Want to Protect Your Brain From Alzheimer’s? A 16-Year Study Suggests a Simple Thing to Do Right Now

Maintaining adequate vitamin D levels in midlife may help reduce the risk of Alzheimer’s-related brain changes later in life, according to a 16-year study published in April 2026.

The research, conducted by an international team led by neuroscientist Martin David Mulligan of the University of Galway in Ireland, followed 793 adults with an average age of 39 at the study’s start. None showed signs of dementia or serious memory problems initially.

Participants had their vitamin D levels measured once at baseline. Those with higher vitamin D levels in midlife tended to have lower levels of tau protein tangles in the brain 16 years later, when they were in their mid-50s. Tau tangles are a hallmark of Alzheimer’s disease and can disrupt healthy brain cell function.

About a third of participants had low vitamin D levels, defined in the study as less than 30 nanograms per milliliter of blood. Only about 5 percent were taking vitamin D supplements at the start of the study.

The findings suggest that maintaining healthy vitamin D levels during midlife could be a modifiable risk factor for reducing the likelihood of developing Alzheimer’s disease years later. As Dr. Mulligan noted, “Mid-life is a time where risk factor modification can have a greater impact.”

The study did not assess dementia diagnoses directly but used PET scans to measure tau and amyloid-beta buildup as proxies for Alzheimer’s-like brain changes. Researchers emphasized that while the results show a strong association, they do not prove direct cause and effect, and further research is needed.

Vitamin D can be obtained through sunlight exposure, dietary sources such as fatty fish and fortified foods, and supplements. Individuals concerned about their vitamin D levels should consult a healthcare provider for testing and personalized guidance.