Which vitamin can the human body produce?

The human body has the capability to synthesize vitamin D through a process initiated by exposure to sunlight. Specifically, ultraviolet (UV) rays from the sun transform a cholesterol derivative in the skin into vitamin D3 (cholecalciferol). This synthesized form then undergoes further conversion in the liver and kidneys to become the active hormone calcitriol, which plays a crucial role in calcium and phosphate metabolism, ensuring proper bone health and immune function.

In contrast, vitamins A, C, and K must be obtained through dietary sources, as the body cannot produce them in sufficient quantities. Vitamin A is derived from carotenoids in fruits and vegetables, vitamin C is primarily sourced from fruits and vegetables, and vitamin K is found in green leafy vegetables and certain oils. The inability of the body to produce these vitamins emphasizes the importance of a balanced diet to prevent deficiencies.