The May 2009 issue of the Journal of Alzheimer's Disease explains why further investigation is needed to identify any causative linkages between vitamin D and dementia, including the type known as Alzheimer's disease. As an example of how risk factors for the development of Alzheimer's 
disease and vascular dementia could be directly related to vitamin D deficiencies, Dr. Grant cites several studies that have correlated tooth loss with the development of cognitive impairment and Alzheimer's or vascular dementia. Tooth loss is the result of dental caries and/or periodontal disease -- and both those conditions are linked to low levels of vitamin D.
In addition, Dr. Grant's article explains that ample biological evidence has accumulated showing how critical vitamin D is to healthy brain development and function. In fact, vitamin D in sufficient amounts seems to protect brain cells and reduce inflammation. A lack of vitamin D has been associated with increased inflammation and a pro-inflammatory state has been linked, in turn, with dementia.
Dr. Grant is calling for studies of levels of vitamin D in people before dementia is diagnosed and research to determine if vitamin D supplementation is warranted to potentially prevent dementia. In addition, because elderly people are frequently deficient in vitamin D, he suggests that those over 60 years old should consider having their serum vitamin D level tested and, if their vitamin D status is low, he recommends taking 1000 to 2000 IU a day of vitamin D3 supplements and/or increasing the time they spend in the sun year round.
"There are established criteria for causality in a biological system. The important criteria include strength of association, consistency of findings, determination of the dose-response relation, an understanding of the mechanisms, and experimental verification," Dr. Grant states in the Journal of Alzheimer's Disease article. "To date, the evidence includes observational studies supporting a beneficial role of vitamin D in reducing the risk of diseases linked to dementia such as vascular and metabolic diseases, as well as an understanding of the role of vitamin D in reducing the risk of several mechanisms that lead to dementia.
"Finding out how vitamin D might be able to help prevent and perhaps treat Alzheimer's and other dementias can't come a moment too soon. The Alzheimer's Association recently reported that 5.3 million Americans currently have Alzheimer's disease. It is the seventh-leading cause of death in the U.S.
