Carotenoids As a Food Factor for Cancer Prevention: Questions to Be Solved

Abstract

Epidemiological studies have strongly suggested that consumption of carotenoid-rich foods is inversely related to the incidence of cancer and other degenerative diseases. Recent intervention studies warrant research on the role of dietary carotenoids in cancer prevention. A wide variety of carotenoids are distrubuted in fruits and vegetables, and hu-mans accumulate them in their plasma and tissues. However, many questions remain to be solved concerning absorption and transportation into the body and metabolie conversion in tissues. Physiological functions in relation to cancer preven-tion are still obscure. We have demonstrated that that ß-carotene liberates 2 moles of retinal by the central cleavage pathway in pig intestine and liver preparation. A lower, but significant, activity of the central cleavage enzyme was found in brain, kidney, and lung. We also found that increase of lyco-pene and other carotenoids in human low density lipoprotein by dietary in take of tomato juice elevated resistance against single oxygen oxygenation in vitro. This indicates that lycopene, a non-provitamin A carotenoid, acts as an effective singlet oxygen quencher in human plasma.