Vitamin D has long been known to be important for healthy bone growth, but new evidence suggests it also may help keep the brain sharp as people age. The problem is that most older people don’t get enough of it.
With a new $4.7 million grant from the National Institutes of Health, UC Davis researchers will launch a first-of-its-kind study to determine if vitamin D supplementation in the elderly can effectively help prevent cognitive decline, and whether the association is stronger among African Americans and Latinos.
“Vitamin D deficiency disproportionately affects the elderly because as people age the skin no longer synthesizes vitamin D effectively,” said John Olichney, professor of neurology, clinical core leader for the UC Davis Alzheimer’s Disease Center and study principal investigator. “And it’s especially a problem among people with darker skin. It’s an epidemic in our elderly, even in sunny California.”
To address the problem, Olichney will lead a 5-year, phase II randomized trial that will involve a diverse group of 180 people in the Sacramento and East Bay areas. One-third of participants will have normal cognition, another third will have mild cognitive impairment (isolated memory loss), and the third group will have mild Alzheimer’s dementia. All participants will get vitamin D supplements, but half will get a high dose – 4,000 international units per day, while the rest will receive the standard intake of 800 international units recommended by the Institute of Medicine.
The clinical trial follows a 2015 study by UC Davis and colleagues at Rutgers University that found that 61 percent of elderly people have insufficient vitamin D blood levels, and that the number climbs to about 70 percent among Latinos and African Americans. The study also found that vitamin D insufficiency was associated with faster rates of decline in executive function (the ability do complex problem solving and planning), and in episodic memory.
Participants in the new study will be tested on executive function using a standard Spanish-English Neuropsychological Assessment Scale. They also will undergo brain imaging studies to gauge decreases in white matter volume or other white matter abnormalities. In addition, they will have their blood and urine tested for biomarkers associated with cognitive decline.
Olichney points out that unlike vitamin B12, vitamin D insufficiency has not been proven to cause dementia, but research has shown that it appears to worsen cognition. And he notes that it’s plausible that vitamin D helps protect brain function because it has antioxidant properties, stimulates proteins important for nerve cell function and has beneficial effects that promote the clearance of beta amyloid through the immune system. Beta amyloid is the main component of the amyloid plaques found in the brains of Alzheimer patients.
Olichney said the data gathered over the course of the study could eventually lead to an important new understanding of the role of vitamin D in brain health.
“If vitamin D supplementation improves cognitive outcomes, this could have a large impact on public health, especially among Latinos and African Americans,” he said, “because vitamin D status is easily treatable and may help prevent dementia.”