A large study published in Alzheimer’s & Dementia examined whether taking vitamin D supplements is associated with a lower risk of developing dementia. The findings were striking: people who used vitamin D had a significantly lower incidence of dementia over time.

What the Researchers Did

The study followed 12,388 adults who were dementia‑free at the start. Participants were grouped into:

• D+: those taking vitamin D supplements
• D−: those not taking vitamin D

Researchers tracked who developed dementia and adjusted for age, sex, education, race, depression, baseline cognitive status, and APOE‑ε4 genotype — the major genetic risk factor for Alzheimer’s disease.

Key Findings

1. Vitamin D users had a much lower risk of dementia

Supplement users showed a 40% lower incidence of dementia compared to non‑users. This is a substantial difference, even after adjusting for multiple health and demographic factors.

2. Some groups benefited more than others

• Women saw stronger protective effects than men
• People with no cognitive impairment at baseline benefited more
• Those without APOE‑ε4 showed the greatest reduction in risk

3. All vitamin D formulations were similarly protective

Whether participants used D2, D3, or combination supplements, the association with lower dementia risk remained consistent.

What This Means for Brain Health

While this was an observational study — meaning it cannot prove cause and effect — the results add to growing evidence that maintaining adequate vitamin D levels may support long‑term cognitive health.

Vitamin D plays roles in inflammation, immune function, and brain signaling pathways, all of which may influence dementia risk over time.

Bottom Line

Vitamin D supplementation was associated with longer dementia‑free survival and a substantially lower risk of developing dementia. More clinical trials are needed, but this study suggests that vitamin D may be a simple, accessible tool for supporting brain health as we age.

Reference

The study is available here: Vitamin D supplementation and incident dementia.