Do seed oils cause inflammation?

Seed oils, extracted from plants like sunflower, soybean, and corn, have become a common ingredient in many diets due to their versatility and affordability. However, they’re now at the center of debate, with some claiming that seed oils contribute to inflammation and adverse health outcomes.

This is largely due to their high omega-6 fatty acid content. Specifically, critics argue that linoleic acid, an omega-6 found in high amounts in seed oils, may promote inflammation by increasing levels of another omega-6 fatty acid, arachidonic acid, in the body.

In the human body, linoleic acid is converted, via a multistep pathway, into another omega-6 fatty acid called arachidonic acid, which is involved in pro-inflammatory responses. So, by this understanding, more linoleic acid in the diet (through more seed oils) increases arachidonic acid and results in more inflammation.

However, evidence shows us this is not how it actually works in the body.

A systematic review looked at the results in 36 human intervention studies on whether more linoleic acid in the diet resulted in more arachidonic acid.

It did not.

Increasing the levels of linoleic acid by up to 551% did not significantly increase the levels of arachidonic acid in the plasma, serum, and red blood cells.

But what if you measure the levels of inflammation in the body after regular consumption of seed oils? Surely, given all the hype around their inflammatory effects, there would be strong evidence for this?

Not quite.

Studies have also debunked the prevailing myth that these oils lead to inflammation, showing that they may actually possess anti-inflammatory properties. Yes, you read that right—anti-inflammatory!

“Seed oils contain omega-6 fatty acids. Some argue that too many of these fatty acids are pro-inflammatory, but the research doesn't support that at all. This review of dozens of control studies looked at 10 on the effect of seed oils on inflammatory markers. They found that not a single study found convincing evidence that seed oils increase inflammation, and actually, three of them found seed oils to have an anti-inflammatory effect.” says Dr Idz.

This review failed to find substantial evidence linking seed oils to increased inflammation.

Another systematic review of 15 randomised controlled trials in healthy humans found no significant evidence for dietary linoleic acid increasing a range of inflammatory markers.

The evidence supporting the claims that seed oils cause inflammation is next to zero. Including omega-6 fatty acids from seed oils in your diet is unlikely to spike your risk of disease or premature death.