Substantial evidence relates increased sex hormone concentrations with increased breast cancer risk. Varying omega-3 (n-3) fatty acid (FA) intake may lead to alterations in eicosanoid balance and changes in circulating sex hormones that reduce risk. To clarify effects of dietary fat and n-3 FA intake on breast cancer risk markers, circulating sex hormones and urinary eicosanoids were measured in response to controlled feeding of diets designed to increase plasma concentrations of n-3 FA. A controlled cross-over feeding trial in postmenopausal women was conducted using 3 diets: high fat (HF; 40% energy from fat), low fat (LF; 20% energy from fat), and low fat plus n-3 FA (LFn3; 20% of energy from fat plus 3% of energy from n-3 FA) in 8-wk feeding periods. Plasma phospholipid fatty acid n-3 increased with the LFn3 relative to HF and LF (P < 0.0001). Plasma estradiol increased by 51% with HF (P = 0.03). Urinary prostaglandin E metabolite increased with HF relative to LF (P = 0.02) and urinary 11-dehydro-thromboxane B2 increased with HF (P = 0.01). These results do not support a role of n-3 FA in the reduction of sex hormone levels.
Bibliographical noteFunding Information:
We thank Douglas M. Bibus, Ph.D., for assistance in the phospholipid fatty acids analysis. The work was conducted at the University of Minnesota General Clinical Research Center, Minneapolis, Minnesota. Funding for this work was provided by grants from the Department of Defense (W81XWH-04-1-0448 and W81XWH-06-1-0778) and MO1-RR00400 from the National Center for Research Resources, National Institutes of Health. Salmon of the Americas, Inc., donated salmon fillets for the controlled diets.