This vitamin's main function is to keep blood levels of phosphorus and calcium in balance to support bone mineralizaiton, proper nerve and muscle and cell functions. It acts as a hormone that enhances the absorption of calcium and phosphorus in the small intestine.
Inadequate blood levels of Vitamin D can lead to osteoporosis because it reduces calcium absorption.
There is evidence that it also blocks growth and differentiation of cancer cells. Vitamin D has also shown to be influencial in helping autoimmune conditions.
Look at all the conditions Vitamin D is helpful in:
Osteoporosis prevention and treatment
Polycystic ovary disease
Depression and other mood disorders
Gum disease prevention
Seasonal Affective Disorder
In our lifestyles of going from the "cage to the cave" (home to office or vice versa), we don't get outdoors enough to enjoy the sunshine. Top that with improper use of sunscreens/sunblocks and we really have a problem. I have seen low blood levels of Vitamin D in several of my patients.
Correcting the problem is easy; get out more and enjoy HEALTHY sun exposure. Take Vitamin D supplements. They are very inexpensive. Make sure you get them in the D3 form.
If you want some more info on the subject, you can visit http://www.lanisimpson.com/category/vitamin-d/