Previous smaller studies suggested a diet rich in lycopene might offer some protection, findings that spawned a huge research and marketing effort.
H.J. Heinz lobbied the U.S. Food and Drug Administration to allow it and other tomato processing companies to make health claims on labels. The FDA only allowed them to say that "very limited and preliminary research" suggested eating half to a cup of tomatoes or tomato sauce each week might reduce the risk of prostate cancer.
Now a study that followed 28,000 men over eight years casts doubt on the claim, finding no evidence of a protective effect.
"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 the study's lead author, Ulrike Peters, of the Fred Hutchinson Cancer Research Center in Seattle.
"Unfortunately, this easy answer just does not work."
In the May issue of the journal Cancer Epidemiology, Biomarkers & Prevention, Peters and her colleagues report the results of their study of men between the ages of 55 to 74 with no history of prostate cancer when the study began.
Participants filled out a questionnaire about their health, diet and lifestyle, had regular prostate cancer screening tests and had lycopene levels in their blood measured.
Eat variety of fruits, vegetables
Researchers found no significant difference in blood levels of lycopene between the men diagnosed with prostate cancer and those who were not.
Peters said the study is not definitive, but rather, an incremental step in the scientific process of discovering what role nutrients play in health and disease.
Peters' advice to men who have been eating extra tomato products is, "They should not only rely on tomato products as a preventive agent for prostate cancer."
Still, tomatoes are healthy, Peters said, and their antiioxidant properties could still be proven to have benefits.
Many of the men at a prostate cancer support group meeting in Halifax have added lycopene to their diets hoping for an anti-cancer effect.
"I've been scared once in my life," said George McKelvie, who is not ruling out lycopene. "I'm trying to organize my life around that, and diet is very, very important."
Cancer experts also advise eating a healthy variety of fruits and vegetables.
From the May 23, 2007, Prepared Foods e-Flash