The global rise in neurodegenerative diseases, such as dementia and Alzheimer’s, has spurred increased interest in preventative strategies, including the potential role of vitamins and supplements. Among these, vitamin D has emerged as a significant area of focus, with growing evidence suggesting a link between its levels in the body and the risk of cognitive decline. This article will delve into the relationship between vitamin D and dementia, exploring the current research, potential mechanisms, and implications for prevention.
Based on the latest research, there is a strong link between low vitamin D levels and an increased risk of dementia and Alzheimer’s disease. If you want to learn more, keep reading. and learn the potential benefits of vitamin D supplementation and how it may protect your brain. I’ll also break down the risk factors for vitamin D deficiency and the current research that’s exploring these connections, so you can make the best decisions about your health.
Understanding Vitamin D
Vitamin D is a crucial nutrient vital for various bodily functions, including bone health, immune function, and potentially brain health. The body primarily produces vitamin D through exposure to sunlight. However, it can also be obtained through dietary sources, including foods such as trout, salmon, white mushrooms, milk, and soy. In addition, vitamin D supplements are available for those who may not get enough through sunlight or diet.
Vitamin D deficiency is generally defined as having blood serum levels of less than 30 nanomoles per liter (nmol/L) or 12 nanograms per milliliter (ng/mL). Some studies define deficiency as less than 25 nmol/L. Vitamin D insufficiency is defined as levels between 30 and 50 nmol/L. Testing for vitamin D levels is done through a blood test that measures 25-hydroxyvitamin D. It is also important to note that vitamin D is a fat-soluble vitamin, meaning it can be stored in adipose (fatty) tissue, which can impact the levels circulating in the blood.
The Link Between Vitamin D Deficiency and Dementia
A growing body of research suggests a significant connection between low vitamin D levels and an increased risk of major neurocognitive disorders, including Alzheimer’s disease and vascular dementia.
- A UK Biobank study found that vitamin D deficiency was associated with a 25% increased risk of dementia, while insufficiency was linked to an 11% increased risk.
- A study of over 12,000 participants indicated that taking vitamin D supplements may help ward off dementia, with a 40% reduction in dementia diagnoses in those who took supplements.
- A 2019 meta-analysis found an increased risk of Alzheimer’s disease in individuals with low vitamin D levels.
- A separate meta-analysis of six studies with 10,884 individuals found that patients with serum vitamin D levels less than 25 ng/mL had an increased risk of developing Alzheimer’s disease.
- Further, a study found that individuals who were deficient in vitamin D had approximately a 51% increased risk of all-cause dementia, whereas those who were severely deficient had about a 122% increased risk.
- Several studies have highlighted that low vitamin D levels are associated with a higher risk of dementia and that the risk increases significantly when vitamin D levels are below 50 nmol/L.
- One study found that vitamin D supplementation was associated with living dementia-free for a longer period of time.
- Studies have also suggested that people with the APOEe4 gene may absorb vitamin D better, potentially reducing the effect of supplementation.
- However, one study noted that individuals with darker skin did not show an association between vitamin D levels and dementia risk.
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Mechanisms: How Vitamin D May Protect the Brain

The precise mechanisms through which vitamin D may protect the brain are still being investigated. However, several potential pathways have been identified:
- Vitamin D may help in breaking down beta-amyloid plaques and preventing amyloid-induced neuronal apoptosis.
- It may also offer protection against tau hypo-phosphorylation.
- Vitamin D is involved in the clearance of amyloid in the brain.
- It may protect against the build-up of tau, another protein associated with dementia.
- Vitamin D receptors are present throughout the brain.
- Vitamin D may help to protect against neural inflammation and inhibit pro-inflammatory cytokines.
- It has been suggested to provide neuroprotection, supporting neurotrophy, neurotransmission, and neuroplasticity.
Risk Factors for Vitamin D Deficiency
Certain factors can increase an individual’s risk of vitamin D deficiency:
- Living at higher latitudes with less sunlight exposure is a significant factor.
- Obesity is also a risk factor, as vitamin D can be sequestered in adipose tissue, reducing its availability in the blood.
- Other risk factors include having darker skin, less education, and infrequent milk consumption.
- Vitamin D deficiency is common, with up to a quarter of individuals in the US and up to 40% of Europeans affected.
- Obese adults are three times more likely to experience vitamin D deficiency.
The Role of Vitamin D Supplementation
Given the links between low vitamin D and dementia, supplementation is a potential preventative strategy.
- Studies have shown that taking vitamin D supplements may be associated with living dementia-free for a longer period.
- There is also evidence that people who take vitamin D may have a lower risk of dementia.
- Specifically, one study found that people with vitamin D had 40% less dementia.
- The benefits appear to be more significant in females compared to males, in people with normal cognition compared to those with mild cognitive impairment, and in people who do not carry the APOEe4 gene.
- Research suggests that earlier supplementation may be more beneficial, before cognitive decline sets in.
- It is important to note that the optimal level of vitamin D remains controversial, with some organizations recommending 50 nmol/L and others 75 nmol/L.
- Current government guidelines on supplementation may be inadequate. For example, UK guidelines recommend 10 micrograms per day, while some people take 100 micrograms daily.
Observational vs. Interventional Studies
Many studies on vitamin D and dementia are observational, showing correlations but not proving causation. More interventional studies, such as clinical trials, are needed to determine whether vitamin D supplementation can prevent or delay dementia. There is debate about the evidence that shows that supplementing with vitamin D prevents or reverses diseases. It is also noted that pharmaceutical companies may not fund studies on treatments like vitamin D that they cannot profit from.
