Being severely deficient in vitamin D is associated with a doubling of the risk of dementia according to a US study published in Neurology.
The Cardiovascular Health Study ran from the 1990s and tracked 1658 ambulatory citizens with no history of dementia or cardiovascular or cerebrovascular disease.
After a five year follow up time those who had vitamin D levels below 25 nmol/L had increased rates of dementia 2.2 times that of people who had levels over 50 nmol/L.
Researchers say that there are vitamin D receptors in the brain and vitamin D is thought to enhance macrophages that clear amyloid from the brain cells and reduce neuronal cell death.
(Based in article by Michael McCarthy in BMJ 16 August 14).
A combined European and US study showed that total mortality was increased by 57% for older adults with vitamin D levels below 25 nmol/L. Cardiovascular deaths and cancer deaths were increased in a dose responsive manner.
(Based on and article by Stephen Robinson GP News 23 June 14)
Bizarrely the researchers didn’t think of the obvious solution, advise upping sun exposure or taking supplemental vitamin D, but decided that what this meant was that ill people were often stuck indoors and that was why they had low vitamin D levels.
The US study above does seem to contradict that view since all participants were ambulatory and had no known cardiovascular or cerebrovascular disease at the start of the study. In my own practice in the west of Scotland most patients of all ages had very low levels of vitamin D. All walked into the surgery but had conditions that could have been affected by low vitamin D levels. The only patients who had levels over 50 nmol/L were taking supplements, cycled outdoors all year round, or used sunbeds.