 Methods: A total of 30 subjects of both genders older than 65 years with levels of 25-OH Vitamin D lower than 30 ngml on routine laboratory screening will be referred by the treating family physicianfor screening. Subjects will be required to provide written informed consent for inclusion in the study. Exclusion criteria will include any active or unstable medical condition as determined by the treating physician, known neurocognitive disorder, known affective disorder, the use of any class of antidepressant drugs, the use of supplements containing vitamin D in any dose, significant visual or hearing impairment not corrected by spectacles or hearing aids, and a level of literacy that limits cognitive ability. All subjects will undergo cognitive screening by use of the MoCA test, computerized cognitive assessment using the the Neurotrax Mindstreams computerised cognitive assessment battery, and the 15-item Geriatric Depression Scale. All subjects will undergo repeat testing for level of 25-OH Vitamin D, and where below-normal levels are confirmed patients will receive a supplemental monthly oral dose of 60000 units Vitamin D administered by a nurse for a period of 3 months. At 3 months subjects will undergo repeat testing for level of 25-OH Vitamin D, and repeat computerized cognitive assessment using the Neurotrax Mindstreams battery and the 15-item Geriatric Depression Scale GDS. 