Additional Considerations and Current Research

It is important to emphasize the need to consult with a healthcare provider before starting any vitamin D supplementation.
- Several ongoing studies are exploring the role of vitamin D in cognitive health:
- The VitaMIND study is investigating the effects of vitamin D on memory and thinking.
- The CAN-PROTECT study aims to identify risk factors for dementia prevention.
- A study using the PROTECT online study is also underway.
- Further research is also needed on the long-term experience of individuals who care for people with dementia.
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Conclusion
The current evidence suggests a strong association between vitamin D levels and the risk of dementia and Alzheimer’s disease. Maintaining adequate vitamin D levels appears to be a modifiable risk factor that may play a role in preventing or delaying the onset of dementia. While the precise mechanisms are still under investigation and more interventional studies are needed, the findings to date indicate that addressing vitamin D deficiency may have a beneficial impact on cognitive health.
Note: It is important for individuals to discuss their vitamin D levels with their healthcare providers and consider supplementation when appropriate. If you’re interested in participating in related research, you are encouraged to sign up for studies like PROTECT and CAN-PROTECT.
Frequently Asked Questions: Vitamin D and Dementia
- What is the connection between vitamin D and dementia? Research indicates a significant link between low vitamin D levels and an increased risk of developing dementia, including Alzheimer’s disease and vascular dementia. Studies have consistently shown that people with lower levels of vitamin D in their blood are more likely to be diagnosed with dementia compared to those with sufficient levels.
- How does vitamin D potentially protect against dementia? Vitamin D may protect against dementia through several mechanisms, including:
- Helping the brain clear amyloid plaques, which are abnormal protein clumps associated with Alzheimer’s.
- Providing neuroprotection by supporting the survival, function, and development of neurons.
- Reducing neural inflammation by inhibiting pro-inflammatory cytokines.
- Offering protection against the build-up of tau protein, which is also involved in dementia.
- Improving vascular function, which can reduce the risk of stroke, a risk factor for dementia.
- What are the recommended levels for vitamin D? Vitamin D levels are measured in nanomoles per liter (nmol/L) or nanograms per milliliter (ng/mL). Generally:
- Deficiency is defined as a level below 30 nmol/L (12 ng/mL) or sometimes 25 nmol/L (10 ng/mL).
- Insufficiency is typically considered to be levels between 30 nmol/L and 50 nmol/L (12-20 ng/mL).
- Sufficiency is generally considered to be levels above 50 nmol/L (20 ng/mL), with some experts recommending levels above 75 nmol/L (30 ng/mL).
- What factors can contribute to vitamin D deficiency? Several factors can increase the risk of vitamin D deficiency:
- Limited sun exposure due to living at higher latitudes or spending less time outdoors.
- Diet low in vitamin D-rich foods.
- Obesity, as excess body fat can sequester vitamin D.
- Darker skin, which produces less vitamin D from sun exposure.
- Older age, due to less time outdoors and reduced production capacity.
- Other medical conditions that can impair the body’s ability to produce or absorb vitamin D.
- Who benefits most from vitamin D supplementation? Studies suggest that certain groups may experience greater benefits from vitamin D supplementation:
- Females, compared to males.
- Individuals with normal cognition, versus those with mild cognitive impairment.
- Non-carriers of the APOEe4 gene, which is known to increase the risk of Alzheimer’s.
- Younger individuals (ages 55-64).
- How effective is vitamin D supplementation in preventing dementia? Research indicates that vitamin D supplementation is associated with a lower risk of developing dementia:
- Some studies show that taking Vitamin D is associated with living dementia-free for longer.
- Other studies found up to a 40% reduction in dementia diagnoses in groups that took vitamin D supplements.
- The associations were stronger when supplementation started earlier, particularly before the onset of cognitive decline.
- However, current data comes primarily from observational studies, which show association but don’t prove direct causation. Larger clinical trials are needed to confirm these findings.
- What are the recommended doses for vitamin D? Recommended daily doses of vitamin D can vary, and some experts advise higher doses than current guidelines.
- Are there any study limitations regarding vitamin D and dementia? Yes, there are several limitations:
- Much of the evidence comes from observational studies, which cannot prove direct causation.
- It is difficult to control for all the lifestyle and genetic factors that could impact dementia risk, besides Vitamin D.
- Reverse causation is possible, where cognitive decline might lead to dietary changes and reduced outdoor activities, lowering Vitamin D levels.
- There is a lack of large, randomized, controlled trials to show that Vitamin D supplementation prevents dementia.
- Studies can vary significantly in how they classify deficiency, the populations they study, dosages used, and how dementia is assessed.
- Some studies have shown that the link between Vitamin D and dementia may not be as strong in people with darker skin.
- The APOEe4 gene has been identified as a factor that may influence Vitamin D absorption and thus effectiveness of supplements.
- Where can I learn more about vitamin D and dementia research? You can find more information and get involved in ongoing research through:
- The VitaMIND study.
- The PROTECT online study.
- The CAN-PROTECT study.
- What should I do if I think I might be deficient in Vitamin D?
It’s recommended to consult with your healthcare provider to have your Vitamin D levels tested, discuss appropriate supplementation, and to get personalized recommendations based on your individual needs and health status.
*Note: It is important for individuals to discuss their vitamin D levels with their healthcare providers and consider supplementation when appropriate.