Vitamin D's Real Job: One Receptor Steering Thousands of Genes

Vitamin D doesn't act like a simple nutrient. It works through a receptor that sits inside your cells and switches genes on and off, which is why it touches immunity, metabolism and cell growth, not just bones. This review walks through what scientists have learned since the receptor was first cloned in the 1980s. Big gaps remain, including why the same vitamin acts so differently in different tissues.