) Cigarette smoking has been implicated as a major cause of certain human cancers and diseases. The single most effective means of prevention would be to eliminate tobacco use from society; however, this is currently an unrealistic goal. It is estimated that nearly 50 percent of United States adults are current smokers and ex-smokers; a cancer prevention strategy targeting this large high-risk population is necessary. Smokers have less carotenoids and vitamins C and E than do nonsmokers, perhaps due in part to an increased clearance and/or a decreased bioavailability of antioxidant vitamins. Antioxidant vitamins are part of the body's antioxidant defense system; the lower levels in smokers may indicate a weaker antioxidant defense, which could lead to oxidative DNA damage and possibly mutation and cancer. The objective of this study is to develop an intervention strategy that will enable smokers to eat five or more servings of fruits and vegetables (FV)/day (up from two servings) in order to effectively increase and maintain their antioxidant vitamin levels. This should boost their antioxidant defense and reduce cancer risk. Recent findings indicate that intake of carotenes by smokers may be harmful, while FV seldom produce negative side effects. Also, FV contain other kinds of cancer preventive agents. It may be a combined action that provides a greater protection. This four-year randomized, controlled study will focus on the antioxidant effects of FV. Fifty-two male and 52 female smokers (35-65 years old, >15 cigarettes/day for >one year) will be recruited. There will be a two-month run-in and a six-month intervention period. The intervention group subjects will receive at least thirty-five servings of FV and juices weekly during the intervention period. Their weekly FV intake will be calculated from the amounts provided and returned. The control subjects will eat their usual diet throughout the study. During the run-in, the baseline levels of various carotenoids, vitamins C, E and A, two potential oxidative damage biomarkers, 8-hydroxydeoxyguanosine (primary marker) and malondialdehyde (secondary marker), and cotinine will be measured in blood and/or urine. These levels will be monitored monthly during the intervention period. Our hypothesis is that the intervention, unlike taking vitamin pills, will increase the FV intake by smokers to five or more servings/day (year 2000 goal), resulting in a significant and sustained increase in the levels of antioxidant vitamins and perhaps other kinds of cancer preventive agents as well; consequently, oxidative DNA damage and cancer risk may be reduced. This study is significant because the results will be directly applicable to smokers and ex-smokers for assessing the adequacy of FV intake for cancer prevention, and for formulating dietary guidelines regarding diet and cancer.
