In a first of its kind study, higher levels of vitamin D in brain tissue were associated with lower rates of dementia and mild cognitive impairment.

Dietary and nutritional factors have long been linked to thinking or reasoning ability in older adults. But previous studies of vitamin D only looked at dietary intake or measurements of it in the blood, said the study’s lead author, Kyla Shea, PhD, an associate professor at Tufts University.

“We wanted to know if vitamin D is even present in the brain, and if it is, how those concentrations are linked to cognitive decline,” Shea said in a news release.

Researchers examined brain tissue samples from 290 people whose cognitive function had been tracked long-term and prior to any known cognitive decline. The average age of the subjects at time of death was 92 years old. 

The researchers found that vitamin D was present in brain tissue and that people with higher concentrations of vitamin D in the brain also reported higher cognitive function prior to death.  The findings were published this week in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

“This research reinforces the importance of studying how food and nutrients create resilience to protect the aging brain against diseases such as Alzheimer’s disease and other related dementias,” said co-author Sarah Booth, PhD, director of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.

Vitamin D levels were examined in four regions of the brain as part of the study: two regions associated with Alzheimer’s disease, one region linked to blood-flow related dementia, and a fourth region not associated with cognitive decline. 

Further study is needed, the researchers said, particularly because they could not link vitamin D levels with physiological markers associated with Alzheimer’s disease in the brain. Also, vitamin D levels are known to vary by race and ethnicity, and their study was limited by the majority of subjects being white.

Vitamin D is used by the body to build and maintain bones, and is also known to have anti-inflammatory, antioxidant and neuroprotective properties, the Mayo Clinic says. It’s found in a small number of foods, and our skin can convert sunlight into vitamin D. Recommended supplement levels of vitamin D are 400 international units (IU) for children up to age 12 months, 600 IU for people ages 1 to 70 years, and 800 IU for people over 70 years. Taking too much vitamin D in the form of supplements can be harmful, the organization warned.