Consumption of commercial whole and non-fat milk increases the incidence of 7,12-dimethylbenz(a)anthracene-induced mammary tumors in rats.
BACKGROUND
Breast cancer has become the most common cancer among women worldwide. Although the consumptions of milk and dairy products were considered to be a risk factor for breast cancer in some epidemiological studies, the results were inconsistent.


METHODS
In the present study, female Sprague-Dawley rats received a single oral dose of 5mg 7,12-dimethylbenz(a)anthracene (DMBA). One week later, the animals were divided into four groups: whole milk (WM), artificial whole milk (A-WM), non-fat milk (NFM) or artificial non-fat milk (A-NFM) mixed with commercial powder chow. Rats were palpated weekly to monitor tumor development. At week 20 after DMBA administration, rats were decapitated and the volume and weight of mammary tumor were recorded.


RESULTS
Tumor incidence, the cumulative number of tumors and the sums of tumor volume were higher in the WM and NFM groups than in the A-WM and A-NFM groups both at palpation and at autopsy.


CONCLUSIONS
Combining our previous studies, we found the consumption of milk promoted the development of DMBA-induced mammary tumors in rats independent of the fat level.
Qin
Li-Qiang
LQ
Department of Obstetrics & Gynecology, School of Medicine, Yamanashi University, Chuo City, Shimokato 1110, Yamanashi 409-3898, Japan. qinliqiang0326@yahoo.com.cn
Xu
Jia-Ying
JY
Tezuka
Hideo
H
Li
Jue
J
Arita
Jun
J
Hoshi
Kazuhiko
K
Sato
Akio
A
D015127:9,10-Dimethyl-1,2-benzanthracene; D000230:Adenocarcinoma / Q000209:etiology*; D000818:Animals; D004041:Dietary Fats / Q000009:adverse effects*; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000209:etiology*; D008892:Milk / Q000009:adverse effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
D004041:Dietary Fats; D015127:9,10-Dimethyl-1,2-benzanthracene