Vitamin D May Improve Brain Function And Strengthen Memory. Here’s How Much You Need Each Day

In a new study published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, researchers examined vitamin D in brain tissue. They found that higher levels of the vitamin were associated with better cognitive function—a stronger memory and a slower progression of cognitive decline. This study marked the first time vitamin D levels were studied in brain tissue according to the authors—a timely study as experts estimate those living with dementia will surmount 150 million globally by 2050.

“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,” says Sarah Booth, an author on the study and director of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in a press release. 

Using brain tissue from 290 participants—who were part of an ongoing Alzheimer’s study called the Rush Memory and Aging Project—researchers examined vitamin D levels in four regions of the brain. Elevated levels of vitamin D in the brain were associated with a 25% to 33% lower odds of dementia and mild cognitive impairment when measured at the last doctor’s visit before the participant died. 

“It’s kind of resetting the story by looking at the brain levels, and not just the blood levels,” Kyla Shea, author on the study and scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, tells Fortune. “Establishing that vitamin D is in the human brain is an important step to understanding the biology,” while not enough to draw a causal relationship or recommend specific amounts of vitamin D for older adults. In the future, “rigorously designed” studies could begin to outline potential dietary guidelines with specific nutrients to address brain health, Shea says. 

This study did not, however, find any associations between vitamin D levels in the brain and the presence of lewy bodies or amyloid beta build up that signal the development of lewy body dementia and Alzheimer’s respectively. In order to illustrate the mechanisms behind how vitamin D operates in the brain, Shea plans to further study the brain’s structure. 

Vitamin D status also differs by race, and the authors note in the study that their cohort was predominately white. Due to this key limitation, Shea hopes to see if this study’s generalizations can be expanded to a more diverse population in future work using the Minority Aging Research Study. 

“We have a lot more work to do to understand exactly what [vitamin D] is doing,” Shea says. 

Vitamin D can be consumed through food, including a variety of fish like salmon, trout, and tuna, as well as through orange juice or milk fortified with vitamin D. The body also naturally produces vitamin D through sun exposure. Some people may benefit from supplements to boost their levels of the vitamin. 

The recommended dietary allowance of vitamin D is 600 IU a day for those between ages 1 and 70, and 800 IU for those over 70. (For reference: a three-ounce serving of trout has 645 IU and one cup of fortified 2% milk has 120 IU.)

Taking too much vitamin D also poses a risk, specifically when using supplements: it can cause excess calcium buildup, called hypercalcemia, increase the risk for kidney damage, and may cause falling and other injuries, according to Harvard Health. Talk to your doctor to determine how much vitamin D you need and if should consider taking supplements.