DOES BETA-CAROTENE EXPLAIN WHY REDUCED CANCER RISK IS ASSOCIATED WITHVEGETABLE AND FRUIT INTAKE

Increased intake of vegetables, fruits, and carotenoids and elevated b lood levels of beta-carotene are consistently associated with reduced risk of lung cancer in epidemiologic studies. Epidemiologic research a lso suggests that carotenoids may reduce the risk of other cancers, al though the evidence is less extensive and consistent. The simplest exp lanation is that beta-carotene is protective. However, the possible ro les of other carotenoids, other constituents of vegetables and fruits, and associated dietary patterns have not been adequately explored. To evaluate these alternative hypotheses, we are undertaking three lines of research. (a) With dietary data from the 1987 National Health Inte rview Survey and the 1982-1984 Epidemiologic Follow-up of the first Na tional Health and Nutrition Examination Study, we have determined whic h food groups and nutrients are highly correlated with vegetable and f ruit intake. (b) We have developed and characterized a liquid chromato graphy method for optimal recovery and resolution of the common carote noids in blood, specifically lutein, zeaxanthin, beta-cryptoxanthin, l ycopene, alpha-carotene, and beta-carotene. (c) In a population-based case-control study of lung cancer in white men in New Jersey, we are a ssessing whether estimates of the intake of the individual carotenoids might produce stronger inverse associations than estimates of provita min A carotenoids based on current food composition tables.