Dietary patterns and the prevention of non-communicable diseases in aging populations: a narrative review of evidence, mechanisms, and clinical implications

Population aging increases the need for dietary strategies that address chronic disease risk while preserving nutritional status and function. This narrative review examines dietary patterns in relation to cardiovascular disease, type 2 diabetes, selected cancers, cognitive decline, and frailty in older adults, integrating epidemiological findings, biological mechanisms, and clinical implications. Literature searches in four databases, primarily covering publications from 2020 through 2 June 2026, with relevant earlier studies retained, informed a descriptive narrative synthesis; no formal risk-of-bias assessment was performed. Mediterranean, Dietary Approaches to Stop Hypertension (DASH), Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND), and healthful plant-forward patterns share core foods but differ in their targets and supporting evidence. Randomized comparisons support blood pressure reduction and cardiovascular event prevention in selected high-risk populations. Cohort studies associate higher diet quality with favorable diabetes, frailty, cognitive, and mortality outcomes, but confounding, measurement error, and reverse causation limit interpretation. Cancer findings depend on anatomical site and endpoint. The three-year MIND trial did not demonstrate superior cognitive outcomes over an active comparator. Inflammatory, metabolic, vascular, and microbiota pathways provide plausibility rather than proof of clinical prevention. Clinical application requires adequate energy and protein, consideration of multimorbidity and functional limitations, and culturally acceptable foods. Food environments are considered separately as implementation conditions. The narrative design limits completeness and certainty. Dietary counseling can support cardiometabolic prevention, while claims about dementia, cancer, and frailty require outcome-specific caution.