title: Total dietary fat and omega-3 fatty acids have modest effects on urinary sex hormones in postmenopausal women.
abstract: 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.
  
  
  RESULTS
  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:16α-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.
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, Minneapolis, MN, USA. susan.raatz@ars.usda.gov.
authors.forename: Lindsay R
authors.initials: LR
authors.lastname: Young
authors.forename: Susan K
authors.initials: SK
authors.lastname: Raatz
authors.forename: William
authors.initials: W
authors.lastname: Thomas
authors.forename: J Bruce
authors.initials: JB
authors.lastname: Redmon
authors.forename: Mindy S
authors.initials: MS
authors.lastname: Kurzer