Do Seed Oils Cause Inflammation? What the Evidence Really Says
- Alastair Hunt
- May 3
- 4 min read
Updated: 4 days ago
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.
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. Always seek medical guidance if managing inflammatory or autoimmune conditions.
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.
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
Grytten E, Laupsa-Borge J, Cetin K, Bohov P, Nordrehaug JE, Skorve J, Berge RK, Strand E, Bjørndal B, Nygård OK, Rostrup E, Mellgren G, Dankel SN. Inflammatory markers after supplementation with marine n-3 or plant n-6 PUFAs: A randomized double-blind crossover study. J Lipid Res. 2025 Mar 8;66(4):100770. doi: 10.1016/j.jlr.2025.100770. Epub ahead of print. PMID: 40058591; PMCID: PMC11999210.
Jackson KH, Harris WS, Belury MA, Kris-Etherton PM, Calder PC. Beneficial effects of linoleic acid on cardiometabolic health: an update. Lipids Health Dis. 2024 Sep 12;23(1):296. doi: 10.1186/s12944-024-02246-2. PMID: 39267068; PMCID: PMC11391774.
Wang Q, Zhang H, Jin Q, Wang X. Effects of Dietary Linoleic Acid on Blood Lipid Profiles: A Systematic Review and Meta-Analysis of 40 Randomized Controlled Trials. Foods. 2023 May 25;12(11):2129. doi: 10.3390/foods12112129. PMID: 37297374; PMCID: PMC10253160.
Li J, Guasch-Ferré M, Li Y, Hu FB. Dietary intake and biomarkers of linoleic acid and mortality: systematic review and meta-analysis of prospective cohort studies. Am J Clin Nutr. 2020 Jul 1;112(1):150-167. doi: 10.1093/ajcn/nqz349. PMID: 32020162; PMCID: PMC7326588.
Marangoni F, Agostoni C, Borghi C, Catapano AL, Cena H, Ghiselli A, La Vecchia C, Lercker G, Manzato E, Pirillo A, Riccardi G, Risé P, Visioli F, Poli A. Dietary linoleic acid and human health: Focus on cardiovascular and cardiometabolic effects. Atherosclerosis. 2020 Jan;292:90-98. doi: 10.1016/j.atherosclerosis.2019.11.018. Epub 2019 Nov 15. PMID: 31785494.
Innes JK, Calder PC. Omega-6 fatty acids and inflammation. Prostaglandins Leukot Essent Fatty Acids. 2018 May;132:41-48. doi: 10.1016/j.plefa.2018.03.004. Epub 2018 Mar 22. PMID: 29610056.
Su H, Liu R, Chang M, Huang J, Wang X. Dietary linoleic acid intake and blood inflammatory markers: a systematic review and meta-analysis of randomized controlled trials. Food Funct. 2017 Sep 20;8(9):3091-3103. doi: 10.1039/c7fo00433h. PMID: 28752873.
Farvid MS, Ding M, Pan A, Sun Q, Chiuve SE, Steffen LM, Willett WC, Hu FB. Dietary linoleic acid and risk of coronary heart disease: a systematic review and meta-analysis of prospective cohort studies. Circulation. 2014 Oct 28;130(18):1568-78. doi: 10.1161/CIRCULATIONAHA.114.010236. Epub 2014 Aug 26. PMID: 25161045; PMCID: PMC4334131.
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