Written by Randy Yan and Edited by Ashima Seth
According to the National Institute of Aging, Alzheimer’s disease is the sixth leading cause of death in the U.S. [1]. Alzheimer’s disease is a progressive, degenerative neurological disorder that causes deterioration in memory and critical thinking skills over time. When we think about Alzheimer’s disease, we typically think about the elderly. This is because a majority of those who have Alzheimer’s disease are 65 years or older. Alzheimer’s disease is a form of dementia known as senile dementia. Dementia is not a specific disease; rather, it describes a group of symptoms that affect memory, thought processes, and day-to-day functioning.
Although there is currently no cure for Alzheimer’s, there are clues as to what leads to the onset of Alzheimer’s. Learning more about these factors may one day help contribute to the prevention of Alzheimer’s disease. Plaques, which are clumps of a protein called amyloid-β, and aggregates of the fibrous tau protein are found in the brains of those who have Alzheimer’s [2]. A study conducted by the University of California, Davis Alzheimer’s Disease Center showed that Vitamin D deficiency correlated with significantly faster declines in both episodic memory, which is a collection of past personal experiences that have occurred at a particular time and place, and executive function performance, which may lead to an increased risk for Alzheimer’s disease. The study shows significant differences in Vitamin D levels amongst those with normal cognition, mild cognitive impairment, and dementia [3]. Alzheimer’s disease causes a loss of connections between brain cells, thereby leading to neurodegeneration and impeding the brain’s ability to communicate with various muscles and organs in the human body. Once these brain cells, otherwise known as neurons, lose the connections, the neurons stop functioning and die.
New research suggests that low Vitamin D concentrations could be involved in the pathogenesis, or development, of dementia. Vitamin D helps promote calcium absorption, modulation of cell growth, neuromuscular and immune function, and reduction of inflammation. The vitamin also plays a role in modulating the regulation of cell division, the development of cells into various cell types throughout the body, and cell death [4]. With regards to neurological functioning, Vitamin D plays a heavy role in the central nervous system, and its metabolites are found in the human cerebrospinal fluid, the bodily fluid that circulates and surrounds the brain. The Vitamin D receptor and enzyme are also found to be densely located in areas that are associated with memory and higher order cognition, the process of understanding, and thought [5,6]. Cognition is extremely important to evaluate when assessing the possibility of dementia due to the disease’s beginnings at the hippocampus, the center of memory and emotion in the brain.
Potential mechanisms have been identified that link Vitamin D deficiency and Alzheimer’s disease. One of these mechanisms suggests that Vitamin D plays a role in reducing cell toxicity due to beta-amyloid plaques, as well as in preventing cell death (apoptosis) in neurons specific to the cortex of the brain. Amyloid-β (Aβ) is the main constituent of plaques in Alzheimer’s disease. Results from a research study that experimented with Amyloid-β determined that it triggers neurodegeneration and once Vitamin D was administered, cytotoxicity and apoptosis were prevented [7]. By gaining an understanding of how these Vitamin D receptor pathways function in protecting neurons, researchers might one day be able to determine new approaches to treating and preventing Alzheimer’s disease.
Overall, studies and science have shown that there are potential links between Vitamin D deficiency and Alzheimer’s disease. Since there are currently no cures to Alzheimer’s, now is a critical time to determine and pinpoint all the possible risks that could lead to the development of the disease. Although Alzheimer’s is not presently avoidable, we must remain optimistic that the research being done today could help find the cure tomorrow.
References:
- “Alzheimer’s Disease Fact Sheet.” National Institute on Aging, National Institutes of Health. https://www.nia.nih.gov/health/alzheimers-disease-fact-sheet
- “Dementia.” Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/dementia/symptoms-causes/syc-2035203
- Miller, J.W., Harvey, D.J., Beckett, L.A., et al. (2015). Vitamin D Status and Rates of Cognitive Decline in a Multiethnic Cohort of Older Adults. JAMA Neurology, 72: 1295–1303.
- “Vitamin D.” Office of Dietary Supplements, National Institutes of Health. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
- Littlejohns, T.J., Kos, K., Henley, W.E., Kuzma, E., Llewellyn, D.J. (2015). Vitamin D and Dementia. The Journal of Prevention of Alzheimer’s Disease, 3: 43-52.
- Littlejohns, T.J., Henley, W.E., Lang, I.A., Annweiler, C., Beauchet, O., Chaves, P.H., et al. (2014). Vitamin D and the Risk of Dementia and Alzheimer Disease. Neurology, 83: 920-928.
- Erdinc, D., Duygu, G., Selma, Y. (2011). A Novel Perspective for Alzheimer’s Disease: Vitamin D Receptor Suppression by Amyloid-β and Preventing the Amyloid-β Induced Alterations by Vitamin D in Cortical Neurons. Journal of Alzheimer’s Disease, 23: 207-219.