BACKGROUND: Vitamin D is implicated in many processes in the central nervous system (CNS), such as neurogenesis, neurotransmitter synthesis, synaptogenesis and protection against oxidative stress, thereby exerting a neuroprotective effect. OBJECTIVE: In the present review, we aimed to evaluate the potential benefit(s) of vitamin D supplementation for CNS aging in different clinical contexts. METHODS: We performed a literature search, looking for clinical trials and randomized clinical trials evaluating the effect of vitamin D supplementation on different endpoints related to cognitive outcomes. RESULTS: Firstly, we identified 16 papers dealing with the impact of vitamin D supplementation on cognitive function in healthy subjects; the current literature suggests a real role for vitamin D supplementation in the prevention of cognitive decay in this clinical setting. Conversely, two papers suggest that vitamin D supplementation may be beneficial in patients with mild cognitive impairment (MCI). Finally, current data on vitamin D in Alzheimer's disease are contradictory. CONCLUSION: Vitamin D supplementation may improve the cognitive outcomes of patients with MCI, whereas there is no evidence that it may prevent dementia or modulate the course of Alzheimer's disease.