Can vitamin D help preserve memory?

A small study suggests that older adults who had both sleep issues and mild cognitive impairment performed better on a thinking test if they said they were taking high-dose vitamin D supplements. The finding prompts new questions about whether vitamin D levels may play a role in brain health during the early stages of cognitive decline.

The research included 54 adults with sleep disturbances and mild cognitive impairment, a condition marked by measurable changes in thinking or memory that do not necessarily mean dementia.

Those who reported taking at least 5,000 international units of vitamin D each day scored more than 13 percent higher on the Montreal Cognitive Assessment than participants who took none, even after researchers accounted for other factors.

The Montreal Cognitive Assessment, or MoCA, is a screening test designed to measure several thinking skills. A higher score on its own does not prove that someone will not develop dementia.

Lower reported doses were not associated with the same benefit. Researchers also found similar scores among people using vitamin D2 and vitamin D3.

Vitamin D is involved in muscle and nerve function and has also been studied for possible links to sleep. Sleep problems can accompany cognitive decline, making the overlap an area of scientific interest.

Differences in how much supplement people may need are one reason scientists are exploring more individualized vitamin D guidance.

Still, the study did not randomly assign participants to different vitamin D doses. People who take supplements may differ from those who do not in diet, overall health, medical care or other factors that can affect test results.

The small sample size also limits certainty. The researchers could not conclude that vitamin D caused the stronger scores or that increasing intake would improve memory.

The amount reported, 5,000 international units per day, is a high dose and should not be taken as a general recommendation based on this research alone.

The study examined a specific group with both cognitive and sleep difficulties. It does not show the same relationship in healthy older adults or in people diagnosed with Alzheimer’s disease.

Future randomized trials could help determine whether vitamin D supplements affect cognitive performance over time and whether any benefit depends on starting vitamin D levels.

Published in Sleep Medicine, the findings point to a possible connection that deserves more study rather than proof that high-dose vitamin D prevents dementia.

That distinction between association and treatment effect matters because supplement use was self-reported. A randomized study would need to measure vitamin D levels, assign doses and track cognitive outcomes over time before firmer conclusions could be made.

The study appeared in Sleep Medicine.

If you are interested in this topic, please read articles about Vitamin D could reduce dementia risk, study finds, and Can Too Much Vitamin D Slow Your Brain?.

For more information, please see articles about Vitamin D and cognitive function: What you need to know, and Vitamin D deficiency linked to higher dementia risk, study finds.

Source: Emory University.