What vitamin is activated by the kidneys to regulate the absorption of calcium?

Vitamin D plays a crucial role in regulating calcium absorption in the body. When vitamin D is produced in the skin through sunlight exposure or obtained from dietary sources, it is initially in an inactive form. The kidneys are responsible for converting this inactive vitamin D into its active form, calcitriol. Calcitriol then facilitates the absorption of calcium in the intestines, ensuring that the body maintains adequate calcium levels for various physiological processes, including bone health, muscle function, and nerve signaling.

This activation process is vital, especially for maintaining calcium homeostasis, as it helps regulate how much calcium is absorbed from the food we consume, how much is stored in bones, and how much is excreted through urine. Without sufficient active vitamin D, the body would struggle to absorb calcium effectively, potentially leading to conditions such as rickets in children or osteomalacia in adults.