The role of calcium, magnesium, and zinc in carcinogenesis.

The effects of calcium, magnesium, and zinc supplementation and of magnesium depletion on carcinogenesis are comprehensively reviewed, including epidemiologic and experimental investigations. Some data on the effects of neoplasia on the homeostasis of these metals are also presented. Despite many conflicting results, this review reveals that calcium supplementation is more likely to enhance than inhibit chemical carcinogenesis; magnesium or zinc supplementation tends to inhibit carcinogenesis; magnesium deficiency increases the incidence of neoplasia in humans and animals; parenteral administration of magnesium along with a carcinogen produces local anticarcinogenic effects, while zinc's activity tends to be systemic; and there is a simple correlation between the inhibition of carcinogenesis by the magnesium and zinc supplementation and the reduction of carcinogen binding to cells and DNA. The mechanisms of these effects are not clear. They may involve molecular interactions between metal and carcinogen at different enzymatic and regulatory sites of target cells undergoing neoplastic transformation, as well as stimulation of the host immune system.