The synthesis of vitamin D is accomplished by sunlight, and production of vitamin D ultimately triggers the growth of new bone cells, which makes bones healthy and strong. Vitamin D is considered a fat-soluble vitamin and is not manufactured naturally by the body. This vitamin occurs in very few food sources and is primarily obtained through exposure to sunlight or by taking supplements and eating vitamin-fortified foods.
Exposure to sunlight is one of the simplest, cheapest and most effective methods of obtaining adequate amounts of vitamin D. When skin is exposed to the sun, ultraviolet rays penetrate the surface, which ultimately triggers the synthesis of vitamin D.
Two steps must occur for bodies to create vitamin D and convert it into usable form. This is accomplished through a series of two hydroxylations, which occur first in the liver and then in the kidneys. In the first reaction, the body converts Vitamin D into a vitamin called calcidiol. The next reaction produces a second type of vitamin called calcitriol. These vitamins collectively form vitamin D, which is then used to stimulate bone growth. Vitamin D allows the body to absorb calcium, which is another mineral essential for skeletal development. These minerals create osteoblasts and osteoclasts, which make bones dense and strong and reduce the risk of bone diseases such as osteoporosis and rickets.