Recently Dr. Dickens and his colleagues reviewed data about vitamin D and dementia, noting that by the year 2040, 81 million people in the world will be demented. The numbers of demented persons will double every 20 years, unless something is found to affect the disease (technically diseases, as a number of different disease processes result in impaired cognition).
Study after study shows that people with low vitamin D levels are 2-3 times more likely to have dementia than those with higher levels. However, it could be a case of correlation and not causation; either vitamin D prevents dementia, or those with dementia just do not go outside as much. While Dr. Dickens fails to emphasize this point, several studies have figured that the later possibility is unlikely.
First, in studying only mild dementia (people with mild cases are unlikely to have different sunning habits than normal), researchers find the same relationship: the lower your vitamin D levels, the more demented you are. Secondly, at least two studies have strictly controlled for sun exposure in their study groups, and both have found a consistent relationship between low levels of vitamin D and dementia.
Particularly interesting were the test tube studies that Dr. Dickens reviewed. One such study showed that activated vitamin D stimulated the phagocytosis and clearance of amyloid by macrophages (it helped the garbage collecting cells of the body get rid of the junk thought to be responsible for Alzheimer’s disease). This implies, of course, not just prevention, but also a treatment effect.
As far as Dr. Dickens conclusions, he punted. While calling for “urgent needed” controlled trials, he failed to call for treatment of vitamin D deficiency in dementia or in preventing dementia. After reeling off study after study implicating that levels below 30 ng/ml are risky in pertinence to dementia, he failed to recommend to physicians the need to raise low vitamin D blood levels. Instead, he essentially called for the medical field to wait for more money for more scientists to conduct more studies.
As usual, no controlled trials exist proving that vitamin D prevents dementia. Thus, we are left, as we so often are, with the option of acting on what we know now, or not acting on what we know now. As I have pointed out before, ethical physicians have always acted on what is currently known. Waiting for perfect science is to violate the oath all physicians take.