Taking a vitamin D supplement may lower your risk of dementia—especially if you’re older and female, according to new research.

A study published in Alzheimer’s & Dementia this week found that older adults who took vitamin D supplements were 40% less likely to develop dementia over the course of 10 years when compared to those who did not.

It’s estimated that more than 150 million globally will live with dementia by 2050. So it’s imperative to understand how potential lifestyle factors can lower the incidence, keeping people mentally healthier as they age.   

Researchers examined data from more than 12,000 participants with an average age of 71. They discovered that 75% of those who developed dementia over 10 years had not taken vitamin D supplements. Females who had taken vitamin D supplements were nearly 50% less likely to develop dementia than those who had not. Men who had taken vitamin D supplements were also less likely to develop dementia than those who had not, but only by 26%. The outsize benefit to women is welcome, given that worldwide, women with dementia outnumber men two to one.

Those with normal cognition prior at the start of the study who took vitamin D supplements were 56% less likely to develop dementia. Those with mild cognitive impairment who took vitamin D supplements were 33% less likely, researchers found.

Those who took vitamin D supplements consumed one of three formulations: calcium-vitamin D, cholecalciferol, or ergocalciferol. Benefits were similar for all three, according to researchers.

“Our findings give key insights into groups who might be specifically targeted for vitamin D supplementation. Overall, we found evidence to suggest that earlier supplementation might be particularly beneficial, before the onset of cognitive decline,” Zahinoor Ismail, a researcher on the study professor at the University of Calgary and University of Exeter, tells Neuroscience News. 

How does vitamin D help?

Vitamin D can help rid the brain of the amyloid beta protein, which is integral to the development of plaque in Alzheimer’s disease. Low levels of vitamin D and vitamin D deficiency have been associated with a higher risk of developing dementia.

This study builds on previous research on the vitamin’s influence on the brain. A study from Tufts University found that higher levels of vitamin D in brain tissue were correlated with better cognitive function, like memory. 

Nutrients like vitamin D can “create resilience to protect the aging brain against diseases such as Alzheimer’s disease and other related dementias,” wrote Sarah Booth, an author on the study and director of the Jean Mayer USDA Human Nutrition Research Center on Aging at the university, in the study’s press release last year. 

How much vitamin D should you take?

Vitamin D can be consumed through foods like fortified milk and fish, and naturally through sunlight. For those between ages 1 and 70, the recommended dietary allowance of vitamin D is 600 IU. For those over 70, it rises to 800 IU. (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 can cause harm and calcium buildup, which increases the risk for kidney damage, according to Harvard Health. So it’s important to speak with your doctor before deciding to increase your vitamin D exposure using supplements, food, and/or sunlight. 

While increasing vitamin D intake may be beneficial for certain groups, more research needs to be done on how the vitamin directly impacts the brain.