Research Vault / Nutrients
Nutrients · Evidence guide
Vitamin D Evidence Guide
A vitamin and hormone precursor central to calcium regulation.
Reviewed October 1, 2026 · Sources linked below
How it works
Activated vitamin D acts through its receptor to regulate gene expression, including processes involved in calcium absorption and bone metabolism.
01Vitamin D activation
02Receptor signaling
03Calcium and bone regulation
Simplified mechanism map. It does not represent a proven treatment outcome.
What the evidence can tell us
Preventing and treating deficiency is established. Large trials do not support assuming broad disease-prevention benefits from extra supplementation in already sufficient adults.
Safety and important limits
Excess can cause hypercalcemia and kidney injury. Decisions about testing or supplements depend on clinical context and medicines.
This is a learning guide, not a recommendation to begin a supplement. Baseline nutrition, medicines and health conditions affect what is appropriate.