New research data suggests that sufficient levels of vitamin D are associated with a lower risk of dementia and Alzheimer's disease, establishing this vitamin as a potentially modifiable risk factor.

A long-term study followed nearly 800 people without dementia, with an average age of 39, recording their vitamin D levels and examining their brains 16 years later. The results showed that individuals with higher vitamin D levels had lower accumulation of the protein tau, an important biomarker of Alzheimer's disease. However, the researchers emphasize that the link is correlational and does not prove causation.

Previous meta-analyses have shown that low levels of vitamin D are associated with a 49% higher risk of dementia, while its deficiency can significantly increase the likelihood of developing Alzheimer's disease. People with low levels are up to 50% more likely to develop dementia over time.

Scientists believe that vitamin D helps protect the brain by reducing inflammation, protecting nerve cells, and removing toxic proteins, such as amyloid and tau, which are linked to Alzheimer's.

However, experts warn that taking vitamin D supplements is not guaranteed to prevent dementia. More clinical studies are needed to confirm the protective effects.

Despite this, maintaining adequate levels of vitamin D – through sunlight, diet or supplements – is considered one of the simplest strategies for maintaining cognitive health, especially in middle age, where future risk for dementia seems to be largely established.