A common natural source of vitamin D is sunlight, specifically ultraviolet B (UVB) rays that stimulate the production of vitamin D in the skin. When skin is exposed to sunlight, it synthesizes vitamin D from cholesterol, which is essential for calcium absorption, bone health, and overall immune function. Besides sunlight, vitamin D can also be obtained through dietary sources such as fatty fish (like salmon and mackerel), fortified dairy products, and egg yolks. For individuals with limited sun exposure, supplements may be necessary to maintain adequate vitamin D levels, particularly during winter months or for those living in higher latitudes.