Vitamin D3 -- Supporting Bones, Mineral Balance & Gene Regulation

Vitamin D is a fat soluble vitamin found in some plant and animal sources, but primarily produced by the body after exposure to the sun’s ultraviolet (UV) rays. UV rays promote the skin’s production of vitamin D. Vitamin D3 or calciferol is the most active form, while vitamin D2 or ergocalciferol is synthesized by plants and less available to humans.

Vitamin D functions primarily to maintain normal blood levels of calcium and phosphorus. By promoting calcium absorption, vitamin D helps to form and maintain strong bones. Vitamin D also works synergistically with other vitamins, minerals, and hormones to promote bone mineralization. Without vitamin D, bones can become thin, brittle, or misshapen.

In order to be used by the body, vitamin D must be converted by the liver and kidneys to its active form, 1,25 (OH)2 D. Active vitamin D functions as a hormone by sending a message to the intestines to increase the absorption of calcium and phosphorus.
 
Unfortunately with aging, skin cannot synthesize vitamin D as efficiently, and kidneys are less able to convert vitamin D to its active hormone form. It's estimated as many as 30% to 40% of older adults with hip fractures are vitamin D insufficient.

Immune System Supporter & More

Vitamin D has more recently been under the spotlight for immune system support. Vitamin D is thought to promote immune health by supporting regulation of cell growth and differentiation -- the process that determines cell’s “job” in the body.

This regulation is particularly important as the differentiation of cells leads to a decrease in proliferation. Cellular proliferation, while essential for growth and wound healing, may foster harmful mutations if uncontrolled, and can even lead to cancer.

Vitamin D has also shown great promise in promoting the body’s innate immune response as well as soothing violent autoimmune activity. Both these mechanisms are thought result from vitamin D’s regulation of T cell development.

One study showed when vitamin D signals were absent, autoimmune T cells developed. In contrast, when active vitamin D (1,25(OH)(2)D(3) ) and vitamin D receptors were present, the balance in T cell response was restored and autoimmune activity avoided.

Vitamin D is currently being studied in conjunction with autism, mental illness, cancer, and other health conditions. This is surely more to come from this little “sunshine” vitamin.

Studies:

DeLuca HF and Zierold C. Mechanisms and functions of vitamin D. Nutr Rev 1998;56:S4-10. [PubMed abstract]  
Reichel H, Koeffler H, Norman AW. The role of vitamin D endocrine system in health and disease. N Engl J Med 1989;320:980-91. [PubMed abstract] 
Holick MF. McCollum Award Lecture, 1994: Vitamin D: new horizons for the 21st century. Am J Clin Nutr 1994;60:619-30. [PubMed abstract]