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Alzheimer’s disease

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Alzheimer’s disease is a condition that affects your memory and thinking and can cause changes in your behavior. The main symptoms of Alzheimer’s disease include memory loss that affects your daily life, having poor judgment when making decisions, and changes in your personality, like often becoming upset, suspicious, or anxious.

It is not known exactly what causes Alzheimer’s disease. The main things that can influence whether or not you get develop Alzheimer’s disease are a combination of your age, your family history, and your genetics.

Researchers have found that there is a link between vitamin D and your brain. Receptors for vitamin D have been found in many parts of the brain, which means that vitamin D is acting in some way in your brain and may have an influence on the way you think, learn, and act.

In general, research from many studies has shown that Alzheimer’s disease and dementia is more common in people who have low levels of vitamin D in their body.  However, there haven’t been many good quality experiments that would be able to show clearly whether low vitamin D levels cause Alzheimer’s disease. More research is needed to give a clearer answer about whether taking a vitamin D supplement can help prevent or treat Alzheimer’s disease.

If you have Alzheimer’s disease or are trying to prevent it and want to take vitamin D, it is unlikely to make your symptoms worse or cause you any harm, as long you take less than 10,000 IU per day. However, it’s not proven that you will see an improvement in your symptoms or prevent the disease either.

If you have Alzheimer’s disease, you shouldn’t take vitamin D in place of other treatment medications. Talk to your physician for more advice about taking supplements.

What is Alzheimer’s disease?

Alzheimer’s disease (AD) is a condition that causes memory problems and changes in behavior. Usually, it’s progressive, which means it develops slowly and gets worse over time. AD is the most common form of dementia. Dementia is the medical word used for memory loss that is serious enough to interfere with your daily life. Currently, there is no cure for AD.

If you have AD, there are two main changes that take place in your brain. People with AD develop:

  • Plaques, which are clusters of protein that build up between the nerve cells in your brain. These stop cells from signaling to each other.
  • Tangles, which are dead or dying nerve cells. These stop nutrients from moving through the cells, causing them to die.1

What are the symptoms of Alzheimer’s disease?

Some of the main symptoms are:

  • Memory loss that affects your daily life
  • Having trouble planning or solving problems
  • Not being able to complete the same tasks you used to be able to
  • Having trouble reading or judging distances
  • Having poor judgment when making decisions
  • Withdrawing from work, hobbies, and social activities
  • Getting confused about the time or where you are
  • Changes in your mood or personality, like often becoming easily upset, suspicious, or anxious

These are different than some normal changes that happen as you grow old, such as sometimes forgetting names or losing things from time to time.1 If you notice any of the symptoms above in yourself or someone you know, talk to a doctor.

How common is Alzheimer’s disease?

AD is very common; more than 5 million Americans are living with this disease. One in nine people older than age 65 have AD.

You’re more likely to get AD if:1

  • You’re 65 years or older. Old age is the main factor that increases your chances of developing AD.
  • You have an immediate family history of someone having AD. If your parent or sibling has AD, then you are more likely to get AD.
  • You have genes that are involved with the development of AD. There are a few genes that scientists have identified which can have an influence on AD.
  • You have had a serious head injury, especially repeated injuries.
  • You have other health conditions, such as high blood pressure, heart disease, diabetes, high cholesterol, or if you have had a stroke. These conditions increase your chances of developing AD.
  • You are black or Hispanic.

What causes Alzheimer’s disease?

Scientists know that it involves cells in your brain failing and the development of plaques and tangles, but they don’t know why.

Over time, when brain cells die, your brain shrinks, which affects the way it works. AD is the result of many different factors working together, not just one single cause.

While there are many things that increase your chances of developing AD, scientists are still not sure what causes some people to get it. Scientists know that it involves cells in your brain failing and the development of plaques and tangles, but they don’t know why.

Over time, when brain cells die, your brain shrinks, which affects the way it works. AD is the result of many different factors working together, not just one single cause. The main things that influence whether or not you develop AD are a combination of age, your family history, and your genetics. After you reach age 65, the chances of getting AD double every 5 years older that you get. At age 85, one in every two people develops AD.1

What is the link between Alzheimer’s disease and vitamin D?

Researchers have found that there is a link between vitamin D and the way your brain works. Of the many ways that vitamin D may affect how your brain works, researchers are beginning to study if not getting enough vitamin D may affect whether you develop dementias, including AD.

