Carotenoids are pigments widely distributed in the vegetable and animal kingdoms. Their physiological roles were not known except those of beta-carotene and some other carotenes as provitamin. Recent epidemiological and experimental studies revealed that carotenoids might have important roles in prevention of diseases such as cancers, possibly through scavenging harmful radicals and influencing host defense systems, i. e. immune systems. Carotenoids increase antibody production, augment immunological tumor rejection and raise helper cell population. The mechanisms, by which carotenoids scavenge radicals or active oxygens, were well studied and documented, but mechanisms for modulating immune responses were not clarified due to the sophisticated network of immune systems. Many attempts and various approaches are necessary to evaluate the roles of carotenoids in connection with human health.
