A new study recently presented at the annual American Association for Cancer Research (AACR) Meeting in Washington, D.C. has reported that a low dietary omega-6 to omega-3 (n-6/n-3) fatty acid ratio reduces breast density in an animal model. Mammographic density was used as a surrogate marker for breast cancer risk in the study. Although consumption of omega-3 fatty acids has been reported to reduce risk of breast cancer, the optimal n-6/n-3 ratio has not been established. Both n-6 and n-3 fatty acids are essential for normal development and biological functioning. However, both also have metabolizing enzymes in common and may influence each other's metabolism. In the study, the authors attempted to determine the optimal ratio of dietary n-6/n-3 for chemoprevention consistent with avoiding adverse effects on normal development. Groups of nine 32-day old female Sprague Dawley rats were randomly assigned to one of seven dietary regimens with n-6/n-3 ratios ranging between 25 to 1 and 1.1 to 1. Calories from fat was fixed at 30% across all seven diets.

A high omega-6 diet did not cause any increase in mammary gland density in the rats so treated. However, density was found to be significantly reduced in the low omega-6 to omega-3 ratio group. The authors comment that they are in the process of determining the mechanism of action by which the n-6/n-3 ratio influences mammary gland density and related biological processes.