Study: Higher Vitamin D Levels Are Linked to Better Cognitive Function

New research from Tufts University suggests that vitamin D may protect against cognitive decline. However, the scientists emphasize that more research is needed to uncover the mechanisms behind their findings.

Vitamin D is a fat-soluble vitamin and pro-hormone that a person gets through sun exposure or diet. Over the past few years, scientists have focused on vitamin D and its possible relationship with several diseases and conditions, including dementia.

For example, a 2020 research review found a few studies suggesting that low vitamin D levels are associated with an increased risk of cognitive decline, dementia, and Alzheimer’s disease (AD). However, studies with more participants and a longer follow-up period did not find this association.

Recently, scientists from Tufts University in Boston, Massachusetts, investigated the possible links between vitamin D and cognitive function.

Using participants from the Rush Memory and Aging Project (MAP), the researchers found that higher brain concentrations of vitamin D metabolite 25(OH)D3 were associated with better cognitive function. However, vitamin D was not associated with the physiological markers of AD or chronic or microscopic strokes.

They published their findings on December 7 in Alzheimer’s & Dementia — the journal of the Alzheimer’s Association.

To conduct the study, the research team used brain tissue samples from 290 MAP participants. MAP is a long-term community-based study investigating the possible risk factors for AD and other forms of dementia.

At the time of enrollment, MAP participants did not have dementia and agreed to undergo yearly cognitive assessments. They also agreed to donate their organs for research upon death.

The team measured vitamin D levels in four regions of the brain, including the mid-temporal cortex (MT), mid-frontal cortex (MF), cerebellum (CR), and anterior watershed white matter (AWS).

The scientists also obtained the participant’s blood plasma vitamin D levels and cognitive function assessments collected at the last clinical evaluation before they died.

After evaluating the data, the team found that vitamin D was present in the tissue of all four brain regions. They also found an association between high vitamin D levels in the four brain regions and better cognitive function.

According to the study, higher levels of 25(OH)D3 in all brain regions measured were associated with better semantic and working memory. Also, higher 25(OH)D3 concentrations in the AWS were additionally associated with better episodic memory and perceptual speed.

Still, vitamin D levels were not associated with other brain changes linked to AD, such as the buildup of amyloid plaques or Lewy body disease.

The team also discovered that free vitamin D blood plasma levels were moderately similar to levels found in the brain. Free 25(OH)D is thought to be more readily available to tissues in the body.

Their findings suggest that adequate vitamin D in the brain may be associated with less cognitive decline, but the scientists say more research is needed. Specifically, to determine vitamin D’s role in cognitive functions of specific brain regions and the importance of free vitamin D to brain health.

The team also points out that most study participants were white, non-Hispanic individuals, so the results might not generalize to other groups.

In a press release, lead author Kyla Shea, a scientist on the Vitamin K Team and an associate professor at the Friedman School of Nutrition Science and Policy at Tufts University said, “we now know that vitamin D is present in reasonable amounts in human brains, and it seems to be correlated with less decline in cognitive function.”

“But we need to do more research to identify the neuropathology that vitamin D is linked to in the brain before we start designing future interventions,” Shea concluded.

How much vitamin D is enough?

According to the National Institutes of Health (NIH), almost one in four people have vitamin D blood levels that are too low or inadequate for bone and overall health. However, a blood test can easily measure vitamin D levels in the body.

The NIH suggests that blood levels of 50 nmol/L (20 ng/mL) or above are adequate for most people — while vitamin D levels below 30 nmol/L (12 ng/mL) are too low and might negatively impact health.

However, levels above 125 nmol/L (50 ng/mL) are considered too high and might cause health issues. So, a person should use caution when taking supplements.

Vitamin D is available in two forms — vitamin D2 and D3. However, the NIH advises that vitamin D3 might be more effective at raising levels in the body.

Their recommended dose of vitamin D for adults is 600 International Units (IU) per day, while adults 71 years old or older should aim for 800 IU daily.


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