Highlights:
- Higher vitamin D levels in midlife were linked to lower levels of tau protein, a key marker associated with Alzheimer’s disease, years later
- The findings show a connection, but they do not prove that vitamin D directly reduces dementia risk
- Researchers found no link between vitamin D levels and another Alzheimer’s marker, amyloid beta
- More studies are needed to confirm these results and better understand the potential role of vitamin D in brain health
Vitamin D in Midlife Linked to Lower Dementia Marker Years Later
Higher levels of vitamin D in the blood during middle age may be tied to lower amounts of tau protein in the brain years later, according to a study published today (April 1, 2026) in Neurology Open Access, an official journal of the American Academy of Neurology. Tau is a key biomarker associated with dementia.
The researchers emphasize that the findings show a connection, not proof that vitamin D directly reduces tau levels or dementia risk.
“These results suggests that higher vitamin D levels in midlife may offer protection against developing these tau deposits in the brain and that low vitamin D levels could potentially be a risk factor that could be modified and treated to reduce the risk of dementia,” said study author Martin David Mulligan, MB BCh BAO, of the University of Galway in Ireland. “Of course, these results need to be further tested with additional studies.”
Long-Term Study Tracks Vitamin D and Brain Changes
The study followed 793 adults, with an average age of 39, who did not have dementia at baseline. Researchers measured vitamin D levels in participants’ blood at the start.
About 16 years later, participants underwent brain scans to assess levels of tau and amyloid beta proteins, both of which are linked to Alzheimer’s disease. Researchers defined high vitamin D as greater than 30 nanograms per milliliter (ng/mL), while levels below that threshold were considered low.
Overall, 34% of participants had low vitamin D levels, and only 5% reported taking vitamin D supplements.
Higher Vitamin D Tied to Lower Tau but Not Amyloid
After accounting for factors such as age, sex, and symptoms of depression, the researchers found that people with higher vitamin D levels in midlife tended to have lower levels of tau protein years later.
However, vitamin D levels did not appear to be related to amyloid beta levels in the brain.
“These results are promising, as they suggest an association between higher Vitamin D levels in early middle-age and lower tau burden on average 16 years later,” Mulligan said. “Mid-life is a time where risk factor modification can have a greater impact.”
Study Limitations and Future Research
One limitation of the research is that vitamin D levels were measured only once, rather than tracked over time.
Reference: “Association of Circulating Vitamin D in Midlife With Increased Tau-PET Burden in Dementia-Free Adults” by Martin David Mulligan, Matthew R. Scott, Qiong Yang, Ruiqi Wang, Saptaparni Ghosh, Keith A. Johnson, Alexa S. Beiser, Sudha Seshadri and Emer R. McGrath, 1 April 2026, Neurology Open Access.
DOI: 10.1212/WN9.0000000000000057
The study was supported by the National Institute on Aging, National Institute of Neurological Disorders and Stroke, Irish Research Council, and Health Research Board of Ireland.
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Amy rose