ABSTRACT

As reviewed in detail elsewhere in this volume, abundant epidemiological evidence

supports an association between reduced risk of cancer, particularly lung

cancer, and higher b-carotene and other carotenoid intake, or higher carotenoid biochemical status. The observed associations are relatively strong and consistent,

and led to the initiation and conduct of controlled intervention trials of b-carotene supplementation beginning in the 1980s. The latter studies did not substantiate a

protective role for b-carotene supplementation in cancer but instead demonstrated relatively small adverse effects of b-carotene supplementation on cancer incidence and mortality in cigarette smokers. Increased cancer risk was also observed

among heavier drinkers in some of the trials. Subsequent experimental evidence

supported the trial findings, particularly with respect to a harmful interaction

between b-carotene supplementation and tobacco smoke, and provided important leads regarding the biological mechanisms through which b-carotene acted.