Dietary Effects on Gene Expression in Mammary Tumorigenesis
Although a large number of epidemiological studies in humans1–6 and dietary experiments in rats7–14 and in mice15–19 have been published on the relationship of dietary fat to breast cancer incidence, this important health question has not been resolved and has become instead increasingly controversial. Animal studies have strongly suggested that there is a mammary tumor promoting effect of diets high in total fat (approximately 20% fat by weight or 40% fat in calories, which is similar to the American diet) as compared to diets low in total fat (approximately 5% fat by weight or 10% fat in calories, which is similar to the Japanese diet)20. In the animal studies, diets with a greater proportion of unsaturated fats (specifically corn oil) were more effective than diets rich in saturated fats in increasing mammary tumor incidence and/or reducing the latent period of mammary tumor appearance21–23. The epidemiological data in humans have been for the most part based on comparison of breast cancer incidence and fat consumption in different countries worldwide5. Recently, however, two prospective epidemiological studies24,25 involving a large cohort of women have suggested a lack of evidence for a relationship between a high fat diet and human breast cancer for middle-aged and post- menopausal women. These studies did not, however, rule out that dietary fat may have an effect during childhood and adolescence. Also, differences in breast cancer risk due to a low fat diet may be manifested only at fat levels far below what is considered low fat in a Western diet.
KeywordsMammary Gland Mammary Tumor Mouse Mammary Tumor Virus Mammary Tumorigenesis Lactate Mammary Gland
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