We evolved in sunlight, and when our skin is exposed to the sun, an important reaction occurs. The sun’s UVB radiation changes a pre-cholesterol molecule in our skin into Vitamin D3. Vitamin D3 is then carried to the liver in the blood, where it is changed into 25(OH)D (the form that is normally measured in diagnosis of blood levels). From there it travels to the kidneys where it is transformed into active vitamin D, a potent steroid hormone. This hormone interacts with more than 30 tissues and organs and influences the action of some 1000 or more genes.
Upon exposure to the sun, any excess vitamin D produced in skin is destroyed by sunlight, so we cannot become Vitamin D intoxicated from excessive exposure.
Vitamin D has a number of very important roles in the body. It permits the efficient absorption of dietary calcium, which led to the evolution of vertebrates and is vital for the formation of healthy bones.
We now know that vitamin D is a critical sign module used in nearly every system in the body, and at its limit sufficient deficiency can compromise any system, not just our bones.
Research has shown that most cancers, autoimmune diseases and Multiple Sclerosis have an association with vitamin D.