Vitamin D and gastrointestinal cancer.

Vitamin D serves as a precursor to the potent steroid hormone calcitriol, which has widespread actions throughout the body. Calcitriol regulates numerous cellular pathways that could have a role in determining cancer risk and prognosis. Low Vitamin D levels have been implicated in numerous disease processes including fracture risk, falls, cardiovascular disease, hypertension, diabetes mellitus, and cancers. Metabolite of 1, 25-dihydroxyvitamin D3 (1,25[OH]2D3) regulates numerous genes that control gut physiology and homeostasis. 1,25(OH)2D3 serves various functions such as maintaining the integrity of epithelial barrier and absorption of calcium and phosphate, and the host's defense against pathogens, and the inflammatory response by several types of secretory and immune cells. Although epidemiological data remain inconsistent, and randomized control trials in humans do not yet exist to conclusively support a beneficial role for Vitamin D, results from some correlating studies strongly suggest that Vitamin D deficiency increases the risk of developing cancer and that avoiding deficiency and adding Vitamin D supplements might be an economical and safe way to reduce cancer incidence and improve cancer prognosis and outcome. The present review highlights the role of Vitamin D in cancer of the gastrointestinal tract including esophagus, gastric (stomach), liver, pancreas, and colon.