BREAST-CANCER - WEIGHING THE EVIDENCE FOR A PROMOTING ROLE OF DIETARY-FAT

It has been hypothesized that a high-fat diet promotes the development of postmenopausal breast cancer. This contention is supported by data showing high international correlations between fat intake and breast cancer rates, modest positive associations with a high-fat diet in ca se-control studies, and animal model studies that have consistently de monstrated that dietary fat influences mammary cancer development at s everal stages in the carcinogenic process. A number of plausible biolo gic mechanisms have been suggested that may explain such promotional e ffects. In contrast, dietary fat intake is unrelated to the risk of br east cancer in cohort studies. The conflicting findings from cohort st udies have created uncertainty regarding nutritional recommendations a nd breast cancer prevention. After reviewing key scientific findings t hat are relevant to this issue, the following conclusion is drawn: In the absence of data from dietary intervention trials, the weight of av ailable evidence suggests that the type and amount of fat in the diet is related to postmenopausal breast cancer and that the inability to d etect associations within populations (cohort studies) is because of m easurement error and the relative homogeneity of diets measured. It is expected that the results from intervention trials will clarify this issue.