The active form vitamin D is a seco-steroid with multiple neurotrophic and neuroprotective functions in the central nervous system. Robust evidence from studies in animals suggests that vitamin D deficiency may impair brain physiological functioning causing anatomical and behavioral adverse effects. On the other hand, vitamin D has been found to be protective against biological processes associated with Alzheimer's disease and cognition, including amyloid-β deposition, inflammation, calcium homeostasis, and corticosteroid-induced perturbations in cortical areas and the hippocampus. Human studies that examined the relationship between vitamin D status and cognitive function have provided inconclusive results. The majority of cross-sectional and longitudinal studies suggest a potentially protective association, whereas results from clinical trials are mostly negative, or at best, controversial. We review these studies in humans, with particular emphasis on randomized and observational prospective ones.
Keywords: Alzheimer's disease; amyloid; cholecalciferol; cognition; dementia; vitamin D.