Is vitamin D supplementation of potential benefit for community-living people with Alzheimer’s disease?

Background: Vitamin D is associated not only with effects on calcium and bone
metabolisms but also with many chronic diseases. Low vitamin D levels in
patients with Alzheimer’s disease have been widely reported in the literature.
Aim: The purpose of this study was to critically review the potential benefit of
vitamin D supplementation in individuals with Alzheimer’s disease living in the
community. Methods: A systematic literature search was conducted in PubMed,
CINAHL, EMBASE and the Cochrane Library for papers published 2011–2018.
Results: Seven papers were selected, consisting of one clinical trial, five cohort
studies and one systematic review. Studies showed an association only between
vitamin D deficiency and lower attention in older people. None of the reviewed
studies provided evidence of a positive impact of vitamin D supplementation
on cognitive function in older people with Alzheimer’s disease. Conclusion:
There was no evidence that vitamin D supplementation has a direct benefit for
Alzheimer’s disease. The review synthesised the existing body of knowledge and
concluded that optimum levels of vitamin D (neither too low nor too high) do
appear to have positive effects on patient outcomes and quality of life. It is still
unclear why vitamin D intake is inadequate as people age. Further research is
needed to clarify vitamin-D-related aspects of Alzheimer’s disease.