There are two types of vitamin D, D2 and D3. Most supplements contain the more readily bioavailable D3. It is sometimes called ‘The Sunshine Vitamin’ as our main source of vitamin D is from UVB light. Vitamin D is made in the skin when it is exposed to the sun. Vitamin D travels through the bloodstream to the liver, where it’s turned into calcidiol. This is a prohormone or precursor for the vitamin D hormone. The vitamin D prohormone travels through the bloodstream to the kidneys, where it’s turned into the active form, calcitriol. It is released back into the bloodstream where it then regulates how your body uses calcium and phosphorous. Without it, calcium is taken from the skeletal frame, resulting in bone loss. Vitamin D is required for the brain to make norepinephrine, a stress hormone and epinephrine (adrenalin), which may activate the ‘happy’ part of the brain.