Anticancer Effect of Vitamin D
Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis. Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to 25- hydroxyvitamin D [25(OH)D], also known as calcidiol. The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol .Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and to prevent hypocalcemic tetany. It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts . Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults . Together with calcium, vitamin D also helps protect older adults from osteoporosis .Vitamin D has other roles in the body, including modulation of cell growth, neuromuscular and immune function, and reduction of inflammation . Many genes encoding proteins that regulate cell proliferation, differentiation, and apoptosis are modulated in part by vitamin D . Many cells have vitamin D receptors, and some convert 25(OH)D to 1,25(OH)2D
Epidemiological studies indicate that vitamin D insufficiency could have an etiological role in various human cancers. Preclinical research indicates that the active metabolite of vitamin D, 1α,25(OH)2D3, also known as calcitriol, or vitamin D analogues might have potential as anticancer agents because their administration has antiproliferative effects, can activate apoptotic pathways and inhibit angiogenesis. In addition, 1α,25(OH)2D3 potentiates the anticancer effects of many cytotoxic and antiproliferative anticancer agents.