The sun always has been seen as life bringing and essential for human existence. Already in the days of Francis of Assisi he called it his “lord brother sun”, which expressed his appreciation of the special star. Nowadays the sun once more is in focus of interest, this time because of its assumed association with and effect on human cognition triggered by vitamin D. The role of vitamin D in the maintenance of human health is well established in scientific literature, especially regarding its function in supporting the body in absorbing calcium, phosphate and zinc to ensure a healthy skeleton. Other associations also have been discovered–having a sufficient vitamin D level seems to protect against cancer, diabetes and cardiovascular diseases. In the last years another function of vitamin D was brought into the spotlight: Researchers suggest it has neuroprotective potential and therefore is essential to maintain cognitive health.

Humans mainly obtain vitamin D through synthesis in the skin during exposure to sunlight. In this process approximately 90% of the total amount is produced, the rest is gained through our diet, for example from oily fish or eggs, or through supplementation. The sunlight as a never-ending and always available source of energy to produce vitamin D has served us very well in the past, but today our way of life impedes a proper function of the system. Humans spend most of their time inside of buildings and often work in places where little to no natural light is shining. This habit has initiated a common vitamin D deficiency especially in elderly people, whose skin has a reduced capacity in producing it and whose limited mobility makes it more difficult to get outside into sunlight. The result is a total of one billion people suffering with vitamin D deficiency and the number is continuously growing.

Meanwhile, the number of demented people increases year by year–just a coincidence? Dementia is the collective term for several neurodegenerative diseases that cause cognitive decline and impairment in general and problems with memory, language and motivation in special. The most common form of dementia is Alzheimer`s disease. Patients with dementia suffer terribly from the progressive decay of cognitive abilities which leads to a lack of independence in every day life and an urgent need of care. Today nearly 50 million people are suffering with the symptoms of dementia and the number increases dramatically, mainly due to the fact that humans have a substantially longer life expectancy. This all serves to demonstrate how badly needed ways of preventing and curing dementia are, but until now efficient remedies are not found yet. However, researches have discovered a strong association between vitamin D deficiency and dementia. Could vitamin D therefore be a promising tool in fighting the disease?

In a study of Littlejohns and colleagues the researchers examined the connection of being vitamin D deficient and developing dementia. They measured levels of vitamin D in a group of 1,658 healthy elderly adults and also the incidents of the development of dementia 5.6 years later and found a clear connection between deficiency and dementia. Remarkably, they reported an increased risk in getting the disease when being severely deficient: Those people were twice as likely getting dementia than sufficient participants. The authors concluded that vitamin D deficiency is a serious risk factor which should be especially considered in the prevention of dementia.

Furthermore, Annweiler and colleagues could show a positive effect of a vitamin D supplementation to global cognition in patients of a memory clinic, which indicates also a potential in curing or reducing the symptoms of dementia. Nevertheless, it has to be mentioned that other studies reported no effects in treating already demented people with vitamin D. This shows how urgently needed further research in this field is: Much still remains scientifically unclear and has to be examined in further trials to reveal the full potential of vitamin D in preventing and curing dementia. To this point we just know it has neuroprotective functions and can be seen as a risk factor for dementia–which is a pretty promising starting position for further research.

To sum up, it can be said that having a sufficient level of vitamin D leads to many positive outcomes regarding our health, one of them is the reduced risk in getting dementia. And being sufficient is not hard to reach: A little time in the sun every day is all you need! As Francis of Assisi said: “A single sunbeam is enough to drive away many shadows.”.

References
Annweiler, C., Fantino, B., Gautier, J., Beaudenon, M., Thiery, S., & Beauchet, O. (2012). Cognitive effects of vitamin D supplementation in older outpatients visiting a memory clinic: a pre–post study. Journal of the American Geriatrics
Society, 60(4), 793-795.
Littlejohns, T. J., Henley, W. E., Lang, I. A., Annweiler, C., Beauchet, O., Chaves, P. H. & Lopez, O. L. (2014). Vitamin D and the risk of dementia and Alzheimer disease. Neurology, 83(10), 920-928.
Schlögl, M., & Holick, M. F. (2014). Vitamin D and neurocognitive function. Clinical interventions in aging, 9.
World Health Organization. (2012). Dementia: a public health priority.