Tomato-rich diet may lower prostate cancer risk

Men who eat over 10 portions a week of tomatoes have an 18% lower risk of developing prostate cancer, according to a newly published study from the United Kingdom.

J. Brantley Thrasher, MD, a Urology Times editorial consultant, called the research “thought provoking,” but not a game changer.

To assess if following dietary and lifestyle recommendations reduces risk of prostate cancer, researchers at the Universities of Bristol, Cambridge, and Oxford examined the diets and lifestyle of 1,806 men between the ages of 50 and 69 years with prostate cancer and compared them with 12,005 cancer-free men.

The study, published online in Cancer Epidemiology, Biomarkers and Prevention (July 13, 2014), is the first study of its kind to develop a prostate cancer dietary index consisting of dietary components-selenium, calcium, and foods rich in lycopene-that have been linked to prostate cancer.

Men who had optimal intake of these three dietary components had a lower risk of prostate cancer, researchers found.

Tomatoes and tomato products, such as tomato juice and baked beans, were shown to be most beneficial, with an 18% reduction in risk found in men eating over 10 portions a week. This is thought to be due to lycopene, an antioxidant that fights off toxins that can cause DNA and cell damage.

“Our findings suggest that tomatoes may be important in prostate cancer prevention,” said lead author Vanessa Er, PhD, of the School of Social and Community Medicine at the University of Bristol. “However, further studies need to be conducted to confirm our findings, especially through human trials. Men should still eat a wide variety of fruits and vegetables, maintain a healthy weight, and stay active.”

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Dr. Er and colleagues also looked at the recommendations on physical activity, diet, and body weight for cancer prevention published by the World Cancer Research Fund and the American Institute for Cancer Research. Only the recommendation on plant foods-high intake of fruits, vegetables, and dietary fiber-was found to be associated with a reduced risk of prostate cancer.

As these recommendations are not targeted at prostate cancer prevention, the researchers concluded that adhering to these recommendations is not sufficient and that additional dietary recommendations should be developed.

“This study is thought provoking, but how much lycopene is actually being ingested-and even if that is the compound preventing the cancer-is very difficult to determine,” said Dr. Thrasher, of the University of Kansas Medical Center, Kansas City. “We need further studies focusing on lycopenes and prevention of prostate cancer before making too much out of this trial.”

Dr. Thrasher pointed out that the research on lycopenes and their possible preventive effects in prostate cancer is controversial and results in the literature are mixed. One of the weaknesses of the current study is its use of dietary questionnaires to assess lycopene intake.

“Tomatoes are only one source of lycopenes in the diet. It is very hard to get a good assessment of the quantity of intake of lycopenes from such a questionnaire,” he said. “It’s important to understand that to get the benefit of tomatoes, the tomato product must be cooked to release the lycopenes. It’s unclear if that was assessed in this study.”