Beta-carotene and Antioxidant Nutrients in Oral Cancer Prevention

Abstract

Lack of toxicity and easy availability make beta-carotene and vitamin E excellent agents to test for cancer preventive activity. Since intervention trials actually using cancer incidence as the endpoint in the general population are logistically and practically impossible for oral cavity cancer, as is the case for most types of cancer, evidence for chemoprevention must necessarily be indirect: laboratory and animal models, epidemiologic surveys, trials showing reversal of premalignant lesions or cancer prevention in usually high risk groups. In several animal models, beta-carotene and other antioxidant nutrients strongly inhibit oral carcinogenesis. Epidemiologic studies consistently correlate low intake with high cancer risk. Smokers have lower beta-carotene levels in plasma and oral mucosal cells than non-smokers. Beta-carotene and vitamin E produce regression of oral leukoplakia, as has now been found in 8 clinical trials, 5 with beta-carotene alone, 1 with vitamin E and 2 that used a combination. The design and limitations of such chemoprevention studies in oral leukoplakia is discussed. All available evidence supports a very significant disease-preventive role for antioxidant nutrients in oral cancer.