Vitamin D Supplements May Prevent Dementia
Akshay Naik 09 March 2023
Vitamin D supplements have the potential to be a viable dementia prevention method, especially when initiated early, new research suggests. 
The study, published in the scientific journal Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, was undertaken by researchers at the University of Calgary’s Hotchkiss Brain Institute in Canada and the University of Exeter in the UK. They explored the relationship between vitamin D supplementation and dementia in 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. 
Among the participants, 4,637 (37%) took vitamin D supplements, while the rest were considered to be the control group. The survey found that people who took vitamin D supplements were 40% less likely to develop dementia than peers who did not take vitamin D. Across the entire sample, 2,696 participants progressed to dementia over 10 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, 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,” lead researcher Prof Zahinoor Ismail, with the Hotchkiss Brain Institute, explained. 
Analysis of the gathered data indicated that the effects of vitamin D were significantly higher in women, compared to men. Similarly, the effects were higher in people with normal cognition, compared to those who reported signs of mild cognitive impairment which have been linked to a higher risk of dementia. 
Intake of vitamin D supplements and their effects were also found to be significant in people who did not carry the APOEe4 gene, known to present a higher risk for Alzheimer’s dementia, compared to non-carriers. Researchers of this study suggest that people who carry the APOPEe4 gene absorb vitamin D better from their intestines which might reduce the vitamin D supplementation effect. However, this was just a stated hypothesis which was not tested through examination of blood levels in the participants. 
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. Other studies and research have found that vitamin D may provide help to protect the brain against build-up of tau, another protein involved in the development of dementia. 
While the results sound promising, the researchers have cautioned that the study has several limitations. Significantly, there was no recorded data on the dose or duration of vitamin D exposure or baseline serum vitamin D levels. They note that clarification on exposure duration, dose-response relationships and the role of vitamin D deficiency will be necessary to inform intervention studies. 
“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,” said Dr Byron Creese from the University of Exeter.
He further added that the ongoing VitaMIND study at the University of Exeter is exploring this issue in depth, by randomly assigning participants to either take vitamin D or a placebo. They are also examining changes in memory and thinking tests, over a given period of time.
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