Krill Oil in Human Nutrition and Healthy Aging: A Narrative Review of Implications for Intrinsic Capacity and Nutrient Bioavailability

Krill oil (KO) is a marine-derived nutritional ingredient distinguished by its unique structural composition and increasing relevance in human nutrition, particularly in the context of healthy aging and preservation of intrinsic capacity. Approximately 30–65% of its fatty acids are esterified to phospholipids, a molecular configuration associated with enhanced bioavailability and efficient tissue incorporation of omega-3 polyunsaturated fatty acids, even at relatively low doses. Antarctic krill (Euphausia superba) originates from minimally impacted marine ecosystems, contributing to a favorable safety profile characterized by inherently low levels of environmental contaminants, including heavy metals and persistent organic pollutants. Beyond its structural and safety attributes, KO provides a complex nutrient matrix comprising approximately 25% total n-3 polyunsaturated fatty acids (PUFAs), including ~14% eicosapentaenoic acid (EPA) and ~6.5% docosahexaenoic acid (DHA), together with choline and astaxanthin. This compositional synergy may modulate inflammatory pathways, redox balance, membrane dynamics, and cellular signaling, thereby influencing physiological systems implicated in aging biology. This narrative review critically examines how these distinctive characteristics translate into clinically relevant outcomes supporting the multifunctional applications of KO in human nutrition. The analysis is structured within the framework of intrinsic capacity, encompassing locomotion, vitality, sensory, cognition and psychological dimensions, as a conceptual model for healthy aging. Considerations on bioavailability, tolerability, and sustainability are also discussed in the context of nutritional strategies promoting healthy longevity.