Omega-3 fatty acids (EPA / DHA)

EPA and DHA are the two key omega-3 fats. EPA is 20:5n-3; DHA is 22:6n-3. Both are long-chain polyunsaturated fats, found mainly in oily fish and fish oil (or algae supplements, the main source for vegans). Their plant precursor, ALA (alpha-linolenic acid), is in flaxseed, chia, and walnuts. But your body converts ALA into EPA and DHA inefficiently, and the rate varies a lot. EPA and DHA do several jobs. They get built into your cell membranes, changing their fluidity. And they are the raw material for anti-inflammatory 'specialized pro-resolving mediators' (SPMs) like resolvins and protectins. That contrasts with the pro-inflammatory signals made from omega-6 arachidonic acid. At higher doses (2 g/day or more of EPA+DHA), they cut blood triglycerides by 20 to 50%. The REDUCE-IT trial showed that 4 g/day of purified EPA (icosapent ethyl) lowered major heart events in statin-treated patients with high triglycerides, though its mineral-oil placebo has been questioned. Observational data consistently link more oily fish, and a higher blood omega-3 index, to lower death rates. But supplement trials in generally healthy people show smaller, less consistent benefits.

Last reviewed: June 22, 2026

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