25(OH)D	25-hydroxycholecalciferol (25-hydroxyvitamin D)
AD	Alzheimer’s disease
ASQ-3	Ages and Stages Questionnaire, Third Edition
BDI-II	Beck Depression Inventory, Second Edition
BDNF	Brain-derived neurotrophic factor
BMI	Body mass index
CI	Confidence interval
CREB	cAMP (cyclic adenosine monophosphate) response element-binding protein
DALYs	Disability-adjusted life years
DASH	Dietary Approaches to Stop Hypertension
DNA	Deoxyribonucleic acid
ELISA	Enzyme-linked immunosorbent assay
GDS	Geriatric Depression Scale
IU	International unit
LTP	Long-term potentiation
MCI	Mild cognitive impairment
MeDi	Mediterranean diet
MIND	Mediterranean-DASH Intervention for Neurodegenerative Delay
MMSE	Mini-mental state examination
MRI	Magnetic resonance imaging
NHANES	National Health and Nutrition Examination Survey
NOS	Newcastle–Ottawa Scale
PHQ-9	Patient Health Questionnaire-9
PRISMA	Preferred Reporting Items for Systematic Reviews and Meta-Analyses
PUFA	Polyunsaturated fatty acids
RCT	Randomized controlled trial
RoB 2	Risk of Bias 2
SANRA	Scale for the Assessment of Narrative Review Articles
SMD	Standardized mean difference
SYRCLE	Systematic Review Centre for Laboratory animal Experimentation
TrkB	Tropomyosin receptor kinase B
VDR	Vitamin D receptor
WHO	World Health Organization