What is dementia? This syndrome, in which we observe a decline in our cognitive functions (loss of memory, attention, etc.), mainly affects older people, but is not a major component of aging. There are many forms of dementia; 60-70% of cases are associated with Alzheimer’s disease. As for the causes of dementia, they remain a mystery. However several studies already linked vitamin D deficiency and a 2-fold risk of developing dementia or a 3-fold risk of developing Alzheimer’s disease. In this work by scientists from Tufts University (United States of America), the influence of vitamin D finds new light.
Direct analysis of brain vitamin D concentration: a new method
This team analyzed vitamin D levels directly in the brain tissue of 290 participants post mortem. It was never done. The goal: to use vitamin D to study how food and nutrients can create resistance to protect the aging brain against neurological diseases, particularly Alzheimer’s disease. “Numerous studies have shown that dietary or dietary factors impair cognitive function in the elderly, but all are based on vitamin D intake or blood levels.,” explains Kyla Shea, the study’s lead author and an assistant professor at the Friedman School of Nutrition Science and Policy at Tufts.We wanted to know if vitamin D is present in the brain and, if so, how this level is related to cognitive decline“.
The results are published in the journal Journal of the Alzheimer’s Association consistent with the hypothesis that individuals with higher levels of vitamin D in their brains before death had better cognitive function than others.
HORMONE. Despite the name, vitamin D is a hormone that is synthesized when exposed to the sun. It plays an essential role in strengthening our muscle and bone tissues, increasing the absorption of phosphorus and calcium, as well as participating in cellular immunity. It is also found in small amounts in food, especially fatty fish, dairy products and egg yolk.
Brain samples used for this study are from program participants Memory and Aging Project (MAP), a long-term study of Alzheimer’s disease started in 1977. and still continuing. To be accepted into the MAP program, participants must show no early signs of dementia and agree to an annual visit to evaluate the development of their cognitive functions using 19 different tests that assess the following domains: episodic memory, semantic memory, working memory. memory, perceptual speed, and perceptual orientation. They also agree to organ donation after their death.
Brain tissue samples were taken post mortem for people who died between 2005 and 2019, aged 84 to 98 years, and whose tissues were frozen less than 6 years ago. Serological measurements ante mortem and post mortem Participants were also tested to compare blood and brain levels of vitamin D.
Four brain regions analyzed in detail
These are 4 brain areas (middle temporal cortex – TM – , middle frontal cortex – FM – , cerebellum – CR – and frontal white matter – SB – ) that were carefully examined in each participant for vitamin D. Two of the analyzed brains of the domains are associated with Alzheimer’s disease (TM, FM), respectively, one is associated with circulation-related forms of dementia (CR), and one domain remains without a known association with decline. cognitive (SB).
According to the study results, vitamin D was found in every brain region, and high levels of vitamin D in all four brain regions were associated with better cognitive function. Furthermore, serological results show no association between vitamin D blood levels and cognitive degeneration. In other words, only vitamin D in the brain would affect cognitive ability.
Although the study results are very promising for understanding the relationship between vitamin D and dementia, the study results do not allow us to trace a causal relationship between vitamin D levels in the brain and Alzheimer’s disease. Indeed, no correlation was found between brain concentrations of the vitamin and known physiological markers of Alzheimer’s disease. Further research is still needed to identify the underlying factor(s) in the development of neurological diseases and to clarify the role of vitamin D in brain function.
Too much vitamin D is not good for your health
“We now know that vitamin D is present in reasonable amounts in the human brain and appears to be associated with less decline in cognitive function. says KylaShea, lead author of the study.However, before we can develop future interventions, we need to continue our research to identify the neuropathology that vitamin D is associated with in the brain.“
Although this hormone is essential for the proper development and maintenance of our bodies, consuming too much vitamin D can be dangerous. In fact, taking vitamin D supplements can cause hypercalcemia (high levels of calcium in the blood), weakening bone structure and releasing even more calcium into the blood. This can cause digestive problems, increased thirst and diuresis (the urge to urinate). Untreated hypercalcemia can lead to death.