High-dose vitamin D may boost brain heath in older adults at risk of dementia

For this study, researchers recruited 54 adults with an average age of about 67 who had diagnosed or suspected MCI and sleeping problems.

Study participants’ cognition was assessed through the Montreal Cognitive Assessment (MoCA), and their sleep quality was assessed via the Pittsburgh Sleep Quality Index (PSQI) or the Epworth Sleepiness Scale (ESS).

Study participants also self-reported their daily vitamin D consumption and dosage.

“Vitamin D is especially interesting because it’s part of everyday life, yet we’re still learning about the role it may play in cognitive health,” Victoria Pak, PhD, MS, MTR, associate professor at Emory University in Atlanta and senior author of the study, told Medical News Today.

“We focused on people with sleep disturbances and mild cognitive impairment because sleep and cognition are closely connected, and we wanted to understand whether vitamin D supplement intake was associated with differences in cognitive function in this group,” added Pak.

At the study’s conclusion, researchers discovered that study participants who reported taking 5,000 international units (IU) or more of vitamin D each day scored more than 13% higher on the MoCA, when compared to those who did not take a vitamin D supplement.

“Scores differed by approximately four points on the MoCA,” Pak said. “This was an observational study, so we need to be cautious about how we interpret the finding. What makes the result important to investigate further is that we observed this relationship in people with mild cognitive impairment and sleep disturbances.”

“The amount of vitamin D someone needs can vary, so anyone concerned about their levels should talk to their healthcare provider about whether testing is appropriate,” she added.

For the next steps in this research, Pak said they plan to test these findings in a clinical trial to determine whether vitamin D supplementation can influence cognition.

“If the trial shows that vitamin D contributes to the differences in cognitive function we observed, that could open up new possibilities for supporting cognitive health,” she said.

MNT had the opportunity to speak with Manisha Santosh Parulekar, MD, FACP, AGSF, CMD, chief of the Division of Geriatrics and co-director of the Center for Memory Loss and Brain Health at Hackensack University Medical Center.

Parulekar, who was not involved in this study, commented that her first reaction to these findings was one of optimism.

“The findings highlight an accessible, noninvasive intervention for an at-risk group,” she explained. “It reinforces the hypothesis that dietary modifications impact cognitive decline.”

MNT also spoke with Dung Trinh, MD, an internist for MemorialCare Medical Group and chief medical officer of Healthy Brain Clinic in Irvine, CA, who was also not involved in this study.

Trinh said that he found this to be an intriguing and clinically relevant finding, particularly because sleep disturbance is so common in patients with mild cognitive impairment and may contribute to worsening cognitive health over time.

“The study found that participants taking 5,000 IU or more of vitamin D daily had better cognitive scores, but I would emphasize that this was a small, cross-sectional study involving only 54 participants, so it shows an association rather than proving that high-dose vitamin D improves cognition,” he continued.

“Still, the magnitude of the observed difference is enough to justify larger and more rigorous studies,” he emphasized.

When asked how vitamin D might help improve cognitive function in people with sleep disturbances and MCI, Trinh said one possible explanation is vitamin D’s role in regulating inflammation and immune function.

“Poor sleep has been associated with increased inflammatory activity, and neuroinflammation may contribute to cognitive decline and neurodegenerative processes. Vitamin D may help modulate inflammatory signaling, and there is also some evidence that vitamin D status is related to sleep quality. That creates a plausible biological pathway in which adequate vitamin D could potentially support both sleep and brain health, although this study did not directly demonstrate that mechanism and the broader research on vitamin D and cognition remains mixed.”

–Dung Trinh, M.D.

Monique Richard, MS, RDN, LDN, FAND, IFNCP, a registered dietitian nutritionist and owner of Nutrition-In-Sight — who was not involved in this study — added that in addition to inflammation, vitamin D appears to influence other pathways relevant to brain health, including oxidative stress, neuronal signaling, and neurotrophic factors.

“Sleep disturbance itself can also amplify inflammation and metabolic stress, so vitamin D may be one piece of a much larger sleep–brain–immune connection,” Richard continued.

“My perspective is that the greatest potential benefit may be in identifying someone who is insufficient or deficient rather than assuming that ‘more is always better.’ Evidence from larger trials remains mixed, which is an important part of the story, emphasizing the fact that personalizing recommendations is best,” she told us.

“Vitamin D may not be a magic memory pill, but correcting a deficiency could be one modifiable piece of the brain-health puzzle,” Richard added.

For those worrying about their vitamin D intake, Richard recommended first looking at the whole picture rather than immediately reaching for a high-dose supplement of D2 or D3.

“Vitamin D is naturally present in relatively few foods, but fatty fish such as salmon and trout, egg yolks, and fortified milk or plant-based beverages can contribute in meaningful, beneficial amounts. Reading labels, understanding sources and whether that item — irradiated mushrooms, for example — are contributing reliable amounts, are a few additional tips to consider with Vitamin D.”

–Monique Richard, MS, RDN, LDN, FAND, IFNCP

For people with limited sun exposure, low dietary intake, or other risk factors, Richard said supplementation may be appropriate — but ideally based on an individual’s health history, dietary pattern, medications, ethnicity, conversion rate, and, when clinically indicated, a 25-hydroxyvitamin D blood test.

“Importantly, the 5,000-IU dose in this study should not be interpreted as a universal recommendation,” she continued. “The NIH lists 4,000 IU/day as the tolerable upper intake level for most adults from food and supplements combined, although higher doses may sometimes be used under medical supervision to treat deficiency.”

“Consulting with a registered dietitian nutritionist (RDN) can help meet people where they are at and tailor an appropriate recommendation and game plan for their needs,” Richard added.

“The goal with vitamin D is to identify whether it is a missing piece of that individual’s health picture and then how that piece can be addressed most appropriately to reap the benefits and support the body and mind’s needs,” the dietitian concluded.