Dementia is a syndrome usually progressive and chronic in nature. Global incidences of dementia is increasing at a rate of one new case every three seconds with associated medical social and health care costs far exceeding the capacity of most countries. Because of the degenerative nature of the disease sufferers lose their ability to perform routine tasks, experience poor quality of life and loss of autonomy. The role of vitamin D in the etiology of cognitive impairment and dementia is plausible and has been supported substantial mechanistic and epidemiological data. As people age, they tend to spend less and less time outdoors in the sun. It is of great importance as vitamin D deficiency is a worldwide pandemic and is seen most commonly in older adults residing in northerly latitudes, particularly during winter months. Further research needs to be done to see if increasing vitamin D level will improve cognitive health (Aspell, Lawlor, O'Sullivan, 2018).