The future just got brighter, thanks to the sunshine vitamin.
Scientists in Ireland have added to a growing stack of research on the relationship between vitamin D levels in the blood and a possible lower risk of dementia.
A 16-year study found that higher vitamin D intake during middle age could have something to do with the level of tau protein deposits in the brain — a key indicator of dementia — in old age.
Nearly 800 dementia-free participants were recruited for the study, with an average age of 39. Each had their vitamin D levels tested at the outset, and then received a brain scan roughly 16 years later to measure their levels of tau and amyloid beta proteins, another sign of Alzheimer’s disease.
Participants’ vitamin D levels were considered high if they were greater than 30 nanograms per milliliter (ng/mL) and low if they fell below that figure.
While no correlation was found between vitamin D levels and amyloid beta proteins, those who had more vitamin D in their blood at the start tended to have lower amounts of tau in their brains years later. (It’s notable that the participants only had their vitamin D levels tested at the start of the study.)
The researchers clarified that while this doesn’t necessarily mean that higher vitamin D is the direct cause of lower tau proteins, there was a clear association between the two.
Midlife is a crucial time for lifestyle interventions that could have benefits for a variety of health issues down the line, helping to prevent things like bone and muscle loss as well as cognitive decline.
The study’s author, Martin David Mulligan of the University of Galway, believes these findings could lead to better and more effective preventative care for people at risk of developing dementia later in life, noting that low vitamin D levels are easily modifiable and treatable.
“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,” he said. “Midlife is a time where risk factor modification can have a greater impact.”
An analysis from 2025 revealed a similar connection between vitamin D levels and Alzheimer’s risk, suggesting that low vitamin D can increase a person’s likelihood of developing dementia by a whopping 49%.
A report published in The Lancet about the growing global dementia burden stated that by 2030, a projected 82 million people worldwide will be living with dementia, with an associated cost of close to $2 trillion.
And while there is not yet a cure for dementia, relatively small tweaks to several lifestyle factors, including diet, have been shown to decrease a person’s risk.
Taking up new hobbies, whether it’s cooking meals at home or gardening, has been shown to help keep dementia at bay.
Vitamin D is an essential nutrient that can affect immune and muscle function, skeletal health, cardiovascular health and risk of heart attack and even depression and anxiety. But an estimated two-thirds of Americans are considered vitamin D deficient, according to a nutritionist from the University of Miami.
Not only is vitamin D associated with fewer tau proteins in the brain, but it can also help ward off osteoporosis and osteopenia and keep energy levels up.
While you’re ideally getting enough vitamins and minerals from the whole foods you eat, there aren’t many foods that are naturally high in vitamin D, aside from beef liver, egg yolks, cheese and fatty fish like salmon, according to the National Institutes of Health.
Dietary supplements can fill in the gaps, as can regular exposure to sunlight — helping you to shine on for years to come.
