Elevated fat and cholesterol levels -- common in the Western diet -- may increase the risk of breast cancer, U.S. researchers suggest. Biologist Philippe G. Frank of Thomas Jefferson University says the incidence rate of breast cancer is five times higher in Western countries than in other developed countries.

The researchers used the PyMT mouse model believed to closely parallel the pathogenesis of human breast cancer. The PyMT mice were placed on a diet that contained 21.2 percent fat and 0.2 percent cholesterol, reflective of a typical Western diet, while a control group of PyMT mice received food containing 4.5 percent fat and negligible amounts of cholesterol.

The study published in The American Journal of Pathology found tumors began to develop quickly in mice fed the fat/cholesterol-enriched chow, the number of tumors almost doubled and they were 50 percent larger than those observed in mice that ate a normal diet.

"The consumption of a Western diet resulted in accelerated tumor onset and increased tumor incidences, multiplicity, and burden, suggesting an important role for dietary cholesterol in tumor formation," Frank says in a statement. In addition, there was also a trend toward an increased number of lung metastasis -- cancer spread -- in mice fed the fatty diet, Franks adds.