Caffeine inhibits development of benign mammary gland tumors in carcinogen-treated female Sprague-Dawley rats

Summary The purpose of this study was to assess the influence of caffeine on the incidence of benign mammary tumors in carcinogen (DMBA) treated female Sprague-Dawley rats. Four different animal models were used in these studies, i.e., the administration of DMBA to: [1] 55 day old virgin rats; [2] 53 day old ovariectomized, estrogen treated virgin rats; [3] 135 day old virgin rats and [4] 135 day old parous rats. A high incidence of benign mammary fibroadenomas was observed in each of the four animal models. In addition, in the estrogen treated ovariectomized animals, a high incidence of secretory mammary gland cysts was observed. Caffeine (500 mg/L drinking water) was administered daily throughout the study commencing 3–31 days after carcinogen treatment. Caffeine treatment significantly (P<0.05 to P<0.001) reduced the incidence of benign mammary fibroadenomas in the 55 day old virgin rat model (P<0.01), in the 53 day old estrogen treated ovariectomized virgin rat model (P<0.05 to P<0.001) and in the 135 day old virgin rat model (P<0.05). The number of benign mammary fibroadenomas was reduced by caffeine in the 135 day old parous rat model but this reduction was not significant (P<0.10). In addition, in the estrogen treated ovariectomized virgin rat model, caffeine significantly (P<0.05 to P<0.001) reduced the incidence of mammary gland cysts. Caffeine treatment either increased or had no significant effect on body weight gains, depending upon the animal model. Thus, caffeine consumption can influence the development of benign mammary tumors (fibroadenomas and cysts) in carcinogen treated female Sprague-Dawley rats, an influence that was shown to be consistently inhibitory.