Final answer:
Skin exposure to ultraviolet radiation primarily converts cholesterol-related steroids into vitamin D, which is crucial for bone health. While tanning is a defense response to UV exposure, excessive UV exposure can be harmful, leading to skin cancer risks.
Step-by-step explanation:
Skin exposure to small amounts of ultraviolet radiation serves to convert a steroid related to cholesterol into vitamin D. This process is essential for maintaining healthy bones and preventing diseases such as rickets and osteoporosis. While our bodies indeed produce a pigment called melanin in response to UV exposure, which can lead to a tanned appearance and provides some protection against future UV damage, it's the production of vitamin D that is a direct beneficial outcome of moderate UV exposure. Additionally, it's important to acknowledge that too much UV exposure can increase the risk of skin cancer and that the tanning response is a defense mechanism rather than a benefit. Therefore, it is recommended to obtain vitamin D through diet or supplements and use sunscreen to protect against excessive UV exposure.