Vitamin D is often called the “sunshine vitamin” because your body primarily produces it in response to sunlight exposure, specifically UVB rays. When sunlight hits the skin, it triggers the synthesis of vitamin D, which is then converted by the liver and kidneys into its active form. This vitamin plays a vital role in calcium absorption, making it essential for healthy bones and teeth. It also contributes to immune system function, muscle strength, and may even influence mood and mental health. A deficiency in vitamin D can lead to conditions such as rickets in children or osteoporosis in adults. While vitamin D can also be obtained from fortified foods like milk or cereal and from supplements, sunlight remains the most natural and efficient source. Just 10–30 minutes of sun exposure a few times per week can help maintain healthy levels, although factors like skin tone, age, location, and sunscreen use can influence absorption.