Background: Total fat and omega-3 fatty acids in the diet may affect breast cancer risk by altering estrogen metabolism. The purpose of this study was to elucidate the effects of differing total fat and omega-3 fatty acid content of diets on a panel of urinary estrogens and metabolites. Findings. A controlled, cross-over feeding trial was conducted in postmenopausal women using three test diets: high fat diet (HF; 40% energy from fat), low fat diet (LF; 20% of energy from fat) and low fat, high omega-3 diet (LFn3; 23% energy from fat; 3% omega-3 fatty acids) for 8 week periods. Urinary hormone concentrations for 16 women were compared among diets using a linear mixed model, and within diet comparisons were made using paired t-tests. Urinary excretion of estrone was greater after the LF and LFn3 compared to the HF (P = 0.004). Estrone excretion was increased from baseline within the LF only (P = 0.02). Total estrone + estradiol + estriol increased from baseline with LF (P = 0.02) and was greater than the other two diets at 8 weeks (P = 0.03). There were no effects on estrogen metabolites, including the 2-hydroxy estrone:16 α-hydroxy estrone ratio. Conclusions: The results of this study indicate that urinary sex hormone metabolism was modestly altered in postmenopausal women by a low fat dietary intervention.
Bibliographical noteFunding Information:
Funding for this work was provided by grants from the Department of Defense (W81XWH-04-1-0448 and W81XWH-06-1-0778) and the National Center for Research Resources, National Institutes of Health (MO1-RR00400). This study was carried out at the General Clinical Research Center, University of Minnesota Medical School, Minneapolis, MN, USA.
- Dietary fat
- Low fat diet
- Omega-3 fatty acids
- Postmenopausal women
- Urinary estrogens