Ireland is predicted to have the highest older adult population growth of any European Union country. A substantial economic and social challenge of this projected growth is the increased incidence of cognitive impairment and the likelihood of progression to dementia. Dementia's, such as Alzheimer's disease, typically have a long prodromal stage with brain changes identifiable from the earliest stages of neuropathology, providing an opportunity for intervention. Switching to a strategy of earlier identification and prevention would significantly reduce prevalence and the associated cost.

The purpose of this pilot study is to evaluate the use of vitamin D supplements in community dwelling older adults as a lifestyle approach that may support cognitive and physical functioning. The research will incorporate several stages including an initial in-depth screening process, a novel and sensitive cognitive battery, 6 month double blind placebo controlled intervention of vitamin D3 (cholecalciferol) and a concluding participant feedback interview.

These results will be used to assess the feasibility of recruiting and assessing community dwelling older adults for extensive nutrition related cognitive studies.

Inclusion Criteria:

• Community Dwelling healthy volunteers
• Ability to provide written consent.

Exclusion Criteria:

• Measures low or high serum vitamin D, defined as < 15nmol/L or >125nmol/L
• Current use of supplemental vitamin D ≥800 international units/d
• Screen positive for cognitive impairment using the Telephone Cognitive Screen (TCogS)
• Measured hypercalcaemia, defined as corrected serum calcium > 2.7nmol/l
• Hyperparathyroidism
• Epilepsy
• Stroke
• Renal disease
• Schizophrenia
• Bipolar affective disorder
• Recurrent psychotic depression
• Alcohol and drug abuse within the past 5 years
• Anti-convulsants
• Anti-psychotic medications
• Significant hearing difficulties even when wearing hearing aid
• Illness that caused permanent decrease in memory or other mental function