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TUESDAY, July 10 (HealthDay News) -- There's little hard evidence that a diet rich in tomatoes and the tomato antioxidant lycopene can ward off cancer, according to research from the U.S. Food and Drug Administration.
Reporting in the July 10 issue of the Journal of the National Cancer Institute, FDA experts lay out in great detail the evidence -- or mostly lack of it -- behind their November 2005 statement that tomato consumption is not linked to any reduction risk of tumors of the prostate, ovary, stomach and pancreas.
The agency had previously found no evidence that tomatoes could cut risks for lung, colorectal, breast, cervical or endometrial tumors, either.
The November 2005 statement contended that, "there is no credible evidence to support qualified health claims for lycopene, as a food ingredient, component or food, or as a dietary supplement, and reduced risk of any of the cancers in the petition."
The petition for approval of the claims was submitted by a supplement maker, American Longevity.
The FDA has now put the evidence behind its decision in print, said Paul Coates, director of the office of dietary supplements at the U.S. National Institutes of Health and the author of a related journal editorial.
The new data review "gives people some idea of what the process is," Coates said. That's important, he said, because "one of the things that people are concerned about is how are these decisions arrived at. Making the process transparent and open will be helpful."
As part of its review, the FDA pored over data from 107 observational studies comparing the level of consumption of either tomatoes or lycopene with people's general cancer risk. They also looked at 23 studies that focused on blood levels of lycopene, although most of those trials were deemed unreliable, either because there were too many confounding factors or because most focused on cancer patients, not healthy people.
The agency also included dozens of studies comparing lycopene or tomato intake against the risk of individual cancers such as prostate, colon and breast malignancies.
The bottom line, according to the FDA: There's just not enough evidence to recommend that Americans boost their tomato intake to ward off cancer.
However, the new report is certainly not the last word on cancer-preventing claims for lycopene, Coates added.
"It just codifies the fact that the information about lycopene and cancer is not very robust," he said. "It may well be that if more studies are done, a greater effect might be found. But now, when you look at similar studies done by different people, they come to the same conclusion."
For its part, the American Cancer Society prefers to stay away from recommending any one food as a cancer preventive agent, said Marji McCullough, director of nutritional epidemiology for the organization.
"In our guidelines, we encourage people to eat a variety of foods, especially fruits and vegetables," she said. "Several studies have suggested a lower risk of cancer with some kinds of foods, including tomatoes, but we encourage variety."
The society encourages consumption of "dark deep-colored vegetables, because some studies have found an association between them and lower cancer risk," McCullough said.
The society also encourages fruit and vegetable consumption, because it helps prevent weight gain, she said.
But endorsement of specific foods won't come until research shows that they clearly are associated with lower cancer risk, McCullough said. As for supplements, "most of the evidence comes from studies of foods," she said.
More information
There's more on lycopene at the American Cancer Society.
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