Nov. 4, 2003 -- Tomatoes are considered a potent prostate cancer-fighter, but a new study finds that the much-ballyhooed active ingredient usually singled out as the reason why may not be so active on its own.
Until now, the reason why tomatoes were considered to help reduce risk of prostate cancer was because of their high amounts of lycopene, a powerful antioxidant that may also protect against breast cancer.
But is it the lycopene itself or the foods that contain it?
It's the food, the first head-to-head animal study to compare the cancer-preventing potential of tomato products with those of lycopene shows. This study is in the latest issue of the Journal of the National Cancer Institute.
"In this study, we didn't see a sign benefit from lycopene alone," says researcher Steven K. Clinton, MD, PhD, of Ohio State University. "But we did see a significant benefit from tomato products." Lycopene is now available in supplement form.
Specifically, in rats made to develop prostate cancer in the laboratory, those who were fed a diet containing tomato powder experienced a longer survival prior to developing cancer and were 26% less likely to die from prostate cancer compared with those on a "control" diet containing no tomato or lycopene foods.
In rats fed a diet of lycopene alone, the death rates from prostate cancer were similar to those rats fed a control diet. .
Does this mean that lycopene isn't worthy of its reputation? Not really.
"Rather, it suggests that there is more to tomatoes and their health benefits than just lycopene," Clinton tells WebMD. "We already know that tomatoes contain dozens of potentially biologically active substances [that may help inhibit cancer]."
Translation: Continue to eat tomatoes and other healthy foods containing this compound. But don't depend on cancer protection from lycopene supplements, he says.
Agreed, says Edward L. Giovannucci, MD, ScD, of Harvard Medical School, whose early research on the prostate-protecting effects of tomatoes is largely responsible for promoting the fruit to superfood status.
"There is no evidence, from a human perspective, that lycopene supplements are beneficial. But there are many good studies showing a tomato-rich diet is helpful," he tells WebMD.
"That's not to say that the supplements aren't good; there just isn't any data to say they are. In doing these studies, you need to focus on a single compound."
So why has lycopene been the focus of the research - rather than the dozens of other compounds in tomatoes?
"It is fairly easily measured [in food]," says Clinton. "And as a known antioxidant, it feeds into people's preconception about the mechanism that underlies its ability to inhibit cancer."