What provides vitamin D to the skin?

Sunlight is the primary source of vitamin D for the skin, as it plays a crucial role in the synthesis of this vitamin. When the skin is exposed to ultraviolet B (UVB) rays from the sun, a chemical reaction occurs that converts a compound in the skin into vitamin D3, which is then further processed by the liver and kidneys to form active vitamin D. This process is essential for maintaining calcium levels and promoting bone health in the body.

While it's true that food sources and supplements can also provide vitamin D, they are not the primary means by which the skin obtains this vitamin. Water plays no role in vitamin D synthesis, and although massage can have various health benefits, it does not contribute to the production of vitamin D in the skin. Hence, sunlight stands out as the key factor in vitamin D synthesis.