Tomatoes fail as prostate cancer preventive

NEW YORK (Reuters Health) - A new study suggests that eating lycopene-rich tomatoes offers no protection against prostate cancer, contrary to the findings of some past studies. In fact, the researchers found an association between beta carotene, an antioxidant related to lycopene, and an increased risk of aggressive prostate cancer.

In a written statement, Dr. Ulrike Peters of the Fred Hutchinson Cancer Research Center in Seattle said the finding is "disappointing, since lycopene might have offered a simple and inexpensive way to lower prostate cancer risk for men concerned about this common disease. Unfortunately, this easy answer just does not work."

It's thought that antioxidants may help shield against cancer and heart disease by neutralizing harmful molecules known as oxygen free radicals. But studies to date on the role of lycopene in prostate cancer have been mixed; some suggest a protective effect, while others yield contradictory or inconclusive results.

The current study involved 28,243 men between the ages of 55 and 74 with no history of prostate cancer who were enrolled in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. As part of the trial, the men provided a blood sample and completed a questionnaire related to their health, diet and lifestyle.

During follow-up of up to 8 years, 692 men developed prostate cancer, and were matched to 844 men who were free of prostate cancer.

Data analysis failed to show any significant difference in blood lycopene levels between men who developed the disease and those who did not. "Our results do not offer support for the benefits of lycopene against prostate cancer," Peters said.

The study, published in the current issue of Cancer Epidemiology, Biomarkers & Prevention, is one of the largest to evaluate the role of blood levels of lycopene and similar antioxidants in preventing prostate cancer.

Unexpectedly, the investigators noted an association between an increased risk of aggressive prostate cancer -- defined as disease that has spread beyond the prostate -- and higher intake of beta carotene, another antioxidant found in many vegetables and commonly used as a dietary supplement.

Although this observation "may be due to chance," Peters added, "beta carotene is already known to increase the risk of lung cancer and cardiovascular disease in smokers."