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Research study suggests vitamin D could reduce dementia risk

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Researchers have found that vitamin D supplementation could help to ward off dementia.

The large-scale study involving 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 per cent (4,637) took vitamin D supplements.

In the study, 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 10 years; amongst them, 2,017 (75 per cent) had no exposure to vitamin D throughout all visits prior to dementia diagnosis, and 679 (25 per cent) had baseline exposure.

Furthermore, 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.

Professor Zahinoor Ismail, of the University of Calgary and University of Exeter, who led the research, commented: “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.”

Co-author, Dr Byron Creese, at the University of Exeter, added: “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.”

In other vitamin D news, a new review published in Cochrane Library has suggested that vitamin D does not play a role in easing asthma.

Cochrane Review conducted an updated metaanalysis to include data from new trials to evaluate the effectiveness and safety of administration of vitamin D or its hydroxylated metabolites in reducing the risk of severe asthma exacerbations
(defined as those requiring treatment with systemic corticosteroids) and improving asthma symptom control.

Twenty studies were included in this review; 15 trials involving a total of 1,155 children and five trials involving a total of 1,070 adults contributed data to analyses. Participant ages ranged from one to 84 years, with two trials providing data specific to participants under five years and eight trials providing data specific to participants aged five-16. The duration of trials ranged from three to 40 months; all but two investigated the effects of administering cholecalciferol (vitamin D3). As
in a previous Cochrane Review, the majority of participants had mild to moderate asthma, and profound vitamin D deficiency (25‐hydroxyvitamin D (25(OH)D) < 25 nmol/L) at baseline was rare.

It was found that administration of vitamin D or its hydroxylated metabolites did not reduce or increase the proportion of participants experiencing one or more asthma exacerbations treated with systemic corticosteroids. They also found no effect of vitamin D supplementation on the rate of exacerbations requiring systemic corticosteroids or the time to first exacerbation. “Vitamin D supplementation did not influence  any secondary efficacy outcome meta‐analysed, which were all based on moderate‐ or high‐quality evidence,” the researchers reported, adding that they observed no effect on the incidence of serious adverse events.

The study continued: “In contrast to findings of our previous Cochrane Review on this topic, this updated review does not find evidence to support a role for vitamin D supplementation or its hydroxylated metabolites to reduce risk of asthma exacerbations or improve asthma control. Participants with severe asthma and those with baseline 25(OH)D concentrations < 25 nmol/L were poorly represented, so further research is warranted here.”

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