Vitamin D may reduce the risk of dementia because it clears amyloid that accumulates in the brain.
Dementia diagnoses decreased by 40% in patients who took vitamin D supplements, according to a study published in Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring. However, the benefits of supplementation were greater for people who have normal cognition.
“We know that vitamin D has some effects in the brain that could have implications for reducing dementia, however so far, research has yielded conflicting results. Our findings give key insights into groups who might be specifically targeted for vitamin D supplementation,” said lead investigator Zahinoor Ismail, University of Calgary and University of Exeter, in a press release.
Over the 10-year study period, 2696 (22%) patients examined in the research developed dementia. Among those diagnosed, 75% were not exposed to any variation of a vitamin D supplement, whereas 25% had taken vitamin D supplementation at baseline.1
Previous research found that low levels of vitamin D are associated with the risk of dementia. Vitamin D may reduce the risk because it clears amyloid (a marker of Alzheimer disease) that accumulates in the brain, and it can protect against the build-up of tau, a protein that may contribute to dementia, according to the investigators.1
“Preventing dementia or even delaying its onset is vitally important given the growing numbers of people affected,” said Byron Creese, University of Exeter, in the press release.1
Investigators at the University of Calgary in Canada and the University of Exeter in the UK conducted the VitaMIND study to better understand the link between dementia and vitamin D supplementation. The cohort included 12,388 participants (mean age 71 years) from the US National Alzheimer's Coordinating Center without dementia at enrollment. Among participants, 37% took a vitamin D supplement.1
Vitamin D significantly reduced the risk of dementia in females compared to males.1 It also presented a more favorable response in patients with normal cognitive function compared to those with mild cognitive impairment.1 The 5-year dementia-free survival rates were 83.6% in the supplement group and 68.4% in the no-supplement group.2
The APOEe4 gene could be a relevant marker for vitamin efficacy, because those with the gene had better outcomes with vitamin D supplementation. The authors hypothesize that people who carry the gene absorb vitamin D in the intestine, which prevents the supplement from being absorbed to other parts of the body.1
However, the research is still unclear, according to Ismail.2 Claire Sexton, DPhil, senior director of scientific programs and outreach at the Alzheimer's Association in Chicago, adds that the study cannot establish causation, nor is it recommended to take a supplement to reduce risk.2
Nevertheless, “the link with vitamin D in this study suggests that taking vitamin D supplements may be beneficial in preventing or delaying dementia,” Creese said in the press release.1 “We now need clinical trials to confirm whether this is really the case.”