We have been exploring environmental risk factors in dementia. One factor we discussed in a previous blog is air pollution. In this blog, we explore the link between Vitamin D and dementia risk.
In recent years a lot of research has started to point towards the importance of Vitamin D in human health. Many conditions have been linked to Vitamin D deficiency. These include neurodegenerative diseases, such as Multiple sclerosis and Dementia.
Vitamin D is an essential nutrient that our bodies require to function normally. We can produce Vitamin D or absorb it through our diet. Around 90% of Vitamin D is produced in the skin from 7-Dehydrocholesterol as a reaction to sunlight. There are different factors that reduce the production of Vitamin D:
Approximately 1 billion people worldwide have inadequate Vitamin D levels, mainly due to a lack of sunlight exposure. Nutrition is another important source of Vitamin D, especially when exposure to sunlight is reduced. For example, some foods high in Vitamin D include fatty fish or Vitamin D fortified foods.
Research suggests that low levels of Vitamin D may be associated with an increased risk of developing Alzheimer’s disease or other dementias. Vitamin D has various roles that are important for brain function. These include:
Although some physiological mechanisms have been suggested, we have not yet determined the exact role Vitamin D plays in the brain. Animal studies suggest that a lack of Vitamin D may impair the functioning of brain cells (neurons).
A study by Eyles and colleagues shows that the Vitamin D3 receptor is widespread in the brain. Using staining techniques, the researchers were able to show that the Vitamin D3 receptor and its connected enzyme had the strongest presence in the hypothalamus and the substantia nigra. Based on this distribution, researchers suggest that Vitamin D may act in a similar way to neurosteroids.
A meta-analysis of studies by Sommer and colleagues (2017) analyzed data from 18639 participants. It showed that people with a serious lack of Vitamin have a statistically significantly higher relative risk of 1.54 to develop dementia compared to people with sufficient Vitamin D. However, the quality of this evidence is very low. This is because many of the studies included were observational in nature, and often important confounding variables were not considered.
Research so far has only indicated that Vitamin D deficiency may be associated with dementia risk. However, no studies have established a causal link between the two. Therefore, future research needs to focus on environmental risk factors, such as Vitamin D, and establish what contributions (if any) these may have. This is particularly important as one third of dementia remains unexplained and these environmental risk factor could potentially play a pivotal role.
Some of the key questions we need to answer include: Can Vitamin D supplements mitigate the risk of developing Dementia? And if yes, at which stage in life would they have to be introduced?
Vitamin D certainly does seem to play a key role in our health. However, it remains to be seen how exactly this “Wunderkind” of a nutrient will alter the landscape of dementia research.