THURSDAY, May 29 (HealthDay News) -- Dried tomatoes, anyone?

A study in the June 1 issue of Cancer Research finds that the type of tomato product you eat may play a role in whether it can fight prostate cancer.

Specifically, an organic carbohydrate known as FruHis, which is produced when tomatoes are dehydrated, could be the secret ingredient.

But the study only looked at animals and, the authors warned, FruHis is not ready for the doctor's office or medicine cabinet just yet.

"This study was conducted in a rat model, and you cannot possibly draw any conclusions for people," said study author Valeri Mossine, a research assistant professor of biochemistry at the University of Missouri. "That's something we need to do next. But before you enter a study with humans, you have to prove that something works with animals. If it works, then you go on."

Several studies have pointed to a prostate cancer-fighting quality in tomatoes, but the exact mechanisms have been elusive.

In fact, the U.S. Food and Drug Administration laid out evidence or rather, a lack of it, behind a previous statement the agency had issued that tomato consumption is not linked to any reduction in risk of prostate tumors (or ovarian, stomach or pancreatic malignancies).

The November 2005 statement issued by the FDA 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."

But other experts, including the authors of the current study, are speculating that some other compound in tomatoes might interact with lycopene to produce the protective effect.

As the study points out, processing of edible plants (heating, grinding, mixing, drying, etc.) may have an effect on the nutritional value of the product, largely due to changes that occur in organic carbohydrates.

And a dietary component to prostate cancer risk and protection could help explain well-known geographical differences in the incidence of the disease.

"We were trying to show that a combination of two different entities in tomato products which appear out of the preparation of tomato powder might interact together," Mossine said.

For this study, rats were divided into four groups of 20: one group received a control diet, another group received a diet that included tomato paste, a third group received a diet including tomato paste plus additional FruHis, and the final group received tomato powder alone.

All rats were injected with chemicals to induce prostate cancer.

Rats fed the tomato paste-plus-FruHis survived the longest, 51 weeks without developing tumors, compared with 50 weeks in the tomato powder group, 45 weeks in the tomato paste group, and 40 weeks in the control group. The study only lasted 51 weeks, so the tomato paste plus FruHis group could have even longer survival times, Mossine noted.

Prostate tumors were found in 10 percent of the animals that had consumed tomato paste plus FruHis, compared with 30 percent of animals receiving tomato powder alone, 25 percent receiving tomato paste alone and 60 percent in the control group.

"Our study shows that one of these carbohydrates that we were suspecting interacts with lycopene, at least in that model that we were using," Mossine said.

"This is a very reasonable basic laboratory assessment of this issue with regard to prostate cancer risk," said Dr. K. Scott Coffield, a professor of surgery at Texas A & M Health Science Center College of Medicine and a urologist-oncologist with Scott & White. "What will be necessary at this point will be some translational research to take this into a clinical setting."

More information

Visit the National Cancer Institute for more on prostate cancer.

SOURCES: Valeri V. Mossine, Ph.D., research assistant professor, biochemistry, University of Missouri, Columbia; K. Scott Coffield, M.D., professor, surgery, Texas A&M Health Science Center College of Medicine, and urologist-oncologist, Scott & White, Temple, Texas; June 1, 2008, Cancer Research

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