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Total dietary fat and omega-3 fatty acids have modest effects on urinary sex hormones in postmenopausal women

Young, Lindsay R., Raatz, Susan K., Thomas, William, Redmon, J. Bruce, Kurzer, Mindy S.
Nutrition & metabolism 2013 v.10 pp. 1
breast neoplasms, dietary fat, energy, estradiol, estriol, estrone, excretion, experimental diets, fatty acid composition, high fat diet, hormone metabolism, linear models, low fat diet, metabolites, omega-3 fatty acids, risk, women
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: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.