How do we get vitamin D from sunlight?

VITAMIN D ISN’T an ingredient of sunlight; sunlight triggers the reaction that makes it. Vitamin D is a group of related compounds and D3 is the one that requires sunlight. Cholesterol in our diet is first converted to 7-dehydrocholesterol and then UVB radiation in sunlight triggers a reaction that creates first previtamin D3, and then vitamin D3 proper. In the UK, you need the sunshine levels of a summer’s day to create vitamin D and it only works outdoors, because glass blocks UVB radiation.