Vitamin D and Alzheimer’s Disease

One of the more important—and often overlooked—nutrients for brain health is vitamin D. In my own experience with thousands of patients, optimizing vitamin D levels is a critical component for improving mental health. And, as a recent article highlights, the support that vitamin D provides isn’t just isolated to depression or anxiety symptoms. Vitamin D also appears to be a factor in the prevention of Alzheimer’s disease and other forms of dementia.

Vitamin D Deficiency and Dementia Risk

A recently published meta-analysis found that low levels of vitamin D, under 25 ng/mL, are associated with an almost 60% increased risk for dementia (Pinzon 2023). A 60% increased risk is a staggering finding, especially considering the already epidemic levels of dementia that are continuing to increase as the population ages.

While the article shows low vitamin D is associated with dementia, it did not investigate if vitamin D supplementation can reduce the risks. The authors state that additional research is needed on whether vitamin D can directly lower the incidence of Alzheimer’s disease.

Vitamin D Supplementation and Dementia

Fortunately, an earlier study published in March 2023 explores that question directly (Ghahremani 2023). The study followed over 12,000 elderly individuals who were initially free of dementia symptoms. The subjects were divided into two groups, those who had previously taken vitamin D and those who had not. If a participant who hadn’t been taking vitamin D started taking vitamin D during the study, they were excluded from the findings. Of the participants, 4637 were considered to have vitamin D exposure.

Over the following ten years, 74.8% of individuals with no exposure to vitamin D developed dementia. For those with a history of taking vitamin D, only 25.2% developed dementia. After adjusting for confounding factors, vitamin D supplementation was associated with a 40% reduction in dementia risk.

Vitamin D Deficiency

Considering the incidence of vitamin D deficiency, vitamin D supplementation could have a profound impact on reducing the tragic consequences associated with Alzheimer’s disease and dementia. In the United States, recent data shows that upwards of 25% of the population are deficient in vitamin D with 5.9% of cases being defined as severe (Schleicher 2016).

Levels in a number of other countries are even worse, with Europe having 40% of their population being found to be deficient (Cashman 2016). In India, Pakistan and Afghanistan, severe deficiency exceeds 20% of the population (Cashman 2019).

Conflicting Data?

While the findings above are intriguing, it is also worth mentioning a separate study claiming that “vitamin D” supplementation increases the risk for dementia progression (Lai 2022). While the study’s title is provocative, the study protocol was actually investigating dementia risk and calcitriol, a prescription medication which is not recommended for treating the most common forms of vitamin D deficiency.

Generally, calcitriol is only prescribed for patients where the kidneys’ ability to activate vitamin D is impaired, usually in cases of severe kidney failure or hypoparathyroidism. It is also worth noting that patients with hypoparathyroidism or kidney disease have higher risks for developing dementia (Sardella 2021, Etgen 2015).

Based on the fact that the study focused on calcitriol, the statement that vitamin D supplementation, which is typically provided as cholecalciferol (vitamin D3) or ergocalciferol (vitamin D2), is a cause of worsening dementia is unfounded. In reality, it shouldn’t be too surprising that patients taking calcitriol due to kidney failure or hypoparathyroidism have a higher risk for severe outcomes, including dementia. Thus, the study’s findings should not be extrapolated beyond calcitriol to standard forms of vitamin D supplementation.

Takeaway

As a supplement, vitamin D plays an important role in mental health. Based on the latest findings, supplementation may also have a significant role to play in addressing the epidemic of Alzheimer’s disease and dementia. Considering the devastating costs of dementia, both financially and to individual families, significantly reducing its incidence could provide immeasurable benefits.

References

Cashman KD, Dowling KG, Škrabáková Z, et al. Vitamin D deficiency in Europe: pandemic?. Am J Clin Nutr. 2016;103(4):1033-1044. doi:10.3945/ajcn.115.120873

Cashman KD, Sheehy T, O’Neill CM. Is vitamin D deficiency a public health concern for low middle income countries? A systematic literature review. Eur J Nutr. 2019;58(1):433-453. doi:10.1007/s00394-018-1607-3

Etgen T. Kidney disease as a determinant of cognitive decline and dementia. Alzheimers Res Ther. 2015;7(1):29. Published 2015 Mar 17. doi:10.1186/s13195-015-0115-4

Ghahremani M, Smith EE, Chen HY, Creese B, Goodarzi Z, Ismail Z. Vitamin D supplementation and incident dementia: Effects of sex, APOE, and baseline cognitive status. Alzheimers Dement (Amst). 2023;15(1):e12404. Published 2023 Mar 1. doi:10.1002/dad2.12404

Lai RH, Hsu CC, Yu BH, et al. Vitamin D supplementation worsens Alzheimer’s progression: Animal model and human cohort studies. Aging Cell. 2022;21(8):e13670. doi:10.1111/acel.13670

Pinzon RT, Handayani T, Wijaya VO et al. Low vitamin D serum levels as risk factor of Alzheimer’s disease: a systematic review and meta-analysis. Egypt J Neurol Psychiatry Neurosurg. 2023;59(88). https://doi.org/10.1186/s41983-023-00676-w

Sardella A, Bellone F, Morabito N, et al. The association between hypoparathyroidism and cognitive impairment: a systematic review. J Endocrinol Invest. 2021;44(5):905-919. doi:10.1007/s40618-020-01423-1

Schleicher RL, Sternberg MR, Looker AC, et al. National Estimates of Serum Total 25-Hydroxyvitamin D and Metabolite Concentrations Measured by Liquid Chromatography-Tandem Mass Spectrometry in the US Population during 2007-2010. J Nutr. 2016;146(5):1051-1061. doi:10.3945/jn.115.227728