- Solar UVB light may reduce the risk of dementia by producing vitamin D.
- Vitamin D may reduce the risk of dementia through several mechanisms including reducing the risk of diseases that may precede dementia.
Dementia is a loss of brain function. It often occurs with certain diseases. Dementia affects memory, thinking, language, judgment, and behavior. Two common types of dementia are Alzheimer’s disease and vascular dementia.
Dementia risk factors include:
- Diet: Some foods are associated with an increased risk of Alzheimer’s disease. Large amounts of animal products, such as fatty red meat, are a risk factor. A diet low in omega-3 fatty acids and vegetables is also linked to Alzheimer’s.
- Genetics: related to cholesterol and insulin also play a role in Alzheimer’s.
- Sedate lifestyle: Moderate exercise helps reduce the risk of dementia.
- Inflammation in the brain: This is an important risk factor for Alzheimer’s.
Sunlight exposure and dementia risk
There are no reported studies on sunlight and the risk of dementia.
However, in Japan, solar ultraviolet-B (UVB) exposure has been used as therapy for dementia. UVB raises vitamin D blood levels and reduces the risk of osteoporosis.
Vitamin D and dementia
Vitamin D levels
Studies indicate that vitamin D may be beneficial for people with dementia:
- Lower vitamin D levels are linked to higher risk or rates of thought impairment. This impairment often occurs before dementia.
- A number of diseases are both vitamin D–sensitive and precursors to dementia. These include cardiovascular diseases, diabetes mellitus, and depression.
- People with lower vitamin D levels had higher rates of dementia and Alzheimer’s.
- A 2010 literature review concluded that vitamin D may reduce the risk of dementia, especially Alzheimer’s disease. The researchers suggested that further studies were needed.
- The relationship between vitamin D levels and dementia was studied in geriatric inpatients in France. Patients with severe vitamin D deficiency (less than 10 ng/mL [25 nmol/L]) had twice the risk of moderately severe to severe dementia.
How vitamin D works
Vitamin D may work in several ways to counter dementia:
- All cells in the body have vitamin D receptors (VDRs). VDRs are triggered by calcitriol, the active form of vitamin D. They help turn genes on and off.
- Vitamin D may also reduce inflammation in the brain.
- A vitamin D–rich diet may decrease the number of amyloid plaques. These plaques are a hallmark of Alzheimer’s. However, it is not clear whether they cause Alzheimer’s.
- Vitmain D may increase a nerve growth factor in brains. This has only been confirmed in studies of mice.
Vitamin D may reduce the risk of dementia by lowering the risk of diseases that often precede dementia. Low vitamin D levels are associated with increased risk of two of these diseases, cardiovascular disease and stroke, which have many of the same risk factors as vascular dementia.
Those with dementia often have low vitamin D blood levels. Studies in Japan found that people with Alzheimer’s could increase vitamin D levels with solar UVB light.
Vitamin D may aid clearance of beta-amyloid, a hallmark of Alzheimer’s, by stimulating macrophages. Macrophages are a type of white blood cell that fights infection. However, it has not been shown that removing beta-amyloid reduces the progression or severity of Alzheimer’s disease.
Find out more…
We will be adding a detailed evidence summary on this topic in the near future. Please check back soon to find out more.
Page last edited: 21 September 2011