In the May issue of Cancer Epidemiology, Biomarkers & Prevention, researchers based at the National Cancer Institute, Rockville, MD, and the University of Washington’s Fred Hutchinson Cancer Research Center, Seattle, report that lycopene, an antioxidant predominately found in tomatoes (and to a lesser degree in guava, watermelon and some other pink-to-red foods), does not effectively prevent prostate cancer. However, they did find an association between beta carotene and an increased risk for aggressive prostate cancer.
The researchers investigated the association between carotenoids (lycopene, alpha carotene, beta carotene, beta cryptoxanthin, lutein and zeaxanthin) and risk of prostate cancer in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, a study designed to examine methods of early detection and risk factors for cancer. The study included 692 prostate cancer cases, including 270 aggressive cases.
Analysis of these cases showed that “lycopene and other carotenoids were unrelated to prostate cancer,” note the authors. “Consistent with other recent publications, these results suggest that lycopene or tomato-based regimens will not be effective for prostate cancer prevention.”
Surprisingly, the researchers did find that beta carotene was associated with an increased risk of aggressive prostate cancer. Such findings “may be due to chance,” notes Ulrike Peters, Ph.D., M.P.H., research assistant professor of Epidemiology, the Fred Hutchinson Cancer Research Center and lead author of the study. “However, beta carotene is already known to increase risk of lung cancer and cardiovascular disease in smokers.” Although she wouldn’t advise that people stop eating carrots and leafy vegetables, “I would say to be cautious about taking beta carotene supplements, particularly at high doses.” The other carotenoids studied were not associated with prostate-cancer risk.
As noted in a press release from Philadelphia-based American Association for Cancer Research issued today communicating these findings, previous studies have suggested that a diet rich in lycopene protected against prostate cancer, spurring commercial and public interest in the antioxidant. Antioxidants protect against free radicals, highly reactive atoms and molecules that can damage DNA and other important molecules in the cell. Since free radical damage increases with age, there has been a long-held suspicion in the scientific community that free radical damage could increase the risk of prostate cancer, a disease that has been clearly associated with age.
“It is disappointing, since lycopene might have offered a simple and inexpensive way to lower prostate cancer risk for men concerned about this common disease,” said Peters. “Unfortunately, this easy answer just does not work.”
Funding for this study was provided through the National Cancer Institute and the U.S. Department of Health and Human Services.
