Fat-protein interaction, defined 2-generation studies

Mammary tumor burden, in rats fed either normal or high fat diets related positively to the level of protein in the diet. This relationship existed with either a direct (NMU) or indirect carcinogen (DMBA). Significant differences in body growth, sexual maturation, morphologic structures in the mammary duct, and hormone activities during the estrous cycle probably contributed to lower tumor burden in the low protein-normal fat (LP-NF) group. Animals fed a high protein-normal fat (HP-NF) diet throughout their entire life have, with the exception of early sexual maturation, no distinctive characteristics compared to the control group. Inspite of these physical and physiologic similarities, increased dietary protein enhanced the effect of administered carcinogens. Animals fed a high protein-high fat (HP-HF) diet were compared to rats fed a normal protein-high fat (NP-HF) diet. Increased dietary protein further enhanced the effect of the high fat diet resulting in an increased carcinogen-induced tumor burden. These studies indicate that the design of the animal model, i.e. age of initiation of a test diet, appears to have a significant bearing on mammary tumor development. The biologic mechanisms which respond to diet modifications and which may influence breast tumor growth have not been thoroughly elaborated and require additional study.