Sun exposure plays a crucial role in the synthesis of vitamin D, a vital nutrient for maintaining healthy bones and immune function. When skin is exposed to ultraviolet B (UVB) rays from the sun, it converts a type of cholesterol into vitamin D3. This vitamin is then metabolized in the liver and kidneys into its active form, which aids in the absorption of calcium and phosphorus. Insufficient sunlight can lead to deficiencies, which are linked to various health issues, emphasizing the importance of balancing safe sun exposure with skin cancer risk.