Polyphenols Regulate Glutatione
Should you choose red wine or green tea? How about both: Compounds from both beverages have been found to inhibit growth of colon cancer.
Scientists from Italy’s University of Florence concluded this after an experiment that involved treating rats with a chemical known to cause promotion of colon cancer (azoxymethane). They divided rats into four groups: a control group receiving azoxymethane and fed a normal diet, and three groups receiving azoxymethane plus a diet supplemented with polyphenols from either red wine, black tea or green tea. The amount of polyphenols in the diet was equivalent to what a moderate wine drinker or tea drinker would ingest. Although the green tea group had little or no effect, both the wine and the black tea polyphenol groups produced fewer tumors in response to azoxymethane. The scientists went further to look for biochemical differences in tumors by examining levels of a specific enzyme found in the tumors.
Glutathione S-transferase (GST) is an enzyme that regulates glutathione levels in cells. Glutathione is an important antioxidant in most cells. However, when levels of GST are increased in tumor cells, it can cause failure of chemotherapy, acting as sort of a cell protector in the tumors. In the study, GST levels were increased in tumors from control animals compared to non-tumor tissues and were also greater in tumors from control animals compared to the red wine- and black tea-treated groups.
This suggests that perhaps GST is involved in cancer progression and that the polyphenols found in wine and tea were able to inhibit the progression of cancer by inhibiting the GST enzyme levels. However, another important aspect of inhibiting GST enzymes is that by inhibiting these enzymes, a cancer cell could become more susceptible to chemotherapy, therefore rendering chemotherapy more effective in treating cancer. Studies have not yet been conducted to determine if that is the case. This study is particularly interesting, because although nutrition has been implicated in cancer prevention for some time now, this study suggests nutrition also may be important in treatment regimes for cancer.
Luceri, C., et al. “Red wine and black tea polyphenols modulate the expression of cycloxygenase-2, inducible nitric oxide synthase and glutathione-related enzymes in azoxymethane-induced F344 rat colon tumors.” The Journal of Nutrition 2002, 132: 1376–1379.
Cindy Jones, Ph.D.