Higher levels of vitamin D during midlife may play a more important role in long-term brain health than previously understood, according to a new long-term study examining links between the nutrient and markers associated with dementia.
Researchers found that individuals with higher vitamin D levels in their 30s and 40s showed lower accumulation of tau protein in the brain nearly two decades later. Tau is widely recognised as a key biomarker linked to Alzheimer’s disease and other forms of dementia.
The findings were published in the journal Neurology Open Access and are based on data from almost 800 adults tracked over more than 16 years.
Midlife vitamin D as a potential protective factor
The study followed 793 adults with an average age of 39 at the start, all of whom were free of dementia at the beginning of the research. Blood samples were taken to measure vitamin D levels, with readings of around 30 ng/mL or higher classified as high, and lower levels considered deficient.
Researchers then tracked participants for around 16 years before conducting brain imaging scans to measure the presence of tau protein and beta-amyloid, two proteins strongly associated with Alzheimer’s disease.
Stronger link with tau protein
After adjusting for factors such as age, sex, and depressive symptoms, scientists found a clear association between higher vitamin D levels in midlife and reduced tau accumulation later in life.
However, no similar link was observed between vitamin D levels and beta-amyloid buildup, suggesting a more specific biological effect.
Possible modifiable risk factor
Researchers say the findings are promising because they point to vitamin D as a potentially modifiable risk factor for dementia.
“Higher vitamin D levels in midlife may help protect against tau accumulation in the brain,” said one of the study authors, adding that midlife could be a critical period for reducing long-term dementia risk through lifestyle or health interventions.
However, experts caution that further studies are needed to confirm the results and fully understand the relationship.
The study also notes limitations, including the fact that vitamin D levels were measured only once rather than repeatedly over time. This means they may not fully reflect long-term exposure or fluctuations in the body.
