Omega-3 fatty acids (EPA / DHA)

Eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) are long-chain polyunsaturated fatty acids found principally in fatty fish, fish oil, and algal supplements, which serve as the primary dietary source for vegans. Their principal dietary precursor, alpha-linolenic acid (ALA), is found in flaxseed, chia, and walnuts, but conversion to EPA and DHA in humans is inefficient and highly variable. EPA and DHA are incorporated into cell membranes altering fluidity and lipid-raft composition, and serve as substrates for anti-inflammatory specialized pro-resolving mediators (SPMs) including resolvins and protectins, in contrast to the pro-inflammatory eicosanoids generated from omega-6 arachidonic acid. At pharmacological doses (≥2 g/day EPA+DHA), they reduce serum triglycerides by 20–50%; the REDUCE-IT trial showed that 4 g/day icosapentaenoic acid (EPA-only) reduced major cardiovascular events in statin-treated hypertriglyceridemic patients, though the mineral oil placebo has been questioned. Observational data consistently associate higher oily-fish intake and blood omega-3 index with lower all-cause and cardiovascular mortality; supplementation trials in generally healthy populations show more modest and inconsistent benefits.