Carotenoids in cancer, mastalgia, and AIDS: prevention and treatment--an overview.

In 1980, two carotenoids, beta-carotene (BC) and canthaxanthine (CX) with and without pro-vitamin A activity, respectively, were orally administered to female Swiss albino mice and were found to substantially prevent skin carcinogenesis induced by benzo(a)pyrene (BP). This preventive effect was observed in darkness by means of photocarcinogenic enhancement (PCE) following UV (300 to 400 nm) irradiation. In 1984, the same experiment produced antitumorigenic activity when applied to breast carcinogenesis induced in mice by 8-methoxypsoralen (8-MOP) plus UV-A light and, in 1985, when directed toward gastric carcinogenesis induced in rats by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). These data suggested a rationale for human intervention to prevent, by carotenoid supplementation, a second primary malignancy after the primary malignancy has been radically excised. In the 1980s, a pilot clinical study (15 cases) showed a longer than expected disease-free interval in all surviving patients. It was also subsequently found that, if treated daily with 20 mg of BC and intermittently with retinol 150 to 300,000 IU daily for seven days just prior to menses, women suffering from cyclical mastalgia were relieved from pain, without any toxic side effects. When BC was given in high daily doses (60 mg) to 60 drug addicts suffering from AIDS-related complex (ARC), they recovered from their objective and subjective symptoms (but not from lymphadenopathy) with improvement in their general health and increased performance status. At higher doses, BC (with or without hyperthermia) was effective even in patients in advanced stages of AIDS. A debate has arisen concerning a recent statement by the U.S. Government that "beta-carotene supplements do not protect Americans against cancer or heart disease, and may actually increase the risk of deadly lung tumors in smokers".