Research Finds Common Vitamin Linked to 13 Percent Better Brain Performance - Video

Higher vitamin D supplement intake was associated with better cognitive performance in older adults with mild cognitive impairment and sleep disturbances, according to researchers at Emory University.

The preliminary study, published in Sleep Medicine, examined 54 adults with sleep problems and mild cognitive impairment (MCI), a condition involving subtle changes in memory and thinking that can precede dementia.

Participants who reported taking 5,000 IU or more of vitamin D daily scored more than 13% higher on the Montreal Cognitive Assessment (MoCA) than those who did not take vitamin D, even after researchers adjusted for other factors.

The MoCA is a commonly used screening tool that assesses memory, attention, language and other thinking abilities. Researchers did not observe similar cognitive benefits among participants taking lower daily amounts of vitamin D.

The study also examined whether the type of vitamin D mattered. Cognitive performance was similar among participants taking vitamin D2 and those taking vitamin D3, suggesting that the observed association was not specific to one form of the supplement.

Researchers highlighted the potential importance of addressing modifiable factors during MCI, when cognitive changes may be emerging but before dementia has fully developed. Sleep disturbances are also common in people with cognitive impairment and Alzheimer's disease, and previous research has linked vitamin D deficiency with problems such as insomnia and nighttime awakenings.

However, the researchers emphasized that the findings are preliminary and do not show that high-dose vitamin D prevents or treats dementia. The study was small and based on reported supplement use, so larger and longer-term studies are needed to determine whether vitamin D supplementation directly improves cognitive function.

Importantly, 5,000 IU per day is a high supplemental dose, and people should not start taking this amount without medical guidance, as excessive vitamin D can cause harmful calcium buildup and other complications.

REFERENCE: Sirui Zhou, Paul Sudeshna, Lynn Marie Trotti, Donald Bliwise, Victoria Pak. Vitamin D supplement intake is associated with better cognition in persons with sleep disturbance and mild cognitive impairment. Sleep Medicine, 2026; 146: 108960 DOI: 10.1016/j.sleep.2026.108960