Two new studies have provided evidence that the connection between dietary lycopene and reduction of cancer risk is weak, at best. Earlier studies had reported that lycopene, an antioxidant found in tomatoes, has been associated with a decreased risk of some cancers, particularly prostate cancer.
An FDA review found very limited evidence for associations between tomato consumption and reduced risk of prostate, ovarian, gastric, and pancreatic cancers. FDA decided to allow qualified health claims for a very limited association between tomatoes and these four cancers. However, its analysis found no credible evidence that lycopene, either in food or in a dietary supplement, was associated with reduced risk of any of the cancers evaluated, as reported in an online edition of the Journal of the National Cancer Institute earlier this month.
"Very limited and preliminary scientific research suggests that eating one-half to one cup of tomatoes and/or tomato sauce a week may reduce the risk of prostate cancer. FDA concludes that there is little scientific evidence supporting this claim," FDA said in a statement.
A second study, conducted by researchers from the National Cancer Institute, Bethesda, MD, and Fred Hutchinson Cancer Research Center, Seattle, reached similar conclusions (Cancer Epidemiol Biomarkers Prev 2007; 16:962-8).
The researchers followed more than 28,000 men between the ages of 55 and 74 years who were enrolled in the Prostate, Lung, Colorectal, and Ovarian Cancer Trial. None of the men had a history of prostate cancer. The men were initially screened through a PSA test and digital rectal exam, and were then followed through routine exams and screenings until first occurrence of prostate cancer, death, or the end of the trial in 2001. Researchers found no significant difference between those who had prostate cancer and those who did not in relation to the concentration of lycopene in their bloodstream.
"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 Ulrike Peters, PhD, MPH, of Fred Hutchinson. "Unfortunately, this easy answer just does not work."