Insight into the roles of vitamins C and D against cancer: Myth or truth?

The consumption of vitamins C and D for prevention and treatment of cancer is still an uncertain recommendation due to their controversial roles in cancer. The epidemiological studies document that vitamins C and D possess potential antineoplastic property. In addition, accumulating experimental studies strongly support their anticancer efficacy both in vitro and in vivo, although the mechanisms of action are not completely clear. Vitamin C at pharmacological concentration has cancer-selective cytotoxicity in several cancer cell lines. Moreover, the cognition of vitamin D has become “hormone D”, which modulates a variety of molecular targets and signaling pathways, contributing to the inhibition of cancer. Furthermore, limited small-scale clinical trials favor their roles as the adjuncts of standard cancer therapies. On the other hand, opposite opinions also exist, and high-quality evidence are still lacking to ascertain the roles of vitamins C and D in cancer. In general, in light of the potential and promising anticancer values of vitamins C and D, it is essential to gain insight into their roles in cancer based on current epidemiological, experimental and clinical studies.