24 May Prostate Cancer: Tomato Products May Reduce Risk
MedicalResearch: What are the main findings of the study?
Dr. Giovannucci: In 50,000 men followed over 24 years, we found that those regularly consuming tomato products, which are high in lycopene, had a 30% lower risk of developing lethal prostate cancer. Among men being screened regularly with PSA, the risk reduction from high tomato consumption was 50%. We also examined the prostate cancer tissue and found that higher dietary lycopene intake was associated with less new blood vessel formation, which may help explain why the cancers were less likely to progress.
MedicalResearch: Were any of the findings unexpected?
Dr. Giovannucci: The literature on this topic has been mixed. The key feature of our analysis is that we separated lethal prostate cancer from all prostate cancers. From our data, it appears that lycopene or other compounds in tomatoes appear to inhibit prostate cancer progression rather than initiation. Thus, the men with higher dietary lycopene intake were not less likely to get prostate cancer, but were less likely to develop more lethal forms of prostate cancer. Most previous studies have examined total prostate cancer rather than lethal forms of the disease, which may explain the inconsistencies in the literature.
MedicalResearch: What should clinicians and patients take away from your report?
Dr. Giovannucci: Although not definitive, it appears that a diet high in tomato products, such as 2 servings a week of tomato sauce, may reduce risk of dying of prostate cancer. It is likely that this benefit may be optimized with long-term diet well before the diagnosis. We have no evidence that high doses of lycopene, especially in supplementary form, would have much impact on prostate cancer after diagnosis. We don’t think our findings should dramatically alter current dietary recommendations, which encourage high fruit and vegetable consumption for multiple health reasons. However, in the context of current recommendations, including some tomato products may potentially have some unique benefits.
MedicalResearch: What recommendations do you have for future research as a result of this study?
Dr. Giovannucci: Most studies on prostate cancer have focused either on prevention of the cancer or treatment. It is well known that prostate cancers have a very wide spectrum of aggressive potential. Our findings suggest that long-term dietary factors may affect the aggressive potential of the cancer. The formation of new blood vessels (angiogenesis) is a critical factor in cancer progression. Given our preliminary data that dietary factors such as lycopene may inhibit angiogenesis, examining this mechanism in more detail, as well as how other factors may help reduce new blood vessel formation, may have promise in reducing mortality from prostate cancer.
Dietary Lycopene, Angiogenesis, and Prostate Cancer: A Prospective Study in the Prostate-Specific Antigen Era JNCI J Natl Cancer Inst djt430 doi:10.1093/jnci/djt430 first published online January 24, 2014
Ke Zu, Lorelei Mucci, Bernard A. Rosner, Steven K. Clinton, Massimo Loda, Meir J. Stampfer, and Edward Giovannucci