There’s long been talk in nutrition circles about the omega-6 to omega-3 ratio and whether our modern diets are fuelling inflammation due to an imbalance between the two. While health authorities universally advise replacing saturated fats with omega-6 vegetable (seed) oils, some claim that high omega-6 intake is harmful. So what does the evidence actually say?
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. Links to supporting studies and resources are shared at the end of page.
What are Omega-3 and 6 Fatty Acids?
First, it’s worth understanding what these fats are. Both omega-6 and omega-3 are essential polyunsaturated fatty acids, meaning our bodies can’t produce them and we must get them through diet.
Omega-6 fats are commonly found in vegetable oils such as canola, sunflower, corn and soybean oil, as well as in processed and fried foods. Linoleic acid is a key component.
Omega-3s, particularly EPA and DHA, are found in oily fish like salmon, sardines and mackerel. Plant-based ALA comes from sources like flaxseeds and walnuts.
The Ratio of Fats and Inflammation
Over the past century, the Western diet has undergone a significant shift, marked by a sharp rise in omega-6 fat consumption - while omega-3 intake has remained comparatively low. This imbalance has fuelled concerns about the omega-6 to omega-3 ratio, now often estimated at 15:1 or higher, compared to the presumed pre-industrial ratio of around 1:1 or 2:1.
However, the relationship between omega-6 fats and inflammation is more complex than it first appears. Linoleic acid, the dominant dietary omega-6 fat, is frequently criticised for its potential conversion to arachidonic acid, a precursor to pro-inflammatory molecules. Yet, since we moved away from mousal research, human studies have consistently shown that this conversion is tightly regulated. While direct supplementation with arachidonic acid or gamma-linolenic acid can raise tissue arachidonic acid levels, increasing dietary linoleic acid alone does not have the same effect.
Since 2011 large scale meta-analyses (Rhett et al, 2011; Grosso et al, 2022), have found no consistent evidence that linoleic acid promotes inflammation in humans. In fact, even substantial changes in dietary linoleic acid intake lead to only minor shifts in arachidonic acid levels, and some linoleic acid derived metabolites may have anti-inflammatory properties.
A 2024 UK Biobank study (Zhang et al) of over 85,000 participants followed for 13 years found that those with higher blood omega-6 to omega-3 ratios had higher mortality risks from all causes, cancer and heart disease - but note the detailed explanation provided by the study's authors...
"Individually, high levels of omega-6 fatty acids and high levels of omega-3 fatty acids were both associated with a lower risk of dying. But the protective effects of omega-3 were greater. For example, individuals with the highest levels of omega-6 fatty acids were 23% less likely to die of any cause. By comparison, those with the highest levels of omega-3s were 31% less likely to die. The stronger protection offered by high levels of omega-3s likely explains why having a high ratio of omega-6s to omega-3s was linked to harm."
The omega-6 to omega-3 ratio is important, but a high ratio typically reflects insufficient omega-3 intake rather than excessive or harmful omega-6 consumption.
A 2024 study by Jackson et al. argues that the omega-6 to omega-3 PUFA ratio is not a useful metric for assessing health, as it’s based on flawed assumptions: that all omega-6s are harmful, all omega-3s are beneficial, and that they act in direct opposition. It highlights that PUFAs within each group have different functions and health effects, so grouping them into a single ratio is misleading. Moreover, similar omega-6:omega-3 ratios can produce vastly different biological outcomes depending on which specific fatty acids are consumed. Since ratios vary across blood and tissue compartments, there’s no standard target. Instead, the study emphasises that absolute intake of individual fatty acids - particularly EPA and DHA - is far more important than any ratio. The authors stating:
"When EPA and DHA are consumed in reasonable amounts, neither the LA to ALA nor the n-6 to n-3 PUFA ratio of the diet is useful. All in all, the use of the n-6 to n-3 PUFA ratio, dietary or otherwise, should be discontinued."
Omega-3 Deficiency
Without enough omega-3s in the system, the body’s ability to regulate inflammation is compromised. Omega-3s serve as raw materials for anti-inflammatory signalling molecules called resolvins and protectins, helping the body to shut down unnecessary inflammation after it's done its job. So rather than demonising omega-6s, the focus should be on increasing omega-3 intake. Most people simply don’t get enough EPA and DHA in their diet. Public health guidelines recommend at least two servings of oily fish per week but many fall short.
Plant-based omega-3s like ALA can help but the body converts them to EPA and DHA inefficiently, so they're not a reliable substitute on their own but their whole food sources - primarily nuts and seeds - provide other health benefits including proteins, fibre and polyphenols.
For those looking to improve their omega fat profile, a good starting point is to include more omega-3-rich foods like sardines, mackerel, salmon, plus some flaxseed and chia. Supplementation may be helpful in many cases but there are concerns with the quality of many supplements.
Final Thoughts
The conversation around omega-6 and omega-3 fats is complex but the solution doesn’t need to be. Too much of anything can be harmful to health, especially processed and ultra-processed foods - the greatest sources of dietary omega-6 fatty acids. Stir frying vegetables in a little sunflower or canola oil is not the problem.
Rather than obsessing over ratios, we’re better off ensuring that omega-3s are no longer the missing piece in our diet. By restoring what’s lacking, the body can take care of the rest.
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Related Studies and Resources
Li Y, Tang H, Yang X, Ma L, Zhou H, Zhang G, Chen X, Ma L, Gao J, Ji W. Associations of ω-3, ω-6 polyunsaturated fatty acids intake and ω-6: ω-3 ratio with systemic immune and inflammatory biomarkers: NHANES 1999-2020. Front Nutr. 2024 Jun 7;11:1410154. doi: 10.3389/fnut.2024.1410154. PMID: 38912301; PMCID: PMC11190316.
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.
Zhang Y, Sun Y, Yu Q, Song S, Brenna JT, Shen Y, Ye K. Higher ratio of plasma omega-6/omega-3 fatty acids is associated with greater risk of all-cause, cancer, and cardiovascular mortality: A population-based cohort study in UK Biobank. Elife. 2024 Apr 5;12:RP90132. doi: 10.7554/eLife.90132. PMID: 38578269; PMCID: PMC10997328.
Grosso G, Laudisio D, Frias-Toral E, Barrea L, Muscogiuri G, Savastano S, Colao A. Anti-Inflammatory Nutrients and Obesity-Associated Metabolic-Inflammation: State of the Art and Future Direction. Nutrients. 2022 Mar 8;14(6):1137. doi: 10.3390/nu14061137. PMID: 35334794; PMCID: PMC8954840.
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.
Rett BS, Whelan J. Increasing dietary linoleic acid does not increase tissue arachidonic acid content in adults consuming Western-type diets: a systematic review. Nutr Metab (Lond). 2011 Jun 10;8:36. doi: 10.1186/1743-7075-8-36. PMID: 21663641; PMCID: PMC3132704.
Hussein N, Ah-Sing E, Wilkinson P, Leach C, Griffin BA, Millward DJ. Long-chain conversion of [13C]linoleic acid and alpha-linolenic acid in response to marked changes in their dietary intake in men. J Lipid Res. 2005 Feb;46(2):269-80. doi: 10.1194/jlr.M400225-JLR200. Epub 2004 Dec 1. PMID: 15576848.
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