Vitamins
Nicknamed:
The Sunshine Vitamin

Where does it come from?
Vitamin D is manufactured by the body during full body exposure to ultraviolet light (UV) rays from the sun.  When the sun is at its fullest in the mid-day, the UV rays are the strongest.  The earth's atmosphere blocks the UV light rays when the sun is rising and setting,  Vitamin D production is at its lowest during those times.  

Sunscreen, established suntans, long sleeves, hats, long pants, and long dresses all effectively block exposure to the sun.  They also inhibit the bodies ability to make Vitamin D.  Fish oil and vegetable sources are available in supplement form.  But, years of fortifying our foods with Vitamin D-2, Ergo-Calciferol (vegetable source) has proven in-effective.  Vitamin D-3, Cole-Calciferol (from fish oils) are the preferred supplements.

What is it used for? 
Vitamin D is required by the body in the formation of bones and teeth.  Calciferol works with Vitamin C and A to improve immune function.  Vitamin D-3 (the preferred version) is being prescribed for osteoporosis and cancer, as these conditions have been identified as nutritional deficiency symptoms.

How much do I take?
Vitamin D-3 is a fat soluble (stored in the body) nutrient.  The Institute of Medicine sets the Dietary Reference Intake (DRI) at 600 International Units (IU).  After a blood test reveals low levels of Calciferol, typically, prescriptions are written for 35,000 to 50,000 IU weekly. Nutritional  supplements range from 400 IU to as high as 10,000 IU.
Vitamin D
Calciferol