) does not support the claim that seed oils cause inflammation in humans. The biochemical mechanism people often cite (linoleic acid being converted to arachidonic acid and driving inflammation) does not appear to operate at meaningful levels in the diets people actually eat.

The legitimate concerns about seed oils are about how they are used: in ultra-processed foods that are unhealthy for many reasons, and in repeatedly reheated frying oil that creates oxidation products. Neither of these is an inherent property of the oils themselves.

Remember: no single food is ever the enemy. It is about the overall diet.

For a deeper dive, see explainer by Nutrition Made Simple:

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