In the Mexico City Prospective Study — 144,900 adults followed for up to 24 years — higher circulating omega-3 fatty acids were consistently linked to lower all-cause mortality. Per interquintile range, hazard ratios were 0.94 for DHA, 0.83 for non-DHA omega-3, and 0.88 for total omega-3. The most striking finding: participants in the top quintile of non-DHA omega-3 faced a 20% lower mortality hazard than those in the bottom quintile. Linoleic acid alone showed no mortality association, but total omega-6 and non-LA omega-6 were also inversely linked to death.
This is one of the largest prospective fatty acid studies ever conducted, and its value extends well beyond sample size. Most omega-3 mortality data come from European or East Asian cohorts with high fish consumption — this Latin American population has a distinct dietary pattern and genetic background, making the consistent inverse association particularly meaningful. The use of plasma biomarkers rather than dietary recall eliminates a major source of measurement error that plagues nutrition epidemiology. The non-DHA omega-3 signal (likely reflecting alpha-linolenic acid from plant sources) being stronger than DHA itself challenges the conventional narrative that marine-derived omega-3s dominate mortality benefits. Observational design prevents causal inference, and residual confounding remains plausible. Still, the magnitude of the effect, the large sample, and the biological plausibility through inflammation and cardiovascular pathways make this confirmatory and clinically relevant — supporting routine omega-3 optimisation as a longevity strategy worth discussing with a physician.
