system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does the sun provide Vitamin D? How is it possible for UV light to produce a vitamin?
gpt
There is a form of cholesterol, *7-dehydrocholesterol* present in your skin. Imagine this as sort of like a chunk of frozen vitamin D. Sunlight contains ultraviolet B energy (UVB) and converts the cholesterol into vitamin D3, then D3 goes to your liver, then your kidneys to become active vitamin D.