Despite carrying the misnomer “vitamin”, vitamin D is one of the many essential molecules (other than ions and some amino acids) that you have to get through your diet that we collectively call vitamins. Of course, vitamin D can be created by yourown body (and is thus not a “true” vitamin) with the help of sunlight.
The detailed video under this paragraph explains the biological activity and metabolism of vitamin D. Of course, this video does not discuss the most surprising recent find: vitamin D levels have a significant impact on the potential development of neurodegenerative conditions in old age; Alzheimers and dimentia.
A recent study by an international team, led by Dr David Llewellyn, at the University of Exeter Medical School, found that people who were severely deficient in vitamin D were more than 2x as likely to develop Alzheimer’s disease and dementia. Those were moderately deficient had an increased risk of 53%.
The study looked at 1,658 adults aged 65 and over, who were able to walk unaided and were free from dementia, cardiovascular disease and stroke at the start of the study. The participants were then followed over 6 years to investigate who would go on to develop Alzheimer’s disease and other forms of dementia.
Although clinical trials are needed before we can surely say that eating oily fish or going out in the sun will surely prevent dementia, the evidence seems to point in that direction. As is always important to mention: humans need a lot of things to remain healthy and sane and having too much (or too little) of any vitamin, food, or mineral is bad for your health.