CAROTENOID DOSE LEVEL and PROTECTION AGAINST UV-B INDUCED SKIN TUMORS

Abstract— Two groups of workers have reported that low levels of carotenoids (0.07 and 0.01%) were effective in preventing tumor development in experimental animals. To see whether these low concentrations were effective in preventing the development of UV-B induced skin tumors, groups of hairless mice were fed beta-carotene beadlets or canthaxanthin beadlets or the equivalent weight of placebo beadlets at these two final concentrations of carotenoid, and also at a final concentration of 2%, the amount found effective by us in past experiments. The mice received their pigments either for 4 days (the group receiving 0.01%), one month (the group receiving 0.07%) or for 12 weeks (the group receiving 2%) before irradiation started, in order to duplicate the conditions used in the previously reported experiments, and continued to receive their respective diets during the irradiation and observation period. All groups received a total dose of 10.8 J/cm² of UV-B radiation. At 2 and 0.07%, beta-carotene and canthaxanthin each conferred significant protection against skin tumor development. However, at 0.01 %, neither carotenoid offered protection against tumor development.