Our relationship with vitamins and supplements may be approach-avoidance. On one hand, if they are beneficial and patients are motivated to take them, we do not complain. This is likely a marker of motivated patient who may heed other health promotional advice that we proffer. On the other hand, it is difficult to keep up with the massive amount of good and bad literature about them. Patients can challenge us on our medical knowledge, pinging our opinions about the latest findings tweeted out while we struggle to keep up with all the wheelchair forms.
Vitamins are clearly not consistently beneficial. B vitamins may increase lung cancer risk in smokers. Vitamin D, however, seems to have some of the greatest “staying power” in the clinical realm and has a good reputation as far as vitamins go. Vitamin D is probably good for the heart, but how about the head? Could low D cause dementia? If so, how?
Previous studies of the relationship between vitamin D and dementia have not shown consistent results. Thomas Littlejohns, M.Sc., and colleagues have published a fantastic piece of work (Neurology 2014 Aug. 6 [doi: 10.1212/WNL.0000000000000755]) that sheds some light. They evaluated a prospective cohort of 1,658 elderly ambulatory adults with no history of dementia, CVD, or stroke who had baseline 25-hydroxyvitamin D [25(OH)D] concentrations at baseline. Severely low levels of 25(OH)D and deficiency (≥25 to <50 nmol/L) were associated with a significantly increased risk for all-cause dementia and Alzheimer’s dementia.
Several hypotheses exist as to why vitamin D helps the brain. Vitamin D may attenuate amyloid-induced cytotoxicity and neural apoptosis. It also may reduce the risk of strokes by promoting healthy cerebral vasculature.
The Institute of Medicine recommends a serum concentration of 25(OH)D at 50 nmol/L. This study would suggest that sufficiency to this level is neuroprotective. The next step is to see if supplementation can modify baseline risk, but many of my patients may wait for these data to come out before starting their vitamin D supplements.
Dr. Ebbert is professor of medicine, a general internist at the Mayo Clinic in Rochester, Minn., and a diplomate of the American Board of Addiction Medicine. The opinions expressed are those of the author. The opinions expressed in this article should not be used to diagnose or treat any medical condition nor should they be used as a substitute for medical advice from a qualified, board-certified practicing clinician.