A hormone is defined as a biochemical substance that is made in one part of the body, and is then transported through the circulatory system to coordinate the physiology and behavior of a target organ at a distant location. For example, Insulin is made in the pancreas, but functions at many distant locations in the body to control blood sugar. Vitamin D also shares this type of behavior.
Like our sex hormones (Estrogen, Testosterone, etc…), Vitamin D is synthesized from Cholesterol. In the skin Cholesterol is converted into Cholecalciferol (or Vitamin D3) using ultraviolet radiation. Vitamin D3 is then transported first to the liver where it is chemically altered to 25-OH Vitamin D3. Afterwards 25-OH Vitamin D3 gets transported to the kidneys where it is converted to 1-25-OH Vitamin D3. 1-25-OH Vitamin D3 is the active form of Vitamin D. Like other hormones 1-25-OH Vitamin D3 has actions on cells throughout the body.
Fortunately for us we don’t always need sun exposure in order to get adequate Vitamin D. In fact, the body doesn’t distinguish between the Cholecalciferol that is created in the skin vs. the Cholecalciferol that is ingested when we take a Vitamin D supplement. Both forms of Cholecalciferol travel to the liver and are converted to 25-OH Vitamin D3.
In Medical School I learned about the importance of Vitamin D in regulating calcium balance in the human body. However, since then the scientific literature has been exploding with information on the health benefits of Vitamin D. Adequate Vitamin D is needed for control of blood sugars. It also lower risks for cancer and cardiovascular disease. Vitamin D improves neuromuscular function. Vitamin D has a strong immunologic role in controlling infections in the body as well as many other positive effects.
The best way to make sure you have enough Vitamin D is to check your blood level of 25-OH Vitamin D3. Most experts agree that a Vitamin D level below 40 ng/ml to be an insufficient Vitamin D level. They recommend a level of 40 – 80 ng/ml as adequate with a level of 60-80 ng/ml as ideal.
25-OH Vitamin D3 is typically reported in either ng/ml or nmol/L.
Good vitamin D supplementation is crucial to optimal health.