Why Do We Need Sunlight to Get Vitamin D?

Lorelai: Why do we need sunlight to get vitamin D? Lorelai: There's a whole chemical pathway that it goes down where it starts as a form of cholesterol and ends up as vitamin D. You're not absorbing vitamin D directly from the sun, you're absorbing UVB rays which cause a reaction in your body that turns cholesterol into vitamin D. The way this happened was incredibly slowly over the course of thousands of years. Creatures that had this ability to utilize the sun's rays to convertolesterol into vitamin D in their own bodies had an evolutionary survival advantage over those who didn't.