Big effect
A meta-analysis of 962 patients found vitamin D supplementation slashed depressive symptom scores by nearly a full standard deviation — a remarkably large effect — but the same analysis found no impact on body weight or inflammation markers like interleukin-6.
This is among the first systematic reviews to test vitamin D specifically for diagnosed depression, so while the effect size is unusually strong, it needs replication before you can count on it as an add-on treatment.
Researchers pooled data from multiple randomized trials and found that taking up to 5,000 IU of vitamin D daily was linked to a big drop in depression scores compared to placebo. However, the supplement did not budge body weight or several inflammatory markers, suggesting its benefit may be specific to mood pathways rather than a general health overhaul.
Where this fits in the evidence
This is among the first studies we've indexed on Vitamin D for Improved Depressive Symptoms — treat it as an early signal until more research accumulates.
The study
- Systematic Review
- n = 962
- 2026-03-17
- Frontiers in nutrition
This is a plain-language summary of a research finding, not medical advice. Pillser surfaces research signals to help you decide what's worth investigating — always consult a qualified professional before changing what you take.