Effect of low- and high-fat intakes on the hormonal milieu of premenopausal women.

To compare the influence of low- and high-fat diets on hormone metabolism, we studied six premenopausal women over two complete menstrual cycles. After an initial 7-10 d dietary adjustment subjects were randomly assigned to either low- (25% of calories) or high-fat (46% of calories) diets. The diets were isocaloric and similar in proportions of protein, polyunsaturated:saturated fatty acid ratio, fiber, and cholesterol. All subjects completed both diets in a crossover experimental design. Fasting blood and 24-h urine samples were collected every other day. No significant differences in plasma luteinizing hormone, progesterone, prolactin, estrone (E1), and estradiol-17 beta (E2) or in urinary E1, E2, and estriol were observed. Prolactin secretion in response to thyrotropin-releasing hormone stimulation was also unchanged. Dietary fat may influence breast-cancer incidence by modulating the hormonal environment; however, an increase in short-term fat intake from 28 to 51 g/1000 kcal did not lead to substantial differences in the hormonal milieu.