BLACK TEA AND MAMMARY-GLAND CARCINOGENESIS BY 7,12-DIMETHYLBENZ[A]ANTHRACENE IN RATS FED CONTROL OR HIGH-FAT DIETS

Epidemiological studies suggest that tea may reduce cancer risk, and i n laboratory rodents, chemopreventive effects of tea or purified extra cts of tea have been demonstrated in lung, gastrointestinal tract and skin. There is some evidence of chemoprevention by tea in the mammary gland, but the data are not conclusive, In order to evaluate more full y the possible influence of black tea on 7,12-dimethylbenz[a]anthracen e (DMBA)-induced mammary gland tumors in the female S-D (Sprague-Dawle y) rat, three large studies were performed: experiment 1, tumorigenesi s in rats fed AIN-76A diet and given 25 mg/kg DMBA and 1.25 or 2.5% wh ole tea extract or water to drink; experiment 2, tumorigenesis in rats given 15 mg/kg DMBA and the same diet and fluids as in experiment 1; experiment 3, tumorigenesis in rats fed control or HF (high fat, corn oil) diet and given 15 mg/kg DMBA and 2% tea or water to drink. Tea wa s given throughout the experiment; DMBA was given by gastric gavage at 8 weeks of age. There was no consistent effect of tea on tumorigenesi s in rats fed AIN-76A diet; there was, however, evidence in experiment 3 of a reduction of tumorigenesis by tea in rats fed the HF diet. In experiment 3, rats fed the HF diet and given water showed the expected increase in tumor burden (number and weight) compared with rats fed c ontrol diet. However, rats fed the HF diet and given 2% tea showed no increase in tumor burden; their tumor burden was significantly lower t han in rats fed the HF diet and given water (P < 0.01) and was not dif ferent from rats fed control diet and given water or tea, In addition, in experiment 3, the number of malignant tumors per tumor-bearing rat was increased by the HF diet in water-drinking rats (P < 0.01) but no t in tea-drinking rats. Therefore, it appears that tea partially block ed the promotion of DMBA-induced mammary tumorigenesis by the HF diet.