Potential Link Between Vitamin D Supplementation and Brain Health in Older Adults

Recent research from Emory University suggests a potential connection between vitamin D supplementation and cognitive health, particularly in older adults at risk of dementia. This study focused on those experiencing mild cognitive impairment (MCI) and sleep disturbances, conditions associated with a higher risk of Alzheimer’s disease.

Mild cognitive impairment serves as a stage between normal aging memory changes and dementia. Sleep issues are common among MCI patients, affecting nearly 50% and possibly increasing cognitive decline risk. “Our findings give us an interesting lead on vitamin D supplement intake and cognitive performance,” stated Victoria Pak, associate professor at Emory University’s Nell Hodgson Woodruff School of Nursing.

The study included 54 adults, aged 50 and above, with both sleep disturbances and diagnosed or suspected MCI. Researchers assessed cognitive function using the Montreal Cognitive Assessment (MoCA), also gathering data on vitamin D supplement use, including dosage and type.

After considering variables like age, sex, body mass index, and education, the study found those taking 5,000 international units (IU) or more of vitamin D daily showed notable cognitive test improvements compared to non-supplement users. Lower doses did not show significant results.

Although higher-dose vitamin D supplementation was linked to better cognition in this group, researchers advocated caution in interpreting the results. The sample size taking 5,000 IU or more was small, and the study was observational, not a clinical trial proving cause and effect.

“The findings do not affirm vitamin D improves memory or prevents dementia, as reverse causation cannot be ruled out,” the researchers noted.

No significant difference was found between vitamin D2 and D3, suggesting dose importance over supplement type. Biological explanations for the link include vitamin D’s role in regulating inflammation, while poor sleep is tied to increased inflammation and cognitive decline. Neuroinflammation could connect sleep issues and cognitive decline.

Future research will involve randomized clinical trials to examine vitamin D supplementation’s direct effects on cognition. Such studies may reveal if vitamin D supports cognitive health as a strategy.

While promising, larger studies are needed. As it was an observational study, high-dose vitamin D recommendations cannot yet be made. Pak advised, “Supplementation suitability depends on individual circumstances, so consult healthcare providers.”

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.