...when we’re exposed to UVB rays, our bodies make vitamin D3 sulfate. This is a water-soluble form of vitamin D3. The vitamin D3 available in supplement form is un-sulfated and is not water-soluble. It relies on LDL to carry it to receptors in the body, whereas sulfated vitamin D needs no carrier. Un-sulfated vitamin D may not provide the same benefits because of its lack in mobility and perhaps availability in the body.