Vitamin D supplements could prevent dementia

Vitamin D may be a potential agent for dementia prevention after a new large-scale study showed supplementation led to higher dementia-free survival and lower dementia incidence rates over 10 years.

The study, published in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, found that vitamin D exposure was associated with 40% lower dementia incidence versus no exposure, and effects were significantly greater in females versus males and in normal cognition versus mild cognitive impairment.

Researchers at the University of Calgary’s Hotchkiss Brain Institute in Canada and the University of Exeter in the UK explored the relationship between vitamin D supplementation and dementia in more than 12,388 participants of the US National Alzheimer’s Coordinating Center, who had a mean age of 71 and were dementia-free when they signed up. Of the group, 37% (4,637) took vitamin D supplements.

Across the entire sample, 2,696 participants progressed to dementia over ten years; amongst them, 2,017 (75%) had no exposure to vitamin D throughout all visits prior to dementia diagnosis, and 679 (25%) had baseline exposure.

Early vitamin D supplementation is beneficial

Professor Zahinoor Ismail, of the University of Calgary and University of Exeter, who led the research, said: “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. Overall, we found evidence to suggest that earlier supplementation might be particularly beneficial, before the onset of cognitive decline.”

The effects were also significantly greater in people who did not carry the APOEe4 gene, known to present a higher risk for Alzheimer’s dementia, compared to non-carriers. The authors suggest that people who carry the APOEe4 gene absorb vitamin D better from their intestine, which might reduce the supplementation effect. However, no blood levels were drawn to test this hypothesis.

Previous research has found that low levels of vitamin D are linked to higher dementia risk. It is involved in the clearance of amyloid in the brain, the accumulation of which is one of the hallmarks of Alzheimer’s disease. Studies have also found that vitamin D may provide help to protect the brain against build-up of tau, another protein involved in the development of dementia.

Co-author Dr Byron Creese, at the University of Exeter, said: “Preventing dementia or even delaying its onset is vitally important given the growing numbers of people affected.  The link with vitamin D in this study suggests that taking vitamin D supplements may be beneficial in preventing or delaying dementia, but we now need clinical trials to confirm whether this is really the case.  The ongoing VitaMIND study at the University of Exeter is exploring this issue further by randomly assigning participants to either take vitamin D or placebo and examining changes in memory and thinking tests over time.”

The VitaMIND study is run via PROTECT, an online study open to people aged 40 and over. In PROTECT annual questionnaires on detailed lifestyle factors combine with cognitive testing, to determine what keeps the brain sharp in later life. To find out more or to sign up, visit their website. In Canada, CAN-PROTECT, is a linked online study on aging, in people aged 40 and over, with an additional focus on caregiving in dementia.