Catechin, a potent antioxidant found in red wine, successfully delayed tumor formation when fed to mice that are predisposed to developing tumors, report researchers at the University of California, Davis.

This finding supports earlier research indicating that diet can play an important role in preventing certain types of cancer. Furthermore, the study suggests that different food-processing methods may significantly affect the preventive qualities of wines and other foods and beverages.

Results from this study will be reported in the October issue of the American Journal of Clinical Nutrition.

The study, conducted by wine chemist Susan Ebeler and nutrition scientist Andrew Clifford, both of UC Davis, focuses on the effects of dietary catechin, one of a group of compounds called polyphenols that are found in some plant-based foods. Polyphenols are thought to protect against cardiovascular disease and cancer by preventing oxidation, a process that has been linked to narrowing of the arteries, blood-clot formation and tumor growth.

"This study builds on a growing body of evidence indicating that certain foods and beverages derived from plants may help prevent some forms of cancer," said Ebeler. "Our data suggest that dietary levels of specific polyphenol compounds like catechin, rather than total polyphenol concentrations, may be critical in this protective mechanism."

Ebeler's study was conducted with transgenic mice that are an animal model for a type of human cancer called neurofibromatosis. External tumors readily appear on these animals.

All of the mice were fed a nutritionally complete powdered diet. The test animals' diets were supplemented either with catechin or with dehydrated and dealcoholized red wine, called wine solids.

The study consisted of three experiments. In the first, individual mice were fed at one of four different levels of catechin supplementation. In the second experiment, the mice received a diet with double the four levels of catechin in the first experiment. And in the third experiment, all of the test mice were fed a diet with added wine solids, but the wine solids contained very low levels of the polyphenol catechin.

In each of the three experiments, the researchers observed when tumors first appeared in each of the mice. They also monitored the growth of the mice in the second and third experiments.

The experiments yielded these findings:

Tumor Delay

In the first and second experiments, the mice fed catechin in their diets developed tumors much later than did the mice that received the control diet without catechin. Those eating the highest levels of catechin remained tumor-free for 32 days longer than did those on the control diet, which is a 45 percent extension of the tumor-free period.

Catechin Found in Bloodstream

As might be expected, catechin levels in the bloodstream rose with increasing concentrations of catechin in the diets of the mice, indicating that the mice were absorbing the catechin in their food. And the mice with higher levels of catechin in their bloodstream also went longer before developing tumors.

Mice in both the control and the catechin-supplemented groups grew well and remained healthy, indicating there were no apparent ill effects from the added catechin.

Importance of Specific Polyphenol Concentrations

In the third experiment, the mice that were fed wine solids in their diet did not experience a delay in the onset of tumors. This finding was of particular interest when compared with Ebeler's earlier research, which did find a significant delay in tumor onset among mice fed wine solids.

An explanation for this may lie in the fact that although the wine solids in both the current and previous studies had similar concentrations of total polyphenols, the current study's wine solids had only one-fourth of the catechin found in the wine from the earlier study.

Processing Techniques Critical

The wide disparity in the levels of catechin found in the wine solids used in the current and previous studies may be due to differences in processing methods. Catechin is primarily found in the seeds of the grape. In processing wine solids for the earlier study, the seeds and skin were left in with the juice for up to six weeks, compared to just seven days for the current study's wine solids.

"This is a clear reminder that, due to differences in processing, not all wines are the same in terms of potential health benefits," Ebeler said.

She noted that further studies are needed to explore the nature of the mechanisms responsible for the apparent cancer-preventive qualities of food components like catechin and other polyphenols. Extensive research is also needed to examine the ways in which these protective mechanisms are affected by processing.

This study was supported by funds from the U.S. Department of Agriculture, the American Cancer Society, the Wine Institute, the California Prune Board, the National Institute of Environmental Health and Safety and the University of California.