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

Abstract

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.