Vitamin D is primarily obtained from which source?

Vitamin D is primarily obtained from direct exposure to sunlight, specifically ultraviolet B (UVB) rays, which facilitate the synthesis of vitamin D in the skin. When the skin is exposed to sunlight, 7-dehydrocholesterol, a compound present in the skin, transforms into previtamin D3 and then into vitamin D3 (cholecalciferol). This process is crucial because it contributes significantly to the body’s vitamin D levels, playing an essential role in calcium absorption, bone health, and immune function.

While dietary supplements can provide vitamin D, along with some foods, such as fatty fish and fortified products, sunlight remains the most significant natural source. Moreover, dietary sources alone may not produce sufficient vitamin D levels to meet the body's needs, especially in individuals with limited sun exposure. Therefore, the sunlight exposure ultimately accounts for a majority of vitamin D synthesis in the human body, making it the primary source.