Vitamin D may be linked to lower tau protein levels in the brain

A 16-year Irish study of nearly 800 adults found that higher vitamin D levels measured in midlife were associated with lower tau protein burden on brain scans about 16 years later, while no association was seen with amyloid beta.

Researchers in Ireland reported an association between midlife vitamin D levels and a brain marker tied to dementia risk. The study followed nearly 800 participants who were free of dementia at the start, with an average age of 39. Vitamin D concentration was measured at baseline and brain scans to assess tau and amyloid beta proteins were done roughly 16 years later. Investigators reported that higher baseline vitamin D (above 30 ng/mL) was associated with lower tau burden on later scans, and that no link was observed with amyloid beta. Key findings: - The study enrolled nearly 800 dementia-free adults with a mean starting age of 39. - Vitamin D was measured at the study outset; brain imaging for tau and amyloid beta occurred about 16 years later. - Participants with baseline vitamin D levels greater than 30 ng/mL tended to have lower tau protein burden on later scans. - No correlation was found between baseline vitamin D and amyloid beta levels. - Authors cautioned that the association does not prove causation and noted vitamin D was measured only at baseline. - A separate 2025 analysis cited in the report linked low vitamin D to an increased dementia risk in observational data. Summary: The reported association highlights a possible midlife link between vitamin D status and later tau burden that may inform future dementia research. Undetermined at this time.