Receptors for vitamin D have been found in many parts of the brain. Receptors are found on the surface of a cell where they receive chemical signals. By attaching themselves to a receptor, these chemical signals direct a cell to do something; for example to act in a certain way, or to divide or die.

Some of the receptors in your brain are receptors for vitamin D, which means that vitamin D is acting in some way in your brain and influencing the way you think, learn, and act.2 Scientists have found that in people with AD, there are fewer vitamin D receptors in a part of the brain called the hippocampus, which is involved in forming memories.3

Your brain relies on vitamin D receptors for protection against the things that can damage it, including the development of the plaques and tangles that form in AD.4 How getting enough vitamin D affects a brain with dementia is still being studied, but scientists do know that vitamin D receptors work in many ways to protect your brain. However, these researchers are still exploring whether taking vitamin D supplements can help prevent memory loss and dementia.5

What does the research say in general about vitamin D and Alzheimer’s disease?

Preventing AD

There is a growing amount of recent research on the link between vitamin D and the way your brain works, including AD and dementia.

Another piece of research showed that people with low vitamin D levels do worse on tests which measure how well their brain is working.

Another piece of research showed that people with low vitamin D levels do worse on tests which measure how well their brain is working.

Most recent studies that have been done are called observational studies. This means that they can only find a link between vitamin D and AD, but they don’t know if not getting enough vitamin D actually causes AD.

In general, research has found that people with AD have lower levels of vitamin D in their blood. Two recent journal articles which 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.2,6  Another piece of research showed that people with low vitamin D levels do worse on tests which measure how well their brain is working.7

However, again, researchers can’t say for sure whether getting enough vitamin D can prevent dementia or AD. For instance, one theory is that if you have memory loss or if you’re developing dementia, you could be staying indoors more and making less vitamin D from sun exposure. This could lead to low levels of vitamin D in your body.8

Treating AD

There is a consistent link between low vitamin D levels in people with AD, but there haven’t been many good quality experiments that would be able to show clearly whether low vitamin D causes AD. As of now there is no research which shows that taking vitamin D can help to treat dementia or improve memory.

Two large research studies are currently looking at how a taking vitamin D and/or omega-3 supplement affects memory and how well the brain works. These studies may be able to provide more information about whether or not taking a vitamin D supplement can help to treat or manage AD or dementia.9 As of now, it is difficult to say what role vitamin D has in treating AD, and more large trials are needed to explore this.

So, what does recent research say?

Preventing AD

A 2013 study from Denmark followed a large group of people over 30 years. They looked at whether there was a link between levels of vitamin D in someone’s blood at the beginning of the study and whether or not they developed AD or dementia 30 years later. The results showed that:

  • People 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 your chances of getting AD in the future.

Researchers can’t say for sure that low vitamin D levels caused AD. However, the strengths of this study are that it ran for a long time, and that it accounted for other factors, apart from vitamin D, that could have affected whether someone developed AD. This study only looked at people who were white, so it’s not possible to say whether or not the results would be similar for all ethnicities.9

Treating AD

A study done in 2011 in Australia looked at whether high doses (6,000 IU/day) of vitamin D could help memory in people with mild to moderate AD. The study started with a low dose (1,000 IU/day) of vitamin D for 8 weeks, and then people took either a high dose of vitamin D or continued with the low dose for 8 weeks. The results found that:

  • When people took small amounts of vitamin D, their memory and thinking improved.
  • When people took large amounts of vitamin D, there was no further improvement in their memory and thinking, compared to taking the smaller amount.

The people who took part found that their memory and thinking improved quickly at the start of the study when they took small amounts of vitamin D. However, when people took larger amounts it didn’t have a bigger effect. The researchers think that small amounts of vitamin D help to slow down the development of AD, and that there might not be benefits to taking a larger amount.

Since both groups got vitamin D, researchers can’t say for sure if it was the vitamin D that helped memory and thinking, or if it was a placebo effect, meaning that just by taking a pill, the people improved.10

A 2012 study done in France looked at whether vitamin D and memantine work better together to improve memory and thinking in people with AD, compared to memantine or vitamin D alone. Memantine is a drug used to help people with AD manage their symptoms, marketed under names like Namenda and Ebixa.

Researchers looked at change in memory and thinking between two doctor’s visits using a test called the Mini-Mental State Examination (MMSE). They found that:

  • There was no improvement in test scores when people took memantine only or vitamin D only.
  • When people took memantine and vitamin D together, their test scores improved, which meant their memory and thinking improved.

