Abstract
BackgroundTotal 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.FindingsA 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.ConclusionsThe results of this study indicate that urinary sex hormone metabolism was modestly altered in postmenopausal women by a low fat dietary intervention.
Highlights
High concentrations of estrogens in blood and urine are associated with increased risk of breast cancer in postmenopausal women [1], and one hypothesis is that this increased risk is mediated by sex hormone metabolism
The results of this study indicate that urinary sex hormone metabolism was modestly altered in postmenopausal women by a low fat dietary intervention
The effects of controlled test diets: a high fat diet (HF; 40% energy as fat, 15% energy as protein, and 45% energy as carbohydrate), a low fat diet (LF; 20% energy as fat, 15% energy as protein, and 65% energy as carbohydrate) and a low fat diet with n-3 fatty acids (LFn3; 23% energy as fat [3% n-3], 15% energy as protein, and 62% energy as carbohydrate) on urinary estrogen metabolism were compared in a randomized, cross-over trial
Summary
High concentrations of estrogens in blood and urine are associated with increased risk of breast cancer in postmenopausal women [1], and one hypothesis is that this increased risk is mediated by sex hormone metabolism. Low fat diets resulted in significant reductions in circulating estrogens in some studies in postmenopausal women [2,3,4]. The purpose of the present study was to determine the effects of diets with varying amounts of fat and n-3 on urinary estrogens and estrogen metabolites in healthy postmenopausal women. 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
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