Vitamin D is best known for helping the body build and maintain strong bones.
Most people get it from sunlight, certain foods, or dietary supplements. In recent years, scientists have also become interested in whether vitamin D plays a role in keeping the brain healthy as people grow older.
Researchers believe it may influence memory, learning, and other thinking skills, but many questions remain about the best amount to take.
A new study from Rutgers University explored this issue by following women aged 50 to 70 who were overweight or living with obesity. This group was chosen because excess body fat can affect how vitamin D is stored and used in the body.
The researchers wanted to discover whether different daily doses of vitamin D would influence memory, learning ability, and reaction time over the course of a year.
The women were divided into three groups. One group received 600 international units (IU) of vitamin D each day, which is the recommended daily amount for many adults. A second group took 2,000 IU daily, while the third group received 4,000 IU each day. All participants were also encouraged to lose weight during the study.
After one year, the researchers found that the women taking 2,000 IU each day performed better on tests of memory and learning than those taking the standard dose. These results suggest that a moderate increase in vitamin D may support certain aspects of brain function, particularly the ability to remember information and learn new tasks.
However, the findings also revealed an unexpected concern. Women taking 2,000 IU, and especially those taking 4,000 IU, showed slower reaction times during testing. Slower reactions may not seem important at first, but they can increase the risk of accidents, particularly in older adults who need to react quickly to avoid trips, falls, or other hazards.
Previous research has reported similar concerns. Some studies have found that older adults taking high doses of vitamin D, including 2,000 IU or more each day, may have a higher risk of falling. Scientists do not yet fully understand why this happens, but the results suggest that taking more vitamin D is not always better.
The study raises several important questions for future research. Scientists still need to determine the safest and most effective vitamin D dose for protecting brain health. They also want to know whether men and women respond differently, whether slower reaction times directly increase the risk of falls, and which groups of people may benefit most from supplements.
The researchers emphasise that vitamin D is only one part of maintaining good brain health. A balanced lifestyle remains essential. Eating a healthy diet, staying physically active, getting enough sleep, and managing health conditions such as high blood pressure and diabetes all contribute to healthy ageing and may lower the risk of memory problems.
Diets such as the Mediterranean diet, which is rich in vegetables, fruits, whole grains, legumes, fish, olive oil, and healthy fats, have been linked to better brain function and a lower risk of dementia. Foods that provide fibre, B vitamins, and antioxidants may also help protect the brain as people age.
The study was led by Sue Shapses from Rutgers University and published in The Journals of Gerontology: Series A.
The findings suggest that while vitamin D may offer benefits for memory, taking very high doses could have unwanted effects. Like many nutrients, vitamin D appears to work best when taken in the right amount rather than the highest amount possible.
If you care about brain health, please read studies about Vitamin B9 deficiency linked to higher dementia risk, and flavonoid-rich foods could help prevent dementia.
For more health information, please see recent studies that cranberries could help boost memory, and how alcohol, coffee and tea intake influence cognitive decline.
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