Vitamin D Supplementation and Its Potential Link to Cognitive Health

Recent research has revealed a possible connection between vitamin D supplements and brain health, targeting older adults at risk for dementia. A study by researchers at Emory University highlights that increased doses of vitamin D may improve cognitive performance among those with mild cognitive impairment (MCI) and sleep disturbances. These two factors contribute to a higher risk of Alzheimer’s disease.

Understanding Mild Cognitive Impairment

MCI is often viewed as an intermediate state between typical age-associated memory changes and dementia. Sleep issues are prevalent in people with MCI, impacting nearly half of them and potentially raising the risk of further cognitive decline.

“Our findings provide a notable insight into the association between vitamin D supplementation and cognitive function, especially in individuals with mild cognitive impairment and sleep disturbances,” stated Victoria Pak, an associate professor at Emory University’s Nell Hodgson Woodruff School of Nursing, in an interview with Newsweek. Pinpointing adjustable factors is crucial, particularly when cognitive symptoms are already evident, Pak elaborated.

The Study Details

The research included 54 participants aged 50 and above, all experiencing sleep disturbances and diagnosed or suspected MCI. Researchers evaluated cognitive function using the Montreal Cognitive Assessment (MoCA), a recognized screening tool for memory and cognitive skills. They also collected data on vitamin D usage, including dosage and type.

After considering variables such as age, gender, body mass index, and educational background, it was found that participants consuming 5,000 international units (IU) or more of vitamin D daily performed significantly better on cognitive assessments compared to those not using supplements. Lower doses did not show a noticeable link to cognitive performance.

The study concludes that high-dose vitamin D supplementation is connected to better overall cognitive function in this specific group of older individuals. However, experts advise interpreting these results with care. The observation is not derived from a clinical trial designed to prove causation, suggesting the findings do not guarantee that vitamin D enhances memory or prevents dementia.

Concerns About Reverse Causation

Researchers noted that reverse causation could not be ruled out, meaning that participants with better cognitive function might be more inclined to follow health-conscious practices, such as taking supplements. The study also observed no significant difference between vitamin D2 and D3, implying the importance of dose over supplement type.

Possible Biological Explanations

Scientific evidence suggests several biological reasons for the potential connection. Earlier studies indicate vitamin D might aid in regulating inflammation, and poor sleep is linked to heightened inflammatory activity and adverse cognitive results. Neuroinflammation has also been suggested as a mechanism linking sleep disturbances to cognitive decline.

It remains uncertain why this association appeared solely among those reporting higher vitamin D intake. Victoria Pak mentioned a randomized clinical trial as the next step to test vitamin D supplementation directly, helping determine its causal effect on cognitive performance and whether it provides a strategy to support cognitive health.

Despite promising findings, more extensive studies are essential. “Given that this was an observational study, we cannot yet recommend high-dose vitamin D,” Pak stated. “Supplementation suitability varies per individual, so consulting with a healthcare provider is important before considering it.”

Reference: Zhou S, Sudeshna P, Trotti LM, Bliwise D, Pak V. Vitamin D supplement intake is associated with better cognition in persons with sleep disturbance and mild cognitive impairment. Sleep Med. 2026 Oct;146:108960. doi: 10.1016/j.sleep.2026.108960. Contact Newsweek editors on this story: Kara Dolman and Emma Lee-Sang