Two new studies add to evidence that older people with low levels of vitamin D may be more likely to suffer from cognitive impairment.
The hope is that vitamin D supplements may be able to slow mental decline -- an intervention that one research team plans to put to the test this summer.
Vitamin D is best known for helping the body absorb calcium, which restores and strengthens bone, protecting against fracture.
But vitamin D also seems to have anti-inflammatory effects that may help keep blood vessels healthy, ensuring nutrient- and oxygen-rich blood flow to brain cells, says Amie Peterson, MD, of Oregon Health & Science University in Portland.
In addition, the presence of vitamin D receptors throughout the brain suggests that it may directly affect brain tissue, she tells WebMD.
Testing Cognitive Impairment
Still, whether vitamin D has a role in memory and cognition is unclear at this point, Peterson says, and studies have had conflicting results.
To help answer the question, Peterson and colleagues studied about 150 people aged 70 and older living on their own. Their average age was 85, and about three-fourths were women.
Participants' vitamin D levels ranged from 9 to 90 nanograms per milliliter of blood. Levels of 30 or higher are considered normal, according to Peterson.
All participants were given a standard 30-point test that is used to screen for cognitive impairment.
Results showed that the lower their score on the test, the lower their vitamin D levels.
The average vitamin D level was 42.8 for the 42 participants with a perfect score of 30 on the test; 36.7 for the 89 participants who scored between 27 and 29 ("still normal but lower," says Peterson), and 34.8 for the 21 people with scores of 22 to 26 ("mild cognitive impairment").
The study also showed that lower vitamin D levels were associated with a greater risk of falling.
This summer, Peterson and colleagues plan to embark on a study of people with Parkinson's disease to look at the effect of vitamin D supplementation on cognition, balance, and gait. Still to be tested is whether the intervention will help older people who are otherwise healthy.