Vitamin D trial finds no clear depression-prevention benefit during supplementation
Depression diagnoses were uncommon; a borderline finding during longer follow-up leaves vitamin D's preventive effects uncertain.
Based on the published abstract. The full paper may contain additional methods, results and limitations.
The 30-second takeaway
Vitamin D supplementation did not clearly reduce new physician-diagnosed major depression during the planned treatment period in older adults who were largely vitamin D sufficient. Longer follow-up produced a borderline signal in the higher-dose group, but it does not establish a delayed benefit or show that one dose worked better than the other.
This abstract-based summary is limited by few depression events and broad confidence intervals. Participants were largely vitamin D sufficient, limiting conclusions about people with low vitamin D levels.
What researchers found
New physician-diagnosed major depression
Each vitamin D dose versus placebo during planned 5-year supplementation; mean follow-up was 4.2 years.
What the follow-up counted
Researchers tracked new physician diagnoses of major depressive disorder. The secondary analysis counted cumulative diagnoses across the extended follow-up, including supplementation. It did not isolate diagnoses made after treatment ended.
Interpreting the later signal
The primary analysis did not find a statistically significant reduction with either dose. The later signal was borderline, so it should not displace the primary result or be treated as proof of dose superiority.
The original publication
Vitamin D supplementation and incidence of major depressive disorder - A randomized clinical trial.
Ahl NM, Hantunen S, Tuomainen TP et al.
Clin Nutr · 2026
- PubMed ID
- 41506003
- Record checked
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