Vitamin D plays a definitive role in the normal growth and upkeep of our body and the quality of our bones. Though classified as a vitamin, it is actually a steroid hormone that is produced by the skin when exposed to sunlight. A vitamin is an organic compound that is essential for the body but is required in very tiny amounts. In that sense vitamin D is a vitamin. However, vitamins are usually not synthesized by the body and for that reason vitamin D is not a vitamin.
Here comes the sun: Vitamin D is a steroid hormone produced by the skin when exposed to sunlight.
Once produced in the skin, vitamin D is still biologically inert, or incapable of biological action till it is sequentially metabolized first in the liver and then the kidneys. After it has been altered by the liver and the kidneys, it binds its receptor, the Vitamin D receptor (VDR), which is found inside cells, and proceeds to make a variety of physiological decisions.
Vitamin D is known best for its role in maintaining the calcium balance in our bones. But over the last four decades, scientists have identified many new biological actions for vitamin D apart from bone growth and upkeep, says Anthony Norman, Distinguished professor of biochemistry and biomedical sciences, Emeritus, University of California, Riverside, US. Anthony Norman discovered the existence of vitamin D in 1967 and VDR in 1969.
In a mini review by Norman and Roger Bouillon titled �Vitamin D Nutritional Policy Needs a Vision for the Future� published in Experimental Biology and Medicine, September 2010, the authors say that VDR has been found in at least 38 different tissues in the body. This means vitamin D has a role to play in those many tissues. The review also says that research has shown that Vitamin D plays a role in muscle function and improving muscle strength. It also stimulates the synthesis of anti-bacterial agents in blood cells, and strengthens our immune cells so that they can fight infection more efficiently. It makes our pancreas secrete insulin, and maintains heart muscle function. It also prevents excessive cell proliferation. In other words it may deter various cancers, including prostate, colon and breast cancer, from gaining a foothold. Read More
Sujata Kelkar Shetty, PhD, writes on public health issues and is a research scientist trained at the National Institutes of Health in Bethesda, US.