Research synthesisHigh evidenceSmall effect4 studies · 3 beneficial · 1 neutral · 0 harmful
Across 4 studies, 3 reported beneficial effects of vitamin D supplementation on reducing parathyroid hormone (PTH) levels, with effect sizes ranging from small to moderate. The most robust evidence comes from meta-analyses in clinical populations (kidney transplant recipients and depressed patients) using doses of up to 5,000 IU/day, with effects typically observed at 8-12 weeks. One neutral finding in a bariatric surgery population suggests the effect may not generalize to all clinical subgroups.
- Effective dose range: up to 5,000 IU/day
- Studied populations: clinical populations (kidney transplant recipients, depressed patients), adults with vitamin D insufficiency
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). The neutral finding in bariatric surgery patients (n=314) highlights potential population-specific heterogeneity. Only 1 of 4 studies reported study duration (median 90 days), limiting assessment of time-to-effect. Most studies did not specify vitamin D form (e.g., D2 vs D3), which may influence effect magnitude.
Generated Jun 12, 2026