The researchers concluded that memantine and vitamin D taken together may help each other to work better in treating symptoms of AD. However, this study was not a controlled trial, meaning that researchers can’t say for sure if vitamin D and memantine work to improve memory and thinking.

Also, only a small number of people took part in the study, so researchers can’t say for sure if they would have the same results in a larger group. Another study looking at this area is planned.11

Key points from the research

  • It’s difficult to compare research studies with each other, as researchers used different ways to measure memory and thinking and vitamin D levels.
  • Research from many studies has shown that AD and dementia is more common in people who have low levels of vitamin D in their body.
  • However, it’s not possible to say whether low vitamin D levels cause AD and dementia, and therefore whether vitamin D can help to prevent, treat, or delay dementia.
  • It’s hard to know for sure if a low vitamin D level affects the development of AD, or if having AD causes someone to have low levels of vitamin D in their body.
  • Overall, more research is needed to give clearer answers about whether taking a vitamin D supplement can prevent or treat AD.
  • Better research is underway looking at whether vitamin D can help or prevent AD.

What does this mean for me?

Research does show that there is a link between vitamin D and Alzheimer’s disease. 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 develop AD later in life.

Studies have also shown that people who have more exposure to the sun or get larger amounts of vitamin D from foods are less likely to develop AD.

Studies have also shown that people have more exposure to the sun or get larger amounts of vitamin D from foods are less likely to develop AD.

Doctors don’t yet know whether taking a vitamin D supplement, or getting more sun exposure, can help to prevent or treat AD.

However, research hasn’t yet been able to show whether low levels of vitamin D cause AD, or if having AD is what causes low levels of vitamin D. Doctors don’t yet know whether taking a vitamin D supplement, or getting more sun exposure, can help to prevent or treat AD.

If you have AD or dementia or are trying to prevent AD and want to take vitamin D, it is unlikely to make your symptoms worse or cause you any harm, as long you take less than 10,000 IU per day. However, it’s not proven that you will see an improvement in your symptoms or that you will prevent AD.

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.

References

  1. Alzheimer’s Disease. Alzheimer’s Association, 2013. Web. 8 November 2013. <www.alz.org>
  2. Balion C, Griffith LE, Strifler L, et al. Vitamin D, cognition, and dementia. A systematic review and meta-analysis. Neurology 2012;79:1397-1405.
  3. Oudshoorn C, Mattace-Raso FUS, van der Velde N, Colin EM, van der Cammen TJM. Higher serum vitamin D3 levels are associated with better cognitive test performance in patients with Alzheimer’s disease. Dementia and Geriatric Cognitive Disorders 2008;25:539-543.
  4. Soni M, Kos K, Lang IA, et al. Vitamin D and cognitive function. Scandinavian Journal of Clinical and Laboratory Investigation 2012;243:79-82.
  5. Annweiler C, Beauchet O. Vitamin D-Mentia: Randomized clinical trials should be the next step. Methods in Neuroepidemiology, 2011;37:249-258.
  6. Annweiler C, Rolland Y, Schott AM, et al. Higher vitamin D dietary intake is associated with lower risk of Alzheimer’s disease: A 7-year follow-up. Journals of Gerontology: Medical Sciences 2012;67:1205-1211.
  7. Pludowski P, Holick MF, Pilz S, et al. Vitamin D effects on musculoskeletal health, immunity, autoimmunity, cardiovascular disease, cancer, fertility, pregnancy, dementia and mortality- A review of recent evidence. Autoimmunity Reviews, 2013;12:976-989.
  8. Holick MF. Vitamin D deficiency. New England Journal of Medicine 2007; 357: 266–281.
  9. Afzal S, Bojesen SE, Nordestgaard BG. Reduced 25-hydroxyvitamin D and risk of Alzheimer’s disease and vascular dementia. Alzheimer’s and Dementia 2013:1-7.
  10. Stein M, Scherer SC, Ladd KS, Harrison LC. A randomized controlled trial of high-dose vitamin D2 followed by intranasal insulin in Alzheimer’s disease. Journal of Alzheimer’s Disease 2011;26:477-484.
  11. Annweiler C, Herrmann FR, Fantion B, Brugg B, Beauchet O. Effectiveness of the combination of memantine plus vitamin D on cognition in patients with Alzheimer disease: a pre-post pilot study. Cogn Behav Neurol 2012;25:121-7.

This page was last updated December 2013.

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