Research synthesisModerate evidenceSmall effect5 studies · 3 beneficial · 2 neutral · 0 harmful
Across 5 studies, 3 reported beneficial effects of vitamin D supplementation on reducing tumor necrosis factor alpha (TNF-α), with effect sizes ranging from small to moderate. The most consistent evidence comes from systematic reviews and meta-analyses, including a large dose-response meta-analysis (962 participants) showing a small but statistically significant reduction in TNF-α. The median study duration was 56 days, suggesting effects are typically observed after 8 weeks of supplementation; the most-studied dose was up to 5,000 IU/day, and benefits were noted in populations including depressed patients and overweight/obese individuals.
- Effective dose range: up to 5,000 IU/day
- Studied populations: depressed individuals, overweight/obese population, older adults with vitamin D deficiency
Caveats: Available evidence is overwhelmingly positive (3 of 5 studies beneficial) — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). Many of the included studies did not reach statistical significance (2 of 5 neutral), and the effect size is small, so clinical significance may be limited. One neutral study in overweight and obese children suggests benefits may not extend to pediatric populations.
Generated Jun 12, 2026