Micronutrients and their influence on mutagenicity and malignant transformation.

Many studies have now indicated that micronutrients, such as the carotenoids, tocopherols, and ascorbic acid, can prevent mutagenesis, genotoxic effects, or malignant transformation in bacteria and mammalian tissue, either in cell culture or in organ culture. In addition, multiple papers report that some of these micronutrients act as anticarcinogenic agents in animals treated with either ultraviolet light, ultraviolet light with chemicals, or chemical carcinogens alone. With respect to the carotenoids, early experiments used pharmacological doses of carotenoids, but more recent reports indicate that relatively small doses can be effective. Inasmuch as these effects are seen with both provitamin A and nonprovitamin A carotenoids, it would appear that these effects are intrinsic to the carotenoid molecule, and not due to the metabolic conversion to retinoids. Partially on the basis of these observations, it has been suggested that the micronutrients may function as chemopreventive agents for reducing the risk of cancer in humans. Numerous human intervention studies are underway to test this hypothesis.