Vitamin D and Alzheimer’s Disease Risk: What We Know So Far

Research done in animals and cells in a laboratory indicates that vitamin D has a neuroprotective effect.

It has been found to decrease amyloid beta production and may also protect against changes in tau protein that may contribute to AD. But it’s not clear whether any aspect of these research results has an effect on humans.

Research has also linked low vitamin D with a higher risk of AD. A 2014 study found that, compared to those with sufficient vitamin D, participants who were deficient in vitamin D had a higher risk of dementia and AD.

Results like these raised the question of whether or not supplementation with vitamin D could reduce the risk of AD. Generally speaking, results have been mixed.

A 2020 review analyzed nine clinical trials of the effects of vitamin D supplements on AD risk. The reviewers didn’t find enough evidence to support the use of vitamin D for preventing AD and note that more research is needed.

A 2023 study explored vitamin D and AD risk. It found that vitamin D exposure was associated with living longer without dementia and 40% lower dementia incidence in general compared to no vitamin D exposure.

The study also highlighted certain groups that may receive the most benefits from vitamin D regarding AD risk. These included:

• people assigned female at birth
• people with standard cognition, as opposed to those with mild cognitive impairment (MCI)
• people who didn’t carry the apolipoprotein E ε4 gene, a known risk factor for AD

While vitamin D has many health benefits, getting too much vitamin D from supplements is potentially harmful. According to the National Institutes of Health (NIH), having too much vitamin D in your blood can lead to:

• nausea or vomiting
• reduced appetite
• excessive urination and thirst
• dehydration
• muscle weakness
• pain
• kidney stones
• confusion

Very high levels can cause irregular heart rate, kidney failure, and potentially death. The NIH also notes that most instances of excess vitamin D are in people taking vitamin D supplements.

The amount of daily vitamin D that’s recommended for you depends on your age. The table below shows daily vitamin D recommendations according to the NIH.

NIH vitamin D recommendations

Your body naturally produces vitamin D in response to sunlight. While some research suggests 5–30 minutes of sun exposure most days of the week can lead to sufficient vitamin D production, this can vary based on:

• the season and length of the day
• whether or not there’s a lot of cloud cover
• air pollution
• sunscreen use
• skin melanin content

Prolonged sun exposure is also linked to the development of skin cancer. As such, it’s also a good idea to enrich your diet with foods that are high in vitamin D.

Some examples of foods that are rich in vitamin D include:

• certain fish, including:
  • fatty fish like trout, salmon, and mackerel
  • canned tuna
  • herring and canned sardines
• egg yolks
• beef liver
• mushrooms
• vitamin D-fortified foods, such as:
  • milk
  • soy milk or almond milk
  • certain yogurts
  • orange juice
  • some breakfast cereal products

Is there a link between vitamin D and worsened Alzheimer’s?

One 2022 study of animal models and a human cohort suggested that vitamin D supplementation worsened AD. However, the authors of a 2023 article questioned this study’s methods and interpretation of results.

Results on whether or not vitamin D improves function in dementia have been mixed. Some studies have seen the benefits of vitamin D for MCI and AD. However, a 2022 review didn’t find enough evidence that vitamin D improves function.

What is the best vitamin supplement for Alzheimer’s?

The National Center for Complementary and Integrative Health (NCCIH) notes that while some studies have shown modest effects for some supplements in preventing cognitive decline and dementia, direct evidence is lacking.

The organization does note that the most consistent positive results have been in studies of omega-3 fatty acid supplements.

How much vitamin D is needed to prevent dementia?

A causal link between low vitamin D and dementia hasn’t been proven. However, it’s known that low vitamin D can cause a variety of health problems. As such, it’s always a good rule of thumb to ensure you’re getting sufficient daily vitamin D.

The NIH recommends that most people get 15 mcg (600 IU) of vitamin D each day for general health.

Research has linked low vitamin D with a higher risk of AD. However, the results of studies on whether or not vitamin D supplementation reduces the risk of AD have been mixed. Overall, more research into this topic is needed.

You can get vitamin D by sun exposure and via your diet. Individuals who cannot get enough vitamin D through these routes may need to take a supplement. Always talk with your doctor before adding any new supplements to your diet.