People with higher levels of vitamin D in midlife may have lower levels of a key Alzheimer’s-related biomarker years later, according to new research. The findings suggest a potential link between vitamin D status and brain changes associated with dementia, though the study does not show that vitamin D directly reduces risk.
The study, published in Neurology, followed 793 adults for an average of 16 years and found that those with higher blood levels of vitamin D in their late 30s had lower levels of tau protein in the brain later in life. Tau is one of the biological markers associated with Alzheimer’s disease.
“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 Martin David Mulligan of the University of Galway in Ireland. “Of course, these results need to be further tested with additional studies.”
Researchers measured participants’ vitamin D levels at the start of the study, defining levels above 30 nanograms per milliliter as higher and levels below that as lower. Brain scans conducted years later were used to assess levels of tau and another Alzheimer’s-related protein, amyloid beta.
Higher vitamin D levels were associated with lower tau levels, but the study did not find a relationship between vitamin D and amyloid beta. This distinction is important because both proteins are involved in Alzheimer’s disease, and changes in one do not necessarily translate to changes in overall disease risk.
The researchers accounted for several factors that could influence brain health, including age, sex and symptoms of depression. Still, the study was observational, meaning it cannot determine whether vitamin D levels directly influence the development of Alzheimer’s-related changes.
Another limitation is that vitamin D was measured only once, which may not reflect long-term levels. Only 5% of participants reported taking vitamin D supplements, so the findings do not provide clear insight into whether supplementation would have the same association.
“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.”
For now, the findings add to a growing body of research suggesting that midlife health factors may play a role in brain aging. While vitamin D is one piece of that picture, overall patterns, including diet, physical activity and other lifestyle factors, remain important for long-term cognitive health.
This study was supported by the National Institute on Aging, the National Institute of Neurological Disorders and Stroke, the Irish Research Council and the Health Research Board of Ireland.