Lycopene and the lung.

The human lung, due to the oxidative and ozone stress to which it is exposed, is particularly vulnerable to oxidative damage. Concentrations of dietary antioxidants in the lung epithelial lining and lining fluids may provide protection against oxidative damage. A randomized clinical trial was conducted to study the effects of supplemental, carotenoid-rich vegetable juice (V-8) on lung function macrophage levels of carotenoids and in moderating ozone-induced lung damage. Healthy young adults (n = 23) were exposed to 0.4 ppm ozone in a chamber for 2 hr after either 2 weeks of antioxidant supplementation (including one can of V-8 juice daily) or placebo. Mean lung concentrations of lycopene increased by 12%, and lung epithelial cell DNA damage as measured by the Comet Assay decreased 20% in supplemented subjects. No change in peripheral blood lymphocyte DNA damage was observed as evidenced by no change in mean comet area or length in supplemented or placebo subjects. We were not able to separate the effects of lycopene from other carotenoids or antioxidants administered in this study; however, lycopene is the predominant carotenoid in V-8 (it represents 88% of total carotenoids). A review of the epidemiologic literature providing evidence for the effect of lycopene (diet or serum) or tomatoes on the risk of lung cancer reveals 27 observational epidemiologic studies (18 case-control and nine cohort studies) reporting relative risk (RR) estimates. RR estimates for cohort studies ranged from 0.63 to 1.24 (mean RR = 0.93, SD = 0.16). Odds ratios (OR) for case-control studies ranged from 0.27 to 0.93 (mean OR = 0.61, SD = 0.16). Both plasma levels (RR = 1.01, OR = 0.37) and estimated intakes of lycopene from dietary sources (mean RR = 0.93, RR range = 0.80-1.05; mean OR = 0.67, OR range = 0.27-0.93) were examined. Seventeen studies, three of which were cohorts, reported their results at the level of tomato consumption rather than, or in addition to, lycopene consumption (mean RR = 0.89, RR range = 0.63-1.24; mean OR = 0.61, OR range = 0.37-0.80). The published epidemiologic literature shows an interaction between study design and the relationship between lycopene and/ or tomatoes and risk of lung cancer. Overall, cohort studies did not show an association, whereas case-control studies showed a decreased risk with greater consumption of lycopene and tomatoes. Although lycopene can be found in the human lung, and there is evidence, albeit weak, for a protective association with lung cancer, its biologic role remains to be elucidated.