Lycopene is potentially effective in the prevention of
breast cancer from laboratory and observational studies. Among 39,876 women initially free of
cardiovascular disease and
cancer, we first conducted a prospective cohort study of dietary
lycopene and its food sources. Participants completed a baseline food frequency questionnaire and provided self-reports of
breast cancer risk factors. Dietary
lycopene levels were divided into quintiles, and
lycopene food sources were categorized. During 9.9 years of follow-up, 1,076
breast cancer cases were confirmed by medical record review. In a nested case-control study, we then identified 508
breast cancer cases and 508 controls matched by age, smoking, and follow-up time. Plasma
lycopene and other
carotenoids were measured. In the prospective cohort study, women with increasing quintiles of dietary
lycopene had multivariate relative risks (RR) of
breast cancer of 1.00 (ref), 0.95, 1.00, 1.10, and 1.00 (P, linear trend = 0.71). Women consuming <1.5, 1.5 to <4, 4 to <7, 7 to <10, and > or =10 servings/week of tomato-based products had RRs of 1.00 (ref), 1.00, 1.20, 1.18, and 1.16 (P, linear trend = 0.11). No individual
lycopene food sources were associated with
breast cancer. In the nested case-control study, women in increasing quartiles of plasma
lycopene had multivariate RRs of
breast cancer of 1.00 (ref), 0.95, 1.15, and 0.93 (P, linear trend = 0.86). The stepwise addition of individual plasma
carotenoids did not impact the RRs for plasma
lycopene, nor were other
carotenoids associated with
breast cancer. In conclusion, neither higher dietary nor plasma
lycopene levels were associated with a reduced risk of
breast cancer in middle-aged and older women.