Did you know that an estimated 1 billion people worldwide have low levels of Vitamin D in their blood?

And did you know that Vitamin D isn't really a Vitamin at all?

It's a prohormone—and prohormones are substances that your body will convert into a hormone. And because of that, unlike vitamins, every cell in your body has a receptor for it.

This also means that it must be broken down from the initial form into a form your body can use. Vitamin D is then circulated throughout the body and in turn, it serves many important functions.