Dietary factors and MRI biomarkers of brain aging in general populations: A comprehensive systematic review

This systematic review examined the associations of dietary factors such as nutrients, food intake, dietary patterns, and dietary biomarkers with structural and functional brain MRI biomarkers, focusing on macrostructural, microstructural, lesion, and perfusion measures and functional activity/connectivity. Articles published in English were systematically searched in PubMed, Embase, and PsycInfo up to July 19, 2024. A total of 38 prospective cohort studies (23 cross-sectional and 15 longitudinal analyses) and 13 intervention studies were included. Cross-sectional analyses revealed heterogenous associations: baked fish correlated with larger hippocampal volumes (β=0.21), while oily fish, dairy products, and tofu adversely related to ventricle grade. Pro-inflammatory dietary patterns were positively associated with silent infarct risk (DII Q4 vs. Q1:OR=1.77), whereas anti-inflammatory patterns tended to favor brain preservation. Longitudinal studies demonstrated more consistent protective associations: green tea consumption (+100 mL/day) reduced hippocampal atrophy by 0.024%/year, prudent dietary patterns preserved +203 mm 3 left hippocampal volume over 4 years, and higher plasma carotenoids decreased medial temporal lobe loss by 0.02 cm³/year. However, null findings were common across multiple dietary factors. Interventions showed limited structural benefits (only 2 of 6 studies effective), while polyphenol-rich supplements more consistently improved cerebral perfusion and functional connectivity. Longitudinal and intervention studies demonstrated more consistent patterns than cross-sectional analyses, however, current evidence remains limited for clinical translation. Findings from cross-sectional analyses, despite being from prospective cohorts, require careful interpretation. Further replication across diverse populations and standardized long-term studies are needed before translating these associations into clinical practice.