Do Seed Oils Cause Inflammation? What the Evidence Really Says
- Alastair Hunt
- May 3
- 6 min read
Updated: Nov 17
Part 3 of the Seed Oils Series
One of the most common criticisms levelled against seed oils is that they promote inflammation in the body, leading to chronic illnesses such as heart disease, diabetes, and even cancer. This claim is rooted in the biological role of omega-6 fatty acids, particularly linoleic acid (LA), and their conversion into arachidonic acid (AA), a precursor for inflammatory molecules known as eicosanoids.
However, while this pathway exists biochemically, human studies tell a different story.Importantly, only about 0.2% of dietary linoleic acid is converted into arachidonic acid in humans, thanks to tightly regulated enzymatic controls. The body’s production of inflammatory mediators depends on overall immune activation, not simply the availability of substrate. In other words, eating more linoleic acid does not automatically ramp up chronic inflammation.
A substantial body of human research supports this. A 2024 systematic review and meta-analysis by Jackson et al. found that higher linoleic acid intake consistently correlated with lower levels of inflammatory biomarkers like C-reactive protein (CRP) and interleukin-6 (IL-6). Similarly, an earlier meta-analysis by Innes and Calder (2018) reviewing over 30 randomised controlled trials concluded that omega-6 PUFA intake did not increase inflammation and in some cases reduced it.
Furthermore, higher circulating levels of linoleic acid are associated with lower risks of cardiovascular disease, stroke, and all-cause mortality. For instance, Marklund et al. (2019) pooled data from nearly 70,000 individuals across 30 prospective studies, finding that higher blood levels of linoleic acid were linked to a 22% lower risk of death from cardiovascular causes.
It is also important to understand that arachidonic acid is not solely pro-inflammatory. It is a precursor not only to inflammatory prostaglandins and leukotrienes but also to anti-inflammatory and inflammation-resolving molecules such as lipoxins and prostacyclin. The inflammatory response is a highly nuanced balance, not a simple "on-off" switch triggered by diet alone.
Likely it is the cooking techniques and outcomes associated with seed oils - frying and browning - that are inflammatory. These are known to lead to the creation of so-called Advance Glycation End Products that promote chornic illness.
Inflammation is a complex biological response influenced by many factors, including diet, infections, body fatness, physical activity, sleep, and stress. While diet plays a role, it is rarely the sole driver of chronic inflammation.
The evidence in humans does not support the idea that normal dietary intake of seed oils causes harmful, chronic inflammation. If anything, linoleic acid appears protective when consumed as part of a balanced, whole-food diet. For more studies on this subject area, scroll to bottom of page. As ever, please talk to your doctor or medical practitioner most familiar with your medical history before implementing any changes in diet, exercise or lifestyle, especially if you are under treatment.
Final Thoughts
While seed oils can be a divisive issue online, we are relatively agnostic when it come to diet and eating patterns. If you enjoy cooking with olive oil, a dab of butter, avocado oil or (as a treat) duck fat, we do too. In the same regard, we are not concerned about a splash of canola in our stir fry and we try to avoid ultra-processed foods as part of our daily eating.
Changing health for the better is about progress, not perfection, and even small changes can make a meaningful difference over time. For most people, improving health is about finding motivation and prioritising self-care - with an ultimate goal of taking action. If you want to take effective and targeted steps that fit into your unique lifestyle and circumstances, The Whole Health Practice is here to help.
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Stay Healthy,
Alastair
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Related Studies
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