Vitamin D is best known for helping us build strong bones, but recent research shows it may also play an important role in keeping our brains sharp as we age. A new study from Rutgers University looked into how different amounts of vitamin D affect thinking and memory in older women—and the results may surprise you.
Vitamin D is often called the “sunshine vitamin” because our bodies make it when we spend time in the sun. It’s also found in some foods and available in supplement form, especially for people who don’t get enough sunlight or have trouble absorbing the vitamin.
Scientists have become more interested in how vitamin D affects the brain, particularly in older adults. As people age, their risk of memory problems, slower thinking, and even dementia increases. Could vitamin D help protect the brain from these changes?
To explore this question, researchers at Rutgers studied a group of women aged 50 to 70 who were either overweight or obese. The women were divided into three groups. Each group took a different amount of vitamin D every day for one year.
The first group took 600 IU (international units), which is the typical recommended daily amount. The second group took 2,000 IU, and the third group took 4,000 IU—more than six times the standard dose. All participants were also encouraged to lose some weight as part of the study.
After a year, the results showed something interesting. Women who took 2,000 IU of vitamin D per day had better memory and were able to learn new things more easily compared to the women in the other groups. This suggests that a slightly higher dose of vitamin D might help the brain stay more active and alert in older age.
However, there was a downside. While memory improved, reaction times actually got slower with higher doses. Women in the 2,000 IU group were a bit slower in how quickly they responded to tasks. And for those in the 4,000 IU group, the delay in reaction time was even more noticeable.
This is important because slower reaction times can increase the risk of tripping, falling, or getting hurt—something that becomes more dangerous as we get older.
In fact, earlier research has shown that taking more than 2,000 IU of vitamin D daily may raise the chance of falls in older adults. So, while vitamin D can help the brain in some ways, too much may create new risks for the body—especially for balance and movement.
The study raises important questions. Does slower reaction time actually lead to more falls? Do men and women need different amounts of vitamin D? What’s the safest and most effective dose for brain health? More research is needed to find the answers.
In the meantime, the Rutgers study, led by researcher Sue Shapses and published in The Journals of Gerontology: Series A, reminds us that vitamins—even those with clear benefits—should be taken in the right amount. For older adults trying to protect their memory and mental skills, getting enough vitamin D is important, but more isn’t always better.
Other healthy habits also matter for the brain. Eating a Mediterranean-style diet, rich in fruits, vegetables, whole grains, and healthy fats, along with getting enough B vitamins, fiber, and antioxidants, can support long-term brain health and may even help prevent conditions like dementia.
In short, vitamin D can support memory as we age, but too much might slow down our reactions. Striking the right balance is key—and it’s always best to talk to your doctor before making big changes to your supplement routine.
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