The primary vitamin produced in the skin in response to sunlight is vitamin D. When exposed to ultraviolet B (UVB) rays from the sun, the skin synthesizes vitamin D3, which is crucial for numerous bodily functions, including calcium absorption and bone health. Adequate levels of vitamin D support immune function, muscle strength, and may lower the risk of certain chronic diseases. However, factors like geographical location, skin type, and exposure duration can affect vitamin D production. Therefore, sun exposure should be balanced with skin protection to prevent damage while maintaining sufficient vitamin D levels.