The major source of vitamin D for humans is sunlight. When our skin is exposed to ultraviolet B (UVB) rays, it synthesizes vitamin D from cholesterol. This process is vital for maintaining healthy bones, as vitamin D helps the body absorb calcium. Additionally, vitamin D can also be obtained through dietary sources such as fatty fish, liver, eggs, and fortified foods. However, reliance on sunlight is crucial, especially in areas with limited sun exposure. For many, adequate sun exposure during the warm months can help ensure sufficient vitamin D levels for overall health.