Vitamin D has become a hot topic in recent years. For many years, vitamin D has been known to play a role in bone health. More recent research suggests it may have a much broader role in multiple body systems.
In regard to the brain, we know that there are receptors for vitamin D in most parts of the human brain. In persons without Parkinson’s disease, some research suggests vitamin D may be related to mood and cognitive function. These data are somewhat limited, however, and a definitive conclusion has not been drawn.
To look more closely at mood, memory and their relationship with vitamin D in persons with Parkinson’s, some colleagues and I conducted an observational study of 286 people with Parkinson’s. We did testing of cognitive function and mood and had blood drawn. When correcting for age, disease duration, and Parkinson’s disability, we found associations between vitamin D concentrations and several measures of language function. These included how many animals or vegetables a person could name in one minute, known as verbal fluency, and how good they were at remembering a list of words. This relationship — between higher vitamin D levels and better language function — was present in those persons with Parkinson’s who were not demented, but not present in those with dementia. In regard to mood, a self reported scale of depression showed an association with vitamin D concentrations — again, just in the non-demented subset of Parkinson’s patients.
It appears that there may be a relationship between vitamin D and cognition and mood in persons with Parkinson’s. Cause and effect cannot be determined from this type of study. It is possible, for example, that persons with Parkinson’s who are depressed are less likely to get outside and therefore have lower vitamin D concentrations.
To determine if a relationship truly exists, good intervention studies are needed to see what happens to cognition and mood when vitamin D concentrations are increased in persons with Parkinson’s. Currently we are pursuing a research project looking at this with a joint OHSU and Portland VA Medical Center study. We hope to have results in the next year or two.