Human evolutionary diets are estimated to have provided an omega-6 to omega-3 ratio of between 1:1 and 4:1. The modern Western diet provides a ratio of between 15:1 and 20:1, driven primarily by the widespread adoption of refined seed oils rich in linoleic acid. Omega-6 fatty acids are pro-inflammatory precursors. Omega-3 fatty acids are anti-inflammatory precursors. These two classes compete for the same enzymes to produce eicosanoids, the short-chain signalling molecules that regulate inflammation throughout the body.
How Linoleic Acid from Refined Oils Drives Inflammation
Linoleic acid from refined sunflower, corn, soybean, and cottonseed oils is metabolised via arachidonic acid to pro-inflammatory prostaglandins and leukotrienes. When the diet provides excessive linoleic acid, the enzymatic pathways that produce anti-inflammatory eicosanoids from EPA and DHA are outcompeted. The net result is a chronic pro-inflammatory state that does not produce acute inflammation visible to the individual but maintains a low-grade inflammatory burden across all tissues.
Correcting the Ratio Through Diet
- Replace sunflower, corn, and soybean oils with extra-virgin olive oil as your primary cooking fat
- Read ingredient labels on packaged foods: refined vegetable oils are the primary hidden source of dietary linoleic acid in ultra-processed products
- Eat two to three portions of oily fish per week to increase EPA and DHA
- Reduce consumption of conventionally raised livestock: grain-fed meat has a much less favourable omega-6 to omega-3 ratio than grass-fed
- Add walnuts, flaxseed, and chia seeds for plant-based ALA, though conversion to EPA and DHA is limited