NIH Office of Dietary Supplements — Vitamin D fact sheet for health professionals

This is an evidence summary, not a new experiment with participants. It explains how vitamin D helps the body absorb calcium and supports bones, muscles, nerves, and the immune system. It reviews research on vitamin D supplements for bone health and other conditions, including cancer, heart disease, and diabetes. The evidence is strongest for preventing or treating deficiency and supporting bone health, while results for many other benefits are mixed. Too much vitamin D can be harmful, so more is not always better.

What this means for you: Vitamin D matters, especially for people who do not get enough, but supplements are not a general-purpose anti-aging treatment. Follow recommended amounts and ask a health professional about testing or supplements if you may be deficient.