Which vitamin is primarily obtained from sunlight?

Vitamin D is primarily obtained from sunlight due to the skin's ability to synthesize it when exposed to ultraviolet (UV) rays. Specifically, when UVB rays hit the skin, they convert a cholesterol derivative called 7-dehydrocholesterol into vitamin D3 (cholecalciferol). This precursor then undergoes further processing in the liver and kidneys to become the active form of vitamin D, which plays a crucial role in calcium absorption, bone health, and immune function.

Vitamin A, while important for vision and immune function, is primarily obtained through dietary sources such as animal liver, fish, dairy products, and certain vegetables. Vitamin C is also sourced from the diet, particularly from fruits and vegetables like oranges and peppers, and does not involve synthesis from sunlight. Similarly, vitamin K is found in leafy greens and is essential for blood clotting, with dietary sources playing a key role in its acquisition. Therefore, vitamin D stands out as the only vitamin that relies fundamentally on sunlight for its synthesis, highlighting the importance of sun exposure for maintaining adequate levels of this nutrient in the body.