Vitamin D supports many functions in the body, including boosting immune responses and maintaining healthy bones. And, according to researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA), it also might play a role in healthy cognitive functioning.
An estimated 55 million people worldwide live with dementia, a number that’s expected to rise as the global population ages. In an effort to understand more about how vitamin D impacts the condition, the researchers examined levels of the vitamin in the brain tissue of adults who suffered from varying rates of cognitive decline.
While many studies have implicated vitamin D as a factor in cognitive performance or function in older adults, those studies are based on either dietary intakes or blood measures of vitamin D. The HNRCA researchers wanted to know if vitamin D is even present in the brain, and if it is, how concentrations of it might be linked to cognitive decline.
The team examined samples of brain tissue from 290 participants in the Rush Memory and Aging Project, a long-term study of Alzheimer’s disease that began in 1997. They looked for vitamin D in four regions of the brain—two associated with changes linked to Alzheimer’s disease, one associated with forms of dementia linked to blood flow, and one region without any known associations with cognitive decline related to Alzheimer’s disease or vascular disease.
They found that vitamin D was indeed present in brain tissue, and high vitamin D levels in all four regions of the brain correlated with better cognitive function.
However, the levels of vitamin D in the brain didn’t correlate with any of the physiological markers associated with Alzheimer’s disease in the brain studied, including amyloid plaque buildup, Lewy body disease, or evidence of chronic or microscopic strokes. This means it’s still unclear exactly how vitamin D might affect brain function. In addition, most of the participants in the original Rush cohort were white, while vitamin D is also known to vary between racial and ethnic populations.
The next step in this work: The researchers are following up with studies that use a more diverse group of subjects, as they seek to deepen our understanding of the role vitamin D may play in staving off dementia.