Tomatoes, Tomato-Based Products, Lycopene, and Cancer: Review of the Epidemiologic Literature

The epidemiologic literature in the English language regardingintake of tomatoes and tomato-based products and blood lycopene (acompound derived predominantly from tomatoes) level in relation to therisk of various cancers was reviewed. Among 72 studies identified, 57reported inverse associations between tomato intake or blood lycopenelevel and the risk of cancer at a defined anatomic site; 35 of theseinverse associations were statistically significant. No study indicatedthat higher tomato consumption or blood lycopene level statisticallysignificantly increased the risk of cancer at any of the investigatedsites. About half of the relative risks for comparisons of high withlow intakes or levels for tomatoes or lycopene were approximately 0.6or lower. The evidence for a benefit was strongest for cancers of theprostate, lung, and stomach. Data were also suggestive of a benefit forcancers of the pancreas, colon and rectum, esophagus, oral cavity,breast, and cervix. Because the data are from observational studies, acause-effect relationship cannot be established definitively. However,the consistency of the results across numerous studies in diversepopulations, for case-control and prospective studies, and fordietary-based and blood-based investigations argues against bias orconfounding as the explanation for these findings. Lycopene may accountfor or contribute to these benefits, but this possibility is not yetproven and requires further study. Numerous other potentiallybeneficial compounds are present in tomatoes, and, conceivably, complexinteractions among multiple components may contribute to the anticancerproperties of tomatoes. The consistently lower risk of cancer for avariety of anatomic sites that is associated with higher consumption oftomatoes and tomato-based products adds further support for currentdietary recommendations to increase fruit and vegetable consumption.