Taking vitamin D could help prevent dementia

Taking vitamin D supplements may help ward off dementia, according to a new, large-scale study by scientists in the UK and Canada, using data from US patients.

Based on 12,388 participants from the US National Alzheimer’s Coordinating Center, who had a mean age of 71 and were dementia-free when they signed up, researchers from the University of Exeter and the University of Calgary explored the link between vitamin D and brain health.

Of the large group included in the study, 37 per cent (4,637) took vitamin D supplements. In a paper, published in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, the team found that taking vitamin D was associated with living dementia-free for longer, and they also found 40 per cent fewer dementia diagnoses in the group who took 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.

‘We know that vitamin D has some effects in the brain that could have implications for reducing dementia,’ said Prof Zahinoor Ismail, of the University of Calgary and University of Exeter, who led the research. ‘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.’

While Vitamin D was effective in all groups, the team found that effects were significantly greater in females, compared to males. Similarly, effects were greater in people with normal cognition, compared to those who reported signs of mild cognitive impairment – changes to cognition which have been linked to a higher risk of dementia.

The effects of vitamin D 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 vitamin D 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. Vitamin D 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 linked to the development of dementia.

‘Preventing dementia or even delaying its onset is vitally important given the growing numbers of people affected,’ said Dr Byron Creese, University of Exeter. ‘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.’