Table 1_Docosahexaenoic acid intake and health in adults and older adults: a narrative review of disparities by country income level.docx

Docosahexaenoic acid (DHA) is a long-chain omega-3 polyunsaturated fatty acid essential for maintaining optimal brain and cardiometabolic health across adulthood and aging. Despite its biological relevance, global evidence indicates substantial variability in DHA intake and status, largely influenced by dietary patterns, food availability, and socioeconomic conditions. This narrative review synthesized observational and interventional studies published between 2014 and 2026 that evaluated DHA intake or biomarkers in adults and older adults, emphasizing disparities according to country income level. Studies were categorized following the World Bank Gross National Income (GNI) classification and analyzed to describe intake patterns, biochemical concentrations, and their reported health associations. Important inequities were observed between countries. Populations in high-income countries (HICs) generally reported higher DHA intake and tissue concentrations, mainly due to regular fish consumption and greater access to supplementation, while evidence from middle-income countries (MICs) was scarce, heterogeneous, and based on small non-representative samples. In HICs, even moderate fish intake significantly improved DHA status, whereas in MICs, mean intakes frequently fell below 200 mg/day, a threshold commonly associated with cardiometabolic and neurocognitive benefits. Higher DHA levels were consistently linked to more favorable lipid profiles, lower triglyceride concentrations, and better cardiovascular indicators, though associations with blood pressure and mortality were inconsistent. Evidence from neurocognitive studies suggested structural and functional advantages, including larger total brain volume, improved white matter integrity, and enhanced cognitive performance, yet findings on memory and dementia outcomes remain inconclusive. Overall, this narrative review highlights global inequities in DHA intake and data availability, particularly in MICs, where national nutrition surveillance remains limited. These disparities may contribute to unequal protection against cardiovascular and neurocognitive decline. Strengthening dietary monitoring, improving access to DHA-rich or fortified foods, and promoting supplementation in vulnerable populations are key strategies to reduce inequities and support healthy aging worldwide.