Alzheimer’s disease (AD) can be devastating. Research to date suggests higher blood levels of vitamin D may help prevent AD and recent animal studies indicate high-dose vitamin D supplementation may help treat the disease by reducing the abnormal proteins in the brain that are associated with the disease. As vitamin D is remarkably safe, we believe middle-aged and older adults should keep their vitamin D blood levels in the higher range of normal (70 – 80 ng/ml; (175 – 200 nmol/l). This usually requires 10,000 IU/day (250 mcg) or more, but such doses should be monitored by having a vitamin D blood level determined once or twice a year. If your loved one has AD, and you want to try high-dose vitamin D treatment, such as 20,000 IU/day (500 mcg), it is imperative that frequent vitamin D blood levels be obtained to ensure vitamin D toxicity does not occur.
Alzheimer’s disease (AD) is an illness that causes memory problems and other cognitive dysfunctions that may result in unpredictable changes in behavior. Usually, it’s progressive, which means it develops slowly and worsens over time. AD is the most common form of dementia. Dementia is the medical word used for loss of cognitive function that is serious enough to interfere with an individual’s daily life. Currently, there is no cure for AD.
There are two main changes that take place in the brain when an individual develops AD:
Some of the main symptoms are:
These are different than the normal changes that happen as some individuals age, such as occasionally forgetting names or losing things from time to time. Did you know older people love it when young people lose their phone or keys, or can’t remember the word they want to use? Such forgetting by young people reminds us that the forgetting that worsens as we age is seldom dementia.
AD is very common; more than five million Americans are living with this disease, and one in nine people over the age of 65 have AD. In 2015, there were approximately 29.8 million people worldwide with AD and 1.9 million deaths from AD.
While there are many factors that increase the chances of developing AD, scientists are still not sure what causes some people to get it. Scientists know that it involves the development of plaques and tangles and failure of brain cells and, but they don’t know why. Additionally, over time, brain cells death causes the brain to shrink, which affects brain function. AD is the result of many different factors, not just one single cause.
You’re more likely to develop AD if:
Researchers have found that there is a link between vitamin D and brain function. This has lead researchers to study if vitamin D status may affect risk of developing AD.
Some of the receptors in the brain are receptors for vitamin D, which means that vitamin D is acting in some way in the brain and influencing the way an individual thinks, learns and acts. Scientists have found that people with AD have fewer vitamin D receptors in a part of the brain called the hippocampus, which is involved in forming memories.
The brain relies on vitamin D receptors for protection, including the development of the plaques and tangles that form in AD. How healthy vitamin D status affects a brain with dementia is still being studied, but scientists do know that vitamin D receptors work in many ways to protect the brain. However, these researchers are still exploring whether taking vitamin D supplements can help prevent memory loss and dementia.
In general, research has found that people with AD have lower levels of vitamin D in their blood. Two recent journal articles reviewed all of the studies involving vitamin D and AD; both showed that vitamin D levels are lower in people with AD than those without AD. Another piece of research showed that people with low vitamin D levels do worse on tests that measure how well their brain is working. A more recent French study found that those with low levels of vitamin D had a three-fold increased risk of AD. 
However, again, researchers can’t say for sure whether maintaining healthy vitamin D levels can prevent dementia or AD. For instance, some researchers theorize that if a person has memory loss or is developing dementia, they could be staying indoors more and making less vitamin D from sun exposure. This could lead to low levels of vitamin D in the body, implying that low vitamin D levels came after AD onset.
There is a consistent link between low vitamin D levels in people with AD, but there haven’t been many high-quality experiments that have clearly shown whether low vitamin D causes AD. As of now, there is no human research that shows vitamin D supplementation may help treat dementia or improve memory, because no such studies have been conducted. Two recent animal studies indicated high-dose vitamin D supplementation both helped prevent and treat AD.
A 2013 study from Denmark followed a large group of people over 30 years. They looked at whether there was a link between serum vitamin D levels at the beginning of the study and whether or not they developed AD or dementia 30 years later. 
The results showed that those who developed AD or dementia during the study had lower levels of vitamin D in their blood. The researchers suggest that a low level of vitamin D may increase an individual’s risk of developing AD in the future.
A study in the U.S. found that people with baseline vitamin D levels below 20 ng/ml (50 nmol/l) were substantially more likely to develop AD over a 4-year observation period.
A 2015 paper in JAMA showed 382 subjects in their 70s were 3 times more likely to develop Alzheimer’s over 5 years if the vitamin D levels were low. This study made headlines around the world.
A 2012 study conducted in France found vitamin D and memantine, a drug used to help people with AD manage their symptoms, work synergistically to improve memory in people with AD, compared to memantine or vitamin D alone. As mentioned above, animal studies using high-dose vitamin D (equivalent of 20,000 IU/day; 500 mcg) found it helped reverse AD.
Studies have concluded that there is a definite link between low levels of vitamin D in the blood in both people who already have AD and people who later develop AD. In our opinion, these findings alone warrant vitamin D supplementation in middle and older ages.
Doctors don’t yet know whether taking a vitamin D supplement, or getting more sun exposure, can help to prevent or treat AD. However, the fact that those with lower vitamin D levels are more likely to develop AD suggests that sun exposure and vitamin D can reduce the risk of developing AD.
If you have AD or dementia, or are trying to prevent AD, it is unlikely to make your symptoms worse or cause you any harm, as long you take less than 10,000 IU (250 mcg) per day. However, it’s not proven that you will see an improvement in your symptoms or that you will prevent AD. Animal studies showing a treatment effect with high dose vitamin D, used equivalent doses well above the equivalent of 10,000 IU/day.
If you have AD, you shouldn’t take vitamin D in place of other treatment medications. Talk to your physician for more advice about taking supplements.
Cannell, J.J., Sturges, M. & Peterson, R. Health condition: vitamin D and Alzheimer’s disease. The Vitamin D Council Health Condition, January 26, 2018.
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This health condition was last updated on January 26, 2018.