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 inlaboratory rodents, chemopreventive effects of tea or purified extracts oftea have been demonstrated in lung, gastrointestinal tract and skin. Thereis some evidence of chemoprevention by tea in the mammary gland, but thedata are not conclusive. In order to evaluate more fully the possibleinfluence of black tea on 7,12-dimethylbenz[a]anthracene (DMBA)-inducedmammary gland tumors in the female S-D (Sprague-Dawley) rat, three largestudies were performed: experiment 1, tumorigenesis in rats fed AIN-76Adiet and given 25 mg/kg DMBA and 1.25 or 2.5% whole tea extract or water todrink; experiment 2, tumorigenesis in rats given 15 mg/kg DMBA and the samediet and fluids as in experiment 1; experiment 3, tumorigenesis in rats fedcontrol or HF (high fat, corn oil) diet and given 15 mg/kg DMBA and 2% teaor water to drink. Tea was given throughout the experiment; DMBA was givenby gastric gavage at 8 weeks of age. There was no consistent effect of teaon tumorigenesis in rats fed AIN-76A diet; there was, however, evidence inexperiment 3 of a reduction of tumorigenesis by tea in rats fed the HFdiet. In experiment 3, rats fed the HF diet and given water showed theexpected increase in tumor burden (number and weight) compared with ratsfed control diet. However, rats fed the HF diet and given 2% tea showed noincrease in tumor burden; their tumor burden was significantly lower thanin rats fed the HF diet and given water (P < 0.01) and was not differentfrom rats fed control diet and given water or tea. In addition, inexperiment 3, the number of malignant tumors per tumor- bearing rat wasincreased by the HF diet in water-drinking rats (P < 0.01) but not intea-drinking rats. Therefore, it appears that tea partially blocked thepromotion of DMBA-induced mammary tumorigenesis by the HF diet.