An epidemiological investigation of the roles of dietary antioxidant nutrients, fruits and vegetables, and residential radon exposure in the etiology of lung cancer

Background. Lung cancer is a leading cause of morbidity and mortality worldwide. Since effective screening tests are currently unavailable, primary prevention represents the most feasible way to reduce the burden of this disease. Although cigarette smoking accounts for the majority of lung cancer cases, dietary factors and residential radon also appear to play significant—albeit less well characterized—roles. Since oxidative stress is implicated in smoking- and radon-induced lung cancers, antioxidant nutrients may afford an important approach to primary prevention.; Methods. This dissertation consists of three separate, yet interrelated, parts. Study I is a population-based case-control analysis of the associations between the five most common dietary carotenoids—α-carotene, β-carotene, β-cryptoxanthin, lutein + zeaxanthin, and lycopene—and lung cancer risk in women. We ultimately examine whether these specific nutrients affect lung cancer risk independent of their primary plant food sources. Study II explores whether selected dietary antioxidant nutrients and/or fruit and vegetable groupings modify the association between indoor radon exposure and lung cancer risk in women. This case-control analysis is strengthened by the use of a biomarker of long-term exposure to residential radon. In study III, we develop a novel dietary antioxidant index (considering contributions of individual carotenoids, flavonoids, vitamin E, vitamin C, and selenium) via principal components analysis, and prospectively apply it to lung cancer risk in a cohort of male smokers.; Results. Study I: Although increased consumption of several individual carotenoids was significantly inversely associated with lung cancer risk, these relationships did not persist with further adjustment for total vegetable intake. Study II: Low intake of most fruit and vegetable groupings and vitamin E, but not individual carotenoids and vitamin C, exacerbated the risk of lung cancer associated with residential radon exposure. Study III: Individuals with the highest antioxidant index scores had the lowest risks of lung cancer; inverse associations were more pronounced among men ingesting greater amounts of prooxidant nutrients.; Conclusions. Increased consumption of antioxidant-rich plant foods rather than single nutrients appears to be a prudent strategy for the primary prevention of lung cancer, particularly among groups that incur oxidative stress due to smoking and/or residential radon exposure.