Different vitamin D doses may influence memory and reaction speed in different ways

Taking more vitamin D does not automatically lead to better brain function. In a study of women in midlife and older age, a moderate daily dose was tied to gains on some memory tests, while larger doses were linked to slower reaction times.

Researchers at Rutgers University examined women between the ages of 50 and 70 who were overweight or had obesity. They set out to see whether varying amounts of vitamin D affected learning, memory and response speed.

The women were given 600, 2,000 or 4,000 international units of vitamin D each day for one year. During the study, all of them were also encouraged to lose weight.

After a year, the group taking 2,000 units showed better results on certain learning and memory measures. At the same time, that dose — and especially the 4,000-unit dose — was associated with slower reaction times.

The findings, published in The Journals of Gerontology: Series A, suggest that different thinking skills may respond differently to vitamin D rather than improving in the same way.

Reaction speed is important because it helps a person respond quickly to changes in the surroundings. Even so, the study did not show that slower test performance caused more falls or injuries.

The results also do not mean that 2,000 units is the right dose for everyone. The trial focused on a specific group of women, so the findings may not apply to men, younger adults or people with other health conditions.

Vitamin D is vital for bone health, and people get it from sunlight, food and supplements. Scientists have been studying possible links between vitamin D and the brain, but evidence for cognitive benefits remains mixed.

Because the participants were also trying to lose weight, the research took place within a broader health program. More studies will be needed to separate the effects of vitamin D dose from other factors and to see whether the changes last.

Memory, learning and reaction speed are distinct abilities, so a supplement can produce different outcomes on different tests. Improvements in a laboratory setting also do not necessarily mean better everyday functioning. Future research will need to look at broader outcomes and consider how starting vitamin D levels affect responses to different doses.

The study underscores an important scientific point: higher nutrient doses do not always affect every function in the same way. More evidence is needed before vitamin D can be considered a dependable way to improve memory or protect cognitive health.

Source: Rutgers University.