Research synthesisModerate evidenceSmall effect4 studies · 3 beneficial · 1 neutral · 0 harmful
Across 4 studies, 3 report beneficial effects of vitamin D supplementation on reducing parathyroid hormone (PTH) levels, with small-to-moderate effect sizes (e.g., MD -4.19 pg/mL, SMD -0.49). Evidence primarily comes from systematic reviews and meta-analyses in clinical populations (depression patients, kidney transplant recipients, healthy adults). A neutral study in bariatric surgery patients found no significant difference between high and moderate doses. The median study duration was 90 days, suggesting effects may require several weeks to emerge.
- Effective dose range: up to 5,000 IU/day
- Studied populations: clinical populations (depression patients, kidney transplant recipients, healthy adults)
Caveats: Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). One study in bariatric surgery patients found no significant effect, suggesting benefits may vary by population.
Generated Jul 12, 2026