Vitamin D Supplementation May Help Prevent Dementia: A Prospective Study

Dementia is a global health challenge that affects millions of people worldwide, and the number of cases is expected to triple by 2050. While there is no cure for dementia, there are ways to reduce the risk of developing it, such as maintaining a healthy lifestyle and managing chronic diseases. In recent years, research has suggested a potential link between vitamin D deficiency and dementia.

A new study prospective study published this week in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoringexplored the associations between vitamin D supplementation and incident of dementia.

According to 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 Study

The study was conducted by the National Alzheimer's Coordinating Center and included 12,388 participants who were dementia-free at baseline. The participants were categorized based on their exposure to vitamin D: D+ for those who had been exposed to vitamin D prior to dementia onset and D- for those who had not. The study included various formulations of vitamin D, and the researchers explored potential interactions between exposure and model covariates.


The study found that vitamin D exposure was associated with significantly longer dementia-free survival and lower dementia incidence rate than no exposure. Participants who had been exposed to vitamin D supplementation had a 40% lower incidence rate of dementia compared to those who had not been exposed.

In fact, 75% of people in the study who didn’t take vitamin D developed dementia within 10 years. Of those who took vitamin D, 25% also developed dementia.

The researchers found that vitamin D gave greater protective benefits among women than men, although protection among both sexes was significant compared to not taking any vitamin D. Also, protection appeared to be better if people started taking the supplement before any signs of cognitive issues.

According to the study, vitamin D exhibited more protective effects among women than men. However, both sexes experienced significant protection compared to non-users. Moreover, the study suggests that starting the supplementation before the onset of cognitive issues may yield better results.

According to the study, individuals who carried the APOEe4 gene, associated with a higher risk of Alzheimer's dementia, had significantly less protective effects from vitamin D than non-carriers. The authors proposed that carriers of the APOEe4 gene may have better clearance of vitamin D from their intestines, potentially reducing the effectiveness of vitamin D supplementation. However, the hypothesis was not tested through blood level measurements.

Previous research has indicated that low vitamin D levels are associated with a higher risk of dementia, and vitamin D can aid in clearing amyloid in the brain, a hallmark of Alzheimer's disease. Furthermore, studies suggest that vitamin D may also offer protection against the buildup of tau, another protein involved in the development of dementia.

Figure 1 - (A) KM curve of dementia-free survival over 10 years, stratified by exposure to vitamin D. (B) Adjusted HR for dementia across vitamin D exposure groups.


Vitamin D is an essential nutrient that plays a vital role in bone health and immune system function. It is known that vitamin D deficiency is widespread, especially in the elderly population. Additionally, vitamin D deficiency has been associated with various health conditions, such as cardiovascular disease, diabetes, and cancer.

The study's findings support the idea that vitamin D may be a crucial factor in preventing dementia. However, the study was observational and not a randomized controlled trial(RCT). This means that it's possible that other factors could have affected the results; for example, people who choose to take vitamin D supplements may have other lifestyle choices that contribute to their health outcomes.The researchers did not intervene in the participants' vitamin D intake.

Therefore, the study cannot establish causation between vitamin D supplementation and dementia prevention. Nonetheless, the results of the study provide valuable insights into the potential benefits of vitamin D supplementation.

It is worth noting that the study did not specify the optimal dose of vitamin D required for dementia prevention. The recommended daily intake of vitamin D varies across different age groups and health conditions. The best way to determine the appropriate dose of vitamin D is to consult a healthcare provider.


Dementia is a global health challenge that requires urgent attention. While there is no cure for dementia, research has suggested that certain lifestyle factors, such as maintaining a healthy diet and exercise regimen, may reduce the risk of developing the disease. The study discussed in this article suggests that vitamin D supplementation may also play a significant role in preventing dementia. Further research is needed to establish causality and also determine the optimal dose of vitamin D required if causality is finally established.

  1. Ghahremani, M, Smith, EE, Chen, H-Y, Creese, B, Goodarzi, Z, Ismail, Z. Vitamin D supplementation and incident dementia: Effects of sex, APOE, and baseline cognitive status. Alzheimer's Dement. 2023; 15:e12404.

  2. Alzheimer's Association. (2021). Alzheimer's disease facts and figures. Alzheimer's & Dementia, 17(3), 327-406.

  3. Annweiler, Cédric, et al. "Cognitive effects of vitamin D supplementation in older outpatients visiting a memory clinic: a pre–post study." Journal of the American Geriatrics Society 60.4 (2012): 793-795.

  4. Knekt, Paul, et al. "Serum 25-hydroxyvitamin d concentration and risk of dementia." Epidemiology (2014): 799-804.

  5. Littlejohns, T. J., Henley, W. E., Lang, I. A., Annweiler, C., Beauchet, O., Chaves, P. H., Kestenbaum, B. R., Kuller, L. H., Langa, K. M., Lopez, O. L., et al. (2014). Vitamin D and the risk of dementia and Alzheimer disease. Neurology, 83(10), 920-928.

  6. Manson, J. E., Brannon, P. M., Rosen, C. J., & Taylor, C. L. (2016). Vitamin D deficiency-is there really a pandemic. N Engl J Med, 375(19), 1817-1820.

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