New research has linked higher vitamin D levels in midlife to lower accumulation of tau protein tangles in the brain, a key marker associated with Alzheimer’s disease, years later.
The findings come from a long-term study of 793 adults who did not have dementia at the start of the research. Participants had their vitamin D levels measured via blood tests at an average age of 39. Brain scans taken approximately 16 years later were used to assess levels of tau and amyloid-beta proteins, both of which are closely linked to Alzheimer’s pathology.
Statistical analysis showed that individuals with higher vitamin D levels in midlife tended to have lower amounts of tau protein tangles detected in later brain imaging. However, no significant association was found between vitamin D levels and amyloid-beta accumulation, another Alzheimer’s-related biomarker.
Researchers emphasized that whereas the study identifies a meaningful correlation, it does not establish causation. “These results suggest that higher vitamin D levels in midlife may offer protection against developing these tau deposits in the brain,” said Martin David Mulligan, MB BCh BAO, a neuroscientist from the University of Galway in Ireland and one of the study’s authors.
He added that low vitamin D levels could potentially be a modifiable risk factor for dementia, noting that further research is needed to confirm whether interventions to maintain adequate vitamin D levels could reduce long-term brain health risks.
Vitamin D, which the body produces when exposed to sunlight, is also obtainable through certain foods and supplements. It plays essential roles in bone health, immune function and inflammation regulation. Maintaining sufficient levels during midlife may represent a simple, accessible step individuals can take to support long-term neurological health.
The study, published in April 2026 in Neurology Open Access, an official journal of the American Academy of Neurology, contributes to growing evidence about lifestyle factors that may influence Alzheimer’s-related brain changes years before symptoms appear.
